Advanced Search
RSS LinkedIn Twitter

Journal Archive

Johnson Matthey Technol. Rev., 2021, 65, (1), 94

doi:10.1595/205651320x15911991747174

泡沫铜上的铱镍薄膜电沉积:负载和溶液温度对碱性水中电催化剂析氢反应性能的影响

氢能应用中催化剂性能和稳定性得到改善

开发高活性、高稳定性、低成本新型析氢反应(HER)催化剂对氢能的应用具有重要意义。本文将铱镍薄膜电沉积在泡沫铜上作为HER电催化剂,并研究了铱镍薄膜的电沉积机理。薄膜的形貌和化学组成分别通过扫描电子显微镜检查法(SEM)和能量色散光谱法(EDS)测定。薄膜的电催化性能通过线性扫描伏安图(LSV)、电化学阻抗谱(EIS)和循环伏安法(CV)进行评估。结果表明,铱镍薄膜附着在多孔结构和中空形貌的基材上。在不添加添加剂的情况下,电解质中镍沉积效果较好,而且能使铱镍薄膜合金化,使得Ir42Ni58薄膜沉积速率较高,随后Ir80Ni20和Ir88Ni12薄膜中铱含量增加。塔菲尔斜率为40–49 mV dec-1的铱镍薄膜对HER表现出高效的电催化活性。铱镍薄膜的电催化活性表现出与负载的相关性。随着溶液温度从20°C升高到60°C,铱镍薄膜的析氢性能得到提高。Ir88Ni12膜的表观活化能值为7.1 kJ mol-1。长期析氢试验表明,碱性溶液具有良好的电催化稳定性。

Electrodeposition of Iridium-Nickel Thin Films on Copper Foam: Effects of Loading and Solution Temperature on Hydrogen Evolution Reaction Performance of Electrocatalyst in Alkaline Water

Improved performance and stability of catalyst for hydrogen energy applications

  • Jianwen Liu, Wangping Wu*, Xiang Wang, Yi Zhang
  • Electrochemistry and Corrosion Laboratory, School of Mechanical Engineering and Rail Transit, Changzhou University, Changzhou 213164, China
  • *Email: wwp3.14@163.com
SHARE THIS PAGE:

Article Synopsis

Developing novel hydrogen evolution reaction (HER) catalysts with high activity, high stability and low cost is of great importance for the applications of hydrogen energy. In this work, iridium-nickel thin films were electrodeposited on a copper foam as electrocatalyst for HER, and electrodeposition mechanism of iridium-nickel film was studied. The morphology and chemical composition of thin films were determined by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), respectively. The electrocatalytic performances of the films were estimated by linear sweep voltammograms (LSV), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The results show that iridium-nickel thin films were attached to the substrate of porous structure and hollow topography. The deposition of nickel was preferable in the electrolyte without the addition of additives, and the iridium-nickel thin film was alloyed, resulting in a high deposition rate for Ir42Ni58 thin film, and subsequently an increase of iridium content in the thin films of Ir80Ni20 and Ir88Ni12. Iridium-nickel thin films with Tafel slopes of 40–49 mV dec–1 exhibited highly efficient electrocatalytic activity for HER. The electrocatalytic activity of iridium-nickel thin films showed a loading dependence. As the solution temperature increased from 20°C to 60°C, the hydrogen evolution performance of iridium-nickel thin films improved. The apparent activation energy value of Ir88Ni12 film was 7.1 kJ mol–1. Long-term hydrogen evolution tests exhibited excellent electrocatalytic stability in alkaline solution.

1. Introduction

The continuous increase in energy consumption on the earth could push for alternative routes of energy generation and storage, in order to make a transition toward a more sustainable system (1, 2). Hydrogen is increasingly considered to be one of the most promising energy carriers (3). Alkaline water electrolysis derived from renewable energy is a promising technology to produce hydrogen (4). However, the energy consumption, which is directly proportional to cell voltage during the production of hydrogen by water electrolysis, is currently high (5). In order to resolve the demand for energy-saving, cathode materials with high catalytic activity can be designed to reduce the overpotential of HER.

Currently, platinum is the most efficient HER catalyst in alkaline electrolytes due to both low overpotential and excellent stability. However, due to the high cost, reducing the use of platinum is of critical importance for developing efficient affordable catalysts for HER. An effective alternative method to decrease the use of precious metals in catalysts is by alloying with transition metals such as nickel, cobalt and iron. The properties of precious metals, such as their lattice parameters, binding energy and bond length, can be tuned by alloying them with non-precious metals to change the adsorption energies and achieve optimal catalytic activity (10). Nickel provides good catalytic activity, chemical and mechanical stability and reasonably low cost compared to other possible materials (11, 12). Nickel binary alloys could provide both a reduced hydrogen overvoltage at the electrode surface and high quantity of hydrogen absorbed.

Iridium has unique physical and chemical properties, such as high melting point, low oxygen permeability, high chemical stability, superior oxidation resistance, high corrosion resistance and high catalyst activity for both hydrogen and oxygen evolution reactions (1319). Iridium oxides, both anhydrous rutile-type IrO2 and hydrated amorphous forms, have been widely considered as oxygen evolution reaction (OER) catalysts (20). The iridium-nickel alloy system is of great interest for catalytic and corrosive environment applications (2024). The iridium-nickel alloy is of particular interest because of the complete miscibility of iridium and nickel, and the absence of intermetallic compounds in the binary phase diagram. Kuttiyiel et al. (21) synthesised core-shell, hollow-structured Ir–Ni–N nanoparticles and then evaluated their HER activity. Coupling nickel nitrides with the IrNi cores enhanced the HER activity of iridium shells to a level comparable to that of Pt/C while reducing iridium loading of the catalyst. Özer et al. (16) explored the potentiostatic electrodeposition process of nickel onto polycrystalline iridium and assessed the electrocatalytic properties of the bimetallic surfaces. An overlayer of nickel on iridium showed superior performance in the acidic and alkaline conditions. Vázquez-Gómez et al. (22) modified porous nickel electrodes by electrodeposition of iridium nuclei from H2IrCl6 solutions at 70°C, with the aim of activating them towards the HER and comparing their performance with those of porous nickel electrodes activated by spontaneous deposition of noble metals. The current efficiency of iridium deposition was very low (1% or lower), which is not commercially useable. Sawy and Birss (23) studied nanoporous iridium and its oxide thin films formed by electrodeposition for a wide variety of electrocatalytic and sensing applications.

Electrodeposition is a powerful cost-effective and reliable film process without vacuum (2428). Electrodeposited nickel-based materials have good repeatability, simple preparation method, low requirements on experimental conditions and good catalytic properties for HER (29). To achieve the electrodeposition process, the operation conditions, such as pH, deposition time, applied current density or potential bath temperature and complexing agents should be precisely controlled (2528). In our publications (3032), the iridium-nickel alloy films were electrodeposited from citrate and oxalic acid aqueous solutions. In citrate aqueous solutions, nickel-iridium alloys with iridium content as high as 37 at% and Faraday efficiency as high as 44% were obtained, the codeposition of nickel-iridium alloy was a normal deposition for IrCl3-Ni2+-citrate acid system. Recently, iridium-nickel thin film electrocatalysts were electrodeposited on copper foam from hexabromoiridate(III) solution, and the HER performance of iridium, nickel and iridium-nickel thin-film electrocatalysts was studied and published in our laboratory (32). Iridium-nickel thin film with large real active area exhibited highly efficient electrocatalytic activity for HER, and achieved a current density of 10 mA cm–2 at an overpotential of 60 mV and a Tafel slope of 40 mV dec –1, which is superior to pure iridium and nickel thin films. The copper foam is used to improve catalyst structure to obtain more active sites on a supported electrode. Fabricating porous materials with unique morphology and microstructure to increase the number of active sites or introducing additional metal or non-metal elements to the catalyst to increase the intrinsic activity of the active site have been proven to be effective ways to further enhance the electrocatalytic performance of the catalysts (33). These methods could help catalysts tune the electronic structures and optimise the absorption energy for HER. The catalysis through increased loading may also expose more active sites per gram (29). However, the research on the effect of loadings and solution temperature on hydrogen evolution performance of electrocatalysts is still rare and limited. Pierozynski and Mikolajczyk (34) studied the HER performance of nickel foam and palladium-activated nickel foam materials in 0.1 M sodium hydroxide solution over the temperature range of 20–60°C. Both Tafel slopes and charge transfer coefficient exhibited temperature-dependent behaviour. Devadas and Imae (35) evaluated the HER efficiency with a small amount of platinum nanoparticles immobilised on graphene oxides, carbon nanohorns and carbon nanotubes by dendrimer-mediated chemical reaction, and found that the high HER efficiency from low loading of platinum contribute to the development of low cost hydrogen energy or battery systems.

In this study, iridium-nickel thin films were electrodeposited on copper foams with different deposition times. The present work aims to study the effects of loadings and solution temperature on the HER performance of iridium-nickel thin films in alkaline solutions, simultaneously to investigate electrodeposition mechanism and the microstructure and chemical composition of iridium-nickel thin films.

2. Experimental

2.1 Chemicals and Electrodeposition

The bath chemistry consisted of trisodium hexabromoiridate (Na3[Ir(III)Br6]) and nickel sulfate hexahydrate (NiSO4·6H2O). All chemical reagents were analytical grade. The bath solution was purged with pure nitrogen for 10 min before turning on the current. A nitrogen blanket was passed over the solution during electrodeposition. In all experiments, a magnetic stir bar was used to stir the solution. Copper foam was supplied by Taili Foam Metal Corporation, China (>99.99% copper, porosity ≥98%). The copper foam samples (10 mm × 10 mm × 0.3 mm) were first immersed in acetone for 40 min and ultrasonically cleaned for 10 min. The samples were then immersed in a mixture solution of nitric acid (HNO3)·H2O (volume ratio = 1:1) at room temperature for 5–10 s in a fume hood. Finally, the samples were washed with pure water and then dried in air. A conventional three-electrode cell was used for electrodeposition of iridium-nickel thin films on a copper foam sheet as the working electrode, platinum foil as the counter-electrode and a reference Ag/AgCl 3 M KCl electrode. The galvanostatical electrodeposition and electrochemical processes were carried out in the cell, using a CHI 660E electrochemical workstation (CH Instruments Inc, China) coupled to a computer with specific data acquisition software installed. The solution pH was examined by a PHS-3C pH meter and was adjusted to the desired value by adding 5.0 M NaOH while being stirred. The volume of the electrolyte in the cell was approximately 15 ml. The solution temperature was controlled by a HH-501 thermostatic bath (Jintan Baita Xinbao Instrument Factory, China). The mass change of the specimens before and after deposition was recorded by an analytical balance (FA2004B, resolution 0.1 mg). Table I shows the composition of the plating bath and the deposition parameters, three specimens were prepared in the same electrolyte, the first specimen #1 was deposited with 1 min, then the second specimen #2 for 3 min and the last specimen #3 for 5 min.

Table I

The Composition of the Plating Bath and Process Parameters

No. [Ir(III)Br6]3+, mM Ni2+, mM pH Temperature, oC j, mA cm–2 Time, min ΔW, mg
#1 13.5 40.5 4 80 20 1 2.3
#2 13.5 40.5 4 80 20 5 3.5
#3 13.5 40.5 4 80 20 10 4.2

Note: j = current density, ΔW = weight gain.

The CV of iridium in the bath of 26 mM Na3[Ir(III)Br6], nickel in the bath of 26 mM NiSO4·6H2O and iridium-nickel in the bath of 26 mM Na3[Ir(III)Br6] and 26 mM NiSO4·6H2O were performed, using an electrochemical workstation (CHI 660E). The electrocatalysts on copper sheets with diameter of 1 cm served as the working electrodes. The platinum foil with diameter of 1 cm served as the counter-electrode and a reference Ag/AgCl 3 M KCl electrode was used. The solutions for CV tests of iridium-nickel, nickel and iridium films were electrolytes at room temperature with a scanning rate of 10 mV s–1.

2.2 Characterisations

The microstructure and morphology of the surface of the films were observed by SEM (SUPRA 55, Sapphire and ZEISS Sigma, ZEISS Microscopy, Germany). The chemical composition of the film was determined by X-ray EDS using x-act detector (Oxford Instruments plc, UK).

The chemical composition and elemental states of the top surface of the iridium-nickel thin film on copper foam before HER performance testing were performed by X-ray photoelectron spectroscopy (XPS), (ESCALABTM 250Xi, Thermo Fisher Scientific, USA) with an ultrahigh vacuum of 3.3 × 10–8 Pa base pressure. The top surface of the iridium-nickel thin film on copper foam was irradiated with an aluminium Kα monochromatic source of 1486.6 eV, and the outcome electrons were analysed by a spherical capacitor analyser using the slit aperture of 0.8 mm. The carbon signal for C 1s at 285 eV was taken as an energy reference for the measured peaks. In order to identify the elements on the film surface, a low-resolution survey spectrum was firstly taken over a wide energy range of 0–1350 eV, with a pass energy of 150.0 eV at increments of 1.0 eV step–1. High-resolution spectra were acquired with a pass energy of 30.0 eV at small increments of 0.05 eV step–1, to allow precise determination of the position of the peaks and their shapes. Curve-fitting was done with Gaussian–Lorentzian functions, using the XPSPEAK 4.1 software. Two fitting parameters, the position of the peak and its full width at half-maximum (FWHM), were fixed within less than about ± 0.2 eV.

2.3 Electrochemical Performance Measurements

The LSV was tested in an alkaline solution at a scanning rate of 5 mV s–1 using a three-electrode system. Nitrogen was bubbled through the 1.0 M potassium hydroxide solution for 1 min before all electrochemical measurements were done. The iridium-nickel electrocatalysts deposited on the copper foam electrode served as the working electrode. The graphite rod and Hg/Hg2Cl2 were used as the counter and reference electrodes, respectively. The catalytic activities of iridium-nickel thin films with different loadings and solution temperatures were compared by LSV testing. Furthermore, the potentials were transferred to a reversible hydrogen electrode (RHE) potential. The formula for calibrating the saturated calomel electrode (SCE) to RHE is as follows (Equation (i)):

(i)

The CV of an iridium-nickel thin film was performed in alkaline solution using an electrochemical workstation (CHI 660E). The iridium-nickel thin film on the copper foam electrode served as the working electrode. In this work, the electrochemically active surface area (ECSA) of iridium-nickel catalysts were compared on a relative scale using the capacitance of the electrochemical double layer (Cdl) on the electrode-electrolyte interface. This comparison is validated as ECSA is proportional to Cdl. Cdl is obtained by the following procedure reported by McCrory et al. (36), which assumes that the measured current at the non-Faradaic region iC is due to the charging of the double-layer capacitor. Thus, the current iC is proportional to the scanning rate vscan (Equation (ii)):

(ii)

CV measurements were conducted at different scanning rates ranging from 10 mV s–1 to 160 mV s–1. The capacitor charging current iC at 0.05 V is plotted against the scanning rate νscan, which shows good linear dependence. Then, Cdl is obtained from the slope of the linear fitting. The relative ECSA of the iridium-nickel catalysts with different loadings are compared by their Cdl values.

Potential values were corrected with the ohmic (iR) drop by the electrolyte resistance obtained from EIS measurements taken in a potentiation mode in the frequency range from 100,000 Hz to 0.01 Hz. The solution temperature was controlled in the range of 20–60°C.

3. Results and Discussion

3.1 Cyclic Voltammograms

In order to better understand the electrodeposition mechanism, the CV measured in electrolytes containing nickel, iridium and both iridium and nickel salts are shown in Figure 1. The reduction peaks of iridium, nickel and iridium-nickel were at −0.56 V, −0.37 V and −0.54 V due to the reduction of Ni(II) to Ni0 and Ir(III) to Ir0, respectively. It can be found that the reduction potentials of iridium-nickel and iridium are very close and their peak currents are much higher than that of nickel, which may lead to much more iridium content in the iridium-nickel deposits. Without the addition of complexing agent in the electrolyte, the reduction potential of Ni2+ ions is higher than that of [Ir(III)Br6]3– ions. Therefore, the deposition of nickel was preferable during the electrodeposition process. The oxidation peak for iridium is present at –0.24 V vs. Ag/AgCl. The oxidation peak was mainly attributed to iridium oxidation, Ir0 → Ir(III). However, the oxidation peak for iridium-nickel is present at around –0.24~–0.15 V vs. Ag/AgCl because the iridium-nickel codeposited film is suggested to be alloyed. There is no oxidation peak for nickel at negative potential. For iridium-nickel film, the current peak at –0.54 V was due to the hydrogen adsorption, while the current peak at around –0.24~–0.15 V was due to the reoxidation of the codeposited deposits. For iridium film, the current peak at –0.56 V was observed due to the hydrogen adsorption, which is higher than the current peak at –0.23 V due to hydrogen desorption. These findings indicate that iridium and iridium-nickel deposits have a significant facility for hydrogen incorporation into the plated deposits (37). The deposition processes of iridium and iridium-nickel films are accompanied by a large amount of hydrogen evolution.

Fig. 1.

Cyclic voltammograms of iridium-nickel electrode in the bath of 26 mM [Ir(III)Br6]3– and 26 mM Ni2+, nickel electrode in the bath of 26 mM Ni2+ and iridium electrode in the bath of 26 mM [Ir(III)Br6]3–

Cyclic voltammograms of iridium-nickel electrode in the bath of 26 mM [Ir(III)Br6]3– and 26 mM Ni2+, nickel electrode in the bath of 26 mM Ni2+ and iridium electrode in the bath of 26 mM [Ir(III)Br6]3–

3.2 Structural Characterisation

Figure 2 shows the plots of the mass gain of the specimens deposited in one electrolyte with different deposition times. There is a nonlinear dependence of the mass gain against deposition time. According to CV curves, nickel is preferentially deposited because the deposition potential of nickel is higher than that of iridium. Therefore, the deposition rate for the first specimen, about 2.3 mg min–1 is larger than that of the others. Subsequently, the deposition rate kept stable, and the nickel content in the films decreased. The slope of the second plot is around 0.35, indicating a deposition rate of about 0.35 mg min–1. The atomic composition of the film by EDS is listed in Table II. The iridium content in the deposits increased remarkably from 1 min to 5 min. This result is in agreement with the above discussion.

Fig. 2.

Plots of the mass gain of the specimens

Plots of the mass gain of the specimens

Table II

Atomic Composition (at%) of Iridium-Nickel Thin Films Determined by EDS

Specimen Content, at%
Nickel Iridium
1 min, 2.3 mg cm–2 58 42
3 min, 3.5 mg cm–2 20 80
5 min, 4.2 mg cm–2 12 88

Figure 3 shows the surface morphology of iridium-nickel electrocatalysts and copper foam. Figure 3(a) shows a large number of dendritic structures for copper foam with diameters 30–60 nm. In Figures 3(b) and 3(c), many pores and hollowed topography can be observed. The grain boundary of the copper foam is clearly visible because of the thin layer. With the increase of deposition time, the thickness of the film also increases. It can be clearly seen that the iridium-nickel thin film is attached to the surface of the substrate (see Figure 3(d)). The cross structure and many pores of copper foam can increase the active area of the thin film, which is advantageous for hydrogen evolution performance. Figure 4 shows the EDS spectrum of the iridium-nickel electrocatalysts with different loadings. The chemical composition of iridium and nickel in the thin films is shown in Table II. EDS elemental mapping to probe nickel and iridium presence for Ir80Ni20 and the distribution on the substrate surface is shown in Figure 5. A large amount of copper is evenly distributed on the surface. It can be observed that the amount of iridium is larger than that of nickel in the image. Ir80Ni20 thin film was almost completely covered on the copper foam surface. The phase and crystallographic structure of the films on copper foam were determined by X-ray diffraction (XRD), however the signals of the films were not detected due to small loading, the information of copper foam was only present. The copper foam was composed of polycrystalline structure.

Fig. 3.

SEM images of copper foam: (a) iridium-nickel films; (b) 2.3 mg cm–2; (c) 3.5 mg cm–2; (d) 4.2 mg cm–2

SEM images of copper foam: (a) iridium-nickel films; (b) 2.3 mg cm–2; (c) 3.5 mg cm–2; (d) 4.2 mg cm–2

Fig. 4.

EDS spectra of the iridium-nickel films: (a) 2.3 mg cm–2; (b) 3.5 mg cm–2; (c) 4.2 mg cm–2

EDS spectra of the iridium-nickel films: (a) 2.3 mg cm–2; (b) 3.5 mg cm–2; (c) 4.2 mg cm–2

Fig. 5.

EDS elemental mapping images of Ir80Ni20 thin film in Fig. 3(c): (a) copper-blue; (b) iridium-red; (c) nickel-green

EDS elemental mapping images of Ir80Ni20 thin film in Fig. 3(c): (a) copper-blue; (b) iridium-red; (c) nickel-green

The chemical composition and elemental states of Ir80Ni20 thin films were deeply analysed by XPS technique. The atomic composition of Ir80Ni20 thin films on copper foam is listed in Table III. Figure 6 shows the XPS depth profile for the top surface of iridium-nickel thin films on copper foam. The elements copper, iridium, carbon, oxygen and bromine were determined on the top surface of as-deposited film. Unfortunately, the signal nickel element was not detected, probably due to the low quantities in the film. The large amounts of carbon and oxygen contents were attributed to ordinary adsorption from the environment (see Table III), significant amounts of oxides formed on the surface of the electrode during electrodeposition. The bromine signal was mainly from the electrolytes. The coverage of the Ir80Ni20 thin film on copper foam was not so perfect that the signal copper was determined. Figure 7 shows the high-resolution XPS spectra of as-deposited Ir80Ni20 thin film on copper foam. The binding energies of iridium were located at 63.6 eV and 60.6 eV for Ir0 4f5/2 and 4f7/2, respectively. It was indicated that the film was composed of the metallic state of iridium, although the nickel signal was not detected (Figure 7(a)). The binding energies of Ir0 4f5/2 and 4f7/2 have weak shifts in iridium-nickel thin films in contrast with pure iridium (63.8 eV and 60.8 eV) (38). This is ascribed to the incorporation of nickel into the electronic structures of iridium, demonstrating the changes in the alloyed phase, in turn enhancing the catalytic performance (3941). In the O-1s spectrum (see Figure 7(b)), the main peak at 530.5 eV is attributed to O 1s of the oxides, and the peaks at 531.3 eV and 531.9 eV are usually ascribed to surface species, such as hydroxyls or absorbed water of the film. An additional broader feature peak is present at a higher binding energy of ~533.2 eV.

Table III

Atomic Composition (at%) of Ir80Ni20 Thin Film on Copper Foam Determined by XPS

Elements Chemical composition, at%
Cu2p 24.87
Ir4f 2.91
C1s 34.37
O1s 37.41
Br3d 0.44

Fig. 6.

XPS depth profile for the top surface of Ir80Ni20 thin film on copper foam

XPS depth profile for the top surface of Ir80Ni20 thin film on copper foam

Fig. 7.

High-resolution XPS spectra of Ir80Ni20 thin film: (a) Ir-4f; (b) O-1s

High-resolution XPS spectra of Ir80Ni20 thin film: (a) Ir-4f; (b) O-1s

3.3 Electrocatalytic Behaviour

The electrocatalytic activities for HER of iridium-nickel thin films with different loadings were investigated in 1.0 M KOH solutions. Figure 8 presents the iR-corrected LSV curves and Tafel slopes of the bare copper foam and iridium-nickel samples. As anticipated, the bare copper foam displays a relatively low catalytic activity which requires an overpotential of 502.5 mV to drive a current density of 10 mA cm–2. In contrast, the iridium-nickel catalyst exhibits excellent catalytic activity, demonstrating a negligible onset potential (8.3–18.3 mV) at 1 mA cm–2 for hydrogen evolution in the electrolyte (see Table IV), which are much lower than the onset potential of copper foam. Here, the onset potential should always be defined on the basis of a specific current density, where the Tafel constant can be considered as the onset potential of HER (42, 43). From an electrochemical point of view, the Tafel constant becomes complementary to the Tafel slope.

Fig. 8.

(a) Linear sweep voltammograms obtained in 1 M KOH solution at room temperature and potential scan rate of 5 mV s–1; (b) Tafel plots

(a) Linear sweep voltammograms obtained in 1 M KOH solution at room temperature and potential scan rate of 5 mV s–1; (b) Tafel plots

Table IV

Comparison of the HER Catalytic Performance of Different Catalysts in 1.0 M KOH at 298 K

Samples Onset potential, mV (at 1 mA cm–2) Overpotential, η, mV (at 10 mA cm–2) Tafel slope, mV dec–1 Exchange current density, mA cm–2
Ir42Ni58 8.3 78 49 0.69
Ir80Ni20 11.4 60 40 0.657
Ir88Ni12 18.3 97 43 0.418
Copper foam 336 500 189 0.022
Pt/C (45) 0 40 29.5 0.75

In order to obtain a current density of 10 mA cm–2, Ir42Ni58, Ir80Ni20 and Ir88Ni12 thin films require overpotential of 76.4 mV, 60 mV and 95.4 mV, respectively (see Table IV). These values are already twice the overpotential of 34 mV at the current density of 10 mA cm–2 for the state-of-the-art Pt/C catalyst tested in the same electrolyte. To shed light on insights about the reaction kinetics, a detailed Tafel analysis has been performed. The Tafel equation is as follows (44) (Equation (iii)):

(iii)

where j is the current density, j0 is the exchange current density (i.e. a constant at η = 0 V) and b is the Tafel slope. The equation indicates that excellent catalysts should have both low Tafel slopes and high exchange current densities. The potential-dependency of current density j is related to the interfacial electrocatalytic reaction n, as the following (Equation (iv)):

(iv)

where n is the number of electrons, F is the Faraday’s constant (96,500 mol C–1). Because the current density j is potential-dependent, ν is also potential-dependent and consisted of three elementary steps as the following Equations (v)(vii):

Initial discharge or Volmer step:

(v)

Atom + ion or Heyrovsky step:

(vi)

Atom + atom or Tafel step:

(vii)

The above elementary steps lead to two mechanisms: Volmer-Heyrovsky and Volmer-Tafel. Three rate determining steps, Volmer, Heyrovsky and Tafel are possible for the above two mechanisms. The linear portions of the Tafel plots were fitted to the Tafel equation, the Tafel slope values for Ir42Ni58, Ir80Ni20 and Ir88Ni12 thin films were 49 mV dec–1, 40 mV dec–1 and 43 mV dec–1 respectively, indicating that the Ir80Ni20 electrocatalyst has much higher intrinsic activity than other catalysts for HER while still being less active than the Pt/C catalyst (28mV dec–1) (45). The Tafel slopes indicate the HER process of iridium-nickel film follows a Volmer-Heyrovsky mechanism, where electrochemical desorption of hydrogen is regarded as the rate-limiting step, i.e. the HER rate is determined by both H2O discharge and desorption of H from the catalyst surface (4648). The exchange current density (j0) of iridium-nickel thin films and copper foam were calculated by the Tafel extrapolation method (see Table IV), which reflects the catalytic activity of the electrode material under the reaction thermodynamic equilibrium conditions. The j0 value of the Ir80Ni20 thin film was 87.6% of the Pt/C catalyst (0.75 mg cm–2, 15 wt% Pt) (45). Therefore, an iridium-nickel thin film has highly efficient electrocatalytic activity for HER. In addition, a summary of the hydrogen evolution performance of electrocatalysts in alkaline solutions is listed in detail in Table V (4981). It can be found that the Tafel slope of the iridium-nickel thin film is low, indicating iridium-nickel thin film has excellent electrocatalytic performance.

Table V

Summary of HER Electrocatalysts in Alkaline Solution on Exchange Current Densities, Overpotential and Tafel Slope

Coatings Substrates Methods Alkaline Temperature, °C j0, mAcm–2 η, mV b, mVdec–1 Refs.
Ni-P10 Mild steel Electroless plating 32% NaOH 30 3.6 × 10–3 323(200) 105 (49)
Ni-Mo Mild steel Electrodeposition 6 M KOH 80 185(300) 175 (50, 51)
Ni-Mo Mild steel ditto 6 M KOH 80 1.86 × 10–2 185(300) 105 (5153)
Ni-Mo-Fe Mild steel ditto 6 M KOH 80 187(300) 165 (54, 55)
Ni83P12C5 Copper ditto 1 M NaOH 25 1.54 × 10–3 201.9(250) 95.2 (56, 57)
Ni71Mo27P2 Copper ditto 1 M NaOH 70 3.10 × 10–3 170(250) 89 (58)
Nickel Arc melting 1 M NaOH 25 3.3 × 10–3 121 (59)
NiMo46 Carbon steel Electrodeposition 5 M KOH 25 5.43 215(100) 147 (60)
Ni-Sn Copper ditto 1 M KOH 25 6.939 × 10–3 121 (61)
Ni-Fe-C Copper ditto 3.5% NaCl 90 70(120) (62)
Ni-S Nickel ditto 30% KOH 25 5.385 141(200) 264.4 (63)
NiMn Graphite ditto 30% NaOH 25 0.6 141(100) 130 (64)
NiCoZn Copper ditto 1 M KOH 25 1.62 140(100) 81 (65)
Ni92P8 Copper ditto 1 M NaOH 70 0.24 171(250) 57 (66)
NiTi Steel Thermal arc spraying 1 M NaOH 25 5.25 283 (67)
NiFeZn Carbon steel Electrodeposition 28% KOH 80 3.778 104(135) 67 (68)
Ni-S Carbon steel ditto 28% NaOH 80 4.6 90(150) 80.9 (69)
Ni–CeO2 Carbon steel ditto 1 M NaOH 25 80.71 × 10–3 157 (70)
Ni–LaNi5 Copper ditto 1 M NaOH 25 13.2 330(250) 101 (71)
Co90W10 Arc melting 1 M NaOH 25 76.5 × 10–3 326(250) 102 (72)
CoNiFe Carbon cloth Electrodeposition 1 M NaOH 70 5.85 × 10–4 151 (73)
Co–Mo45 Mild steel ditto 1 M NaOH 30 49.9 × 10–3 103 (74)
Fe82B18 Rapid solidification 1 M KOH 25 47 × 10–3 430(300) 113 (75)
Ni-P Mild steel Electroless plating 32% NaOH 30 3.98 × 10–6 340(250) 147 (76)
Platinum Heat treatment 8 M KOH 85 2.66 × 10–2 460(100) 390 (77)
Nano-Zr67Ni33 Melt-spinning 6 M KOH 25 2.5 × 10–1 1530(50) 121 (78)
Raney Nickel Perforated nickel sheet Plasma spraying 25% KOH 70 4 119(250) 84 (79)
CoFe Nickel foam Electrodeposition 1 M KOH 25 110(10) 35 (80)
Iron Nickel foam ditto 1 M KOH 25 175(10) 48 (80)
Cobalt Nickel foam ditto 1 M KOH 25 180(10) 60 (80)
Nickel foam 1 M KOH 25 260(10) 96 (80)
Platinum Nickel foam Electrodeposition 1 M KOH 25 40(10) 72 (80)
Porous nickel Nickel Spontaneous deposition 1 M NaOH 25 0.32 298(100) 138 (81)
Porous NiIr Nickel ditto 1 M NaOH 25 2.23 274(100) 166 (81)
Porous NiRu Nickel ditto 1 M NaOH 25 7.2 48(100) 42 (81)
Ir80Ni20 Copper foam Electrodeposition 1 M KOH 25 0.657 60(10) 40 (32)
Nickel Copper foam ditto 1 M KOH 25 0.347 170(10) 112 (32)
Iridium Copper foam ditto 1 M KOH 25 0.398 130.1(10) 69 (32)
Ir42Ni58 Copper foam ditto 1 M KOH 25 0.69 78(10) 49 This work
Ir88Ni12 Copper foam ditto 1 M KOH 25 0.418 97(10) 43 This work

Note: j0=Exchange current density; η= Overpotential, the value in the bracket is the target current density; b=Tafel slope

The ECSA of the catalyst is proportional to the electrochemical double-layer capacitance (Cdl). As shown in Figure 9, the Cdl values for Ir42Ni58, Ir80Ni20 and Ir88Ni12 were 59.82 mF cm–2, 132.91 mF cm–2 and 70.03 mF cm–2, respectively. It indicates that the high hydrogen evolution performance of Ir80Ni20 catalyst was mainly due to the high exposure of effective active sites. On the other hand, the scanning range of –0.15~0.85V for Ir80Ni20 catalyst is larger than the range of –0.25~0.65 V for other catalysts. In our previous publication (32), the initial CV curve of Ir80Ni20 catalyst was measured at a scanning rate of 10 mV s–1. It was found that iridium oxides are electrochemically formed at high positive potential on the surface of Ir80Ni20 thin film during a positive scanning direction, however the formation of iridium oxides cannot easily be reduced to the metal state (32). The formed iridium oxides could result in a significant decrease of HER activity. Therefore, when the scanning range of Ir42Ni58 and Ir88Ni12 thin films was shifted from –0.25 V to 0.65 V, the obtained Cdl values should be valid. Therefore, it is inferred that the hydrogen evolution performance of Ir88Ni12 film is better than that of Ir42Ni58 film, which might be attributed to the increase in iridium content of the film or electrode surface defects, resulting in increasing the number of effective active sites.

Fig. 9.

CV curves with different scan rates for electrodes in the alkaline solution: (a) Ir42Ni58; (b) Ir80Ni20; (c) Ir88Ni12; (d) differences in current density at 0.05 V vs. RHE (Δi = iaic) plotted against scan rate

CV curves with different scan rates for electrodes in the alkaline solution: (a) Ir42Ni58; (b) Ir80Ni20; (c) Ir88Ni12; (d) differences in current density at 0.05 V vs. RHE (Δi = ia–ic) plotted against scan rate

The large active surface area could be related to the porous structure and hollow architecture with crossed branch structure, which results in a significantly enhanced catalytic activity. The rough texture and the porous structure of copper foam facilitate fast mass transport for the enhanced reaction kinetics (82). However, Ir88Ni12 thin film with a good hydrogen evolution performance has a larger electrochemical surface area than Ir42Ni58 film. The electrocatalytic activity of iridium-nickel catalysts show a loading dependence.

Electrochemical impedance measurements were performed to further investigate the reaction kinetics of the HER process under the experimental conditions. Nyquist plots of copper foam, Ir80Ni22, iridium and nickel thin films as a function of overpotential are shown in Figure 10. The preparation of the iridium and nickel electrocatalysts was addressed (32). According to alternating current (AC) circuit theory, impedance spectra obtained for a given electrochemical system can be correlated to one or more equivalent circuit (83). Thus, different equivalent circuits were suggested to model the present data and the relevant model with the minimum number of electrical elements. The model of Ir80Ni22 film consists of the solution resistance (Rs), the low frequency time constant characterising the double-layer capacitance (Cdl) and charge transfer resistance (Rct). The potential dependencies of the obtained data are shown in Table VI. Due to surface heterogeneity of solid electrodes resulting from surface roughness and formation of porous layers, a constant phase element (CPE) is commonly used to replace the capacitance (C) in a real electrochemical process, which mainly depends on a non-ideal capacitance behaviour (84, 85). Rct values of iridium film and copper foam are 72.34 Ω cm2 and 76.64 Ω cm2, respectively. While the charge transfer resistance of nickel and Ir80Ni22 films are large, about 2642 Ω cm2 and 1312 Ω cm2, indicating that the Rct values of iridium film and copper foam are lower than those of nickel and iridium-nickel films. According to the XPS data, there is no iridium oxide on the catalyst surface for Ir80Ni22 thin films. It can be inferred that the iridium thin film was composed of metallic state. On the other hand, copper foam was immersed in nitric acid solution to activate it before the experiment. The absence of oxides in copper foam may result in a charge transfer resistance that is less than other electrocatalysts as a result. For nickel and Ir80Ni22 thin films, the top surface might be composed of some nickel oxides. The surface of nickel-rich nickel-iridium thin films consisted of lots of nickel oxides, the amount of nickel oxides was much more than that of metal nickel (unpublished data). Therefore, there is a contradiction here. The electrocatalytic performance of the thin film involves various factors, such as surface chemical substances, the number of catalytic active sites per unit area, and the electronic effect of the thin film metal. At the cathode, the process of hydrogen reduction for hydrogen gas requires energy to remove electrons from the metal electrode and connect electrons to protons to produce hydrogen. Therefore, the process of transferring electrons from the electrode to the hydrogen ions in the liquid phase has a certain resistance, which is a charge transfer resistance. Iridium electrode with a low resistance could accelerate the electron transfer during the electrocatalytic reaction.

Fig. 10.

(a) Nyquist plots of Ir80Ni20 film, iridium film and copper foam for the HER in 1M KOH; (b) the corresponding equivalent electric circuit models for all samples

(a) Nyquist plots of Ir80Ni20 film, iridium film and copper foam for the HER in 1M KOH; (b) the corresponding equivalent electric circuit models for all samples

Table VI

Electrical Equivalent Circuit Parameters

Samples Rs, Ω cm2 Cdl, F cm–2 Rct, Ω cm2
Iridium 1.218 0.098 72.34
Ir80Ni20 1.485 0.05076 1312
Nickel 13.6 0.003567 2642
Copper foam 1.89 0.005816 76.64

Figure 11 shows the polarisation curves and Tafel curves of the Ir88Ni12 film at different temperatures. As shown in Figure 11(a), the electrode has the best hydrogen evolution performance at 60°C, with only an overpotential of 186 mV to obtain a current density of 30 mA cm–2. At the temperature of 30°C, an overpotential of 212 mV is required. The performance of hydrogen evolution improves from 30°C to 60°C. Interestingly, the hydrogen evolution performance of the catalyst has decreased from 20°C to 30°C. The effect of temperature is not obvious, and the curves are very close. This result can also be derived from the Tafel slopes (see Figure 11(b)). From 20°C to 60°C, the Tafel slope is 46 mV dec–1, 56 mV dec–1, 52 mV dec–1, 43 mV dec–1 and 40 mV dec–1, respectively. The comparison of the HER catalytic performance at different temperatures is shown in Table VII.

Fig. 11.

(a) Linear sweep voltammograms obtained in 1.0 M KOH solution at different temperatures and potential scanning rate of 5 mV s–1; (b) Tafel plots

(a) Linear sweep voltammograms obtained in 1.0 M KOH solution at different temperatures and potential scanning rate of 5 mV s–1; (b) Tafel plots

Table VII

Comparison of the HER Catalytic Performance in 1.0 M KOH at Different Temperatures

Temperature, °C Onset potential, mV Overpotential, η, mV (at 30 mA cm–2) Tafel slope, mV dec–1 Exchange current density, mA cm–2
20 16 192 46 0.54
30 16 212 56 0.62
40 16 204 52 0.53
50 16 193 43 0.44
60 16 186 40 0.40

To investigate the essence of the improvement of HER activity of the iridium-nickel electrocatalyst, the apparent activation energies (Ea) of the film were determined via the following Arrhenius equations (86) (Equations (viii)(x)):

(viii)
(ix)
(x)

where j0 is exchange current density (A cm–2), F is the Faraday’s constant, k is Kohlrausch coefficient (dimensionless), c is the concentration of reactant (constant), Ea is the apparent activation energy (J mol–1), T is the temperature (K), and R is the gas constant (8.314 J mol–1 K–1). The linear relationship between logj0 and 1/T for Ir88Ni12 thin film is displayed in Figure 12. According to Equations (viii)(x), the apparent activation energy of Ir88Ni12 thin film electrocatalyst is calculated as 7.1 kJ mol–1, by the slopes of lines. Compared with the nickel cathode with about 40 kJ mol–1 in standard electrolyte (87), this result indicates that the Ir88Ni12 thin films can remarkably reduce Ea for HER and accordingly result in higher electrocatalytic activity. Hence, the codeposition process of nickel and iridium species on the copper foam provides a large number of active centres for hydrogen adsorption, with the synergetic effect giving electronic structure suitable for HER.

Fig. 12.

Dependence on temperature (Arrhenius plots) of the exchange current density for the Ir88Ni12 film

Dependence on temperature (Arrhenius plots) of the exchange current density for the Ir88Ni12 film

AC impedance characterisation of HER on the Ir88Ni12 electrode in 1.0 M KOH with different temperatures is shown in Figure 13. Nyquist plots of Ir88Ni12 film as a function of overpotential are shown in Figure 13(a). Impedance spectra obtained for a given electrochemical system can be correlated to an equivalent circuit (Figure 13(b)). The temperature dependence of Rct and Cdl parameters for the HER of Ir88Ni12 film examined at the temperature range of 20–60°C is present in Table VIII. The Ir88Ni12 electrode exhibited single, ‘depressed’ semicircles (a single-step charge-transfer reaction) at all reaction temperatures, in the explored frequency range, it is noted that a high-frequency semicircle electrode porosity response, which is typically observed in alkaline media, was practically indiscernible (34). The recorded Rs parameter decreased from 1.572 Ω cm2 at 30°C to 1.038 Ω cm2 at 60°C. Simultaneously, the Rct parameter significantly reduced from 48.34 Ω cm2 to 14.75 Ω cm2 for the same temperature range (see Table VIII). The lower Faraday resistance of the Ir88Ni12 electrode surface accelerates the electron transfer during the electrocatalytic reaction. The Cdl parameter was significantly reduced from 0.02515 F cm–2 to 0.02885 F cm–2. The effect most likely results from partial blocking of electrochemically active electrode surface by fresh hydrogen bubbles (34).

Fig. 13.

(a) Nyquist plots of Ir88Ni12 film for the HER in 1M KOH at different temperatures; (b) the corresponding equivalent electric circuit models

(a) Nyquist plots of Ir88Ni12 film for the HER in 1M KOH at different temperatures; (b) the corresponding equivalent electric circuit models

Table VIII

Electrochemical Parameters for the HER on Ir88Ni12 Thin Film Electrode in Contact with 1.0 M KOH, Studied over the Temperature Range of 20-60°C

Parameters 20°C 30°C 40°C 50°C 60°C
Rs, Ω cm2 1.572 1.366 1.126 1.041 1.038
Cdl, F cm–2 0.02515 0.03417 0.02987 0.03334 0.02885
Rct, Ω cm2 48.34 44.74 24.33 20.53 14.75

Apart from the catalytic activity, stability is another important requirement of catalysts for the HER system. In this case, the long-term stability of Ir80Ni20 film electrocatalyst is assessed in 1.0 M KOH at constant current densities of 10 mA cm–2 for 10 h (see Figure 14(a)). A slight increase in the overpotential has been observed in the V-t curve. The result of the long-term hydrogen evolution tests exhibited excellent electrocatalystic stability in alkaline solution. Polarisation curves recorded after 400 cycles testing for Ir88Ni12 film indicate that there is a little decay while the overpotential exceeds 0.068 V, instead, a slight improvement of the electrocatalytic activity of the electrode at low overpotential (see Figure 14(b)). This slight increase in the catalytic activity was possibly owing to the reduction of surface oxides during the initial period of hydrogen evolution, while the observed increase in overpotential as shown in Figure 14(a) could be a result of increased mass exchange resistance due to the continuous gas bubbling (88).

Fig. 14.

(a) Chronoamperometric durability test for Ir80Ni20 film at a constant current density of 10 mA cm–2 for 10 h; (b) polarisation curves of Ir88Ni12 film initially and after 400 cycles vs. RHE at a scan rate of 5 mV s–1 in 1.0 M KOH solution

(a) Chronoamperometric durability test for Ir80Ni20 film at a constant current density of 10 mA cm–2 for 10 h; (b) polarisation curves of Ir88Ni12 film initially and after 400 cycles vs. RHE at a scan rate of 5 mV s–1 in 1.0 M KOH solution

4. Conclusions

Iridium-nickel thin films were successfully prepared on copper foam by electrodeposition under different deposition times. The morphology, chemical composition and electrocatalytic performance of iridium-nickel thin films were studied. At the same time, the electrodeposition mechanism of iridium-nickel thin film in the electrolyte without the addition of complexing agent was studied. It was found that the deposition of nickel was preferable during electrodeposition of iridium-nickel thin film and the iridium-nickel thin film was alloyed, which could result in high deposition rate for Ir42Ni58 thin film, and subsequently the increase of iridium content in the thin films of Ir80Ni20 and Ir88Ni12. Iridium-nickel thin films have highly efficient electrocatalytic activity for HER. The Tafel slopes of iridium-nickel thin films were 40–49 mV dec–1, indicating that the HER process of iridium-nickel films followed a Volmer-Heyrovsky mechanism. The Ir80Ni20 thin film possesses the good electrocatalytic performance due to the incorporation of nickel into the electronic structures of iridium, enhancing the catalytic performance. The surface of Ir80Ni20 thin film was composed of metallic state of iridium and some oxides. The electrocatalytic activity of iridium-nickel thin film shows a loading dependence. As the temperature raised from 30°C to 60°C, the hydrogen evolution performance of the iridium-nickel thin film became better. The apparent activation energy value of the Ir88Ni12 film was 7.1 kJ mol–1. Long-term hydrogen evolution tests exhibited excellent stability in the alkaline solution.

BACK TO TOP

References

  1. 1.
    F. Orecchini, A. Santiangeli and A. Dell’Era, J. Fuel Cell Sci. Technol., 2006, 3, (1), 75 LINK https://doi.org/10.1115/1.2134740
  2. 2.
    O. Antonia and G. Saur, “Wind to Hydrogen in California: Case Study”, Technical Report NREL/TP-5600-53045, 1051927, National Renewable Energy Laboratory, Golden, USA, August, 2012, 28 pp LINK https://doi.org/10.2172/1051927
  3. 3.
    M. Gong, D.-Y. Wang, C.-C. Chen, B.-J. Hwang and H. Dai, Nano Res., 2016, 9, (1), 28 LINK https://doi.org/10.1007/s12274-015-0965-x
  4. 4.
    D. Merki, S. Fierro, H. Vrubel and X. Hu, Chem. Sci., 2011, 2, (7), 1262 LINK https://doi.org/10.1039/C1SC00117E
  5. 5.
    R. Solmaz and G. Kardaş, Electrochim. Acta, 2009, 54, (14), 3726 LINK https://doi.org/10.1016/j.electacta.2009.01.064
  6. 6.
    S. Anantharaj, K. Karthick, M. Venkatesh, T. V. S. V. Simha, A. S. Salunke, L. Ma, H. Liang and S. Kundu, Nano Energy, 2017, 39, 30 LINK https://doi.org/10.1016/j.nanoen.2017.06.027
  7. 7.
    Q. Chen, Z. Cao, G. Du, Q. Kuang, J. Huang, Z. Xie and L. Zheng, Nano Energy, 2017, 39, 582 LINK https://doi.org/10.1016/j.nanoen.2017.07.041
  8. 8.
    L.-Y. Jiang, X.-X. Lin, A.-J. Wang, J. Yuan, J.-J. Feng and X.-S. Li, Electrochim. Acta, 2017, 225, 525 LINK https://doi.org/10.1016/j.electacta.2016.12.123
  9. 9.
    E. Isarain-Chávez, M. D. Baró, C. Alcantara, S. Pané, J. Sort and E. Pellicer, ChemSusChem, 2018, 11, (2), 367 LINK https://doi.org/10.1002/cssc.201701938
  10. 10.
    Y. Yang, Z. Lun, G. Xia, F. Zheng, M. He and Q. Chen, Energy Environ. Sci., 2015, 8, (12), 3563 LINK https://doi.org/10.1039/C5EE02460A
  11. 11.
    F. Safizadeh, E. Ghali and G. Houlachi, Int. J. Hydrogen Energy, 2015, 40, (1), 256 LINK https://doi.org/10.1016/j.ijhydene.2014.10.109
  12. 12.
    A. Eftekhari, Int. J. Hydrogen Energy, 2017, 42, (16), 11053 LINK https://doi.org/10.1016/j.ijhydene.2017.02.125
  13. 13.
    W. P. Wu and Z. F. Chen, Johnson Matthey Technol. Rev., 2017, 61, (1), 16 LINK https://www.technology.matthey.com/article/61/1/16-28/
  14. 14.
    W. P. Wu and Z. F. Chen, Johnson Matthey Technol. Rev., 2017, 61, (2), 93 LINK https://www.technology.matthey.com/article/61/2/93-110/
  15. 15.
    W. P. Wu, Z. F. Chen and L. B. Wang, Protect. Metals. Phys. Chem. Surf., 2015, 51, (4), 607 LINK https://doi.org/10.1134/S2070205115040358
  16. 16.
    E. Özer, I. Sinev, A. M. Mingers, J. Araujo, T. Kropp, M. Mavrikakis, K. J. J. Mayrhofer, B. R. Cuenya and P. Strasser, Surfaces, 2018, 1, (1), 165 LINK https://doi.org/10.3390/surfaces1010013
  17. 17.
    L. He, Y. Huang, X. Y. Liu, L. Li, A. Wang, X. Wang, C.-Y. Mou and T. Zhang, Appl. Catal. B: Environ., 2014, 147, 779 LINK https://doi.org/10.1016/j.apcatb.2013.10.022
  18. 18.
    B. M. Jović, V. D. Jović, U. Č. Lačnjevac, Lj. Gajić-Krstajić, J. Kovač and N. V. Krstajić, Int. J. Hydrogen Energy, 2015, 40, (33), 10480 LINK https://doi.org/10.1016/j.ijhydene.2015.06.127
  19. 19.
    B. M. Jović, U. Č. Lačnjevac, V. D. Jović, Lj. Gajić-Krstajić, J. Kovač, D. Poleti and N. V. Krstajić, Int. J. Hydrogen Energy, 2016, 41, (45), 20502 LINK https://doi.org/10.1016/j.ijhydene.2016.08.226
  20. 20.
    V. Pfeifer, T. E. Jones, S. Wrabetz, C. Massué, J. J. Velasco Vélez, R. Arrigo, M. Scherzer, Si. Piccinin, M. Hävecker, A. Knop-Gerick and R. Schlögl, Chem. Sci., 2016, 7, (11), 6791 LINK https://doi.org/10.1039/C6SC01860B
  21. 21.
    K. A. Kuttiyiel, K. Sasaki, W. F. Chen, D. Su and R. R. Adzic, J. Mater. Chem. A, 2014, 2, (3), 591 LINK https://doi.org/10.1039/c3ta14301e
  22. 22.
    L. Vázquez-Gómez, S. Cattarin, R. Gerbasi, P. Guerriero and M. Musiani, J. Appl. Electrochem., 2009, 39, (11), 2165 LINK https://doi.org/10.1007/s10800-009-9847-9
  23. 23.
    E. N. E. Sawy and V. I. Birss, J. Mater. Chem., 2009, 19, (43), 8244 LINK https://doi.org/10.1039/B914662H
  24. 24.
    W. P. Wu, Appl. Phys. A, 2016, 122, (12), 1028 LINK https://doi.org/10.1007/s00339-016-0567-9
  25. 25.
    W. P. Wu, N. Eliaz and E. Gileadi, Thin Solid Films, 2016, 616, 828 LINK https://doi.org/10.1016/j.tsf.2016.10.012
  26. 26.
    W. P. Wu, Electrochemistry, 2016, 84, (9), 699 LINK https://doi.org/10.5796/electrochemistry.84.699
  27. 27.
    W. P. Wu, N. Eliaz and E. Gileadi, J. Electrochem. Soc., 2015, 162, (1), D20 LINK https://doi.org/10.1149/2.0281501jes
  28. 28.
    W. P. Wu, J. W. Liu, Y. Zhang, X. Wang and Y. Zhang, J. Appl. Electrochem., 2019, 49, (10), 1043 LINK https://doi.org/10.1007/s10800-019-01348-5
  29. 29.
    R. K. Shervedani, M. Torabi and F. Yaghoobi, Electrochim. Acta, 2017, 244, 230 LINK https://doi.org/10.1016/j.electacta.2017.05.099
  30. 30.
    W. P. Wu, J. J. Jiang, P. Jiang, Z. Z. Wang, N. Y. Yuan and J. N. Ding, Appl. Surf. Sci., 2018, 434, 307 LINK https://doi.org/10.1016/j.apsusc.2017.10.180
  31. 31.
    W. P. Wu, Z. Z. Wang, P. Jiang and Z. P. Tang, J. Electrochem. Soc., 2017, 164, (14), D985 LINK https://doi.org/10.1149/2.0771714jes
  32. 32.
    W. P. Wu, J. W. Liu, N. Johannes, L. Zhang, Y. Zhang, T. S. Hua and L. Liu, Catal. Lett., 2020, 150, (5), 1325 LINK https://doi.org/10.1007/s10562-019-03038-5
  33. 33.
    Z. W. Seh, J. Kibsgaard, C. F. Dickens, I. Chorkendorff, J. K. Nørskov and T. F. Jaramillo, Science, 2017, 355, (6321), eaad4998 LINK https://doi.org/10.1126/science.aad4998
  34. 34.
    B. Pierozynski and T. Mikolajczyk, Electrocatalysis, 2015, 6, (1), 51 LINK https://doi.org/10.1007/s12678-014-0216-z
  35. 35.
    B. Devadas and T. Imae, Electrochem. Commun., 2016, 72, 135 LINK https://doi.org/10.1016/j.elecom.2016.09.022
  36. 36.
    C. C. L. McCrory, S. Jung, I. M. Ferrer, S. M. Chatman, J. C. Peters and T. F. Jaramillo, J. Am. Chem. Soc., 2015, 137, (13), 4347 LINK https://doi.org/10.1021/ja510442p
  37. 37.
    T. Ohsaka, Y. Matsubara, K. Hirano and T. Ohishi, Trans. Inst. Metal Finish., 2007, 85, (5), 265 LINK https://doi.org/10.1179/174591907X229635
  38. 38.
    V. Pfeifer, T. E. Jones, J. J. Velasco Vélez, C. Massué, R. Arrigo, D. Teschner, F. Girgsdies, M. Scherzer, M. T. Greiner, J. Allan, M. Hashagen, G. Weinberg, S. Piccinin, M. Hävecker, A. Knop-Gericke and R. Schlög, Surf. Interface Anal., 2016, 48, (5), 261 LINK https://doi.org/10.1002/sia.5895
  39. 39.
    R. L. Zhang, J. J. Duan, Z. Han, Ji.-J. Feng, H. Huang, Q.-L. Zhang and A.-J. Wanga, Appl. Surf. Sci., 2020, 506, 144791 LINK https://doi.org/10.1016/j.apsusc.2019.144791
  40. 40.
    Q. Chen, Y. Wang, M. Wang, S. Ma, P. Wang, G. Zhang, W. Chen, H. Ji, L. Liu and X. Xu, J. Coll. Interface Sci., 2020, 561, 372 LINK https://doi.org/10.1016/j.jcis.2019.10.122
  41. 41.
    H.-Y. Chen, H.-J. Niu, Z. Han, J.-J. Feng, H. Huang and A.-J. Wang, J. Coll. Interface Sci., 2020, 570, 205 LINK https://doi.org/10.1016/j.jcis.2020.02.090
  42. 42.
    J. D. Benck, T. R. Hellstern, J. Kibsgaard, P. Chakthranont and T. F. Jaramillo, ACS Catal., 2014, 4, (11), 3957 LINK https://doi.org/10.1021/cs500923c
  43. 43.
    A. P. Murthy, J. Theerthagiri and J. Madhavan, J. Phys. Chem. C, 2018, 122, (42), 23943 LINK https://doi.org/10.1021/acs.jpcc.8b07763
  44. 44.
    B. V. Tilak, A. C. Ramamurthy and B. E. Conway, J. Chem. Sci., 1986, 97, (3–4), 359 LINK https://www.ias.ac.in/article/fulltext/jcsc/097/03-04/0359-0393
  45. 45.
    M. Y. Gao, C. Yang, Q. B. Zhang, Y. W. Yu, Y. X. Hua, Y. Li and P. Dong, Electrochim. Acta, 2016, 215, 609 LINK http://dx.doi.org/10.1016/j.electacta.2016.08.145
  46. 46.
    W.-F. Chen, C.-H. Wang, K. Sasaki, N. Marinkovic, W. Xu, J. T. Muckerman, Y. Zhu and R. R. Adzic, Energy Environ. Sci., 2013, 6, (3), 943 LINK https://doi.org/10.1039/C2EE23891H
  47. 47.
    J. Deng, P. Ren, D. Deng and X. Bao, Angew. Chem. Int. Ed., 2015, 127, (7), 2128 LINK https://doi.org/10.1002/ange.201409524
  48. 48.
    D. J. Li, U. N. Maiti, J. Lim, D. S. Choi, W. J. Lee, Y. Oh, G. Y. Lee and S. O. Kim, Nano Lett., 2014, 14, (3), 1228 LINK https://doi.org/10.1021/nl404108a
  49. 49.
    S. M. A. Shibli and V. S. Dilimon, Int. J. Hydrogen Energy, 2007, 32, (12), 1694 LINK https://doi.org/10.1016/j.ijhydene.2006.11.037
  50. 50.
    I. A. Raj and K. I. Vasu, J. Appl. Electrochem., 1990, 20, (1), 32 LINK https://doi.org/10.1007/BF01012468
  51. 51.
    I. A. Raj, J. Mater. Sci., 1993, 28, (16), 4375 LINK https://doi.org/10.1007/BF01154945
  52. 52.
    I. A. Raj, Appl. Surf. Sci., 1992, 59, (3–4), 245 LINK https://doi.org/10.1016/0169-4332(92)90124-G
  53. 53.
    I. A. Raj and V. K. Venkatesan, Int. J. Hydrogen Energy, 1988, 13, (4), 215 LINK https://doi.org/10.1016/0360-3199(88)90088-2
  54. 54.
    I. A. Raj, Bull. Electrochem., 1999, 15, (11), 519 LINK http://cecri.csircentral.net/id/eprint/1255
  55. 55.
    I. A. Raj, Int. J. Hydrogen Energy, 1992, 17, (6), 413 LINK https://doi.org/10.1016/0360-3199(92)90185-Y
  56. 56.
    I. A. Raj and K. I. Vasu, J. Appl. Electrochem., 1992, 22, (5), 471 LINK https://doi.org/10.1007/BF01077551
  57. 57.
    R. K. Shervedani, A. Amini and M. Karevan, J. New Mater. Electrochem. Sys., 2015, 18, (2), 63 LINK https://doi.org/10.14447/jnmes.v18i2.376
  58. 58.
    R. K. Shervedani and A. Lasia, J. Electrochem. Soc., 1998, 145, (7), 2219 LINK https://doi.org/10.1149/1.1838623
  59. 59.
    J. M. Jakšića, M. V. Vojnović and N. V. Krstajić, Electrochim. Acta, 2000, 45, (25–26), 4151 LINK https://doi.org/10.1016/S0013-4686(00)00549-1
  60. 60.
    J. Kubisztal, A. Budniok and A. Lasia, Int. J. Hydrogen Energy, 2007, 32, (9), 1211 LINK https://doi.org/10.1016/j.ijhydene.2006.11.020
  61. 61.
    V. Jeyasankar, S. Mohan, S. A. Kumar, S. R. Suseendiran and S. Pavithra, Int. J. Hydrogen Energy, 2013, 38, (25), 10208 LINK https://doi.org/10.1016/j.ijhydene.2013.06.068
  62. 62.
    L. J. Song and H. M. Meng, Int. J. Hydrogen Energy, 2010, 35, (19), 10060 LINK https://doi.org/10.1016/j.ijhydene.2010.08.003
  63. 63.
    Z. Shan, Y. Liu, Z. Chen, G. Warrender and J. Tiana, Int. J. Hydrogen Energy, 2008, 33, (1), 28 LINK https://doi.org/10.1016/j.ijhydene.2007.08.026
  64. 64.
    A. O. Yüce, A. Döner and G. Kardaş, Int. J. Hydrogen Energy, 2013, 38, (11), 4466 LINK https://doi.org/10.1016/j.ijhydene.2013.01.160
  65. 65.
    R. Solmaz and G. Kardaş, Int. J. Hydrogen Energy, 2011, 36, (19), 12079 LINK https://doi.org/10.1016/j.ijhydene.2011.06.101
  66. 66.
    R. K. Shervedani and A. Lasia, J. Electrochem. Soc., 1997, 144, (2), 511 LINK https://doi.org/10.1149/1.1837441
  67. 67.
    A. Kellenberger, N. Vaszilcsin, W. Brandl and N. Duteanu, Int. J. Hydrogen Energy, 2007, 32, (15), 3258 LINK https://doi.org/10.1016/j.ijhydene.2007.02.028
  68. 68.
    M. J. Giz, S. C. Bento and E. R. Gonzalez, Int. J. Hydrogen Energy, 2000, 25, (7), 621 LINK https://doi.org/10.1016/S0360-3199(99)00084-1
  69. 69.
    Q. Han, K. Liu, J. Chen and X. Wei, Int. J. Hydrogen Energy, 2003, 28, (11), 1207 LINK https://doi.org/10.1016/S0360-3199(02)00283-5
  70. 70.
    Z. Zheng, N. Li, C.-Q. Wang, D.-Y. Li, Y.-M. Zhu and G. Wu, Int. J. Hydrogen Energy, 2012, 37, (19), 13921 LINK https://doi.org/10.1016/j.ijhydene.2012.07.102
  71. 71.
    R. Bocutti, M. J. Saeki, A. O. Florentino, C. L. F. Oliveira and A. C. D. Ângelo, Int. J. Hydrogen Energy, 2000, 25, (11), 1051 LINK https://doi.org/10.1016/S0360-3199(00)00026-4
  72. 72.
    F. Rosalbino, D. Macciò, A. Saccone and G. Scavino, Int. J. Hydrogen Energy, 2014, 39, (24), 12448 LINK https://doi.org/10.1016/j.ijhydene.2014.06.082
  73. 73.
    M. Jafarian, O. Azizi, F. Gobal and M. G. Mahjani, Int. J. Hydrogen Energy, 2007, 32, (12), 1686 LINK https://doi.org/10.1016/j.ijhydene.2006.09.030
  74. 74.
    A. Subramania, A. R. S. Priya, V. S. Muralidharan, Int. J. Hydrogen Energy, 2007, 32, (14), 2843 LINK https://doi.org/10.1016/j.ijhydene.2006.12.027
  75. 75.
    C. I. Müller, T. Rauscher, A. Schmidt, T. Schubert, T. Weißgärber, B. Kieback and L. Röntzsch, Int. J. Hydrogen Energy, 2014, 39, (17), 8926 LINK https://doi.org/10.1016/j.ijhydene.2014.03.151
  76. 76.
    S. M. A. Shibli and J. N. Sebeelamol . Int. J. Hydrogen Energy, 2013, 38, (5), 2271 LINK https://doi.org/10.1016/j.ijhydene.2012.12.009
  77. 77.
    D. M. F. Santos, C. A. C. Sequeira, D. Macciò, A. Saccone and J. L. Figueiredo, Int. J. Hydrogen Energy, 2013, 38, (8), 3137 LINK https://doi.org/10.1016/j.ijhydene.2012.12.102
  78. 78.
    L. Mihailov, T. Spassov and M. Bojinov, Int. J. Hydrogen Energy, 2012, 37, (14), 10499 LINK https://doi.org/10.1016/j.ijhydene.2012.04.042
  79. 79.
    D. Miousse, A. Lasia and V. Borck, J. Appl. Electrochem., 1995, 25, (6), 592 LINK https://doi.org/10.1007/BF00573217
  80. 80.
    P. Babar, A. Lokhande, H. H. Shin, B. Pawar, M. G. Gang, S. Pawar and J. H. Kim, Small, 2018, 14, (7), 1702568 LINK https://doi.org/10.1002/smll.201702568
  81. 81.
    L. Vázquez-Gómez, S. Cattarin, P. Guerriero and M. Musiani, Electrochim. Acta, 2008, 53, (28), 8310 LINK https://doi.org/10.1016/j.electacta.2008.06.056
  82. 82.
    L. Gu, Y. Wang, R. Lu, W. Wang, X. Peng and J. Sha, J. Power Sources, 2015, 273, 479 LINK https://doi.org/10.1016/j.jpowsour.2014.09.113
  83. 83.
    F. E.-T. Heakal, W. R. Abd-Ellatif, N. S. Tantawy and A. A. Taha, RSC Adv., 2018, 8, (7), 3816 LINK https://doi.org/10.1039/C7RA12723E
  84. 84.
    V. A. Alves, L. A. da Silva, L. F. de F. Santos, D. T. Cestarolli, A. Rossi and L. M. da Silva, J. Appl. Electrochem., 2007, 37, (8), 961 LINK https://doi.org/10.1007/s10800-007-9336-y
  85. 85.
    B. Y. Chang and S.-M. Park, Ann. Rev. Anal. Chem., 2010, 3, 207 LINK https://doi.org/10.1146/annurev.anchem.012809.102211
  86. 86.
    A. J. Bard and L. R. Faulkner, “Electrochemical Methods: Fundamentals and Applications”, 1st Edn., John Wiley & Sons, New York, USA, 1980, p. 87
  87. 87.
    V. M. Nikolic, S. Lj. Maslovara, G. S. Tasic, T. P. Brdaric, P. Z. Lausevic, B. B. Radak and M. P. M. Kaninskia, Appl. Catal. B: Environ., 2015, 179, 88 LINK https://doi.org/10.1016/j.apcatb.2015.05.012
  88. 88.
    T. Wang, X. Wang, Y. Liu, J. Zheng and X. Li, Nano Energy, 2016, 22, 111 LINK https://doi.org/10.1016/j.nanoen.2016.02.023

Acknowledgements

This research was partially supported by Changzhou Sci & Tech Program (Grant No. CJ20190041) and the Natural Science Foundation of Jiangsu Province (Grant Number: BK20150260).

Wangping Wu designed the study and supervised MSc student, Jianwen Liu, who performed most of the experiments, and contributed to the first preparation of this article. Wangping Wu and Xiang Wang discussed the results. Jianwen Liu wrote and revised the manuscript. Wangping Wu has carefully revised the manuscript. All authors approved the submission of the final manuscript.

We declare that we do not have any commercial or associative interest that represents a conflict of interest in connection with the work submitted.

The Authors


Jianwen Liu received his BS and MS degrees from Taizhou Institute of Science and Technology, Nanjing University of Science and Technology (NJUST), China, in 2017, and Changzhou University, China, in 2020, respectively. His research focusses on iridium-based metal electrocatalysts by electrodeposition for hydrogen evolution reactions and electrodeposition of rhodium and electrochemical corrosion. He has published nine papers in peer-reviewed international journals and one patent.


Wangping Wu received his PhD in Materials Processing Engineering from Nanjing University of Aeronautics and Astronautics, China, in 2013. He joined the Tel Aviv University, Israel, as a Postdoctoral Fellow from October 2013, and then jointed the Hochschule Mittweida University of Applied Sciences, Germany, and Technische Universität Chemnitz, Germany, from September 2019 as a visiting scholar by the support of China Scholarship Council (CSC). He currently works as a Senior Lecturer at the School of Mechanical Engineering and Rail Transit, Changzhou University, China. His research focuses on the synthesis, characterisation and performance of films and coatings of the noble metals and their alloys, nanopowders dispersed in polymer and electrochemical additive manufacturing. He has published over 60 papers in peer-reviewed international journals.


Xiang Wang received his BS degree from Changzhou University in 2018. He is currently pursuing his MS degree at Changzhou University. His research focuses on the electrodeposition of the noble metals and their alloys and electrochemical corrosion of metal coatings. Up to now, he has published four papers and one patent.


Professor Yi Zhang is Dean of the Mechanical Engineering and Rail Transit department of Changzhou University. He received his PhD in Mechanical Manufacturing and Automation from University of Science and Technology of China in 2000. His research focuses on modern design methods for electromechanical systems, design of electromechanical drives and control systems and design of industrial automation and monitoring systems. He has published more than 100 academic papers and more than 30 patents, one monograph and three textbooks.

Read more from this issue »

BACK TO TOP

SHARE THIS PAGE: