Coupling external conditions and intrinsic structure in non-noble metal electrocatalysts for the HER/OER

Non-noble metal electrocatalysts are central to practical water electrolysis, yet many of the most active motifs do not remain structurally stable under device-level operating windows. Here, a stability-focused and integrated perspective is adopted, in which catalytic performance is understood as the combined result of external operating conditions, such as temperature, potential-current history, electrolyte identity and pH, interfacial wetting and bubble dynamics, contamination, and dissolution, together with intrinsic structural parameters, including active-site configuration, crystal phase and facet exposure, particle size and morphology, electronic structure, lattice strain, defects, and metal-support interactions. Using representative Fe-, Co-, and Mo-based non-noble metal electrocatalysts for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), key kinetic descriptors and evaluation metrics are first summarized, followed by an analysis of how specific external stressors trigger degradation pathways such as sintering, migration-coalescence, electrochemical Ostwald ripening, metal dissolution/redeposition, and carbon corrosion. Intrinsic design levers, including interfacial coupling, defect-dopant pairing, alloying and multimetallic synergy, and robust self-supported electrode architectures, are then discussed in terms of their ability to mitigate these processes while preserving favorable adsorption and transport properties. Particular emphasis is placed on alkaline water electrolysis, where non-noble metal electrocatalysts are currently the most developed. The review concludes with practical design rules and testing protocols for translating mechanistic insight into durable, high-efficiency HER/OER operation under device-relevant current densities.