In a study published in Frontiers in Batteries and Electrochemistry, Yasmin Shabeer, Seyed Saeed Madani, Satyam Panchal, and Michael Fowler systematically investigated the corrosion behavior of a commercial Al-Mg-Si alloy in sodium hydroxide (NaOH) and potassium hydroxide (KOH) electrolytes spanning concentrations from 1 to 10 molar. The team combined three complementary electrochemical techniques—open-circuit voltage monitoring, potentiodynamic polarization, and electrochemical impedance spectroscopy—with X-ray diffraction to assess structural stability. They then trained an artificial neural network on the resulting dataset and optimized it using two genetic algorithm variants, achieving coefficients of determination exceeding 0.999 for both corrosion potential and corrosion current density.

The experimental campaign revealed two distinct corrosion regimes. At low-to-moderate alkalinity, anodic activation dominates: the corrosion potential shifts progressively negative and the corrosion current density climbs as hydroxide concentration increases, reflecting accelerated chemical dissolution of the native Al2O3/AlOOH surface film. At high concentrations, the behavior transitions to transport-limited kinetics, where the accumulation of soluble aluminate species, increased electrolyte viscosity, and hydrogen bubble coverage of 20 to 50 percent of the surface physically throttle the reaction rate. This shift from charge-transfer control to mass-transport control was confirmed by the weak coupling between corrosion potential and current density observed in the high-molarity polarization data.

Perhaps the most striking finding is that the two electrolytes behave very differently despite supplying identical hydroxide activity at the same molarity. KOH consistently produced more negative corrosion potentials and higher corrosion current densities than NaOH at equivalent concentrations. The researchers attribute this to cation-specific interfacial effects: potassium ions have a larger ionic radius, lower hydration energy, and higher mobility than sodium ions, facilitating faster charge transport, stronger double-layer perturbation, and more aggressive hydrogen evolution. In practical terms, this means that electrolyte identity—not just hydroxide concentration—governs corrosion kinetics in alkaline aluminum systems.

Impedance spectroscopy provided mechanistic confirmation of these trends. The charge-transfer resistance decreased markedly with increasing hydroxide concentration in both electrolytes, consistent with progressive activation of anodic dissolution. At equivalent molarities, NaOH consistently exhibited higher charge-transfer resistance than KOH, corroborating the milder corrosion environment inferred from polarization measurements. The constant phase element exponent remained below unity across all conditions, confirming a heterogeneous and dynamically evolving interface shaped by continuous oxide dissolution, aluminate formation, and gas evolution.

X-ray diffraction added a crucial structural dimension to the analysis. The diffraction patterns were dominated by the characteristic reflections of face-centered cubic aluminum, with invariant peak positions across all concentrations and both electrolytes. No crystalline aluminum hydroxides, oxyhydroxides, or aluminate phases were detected under any condition, indicating that corrosion products are predominantly amorphous, nanocrystalline, or highly hydrated. This finding validates the electrochemical evidence for continuous surface dissolution with transient, non-protective films rather than bulk phase transformation.

On the modeling side, the team conducted a comprehensive grid search of 351 artificial neural network configurations, varying network depth, neuron allocation, learning rate, and Adam optimizer parameters. The best-performing model used a three-layer architecture with 20, 25, and 25 neurons, a learning rate of 0.001, and a beta-1 value of 0.92. This configuration achieved R-squared values of 0.999888 for corrosion potential and 0.999945 for corrosion current density, representing an almost perfect mapping between experimental variables and corrosion indicators. Notably, 76 percent of all tested configurations achieved mean validation R-squared values exceeding 0.97, indicating that the underlying electrochemical relationships are highly learnable yet sensitive to architectural choices.

The researchers then applied two fundamentally different optimization strategies to the trained network. A scalar genetic algorithm, which combined the two corrosion objectives into a single weighted fitness function, and a non-dominated sorting genetic algorithm (NSGA-II), which preserved the independence of both objectives and resolved the complete Pareto trade-off front. Remarkably, both approaches converged on the same optimal condition: approximately 1.35 molar KOH, with a predicted corrosion potential of −1.6199 volts and a corrosion current density of 0.0876 A cm−2. This knee-point solution represents the least-compromise operating condition, where further reductions in corrosion current would require a disproportionate loss in corrosion potential stability.

The agreement between the two optimization formulations provides strong validation of the framework. The Pareto front revealed a smooth, continuous trade-off between corrosion thermodynamics and kinetics, with pronounced curvature at low current densities where small increases in corrosion rate yield diminishing gains in potential stability. This nonlinear structure reflects the fundamental electrochemical coupling between anodic dissolution kinetics and corrosion thermodynamics in alkaline aluminum systems, and it underscores why empirical trial-and-error electrolyte selection often fails to identify truly optimal conditions.

The implications extend beyond aluminum-air batteries. The framework demonstrates that integrating systematic electrochemical experimentation with neural network-assisted evolutionary optimization enables rapid, quantitative evaluation of corrosion behavior without exhaustive testing. The researchers suggest that this approach could support the development of digital-twin platforms for the design, optimization, and control of next-generation aluminum-based electrochemical energy systems, where parasitic corrosion losses must be minimized without sacrificing electrochemical stability. As the global transition toward cleaner energy accelerates and demand for alternative battery chemistries grows, such corrosion-aware electrolyte optimization may prove essential for unlocking the full potential of aluminum-based energy storage.

Subject of Research: Machine learning prediction of aluminum anode corrosion kinetics in alkaline electrolytes for aluminum-air batteries

Article Title: Artificial neural network-genetic algorithm prediction of aluminum anode corrosion kinetics in high-concentration NaOH and KOH

Article References: Artificial neural network-genetic algorithm prediction of aluminum anode corrosion kinetics in high-concentration NaOH and KOH. (n.d.). https://doi.org/10.3389/fbael.2026.1815822

Image Credits: AI Generated

DOI: 10.3389/fbael.2026.1815822

Keywords: aluminum-air batteries, corrosion, artificial neural networks, genetic algorithm, NSGA-II, alkaline electrolytes, KOH, NaOH, Al-Mg-Si alloy, machine learning, electrochemistry, energy storage

The research team set out to answer a deceptively simple question: when hydrogen gas bubbles off a nickel electrode in an alkaline solution, which of the surface species that form on nickel is actually doing the catalytic work? Nickel electrodes in alkaline media are never chemically naked. Depending on the applied potential and local conditions, their surfaces can host nickel oxide, nickel hydroxide, and nickel hydride phases, each with distinct electronic structures and bonding geometries. For decades, researchers have debated whether these species are innocent bystanders, harmful blockers, or hidden active sites. Because real electrodes present a patchwork of all three, isolating their individual contributions has been extraordinarily difficult.

The breakthrough of the new work lies in its systematic approach to well-defined nickel surfaces. Rather than studying polycrystalline foams or nanoparticles, where grain boundaries and defects confound interpretation, the researchers prepared carefully controlled nickel surfaces and deliberately generated each candidate species under known conditions. By systematically varying the presence and coverage of nickel oxide, nickel hydride, and nickel hydroxide, and then measuring the hydrogen evolution activity of each configuration, they could assign catalytic roles with a clarity that previous ensemble measurements could not achieve. The strategy echoes a classic theme in surface electrochemistry: only when a surface is well defined can the link between structure and function be drawn unambiguously.

What emerged is a picture in which no single species can claim sole credit. Nickel oxide species, the team found, contribute to the reaction in ways that depend sensitively on their exact chemical state and distribution on the metallic surface. Nickel hydroxide, which forms readily in alkaline environments and has often been invoked as the key promoter of alkaline hydrogen evolution, plays a role that must be carefully separated from the contributions of the oxide and hydride phases. Meanwhile, nickel hydride, the species formed when adsorbed hydrogen penetrates the metal lattice or binds in hydride-like configurations, emerges as a central participant in the hydrogen formation chemistry itself. The study’s central achievement is showing how these three species interact and divide the labor of the reaction rather than acting in isolation.

The distinction matters enormously for the alkaline hydrogen evolution reaction because its mechanism differs fundamentally from the one that operates in acid. In acidic media, the reaction proceeds through adsorbed hydrogen atoms that form directly on the metal surface and combine into hydrogen molecules. In alkaline electrolytes, however, water itself is the proton source, so every hydrogen molecule produced requires a water molecule to dissociate on the surface, cleaving an O-H bond and liberating a hydroxide ion. This initial water dissociation step is widely regarded as the kinetic bottleneck on pure metals, and it is precisely where adjacent oxide or hydroxide species have been proposed to help, by offering oxygen-affine sites that cleave water while neighboring metallic sites assemble the hydrogen. The new results put this bifunctional picture on a much firmer experimental footing for nickel.

For the electrolyser industry, the implications are immediate. Alkaline water electrolysis is the most mature and lowest-cost electrolysis technology on the market, but its cathodes and anodes still trail the performance achievable with platinum-group catalysts. Nickel is already the workhorse electrode material in commercial alkaline electrolysers, prized for its corrosion resistance in concentrated potassium hydroxide and its reasonable activity. If engineers can now identify which surface species to stabilize—and in what proportion—they can rationally tune electrode preparation protocols, whether through surface oxidation treatments, controlled potential cycling, or the deliberate engineering of oxide-hydride interfaces, instead of relying on empirical trial and error. The study effectively converts a long-standing controversy into an engineering design principle.

The findings also carry weight for the broader search for precious-metal-free catalysts. Earth-abundant transition metals such as nickel, cobalt, iron, and molybdenum have all been explored as hydrogen evolution catalysts, and many of the most successful candidates are not pure metals at all but composites in which metallic domains coexist with oxide or hydroxide phases. The nickel study provides a conceptual template for deconvoluting such systems: prepare well-defined versions of each phase, measure their individual kinetics, and then interrogate their combinations. Applied across the periodic table, this methodology could accelerate the discovery of catalysts that match platinum’s performance at a fraction of the cost, a goal that would ripple through green hydrogen production, fuel cells, and carbon-neutral synthesis of fuels and chemicals.

There are also cautionary lessons in the results. Because nickel hydride participates directly in the reaction, the subsurface and bulk hydride chemistry of nickel electrodes deserves renewed attention, particularly under the strongly reducing potentials of cathodic operation where hydride formation is thermodynamically favored. Hydride formation can induce lattice strain, alter electronic properties, and even degrade electrode morphology over time, so understanding its catalytic role may simultaneously illuminate pathways to more durable electrodes. Similarly, the finding that oxide and hydroxide species make separable, state-dependent contributions suggests that the dynamic potential-dependent evolution of surface chemistry during electrolyser start-up, shutdown, and fluctuating renewable power input could shift which species dominates, with consequences for both efficiency and lifetime.

The study arrives at a moment when green hydrogen is scaling from demonstration projects to gigawatt deployments, and every millivolt saved at the cathode translates into real energy and cost savings at industrial scale. By systematically dissecting the individual roles of nickel oxide, nickel hydride, and nickel hydroxide on well-defined nickel surfaces, the researchers have replaced a murky, contested narrative with a mechanistically grounded one. The work does not end the search for better alkaline hydrogen evolution catalysts, but it decisively sharpens it: the target is no longer simply nickel, or nickel oxide, or nickel hydroxide, but the precisely engineered coexistence of all three. For a field racing to strip precious metals out of the hydrogen economy, that clarity may prove as valuable as any single catalyst.

Subject of Research: The individual roles of nickel oxide, nickel hydride, and nickel hydroxide surface species in the alkaline hydrogen evolution reaction on nickel electrodes.

Article Title: The role of individual nickel surface species in the hydrogen evolution reaction on nickel in alkaline electrolytes

Article References: Kozlica, D. K., Finšgar, M., Farinazzo Bergamo Dias Martins, P., Huš, M., Genorio, B., Connell, J. G., Martins, M., Hývl, M., Žibert, T., Andrina Varda, K., Osmić, A., Bele, M., Likozar, B., Tomc, B., Gaberšček, M., & Strmčnik, D. (2026). The role of individual nickel surface species in the hydrogen evolution reaction on nickel in alkaline electrolytes. Nature Catalysis. https://doi.org/10.1038/s41929-026-01605-9

Image Credits: AI Generated

DOI: 10.1038/s41929-026-01605-9

Keywords: hydrogen evolution reaction, nickel, alkaline electrolytes, water electrolysis, nickel oxide, nickel hydride, nickel hydroxide, electrocatalysis, green hydrogen, surface chemistry, precious-metal-free catalysts, Nature Catalysis