Simple Electrolysis Trick Turns Cheap Nickel Into a Powerful Hydrogen Catalyst

Green hydrogen has a stubborn bottleneck, and it sits on the positive side of the electrolyzer. Splitting water into hydrogen is only half the battle; the oxygen evolution reaction (OER) that accompanies it is sluggish, energy-hungry, and stubbornly dependent on catalysts made from iridium and ruthenium, two of the rarest and most expensive metals on Earth. Now a team of researchers at Jingdezhen Ceramic University and Xi’an University reports a strikingly simple answer: a one-step electrodeposition method that grows a hybrid nickel and nickel hydroxide catalyst directly on a copper substrate, using nothing more exotic than carefully chosen salt anions to steer the process. The work, published in the journal Ionics, shows that the resulting electrode needs only 254 millivolts of overpotential to drive a current density of 10 milliamperes per square centimeter in alkaline conditions, a figure that places it among the more competitive nickel-based catalysts reported for this reaction.

The elegance of the approach lies in what the researchers did not do. There is no multi-step synthesis, no high-temperature calcination, no hydrothermal autoclave, and no template removal. Instead, the team applied a direct current to a copper electrode immersed in a plating bath containing nickel salts, and they tuned the chemistry of that bath with two familiar ions: nitrate and chloride. Each ion plays a distinct role. Nitrate is known in electroplating circles for its ability to modify deposit morphology and even darken nickel films by altering how the metal nucleates and grows on the surface. Chloride, meanwhile, influences particle size and film compactness. By adjusting the balance between the two, the researchers could jointly control two things that usually fight each other in catalyst design: the ratio of metallic nickel to nickel hydroxide in the final film, and the mesoporous architecture that determines how much of the catalyst surface is actually reachable by electrolyte.

Why does that dual control matter so much? The answer lies in the complementary weaknesses of the two phases. Metallic nickel is an excellent electrical conductor, but on its own it is a mediocre oxygen evolution catalyst; the reaction intermediates bind to its surface with the wrong energetics, and the kinetics stall. Nickel hydroxide, by contrast, offers far more favorable adsorption sites for the oxygen-containing intermediates that form during water oxidation, but it is a poor conductor and, in many preparations, suffers from structural reconstruction during operation, gradually converting into other phases whose activity can drift over time. The hybrid electrode sidesteps both problems. Metallic nickel domains act as an internal electron highway, shuttling charge to and from the catalytically active hydroxide regions, while the low-crystallinity nickel hydroxide provides the reactive interface where water molecules are oxidized. The result is a composite in which each phase covers for the other’s deficiencies.

The performance numbers back up this design logic. At the benchmark current density of 10 milliamperes per square centimeter, the Ni/Ni(OH)2 electrode required an overpotential of just 254 millivolts, meaning the researchers had to apply only that much extra voltage beyond the thermodynamic minimum to get water oxidation underway at a useful rate. Equally telling is the Tafel slope, a measure of how quickly current rises as additional voltage is applied. The hybrid electrode delivered a Tafel slope of 50.3 millivolts per decade, indicating markedly accelerated reaction kinetics compared with conventional nickel-based catalysts. In practical terms, a lower Tafel slope means the catalyst does not need ever-larger voltage penalties as the electrolyzer is pushed toward industrial current densities, which is precisely where energy efficiency is won or lost.

Durability, the quiet killer of promising electrocatalysts, was also addressed head-on. Many laboratory catalysts post impressive initial numbers only to degrade within hours as their active layers dissolve, delaminate, or restructure. The Jingdezhen team subjected their electrode to a 100-hour chronopotentiometry test at a demanding 50 milliamperes per square centimeter, a current density far closer to real electrolyzer operation than the standard 10-milliamp benchmark. The electrode held its performance throughout, a result the researchers attribute to the in-situ nature of the fabrication: because the hybrid film is grown directly on the copper substrate rather than deposited as a powder and glued on with a polymer binder, the catalyst-substrate interface is intimate and mechanically robust, resisting the bubble evolution and mechanical stress that peel weaker electrodes apart.

Mechanistic analysis of the composite revealed why the interface between metallic nickel and low-crystallinity nickel hydroxide is so productive. The two phases form a coupled system in which electrons generated during the oxidation of hydroxide species can transfer efficiently across the phase boundary into the metallic network, avoiding the charge accumulation that throttles pure hydroxide electrodes. The low crystallinity of the hydroxide component is itself an asset rather than a defect: disordered structures typically expose a higher density of under-coordinated metal sites, edges, and defects that serve as active centers for the four-electron water oxidation sequence. Meanwhile, the anion-regulated deposition produced a mesoporous morphology with finely dispersed particles, maximizing the electrochemically accessible surface area and ensuring that bubbles generated during operation can escape easily rather than blanketing the surface.

The choice of copper as the substrate deserves its own note. Copper is cheap, conductive, and mechanically robust, and it is increasingly favored in the electrocatalysis literature as a support that can even participate chemically in the catalysis, promoting the transformation of nickel hydroxide into higher-valent nickel species that are considered the true active phase for oxygen evolution. By growing the catalyst directly on copper foil or mesh in a single electrochemical step, the researchers eliminated the need for expensive conductive additives, binders, and the energy-intensive processing steps that inflate the cost of conventional electrode manufacturing. For an industry trying to drive down the capital cost of alkaline water electrolyzers, a fabrication route that is essentially room-temperature electroplating is a genuinely attractive proposition.

The broader context makes the result more than a laboratory curiosity. Alkaline water electrolysis is the most mature hydrogen production technology, but its efficiency is capped by the large overpotential of the oxygen evolution reaction at the anode, which can waste hundreds of millivolts of electrical energy per cell. Every millivolt saved translates directly into kilowatt-hours saved per kilogram of hydrogen produced. Nickel-based catalysts have long been the workhorse candidates for replacing precious metals in this role, and recent years have seen an explosion of strategies, from nickel-iron layered double hydroxides to doped nitrides and oxyhydroxides, aimed at squeezing more activity out of earth-abundant elements. What distinguishes the new work is its emphasis on process simplicity: rather than adding complexity, it uses the intrinsic chemistry of two common anions to achieve phase control, morphology control, and interface engineering in a single deposition bath.

The anion-regulation concept also opens a tunable design space that other groups can explore. Because nitrate and chloride each exert distinct effects on nucleation density, particle size, and phase composition, varying their relative concentrations offers a continuous dial for optimizing the catalyst, rather than a discrete choice between recipes. The same principle could plausibly extend to other transition metal systems, including nickel-iron and nickel-cobalt chemistries, where anion-directed electrodeposition might similarly couple conductive metallic phases with active hydroxide phases. The researchers suggest that their work offers a facile route to low-cost, high-performance non-noble-metal OER electrodes with direct implications for industrial alkaline water electrolysis, and the combination of a 254-millivolt overpotential, a 50.3-millivolt-per-decade Tafel slope, and 100 hours of stable operation at 50 milliamperes per square centimeter gives that claim real weight.

Challenges remain before such electrodes see service inside a commercial electrolyzer stack. Long-term testing at even higher current densities, in flowing industrial electrolyte, and under the intermittent loads characteristic of renewable-powered hydrogen plants will be needed to confirm that the hybrid structure survives years rather than days. Scaling from small copper substrates to meter-scale electrode plates will test whether the anion-regulated deposition remains uniform across large areas. Still, the study is a reminder that some of the most consequential advances in clean energy chemistry come not from exotic new materials but from smarter control of the ones we already have. Two cheap ions, one electric current, and a copper plate may turn out to be an unlikely recipe for making green hydrogen a little more affordable.

Subject of Research: Anion-regulated one-step electrodeposition of Ni/Ni(OH)2 hybrid electrocatalysts for the alkaline oxygen evolution reaction

Article Title: NO₃⁻/Cl⁻-regulated one-step electrodeposition for in-situ fabrication of Ni/Ni(OH)₂ hybrid structures toward high-efficiency alkaline oxygen evolution reaction

Article References: Shi, J., Fan, J., Xv, J., Sun, L., Gong, Q., Huang, Y., Zhang, K., & Zhang, H. (2026). NO₃⁻/Cl⁻-regulated one-step electrodeposition for in-situ fabrication of Ni/Ni(OH)₂ hybrid structures toward high-efficiency alkaline oxygen evolution reaction. Ionics. https://doi.org/10.1007/s11581-026-07490-3

Image Credits: AI Generated

DOI: 10.1007/s11581-026-07490-3

Keywords: oxygen evolution reaction, water electrolysis, green hydrogen, electrodeposition, nickel catalyst, nickel hydroxide, nitrate regulation, chloride regulation, copper substrate, Tafel slope, electrocatalyst durability, alkaline media