Watts Nickel Research Articles

Nickel-based composites using tungsten carbides as enhancers for electroactivity for the hydrogen evolution reaction

This study explores the impact of incorporating tungsten carbides into a Watts bath on the fabrication of Ni/WC and Ni/W2C composites, comparing them with conventional Ni Watts electrodeposited electrodes. Results indicate that adding tungsten carbides to the conventional nickel bath forms rougher and more porous structures in the deposited composites. Composite electrodes exhibit significantly enhanced current density for hydrogen evolution in alkaline media compared to nickel Watts electrodes. Differential Electrochemistry Mass Spectrometry (DEMS) elucidates the hydrogen evolution mechanism, providing accurate data for Tafel plots. X-ray photoelectron spectroscopy (XPS) shows minimal impact on nickel's surface chemistry. X-ray diffractograms demonstrate that tungsten carbide particles maintain crystalline structure. X-ray dispersive spectroscopy (EDS) reveals an uneven chemical composition, with Ni/WC and Ni/W2C composites containing approximately 17% tungsten carbides. Electrochemical impedance spectroscopy (EIS) indicates higher electrochemical areas and lower charge transfer resistances in Ni/WC and Ni/W2C composites than in Ni Watts. This study contributes insights for the efficient and economical development of electrolysis systems. Notably, Ni/WC and Ni/W2C composites show promising electrochemical performance, emphasizing their potential in advancing electrolysis technology.

Highly efficient and selective removal of copper from low pH nickel Watts solution through hydrogen sulfide

Highly efficient and selective removal of copper from low pH nickel Watts solution through hydrogen sulfide

Ni/Ru@NC-CeO2 composite for hydrogen evolution reaction in alkaline media: Effect of CeO2 decoration with Ru@NC on the catalytic activity

The design of composites with controlled interfaces has proven to be an efficient approach to obtaining highly active electrocatalysts for the hydrogen evolution reaction with improved stability. In this work, we report the preparation of Ni-based composites by co-depositing commercial CeO2 nanoparticles and Ru nanoparticles with N-doped carbon patches supported onto CeO2 (Ru@NC-CeO2) using a facile electrodeposition method. The Ru@NC-CeO2 nanoparticles were obtained through the impregnation of CeO2 with Ru organometallic precursor and subsequent pyrolysis. A comprehensive chemical, structural and morphological characterization of the synthesized nanoparticles and co-deposit composites is presented. The cyclic voltammetry analysis showed that the composites exhibit a higher current density in comparison to the conventional nickel Watts catalyst; specifically a ∼ 48 % increase for the CeO2-containing composite, and ∼ 105 % for the Ru@NC-CeO2 based composite. This study demonstrates that the small addition of Ru to the CeO2 nanoparticles on the nickel matrix can improve drastically the performance towards HER in alkaline media.

Nickel-coated 3D-printed titanium electrodes for electrochemical flow reactors

ABSTRACT Electrocatalyst-coated metallic electrodes for electrochemical flow reactors have many applications in electrosynthesis, environmental remediation and energy conversion. This work presents novel nickel-coated titanium-alloy electrodes produced by means of direct metal laser sintering and constant current electrodeposition in an additive-free Wood’s nickel strike then a Watts nickel bath. Several 3D porous architectures were created in Ti-6Al-4 V alloy and coated, their digital design being the subject of previous work. Nickel coatings were macroscopically uniform and adherent with a thickness up to 5.8 µm, depending on the surface area of the electrodes. The morphology of nickel was cauliflower-like, with crystallisation growth occurring as spherical grains, as typically found for deposits from pH buffered Watts baths. Some degree of coating porosity was observed at electrodes of large surface area, indicating the need for longer deposition times. The results open the path for further optimisation of electrodeposition parameters and the development of bath additives to tailor deposit properties.

Effect of Nanodiamond Content in the Plating Solution on the Corrosion Resistance of Nickel–Nanodiamond Composite Coatings Prepared on Annealed 45 Carbon Steel

A nickel-nanodiamond composite coating was prepared on the surface of annealed 45 carbon steel by double-pulse electrodeposition. The effect of nanodiamond particle content on the surface morphology, grain size and wear and corrosion resistance of the composite coating were investigated. According to the analysis of the test results of X-ray diffractometry and scanning electron microscopy, it was found that the cathodic polarization of the electrodeposition process was enhanced after the addition of nanodiamond particles to the Watts nickel plating solution. The positively charged nanodiamond particles on the surface facilitate the reduction reaction at the cathode. Nanodiamond particles provide crystalline growth sites for the non-spontaneous nucleation of nickel atoms. As the addition of nanodiamond particles increases, the diffusely distributed nanodiamond particles are able to attract more nickel ions to deposit nuclei, and its fine crystallization effect increases, resulting in improved wear resistance and corrosion resistance of the composite plating. Among the results, the polarization potential was the smallest when the nanodiamond content in the plating solution was 10 g/L. The surface of the prepared nickel-nanodiamond composite coating was relatively flat and smooth, with good density and a uniform grain size distribution, and the content of element C on the surface of the composite coating was the largest, reaching 1.99%.

Optimization of the Preparation Parameters of High-Strength Nickel Layers by Electrodeposition on Mild Steel Substrates.

The electrodeposition process parameters were optimized for the acquisition of high-strength monolithic nickel layers on Q235A substrates based on the Watts nickel plating solution using the DC electrodeposition method. Based on the study of the electrochemical polarization behavior of nickel ions in Watts’ plating solution, 16 experimental protocols were selected according to the orthogonal test method. The residual stress, microhardness, modulus of elasticity, and surface roughness of the nickel plating were tested by X-ray diffractometer, nano-mechanical test system, and surface profilometer, respectively, to investigate the influence of current density, temperature, and PH on the mechanical properties of nickel plating, so as to determine the best process solution for the preparation of high-strength nickel plating. The results of the study show that the mechanical properties of the nickel deposits electrodeposited onto Q235A are optimized when plating at a current density of 3 A/dm2, a bath temperature of 45 °C, and a pH of 3.5. The nickel-plated layer has a minimum grain size of 34.8 nm, a microhardness of 3.86 GPa, a modulus of elasticity of 238 GPa, and a surface roughness Ra of 0.182 μm.

Corrosion Behavior of Electrodeposited Nickel Coating Reinforced by Cr<sub>2</sub>O<sub>3</sub> Particles

The objective of this work is the characterisation of the composite deposits Ni-Cr2O3 on copper substrate; these deposits are obtained from bath of electro-deposition of Nickel watts. The different electrodeposited layers are characterized by various analytical techniques such as adhesion quality, corrosion tests, Vickers microhardness, morphology by scanning electron microscopy Followed by EDX microanalysis and X-ray diffraction. The corrosion tests are realized in a solution of 3.5 % NaCl using lost mass method, polarization and impedance spectroscopy techniques. It was found that the composite coatings Ni-Cr2O3 have an homogeneous and compact morphology, well crystallized and exhibit a high degree of codeposition of Cr2O3 particles incorporated in the nickel matrix. The co-deposited films have very good hardness, adhere perfectly to the substrate and are more resistant to corrosion.

Highly Efficient and Selective Removal of Copper from Nickel Watts Baths Using Hydrogen Sulfide

Highly Efficient and Selective Removal of Copper from Nickel Watts Baths Using Hydrogen Sulfide

Development of numerical model for predicting the characteristics of Ni–SiC nano composite coatings on AISI 1022 substrate

The strength of nano coatings predominantly depends on the selection of optimum combination of input parameters. This problem can be solved by developing an empirical relationship between input parameters to predict microhardness (MH), average surface roughness (Ra), specific wear rate (Ws) and co-efficient of friction (CoF) of the pulse electroplated coating by response surface methodology (RSM). In this paper an attempt has been made to optimize the electroplating process parameters of Ni–SiC nano coating using Grey-RSMapproach. This experiment highlights the use of RSM by designing the three factor three level central composite design. The Ni–SiC nano coating was deposited on AISI 1022 low carbon steel substrates under pulse current electroplating technique using nickel watts bath by varying input parameters such as frequency (Hz), duty cycle (%) and current density (A/Cm2). The optimum electroplating parameter was obtained through grey relational analysis (GRA). The prediction of optimum nano composite coating parameter is found at frequency 10 Hz (F1), duty cycle 10% (D1) and current density 0.2 A Cm−2 (C2), then confirmation experiment is performed to verify the optimum process parameter condition. The influences of those optimized coating parameters over the microstructure, morphology, coating thickness, EDAX, x-ray diffraction and wear rate of Ni-nano SiC composite coatings were also investigated.

One step synthesis of high efficiency nickel/mesoporous TiO2 hybrid catalyst for hydrogen evolution reaction

Nickel-TiO2 hybrid catalysts are synthesized by electrodeposition and their catalytic activity with respect to the hydrogen evolution reaction is analyzed. Two types of titanium oxide particles, which are commercial particles of dense TiO2 and mesoporous TiO2 particles synthesized by an aerosol method, are incorporated into the matrix of the nickel catalyst. Both nickel catalysts containing TiO2 particles presented higher catalytic activity than the conventional nickel Watts catalyst. Mesoporous TiO2-modified nickel catalyst showed the highest catalytic activity towards HER in alkaline medium. In addition, this type of nickel catalyst increases its catalytic activity after ageing treatment, which is an indication of an increase in the electro-active area of the electrode.

Synthesis and Performance of Nickel/Reduced Graphene Oxide Hybrid for Hydrogen Evolution Reaction.

In this work, a simple and reproducible method for the syntheses of hybrid nickel/reduced graphene oxide electrodes is presented. This method consists in a direct modification of a conventional nickel electrodeposition bath, making the synthesis industrially scalable. The synthesized catalyst is structural and electrochemically characterized and compared to the traditional electrodeposited nickel. The kinetics of hydrogen evolution reaction (HER) is studied on both conventional nickel watts (Ni-watts) and nickel/reduced graphene oxide hybrid (NirGO). An increment in the catalytic activity is observed along with the absence of nickel hydrides. Thus, the NirGO catalyst presents a higher catalytic activity towards HER, and the presence of graphene in the Ni matrix inhibits the nickel hidruration.

Codeposition of nickel–phosphorus alloys reinforced with boron carbide microparticles: direct and pulse plating

Nickel–phosphorus alloys were codeposited with boron carbide particles. Two compositions of nickel-phosphorus, one presenting a low phosphorus content in the order of 4% wt. and another one presenting a high phosphorus content of about 12% wt., were deposited from modified Watts nickel electrolytes using both direct and pulse plating. A strong influence of the deposition method was observed on the phosphorus content in the matrix and on the quantity of codeposited particles. Pulse plating was found to significantly increase both of them. Nucleation of the pure nickel–phosphorus alloy and of the codeposit were studied using chronoamperometry and AFM in potentiostatic mode. An instantaneous nucleation mechanism was evidenced on iron and gold substrates. Microhardness was measured and linked to the phosphorous and particle contents.

Diverse electrodeposits from modified acid sulphate (Watts nickel) baths

A diverse range of nickel-based coatings can be cathodically deposited from a classical Watts electroplating bath containing suitable additives by appropriate control over operational conditions. Modern nickel-based electrodeposits are concisely reviewed and can be seen to be longer-term developments from the publication of optimised conditions for rapid nickel plating from an acid sulphate bath by Watts 100 years ago, in 1916. Recent examples of tribological nickel electrodeposits are illustrated by examples from the authors’ laboratory: (i) low friction, hard, wear resistant surfaces (containing 2-D, layered, self-lubricating particles of Ni–P–MoS2), (ii) superhydrophobic layers of Ni–WS2, showing a lotus petal effect (for self-cleaning surfaces), (iii) light emitting, luminescent signal bearing surfaces of Ni–BAM (BaMgAl11O17:Eu2+) metal oxide, (providing an in-situ phosphor wear tracer) and (iv) nanocrystalline surfaces of Ni, Co, Ni–Co and Ni–Co–P (including high surface area electrocatalysts). Important trends in the deployment of the longstanding, versatile Watts nickel electroplating bath are seen to include the development of (a) surfaces having tailored structure, hence special properties, by choice of bath composition and operational conditions, (b) nanostructured composite layers containing mixed inclusions and (c) layers able to diagnose in-service wear and provide an output signal. Subject areas needing further research are suggested.

Fabrication of Tin-Plated Three-Dimensional Copper Nanostructure Using Electroless Plating and Its Anode Performance in Lithium-Ion Battery

Introduction Next-generation lithium-ion batteries with higher energy density are urgently needed for hybrid and electric vehicle applications, among others. Currently, graphite is typically used as the anode active material in lithium-ion batteries, but it is necessary to consider alternative, higher capacity materials. For example, tin has a larger theoretical capacity (991 mAh g-1) than that of graphite (372 mAh g-1). However, the volume of tin changes significantly during charging and discharging, causing it to slip down from the copper current collector, which deteriorates the cycling characteristics. Three-dimensional copper structures are effective at preventing such slippage.1) However, in general, the methods for fabricating such structures are very complicated. We have reported that a three-dimensional copper nanostructure (3DC-1) can be fabricated easily by one-step electrodeposition.2) In this study, a tin layer was formed on the 3DC-1 by electroless deposition, and its anode performance in a lithium-ion battery was evaluated. Experimental An acidic copper sulfate bath1) containing 0.85 M CuSO4∙5H2O + 0.55 M H2SO4 + 2.5×10-4 M polyacrylic acid (MW=5000) was used in the fabrication of the 3DC-1. Electrodeposition was conducted under galvanostatic conditions (1.2 A dm-2) at 25 °C without agitation. A bright Watts nickel plating bath (1 M NiSO4∙6H2O + 0.2 M NiCl2∙6H2O + 0.5 M H3BO3 + 0.01 M saccharin sodium dehydrate + 0.0025 M 1,4-butynediol) was prepared, and electrodeposition was conducted under galvanostatic conditions (3.0 A dm-2) at 25 °C without agitation. Tin was electrolessly plated onto the 3DC-1 at 80 °C for 15 s without agitation. An immersion plating bath containing 0.5 M K4P2O7 + 0.15 M Sn2P2O7+ 3 M thiourea was prepared. The pH was adjusted to 5 with hydrochloric acid. The microstructure of the tin anode was examined using field-emission scanning electron microscopy (FE-SEM). The phase structure of the deposits was analyzed by X-ray diffraction (XRD). A chemical composition analysis was carried out using X-ray fluorescence spectrometry (XRF) and energy-dispersive X-ray spectroscopy (EDX). Electrochemical studies of the tin anode were carried out with coin cells that were assembled in an Ar-filled glove box. Each coin cell consisted of a lithium foil as a counter electrode and a reference electrode. The plating film functioned as the working electrode. The electrolyte was 1 M LiPF6 in ethylene carbonate (EC) and diethyl carbonate (DEC) (1:1 vol%). Cycling tests were performed in the range of 0.02–1.5 V (vs. Li/Li+) at a constant temperature of 25 °C. Results and Discussion Fig. 1 shows a surface SEM image of the tin anode, which reveals that the tin film was plated homogeneously onto the three-dimensional copper nanostructure. Fig. 2 shows a cross-sectional SEM image of the tin anode and corresponding EDX mapping results for copper, nickel, and tin. The tin was distributed homogeneously on the 3DC-1. Fig. 3 compares the cycling characteristics of tin anodes fabricated using 3DC-1 (a) and a flat copper foil (b). For the former, the discharge capacity was about 900 mAh g-1 after the first cycle. Even after 100 cycles, the discharge capacity remained over 700 mAh g-1. In contrast, for the latter, the discharge capacity was 650 mAh g-1 after the first cycle and 250 mAh g-1after 100 cycles. References 1) Shichao Zhang, Yalan Xing, Tao Jiang, Zhijia Du, Feng Li, Lei He, Wenbo Liu; Journal of Power Sources,196, 6915-6919 (2011) 2) S.Arai and T.Kitamura, ECS Electrochemistry Letters, 3 (5), D7-D9 (2014) Figure 1

Electrochemical Fabrication of Gold Nanoparticle Catalyst on CNTs for Glucose Fuel Cells

Introduction Polymer electrolyte fuel cells (PEFCs) operate at low temperatures and have fast startup times, making them suitable for automobile and household power applications. However, due to their low operating temperature, PEFCs require a catalyst. In general, platinum is used as the catalyst and carbon black (CB) is used as a support. Carbon nanotubes (CNTs) have recently attracted attention as an alternative to CB due to their large specific surface area, high mechanical strength, and high electrical conductivity, which collectively would improve the durability of PEFCs. In recent years, glucose fuel cells have been attracting attention. When the diameter of gold nanoparticles is less than 10 nm, they have been reported to be effective as catalysts.1)In this study, the fabrication process for a new gold catalyst supported by CNTs as an anode for glucose fuel cells was examined. Experimental (1) Fabrication of Ni/CNT composite films 2) A Watts nickel plating bath (NiSO4·6H2O, NiCl2·6H2O, H3BO3), polyacrylic acid (MW = 5000), brightener (saccharin Na, 1.4-butynediol) and vapor grown carbon fibers (VGCFs) were used as the basic plating bath, CNT dispersant, and CNTs (Showa Denko). Electrodeposition was carried out under galvanostatic conditions. Reverse electrolysis was carried out to removing Ni deposite on the CNTs. The surface morphologies of the films were observed by field-emission scanning electron microscopy (FE-SEM). (2) Reforming of the CNT surface by plasma treatment Plasma treatment with argon was carried out for 5 min at 10, 50, 100, and 150 W on the Ni/CNT composite plating films. The surface morphologies of the plasma-treated samples were observed by FE-SEM, and the CNT defects were evaluated by Raman spectroscopy. (3) Formation of Au nanoparticles A gold sulfite bath (NaAuCl4·2H2O, Na2SO3·7H2O) was used as the plating bath. Electrodeposition of gold on the Ni/CNT films was conducted under galvanostatic conditions. The surface morphology of the plating was observed using FE-SEM and scanning transmission electron microscopy (STEM). Results and discussion (1) Fabrication of Ni/CNT composite films Ni/CNT composite films with smoother surface morphology were formed than without the addition of brightener (Fig. 1(a) and (b)). The reverse electrolysis process was effective at removing Ni deposits on the CNTs (Fig. 1(c)). The reason is thought to be due to the effect of the brightener. Fig. 2 shows a plot of the ratio of drain to gate voltages, ID/IG, vs. the power used during the plasma treatment. ID/IGincreased with increasing power, indicating that the CNT defects increased with increasing power. (2) Reforming of the CNT surface by plasma treatment Fig. 2 shows a plot of the ratio of drain to gate voltages, ID/IG, vs. the power used during the plasma treatment. ID/IGincreased with increasing power, indicating that the CNT defects increased with increasing power. (3) Formation of Au nanoparticles Compared to non-treated CNTs, smaller gold nanoparticles with sizes of about 10 nm were observed on the plasma-treated CNTs. References 1) M. Pasta, L.Hu, F. Mantia, Y. Cui, Electrochemistry Communications, 1981-84 (2012). 2) S. Arai, A. Fujimori, M. Murai, M. Endo, Materials Letters, 62 35-45 (2008). Figure 1

Reactions in Electrodeposited Cu/Sn and Cu/Ni/Sn Nanoscale Multilayers for Interconnects.

Miniaturization of electronic devices has led to the development of 3D IC packages which require ultra-small-scale interconnections. Such small interconnects can be completely converted into Cu-Sn based intermetallic compounds (IMCs) after reflow. In an effort to improve IMC based interconnects, an attempt is made to add Ni to Cu-Sn-based IMCs. Multilayer interconnects consisting of stacks of Cu/Sn/Cu/Sn/Cu or Cu/Ni/Sn/Ni/Sn/Cu/Ni/Sn/Ni/Cu with Ni = 35 nm, 70 nm, and 150 nm were electrodeposited sequentially using copper pyrophosphate, tin methanesulfonic, and nickel Watts baths, respectively. These multilayer interconnects were investigated under room temperature aging conditions and for solid-liquid reactions, where the samples were subjected to 250 °C reflow for 60 s and also 300 °C for 3600 s. The progress of the reaction in the multilayers was monitored by using X-ray Diffraction, Scanning Electron Microscope, and Energy dispersive X-ray Spectroscopy. FIB-milled samples were also prepared for investigation under room temperature aging conditions. Results show that by inserting a 70 nanometres thick Ni layer between copper and tin, premature reaction between Cu and Sn at room temperature can be avoided. During short reflow, the addition of Ni suppresses formation of Cu3Sn IMC. With increasing Ni thickness, Cu consumption is decreased and Ni starts acting as a barrier layer. On the other hand, during long reflow, two types of IMC were found in the Cu/Ni/Sn samples which are the (Cu,Ni)6Sn5 and (Cu,Ni)3Sn, respectively. Details of the reaction sequence and mechanisms are discussed.

Manufacturing of a LaNiO3 composite electrode for oxygen evolution in commercial alkaline water electrolysis

The LaNiO3 perovskite was chosen for incorporation into a nickel matrix in order to obtain a metallic composite electrode suitable for improving the oxygen evolution reaction (OER) in commercial water electrolysis at elevated temperature. The manufactured LaNiO3 + Ni composite coatings were deposited in a Watts type nickel electrolyte in a specially designed beaker with continuous particle circulation. Activity of the composite coatings was evaluated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and anodic potentiodynamic polarization measurements. The obtained results were compared to a non-catalysed Watts nickel reference sample and the electrochemical measurements confirmed that the coating decreased the OER overpotential by 70 mV. XRD furthermore revealed that a LaNiO3 + Ni composite structure was obtained. Conventional alkaline water electrolysis was carried out at a temperature of 120 °C and a current densities of 0.2 and 0.8 A cm−2. Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Diffraction (XRD) were used for characterization of the morphology.

Preparation and Characterization of Ni Spines Grown on the Surface of Cubic Boron Nitride Grains by Electroplating Method.

Cubic boron nitride (cBN) is widely applied in cutting and grinding tools. cBN grains plated by pure Ni and Ni/SiC composite were produced under the same conditions from an additive-free nickel Watts type bath. The processed electroplating products were characterized by the techniques of scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermoanalysis (TG-DTA). Due to the presence of SiC particles, there are some additional nodules on the surface of Ni/SiC plated cBN compared with the pure Ni plated cBN. The unique morphology of Ni/SiC plated cBN should attain greater retention force in resin bond. Moreover, the coating weight of cBN grains could be controlled by regulating the plating time. cBN grains with 60% coating weight possess the optimum grinding performance due to their roughest and spiniest surface. In addition, Ni spines plated cBN grains show good thermal stability when temperature is lower than 464 °C. Therefore, the plated cBN grains are more stable and suitable for making resin bond abrasive tools below 225 °C. Finally, the formation mechanism of electroplating products is also discussed.

A Comparative Study of Nickel Electrodeposition Using Deep Eutectic Solvents and Aqueous Solutions

Metal electrodeposition using ionic liquid electrolytes and deep eutectic solvents is now well known but to our knowledge for electrolytic deposition of metals such as nickel no direct comparison has thus far been drawn between deposition using aqueous solutions and DES under otherwise identical conditions. In the current study it is shown that nickel deposition can be carried out with similar deposition rates in aqueous and ionic media despite the significant differences in viscosity and conductivity. It is, however, shown that in ionic media the morphology of the deposits is markedly different from that achieved using a Watts nickel bath and that one aspect of these differences manifests itself in significant increase in the coating hardness. It is proposed that the observed morphology differences occur due to the variations of nickel speciation in each electrolyte environment.

Ni-(Ebonex-supported Ir) composite coatings as electrocatalysts for alkaline water electrolysis. Part I: Hydrogen evolution

The hydrogen evolution reaction (HER) was studied at electrodeposited Ni and Ni-(Ebonex/Ir) composite coatings in 1 mol dm−3 NaOH solution at 25 °C. The Ni-(Ebonex/Ir) coatings were electrodeposited from a nickel Watts type bath containing different amounts of suspended Ebonex/Ir(30 wt.%) powder particles (0–2 g dm−3) onto a Ni 40 mesh substrate. The electrodes were investigated by cyclic voltammetry (CV), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electrochemical impedance spectroscopy (EIS) and polarization measurements. It was shown that the roughness factor of coatings increased to a maximum value of 27 with increasing the concentration of Ebonex/Ir particles in the deposition bath, while that of a pure Ni coating was found to be 3.2. In the whole potential range of the HER only one Tafel slope of about −120 mV dec−1 was observed at all polarization curves. Considerably improved intrinsic catalytic activity for the HER compared to pure Ni was achieved with the composite coating deposited from the bath with the lowest concentration of Ebonex/Ir particles (0.1 g dm−3). Further enhancement of the apparent catalytic activity for the HER of Ni-(Ebonex/Ir) composite coatings obtained at higher concentrations of suspended Ebonex/Ir particles in the bath was attributed only to the increase of their electrochemically active surface area.