Potentiostatic electrodeposited of Ni–Fe–Sn on Ni foam served as an excellent electrocatalyst for hydrogen evolution reaction

Ni–Fe–Sn electrocatalyst supported on nickel foam (Ni–Fe–Sn/NF) with high efficiency of hydrogen evolution reaction (HER) has been successfully fabricated through one-step potentiostatic electrodeposition route. The optimized Ni–Fe–Sn/NF displayed an extremely low overpotential of, respectively, 144 and 180 mV at 50 and 100 mA cm^?2 for HER in alkaline condition. Moreover, it could retain its superior stability for at least 12 h. The remarkable electrocatalytic activity of our electrocatalyst is ascribed to the high conductivity originated from synergistic effects between Ni, Fe, and Sn during HER process.     

3D hierarchical nanostructured Ni–Co alloy electrodes on porous nickel for hydrogen evolution reaction

Nanostructured Ni–Co alloys decorated on 3D porous nickel electrodes for hydrogen evolution reaction (HER) are successfully prepared through a facile and effective electrodeposition method. By adjusting the current density of electrodeposition, Ni–Co alloys with different surface morphologies like nanocones, leaf-like structures and flakes can be obtained. The HER catalytic activity has been greatly reinforced with decorated Ni–Co alloys. Meanwhile, the HER performance of nanocone Ni–Co alloys outperforms that of leaf-like and flaky Ni–Co alloys. The nanocone Ni–Co alloys exhibit outstanding HER activity, only requiring an overpotential of 86.7 mV at 10 mA cm⁻², along with a low Tafel slope of 69.8 mV dec⁻¹ and 3.4 Ω charge transfer resistance. This nanocone electrode remains stable for 10 h of chronopotentiometric measurement. Such enhanced catalytic performance stems from the porosity and the high population of sharp edges, as well as surface oxidation/metallic states and synergistic effects between Ni and Co.     

Catalytic activity of electrodeposited ternary Co–Ni–Rh thin films for water splitting process

The influence of the deposition parameters on the composition and structure of Co–Ni–Rh ternary alloys was studied. The catalytic activity of the coatings for the hydrogen evolution process was investigated in 6 M KOH electrolyte. The thin films were deposited from baths containing a mixture of Co²⁺, Ni²⁺, and Rh³⁺ chloride complexes. A wide range of alloy compositions were achieved by applying different deposition potentials from −0.5 to – 0.9 V vs SCE. The obtained coatings were examined by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) techniques. The surface morphology and chemical composition were also characterized with scanning electron microscopy (SEM) combined with EDX. The hydrogen evolution activity of some selected electrodes were examined in 6 M KOH using current-potential curve and electrochemical impedance spectroscopy (EIS) techniques. The SEM results showed that the surface morphology of the electrodes can be tailored by modification of the deposition potential. The higher exchange current densities were observed in catalytic measurements for the ternary alloys, which confirms their better catalytic activity in the water-splitting process.     

Ni/MgO–Al2O3 and Ni–Mg–O catalyzed SiC foam absorbers for high temperature solar reforming of methane

Ni catalyst supported on MgO–Al₂O₃ (Ni/MgO–Al₂O₃) prepared from hydrotalcite, and Ni–Mg–O catalyst are studied in regard to their activity in the CO₂ reforming of methane at high temperatures in order to develop a catalytically activated foam receiver–absorber for use in solar reforming. First, the activity of their powder catalysts is examined. Ni/MgO–Al₂O₃ powder catalyst exhibits a remarkable degree of high activity and thermal stability as compared with Ni–Mg–O powder catalyst. Secondly, a new type of catalytically activated ceramic foam absorber – Ni/MgO–Al₂O₃/SiC – and Ni–Mg–O catalyzed SiC foam absorber are prepared and their activity is evaluated using a laboratory-scale receiver–reactor with a transparent quartz window and a sun-simulator. The present Ni-based catalytic absorbers are more cost effective than conventional Rh/γ-Al₂O₃ catalyzed alumina and SiC foam absorbers and the alternative Ru/γ-Al₂O₃ catalyzed SiC foam absorbers. Ni/MgO–Al₂O₃ catalyzed SiC foam absorber, in particular, exhibits superior reforming performance that provides results comparable to that of Rh/γ-Al₂O₃ catalyzed alumina foam absorber under a high flux condition or at high temperatures above 1000 °C. Ni/MgO–Al₂O₃ catalyzed SiC foam absorber will be desirable for use in solar receiver–reactor systems to convert concentrated high solar fluxes to chemical fuels via endothermic natural-gas reforming at high temperatures.     

Pulse-electrodeposited Ni–Fe–Sn films supported on Ni foam as an excellent bifunctional electrocatalyst for overall water splitting

The development of extremely active bifunctional non-noble electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is pivotal for water splitting but remains challenging. Herein, self-supported Ni–Fe–Sn electrocatalysts were fabricated on nickel foam (NF) through a simple and facile pulse electrodeposition process. Under optimal conditions, the prepared Ni–Fe–Sn electrocatalysts exhibited excellent bifunctional properties in alkaline medium and required ultralow overpotentials of only 27 and 201 mV for HER and OER, respectively, to reach the current density of 10 mA cm^?2. Importantly, the same Ni–Fe–Sn electrocatalyst can be assembled as the anode and the cathode in a two-electrode system. It demanded a fairly low applied voltage of 1.55, 1.72, and 1.87 V to produce 10, 50, and 100 mA cm^?2, respectively, and exhibited excellent long-term stability. The excellent electrocatalytic water splitting performance of the Ni–Fe–Sn film was mainly associated with its intrinsic catalytic activity derived from the modulation of the electronic structures among Ni, Fe, and Sn by using the appropriate atomic ratio of Ni: Fe: Sn.     

Electrodeposited Ni–Co–S nanosheets on nickel foam as bioelectrochemical cathodes for efficient H2 evolution

High overpotential and soaring prices of the cathode electrode are the bottlenecks for the development of microbial electrolysis technology for hydrogen production. In this study, a novel one-step electrodeposition method has been attempted to fabricate electrodeposited cathodes in situ growth of Ni–Co–S, Ni–S, Co–S catalyst on nickel foam (NF) to reduce the overpotential of electrodes. Finally, a uniform nanosheet with a high specific surface area and more active sites is formed on the NF surface, resulting in a lower overpotential than plain NF. At 0.8 V, the Co–S/NF cathode produces a favorable 42% increase in hydrogen yield (0.68 m³·m⁻³·d⁻¹), 40% upsurge in current density (10.6 mA/cm³) and 39% rise of cathodic recovery rate (58.0 ± 3.2%) than bare NF, followed by Ni–Co–S/NF and Ni–S/NF cathode. All the electrodeposited electrodes demonstrate enhanced current density and reduced electron losses, thereby achieving efficient hydrogen production. These innovative varieties of electrodes are highly advantageous as they are relatively inexpensive and easy to manufacture with great potential in reducing costs and further real time application in large scale.     

Controlled synthesis of Mn3O4/Co9S8–Ni3S2 on nickel foam as efficient electrocatalyst for oxygen evolution reaction

Advances in electrochemical interfaces have greatly facilitated the development of new energy systems that can replace traditional fossil fuels. Oxygen evolution reaction (OER) is the core reaction in the new energy conversion system to produce hydrogen. Here, nanorods structure of Mn₃O₄/Co₉S₈–Ni₃S₂/NF-4 was designed and assembled. The Mn₃O₄ has served as an appropriate matrix to build a composite structure with Co₉S₈–Ni₃S₂ to enhance the stability of catalyst. And the introduction of Mn regulated the electronic structure of Ni and Co, which increased the OER activity of matericals. Further characterization and electrochemical testing have suggested that between polymetallic can effectively optimize conductivity and enhance reaction kinetics. Mn₃O₄/Co₉S₈–Ni₃S₂/NF-4 can achieve overpotential of 188 mV at the current density of 10 mA cm^?2 in alkaline solution, with small Tafel slope of 43.2 mV dec^?1 and satisfactory stability of 30 h at 10 mA cm^?2. This work may show a feasible reference in the design of high-efficient OER catalysts.     

Electrochemical evolution of hydrogen on composite La–Ni–Al/Ni–S alloy film in water electrolysis

The composite La–Ni–Al/Ni–S alloy film was obtained by molten salt electrolysis and aquatic electrodeposition in turn. The La–Ni–Al alloy film was prepared in Na₃AlF₆–La₂O₃–Al₂O₃ molten salt electrolyte by galvanostatic electrolysis at 100 mA cm^?2. The results showed that La³⁺ and Al³⁺ ions could be co-reduced on the nickel cathode and form La–Ni–Al film at c.a. ?0.5 V, which is much lower than that of the theoretical decomposition potential of lanthanum and aluminum. With high HER activity, the composite La–Ni–Al/Ni–S film (η₁₅₀ = 70 mV, 353 K) could absorb large amount of H atoms. Instead of the dissolution of the Ni–S film, the absorbed H atoms would be oxidized under intermittent electrolysis effectively and prolong the lifetime of the cathode.     

Electrochemical properties of Ti–Ni–H powders prepared by milling titanium hydride and nickel

Mechanical alloying has been carried out to synthesize a hydrogen storage alloy by milling titanium hydride and nickel. The structure and electrochemical properties such as discharge capacity, charge-transfer, and hydrogen diffusion of the milled powders were investigated. The results of X-ray diffraction showed that an amorphous phase was formed after ball milling. The electrode potentials of the milled powders were −0.989, −0.878 and −0.941 V (vs. Hg/HgO) in the electrolyte of 6 M KOH when the milling periods were 20, 40, and 60 h, respectively. The Ti–Ni–H powders milled for 60 h had a maximum discharge capacity of 102.2 mAh/g at a discharge current density of 60 mA/g. The results of the linear polarization showed that the exchange current density decreased as the hydrogen concentration within the powders decreased. The electrochemical impedance spectroscopy (EIS) demonstrated the same consequence and presented that the hydrogen diffusion decreased by decreasing the hydrogen concentration.     

Hydrogen evolution reaction activities of electrodeposited nanocrystalline Ni–Mo thin films in alkaline baths

The hydrogen evolution reaction (HER) electrocatalytic activities normalized to electrochemically active surface area (ECSA) were systematically evaluated and correlated with its composition (i.e., Mo content up to 26 at. %), crystal structure (i.e., face-centered cubic (fcc) to orthorhombic phase and the mixed phases with different phase ratios), and crystallinity. The electrodeposited with mixed phases exhibited highest ECSA (up to 228 cm² per 1 cm² geometric surface area) compared to deposits with single phase, which serves as the dominant factor to enhance exchange current density and overpotential. Low overpotentials per ECSA were observed with Mo content of 5.16 at% (fcc) and 24.1 at% (mixed phases). After normalizing with ESCA, The Tafel slope and exchange current density were indifference with Mo content, crystal phase, and grain size. The metallic Ni–Mo thin films have low mixed potential and overpotential at 10 mA/cm² of 20 mV and 120 mV, respectively.     

Electrochemical hydrogen storage of ball-milled MmMg12 alloy–Ni composites

MmMg₁₂–Ni amorphous or nanocrystalline composites (Mm: Ce-rich mischmetal) were prepared through the ball-milling method, and their electrochemical hydrogen storage performance was investigated and compared with that of ball-milled CeMg₁₂–Ni composites. It was found that the ball-milled MmMg₁₂–Ni composites had larger initial discharge capacities and better high rate dischargeability. Analysis of electrochemical impedance spectra (EIS) shows that the reaction resistance and hydrogen diffusion resistance of the ball-milled MmMg₁₂–Ni composites are lower as a result of the decrease in Ce content, and thus can contribute to the larger discharge capacity and better high rate dischargeability. Additionally, the cycle performance of the ball-milled MmMg₁₂–Ni composites is better than those of the ball-milled CeMg₁₂–Ni composites. This may be related to the formation of a Nd oxide or Nd(OH)₃ film on surface of the MmMg₁₂ alloys.     

One-step potentiostatic electrodeposition of Ni–Se–Mo film on Ni foam for alkaline hydrogen evolution reaction

Exploring efficient, abundant, low-cost and stable materials for hydrogen evolution reaction (HER) is highly desired but still a challenging task. Herein, Ni–Se–Mo electrocatalysts supported on nickel foam (NF) substrate were synthesized by a facile one-step electrodeposition method. The Ni–Se–Mo film presents high electrocatalytic activity and stability toward HER, with a low overpotential of 101 mV to afford a current density of 10 mA cm⁻² in 1.0 M KOH medium. Such excellent HER performance of Ni–Se–Mo film induced by the synergistic effects from Mo-doped Ni–Se film leads to the fast electron transfer. This work provides the validity of interface engineering strategy in preparing highly efficient transition metal chalcogenides based HER electrocatalysts.     

Fabrication and characterization of nanostructured Ni–IrO2 electrodes for water electrolysis

Nanostructured Ni–IrO₂ electrodes were fabricated by electrodeposition in a two-step procedure: first arrays of nickel nanowires (NWs) were electrodeposited within pores of polycarbonate (PC) membranes, then iridium oxide nanoparticles were deposited on the Ni metal after membrane dissolution, for improving the catalytic activity. The aim was to compare performance of these electrodes with traditional ones consisting of Ni film. Different methods of deposition of the IrO₂ electrocatalyst were investigated and the effect on electrodes stability and activity is discussed. Despite a low coverage of Ni NWs by the electrocatalyst, results indicate a faster kinetics of O₂ evolution in 1 M KOH solution and an improvement of performances for electrolysers having a nanostructured anode.     

Electrochemical properties of ball-milled LaMg12–Ni composites containing carbon nanotubes

Nanocrystalline LaMg₁₂–Ni composites containing carbon nanotubes (CNTs) were prepared by two ball-milling ways, and the resulting microstructure and electrochemical characteristics were investigated. It is found that the discharge capacities and high-rate dischargeabilities (HRDs) of the CNT-containing composites prepared by ball-milling as-prepared nanocrystalline LaMg₁₂–Ni composite and CNTs for 1 h (denoted as Composite-CNT1-1) were obviously higher than that by ball-milling LaMg₁₂ alloy, Ni powder and CNT1 together for 12 h (denoted as Composite-CNT1-2). The highest discharge capacity reaches 999.8 mA h/g. Raman spectra and X-ray diffraction (XRD) patterns show that the structure of the CNTs still exists and the defect increases in Composite-CNT1-1. However, in Composite-CNT1-2, due to the overlong ball-milling time, the crystalline structure of the CNTs has been destroyed and amorphous carbons have formed. Cyclic voltammetry and electrochemical impedance spectra measurements indicate that the CNT modification in Composite-CNT1-1 increases the electrocatalytic activity and surface area, which leads to its higher discharge capacity and HRD. The larger electrochemical reaction resistance caused by amorphous carbon in Composite-CNT1-2 results in its lower discharge capacity and HRD. The CNT modification has negligible effect on the diffusion process of hydrogen from the surface to the bulk of the composites.     

Direct synthesis of binder-free Ni–Fe–S on Ni foam as superior electrocatalysts for hydrogen evolution reaction

Designing the efficient, low-cost and stable electrocatalyst is of great significance for storage and conversion of the renewable energy to hydrogen. Herein, the binder-free Ni–Fe–S electrocatalysts were directly electrodeposited on Ni foam, which exhibited the excellent hydrogen evolution reaction performance with the overpotential of 51.4 mV at the current density of 10 mA cm^?2. Based on the analysis and results of as-synthesized Ni, Ni–Fe and Ni–S, the boosted electrocatalytic activity can be attributed to the composite effect between Ni and the introduced Fe and S. Additionally, the Ni–Fe–S electrocatalysts also displayed the low cell voltage (1.59 V at 10 mA cm^?2), remarkable durability and high Faraday efficiency in overall water electrocatalysis. Moreover, the water electrolysis device with Ni–Fe–S bi-electrodes can be driven by a small wind power generation and producing 4 mL H₂ in 39 min, indicating the prepared Ni–Fe–S electrocatalyst has the great potentials in producing hydrogen via renewable energy.     

Electrochemical oxidation of alcohols on Pt–TiO2 binary electrodes

In this study Pt–TiO₂ binary electrodes were prepared by means of thermal decomposition of chloride precursors on Ti substrates, characterised by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), electrochemical techniques and CO stripping and used as anodes for alcohol oxidation. The minimization of the Pt loading without electrocatalytic activity losses was also explored. TiO₂ was chosen due to its chemical stability, low cost and excellent properties as substrate for Pt dispersion. It was found that TiO₂ loading up to 50% results in Electrochemically Active Surface (EAS) increase. The EAS of Pt(50%)-TiO₂(50%) was found to be almost one order of magnitude higher than that of pure Pt while the EAS of samples with Pt loading lower than 30% was negligible. The above conclusion has been confirmed both by following the charge of the reduction peak of platinum oxide and by CO stripping experiments. All samples have been evaluated during the electrochemical oxidation of methanol and ethanol. In both cases the Pt(50%)-TiO₂(50%) electrode had better electrocatalytic activity than the pure Pt anode. The observed higher performance of the binary electrodes was mainly attributed to the enhanced Pt dispersion as well as the formation of smaller Pt particles by the addition of TiO₂.     

Vermicular Ni3S2–Ni(OH)2 heterostructure supported on nickel foam as efficient electrocatalyst for hydrogen evolution reaction in alkaline solution

Alkaline solution is considered to be more suitable for industrial application of hydrogen production by water electrolysis. However, most of the low-cost electrocatalyts such as Ni₃S₂ has poor ability to dissociate HO–H, resulting in unsatisfied hydrogen evolution performance in alkaline media. In this paper, a novel vermicular structure of Ni₃S₂–Ni(OH)₂ hybrid have been successfully prepared on nickel foam substrate (v-Ni₃S₂–Ni(OH)₂/NF) through a facile two-step containing hydrothermal and electrodeposition processes. The heterostructure consists of rod-like Ni₃S₂ and Ni(OH)₂ nanosheets, in which Ni(OH)₂ is coated on the surface of Ni₃S₂. This structure not only constructs a fast electron transfer channel but also possesses rich heterointerface, thus accelerating the Volmer step and allowing more active sites of Ni₃S₂ to functioning well. As a result, v-Ni₃S₂–Ni(OH)₂/NF exhibited excellent electrocatalytic activity toward HER in 1.0 M KOH solution. It only needs 78 mV and 137 mV to drive current density of 10 mA cm⁻² and 100 mA cm⁻². Moreover, the catalytic stability of this electrocatalyst in alkaline solution is also satisfactory.     

Enhancement of catalytic properties and durability in Ni–B–P/Ni foam for hydrazine electrooxidation

Hydrazine is a promising energy carrier of high power density, high theoretical cell voltage, and zero carbon emission to replace fossil fuel-dominated energy sources. Herein, we present a new Ni–B–P/NF catalyst for hydrazine electrooxidation by a facile electroless plating process. The Ni–B–P/NF catalyst exhibits remarkable catalytic activity (290 mA cm⁻² at 0.3 V) by combining merits of high intrinsic activity, large specific surface area, satisfactory conductivity, and lattice dislocation. Meanwhile, the Ni–B–P/NF catalyst provides excellent long-term durability (5000 s, 94.4%), which is at the leading level among the reported Ni-based electrocatalysts for hydrazine electrooxidation to date. It is found that the phosphorus-containing coating and its tight binding to the substrate contribute to the long-term durability of Ni–B–P/NF. XPS results and electron models are used to elucidate the electron transition mechanism of the Ni–B–P coating. This work presents a novel catalyst for hydrazine electrooxidation and demonstrates its promising application in energy storage and fuel cell systems.