MXene electrocatalysts for hydrogen evolution and methanol oxidation: Interfacial mechanisms, architectures, and emerging design principles for energy-saving electrolysis

Electrochemical hydrogen production is central to renewable and sustainable energy systems, yet conventional water electrolysis remains limited by the sluggish oxygen evolution reaction, high anodic overpotentials, and associated efficiency losses. Coupling the hydrogen evolution reaction (HER) with the methanol oxidation reaction (MOR) offers an energy-saving alternative by replacing oxygen evolution with potentially value-added anodic conversion. In this context, MXenes have emerged as promising electrocatalytic platforms because their metallic conductivity, tunable surface terminations, defect chemistry, and strong interfacial interactions enable regulation of adsorption energetics, charge redistribution, and local reaction microenvironments. This review critically examines MXene electrocatalysts for HER and MOR, with emphasis on interfacial mechanisms, catalyst architectures, and emerging design principles for energy-saving electrolysis. Cross-cutting comparisons show how termination and interlayer control, defect and coordination engineering, atom or cluster anchoring, and heterostructure construction regulate hydrogen adsorption, water activation, interfacial charge transfer, carbonaceous-intermediate conversion, and poisoning resistance. For MOR, particular attention is given to the distinction between activity or CO-tolerance evidence and quantitative product analysis, because high anodic current alone does not establish selective value-added conversion. The review further assesses MXene-enabled HER–MOR full cells and explains how differences in electrolyte, catalyst loading, normalization, and testing protocols constrain cross-study comparisons. Finally, persistent challenges involving termination evolution, asymmetric degradation, methanol crossover, practical current densities, and scalability are identified, together with priorities for operando characterization, product-resolved analysis, standardized benchmarking, and durable electrode design.