2D catalysts for assisted water electrolysis: mechanistic insights and theoretical perspectives for industrial hydrogen generation

The efficiency of conventional water electrolysis is fundamentally constrained by the sluggish kinetics and high overpotential of the oxygen evolution reaction (OER). Assisted water electrolysis has emerged as a promising strategy to overcome this limitation by replacing OER with the selective oxidation of small organic or nitrogen-containing molecules such as urea, ammonia, methanol, ethanol, glycerol, and formic acid. These alternative anodic reactions offer significantly lower thermodynamic oxidation potentials, thereby enabling hydrogen production at reduced cell voltages while simultaneously achieving pollutant remediation and value-added chemical synthesis. Two-dimensional (2D) materials have garnered increasing attention as efficient catalysts for oxidation reactions in assisted water electrolysis, owing to their unique structural and electronic properties. This review summarizes recent progress in 2D catalysts, including layered double hydroxides, transition metal dichalcogenides, MXenes, metallenes, and graphene-based materials, emphasizing their roles in facilitating various oxidation reactions. Key strategies, including doping, defect engineering, and interface modulation, are discussed in relation to enhancing catalytic activity, selectivity, and durability. Thermodynamic analyses and Pourbaix diagrams are introduced to provide insight into the reaction pathways and stability windows of both feedstocks and catalysts under various electrochemical conditions. By integrating rational catalyst design with a comprehensive understanding of various oxidation reactions, assisted water electrolysis using 2D catalysts offers a compelling pathway toward sustainable hydrogen production. The co-benefits of improved energy efficiency and environmental sustainability position this approach as a promising solution to current energy and environmental challenges. Developing 2D materials and understanding reactions are expected to accelerate the implementation of next-generation electrolysis systems aligned with global carbon neutrality goals.