Beyond oxygen evolution: Recent progress in hydrogen production via anodic substitution reactions

With the rise in demand for energy and the increasing depletion of fossil fuels, the development and research of new energy sources have been advancing speedily. Hydrogen energy has attracted particular attention due to its zero-pollution and zero-carbon emissions. However, the high energy demand of traditional water electrolysis remains a major challenge for its industrial application. The slow kinetics of the anodic oxygen evolution reaction (OER) are the major bottleneck the key constraint on hydrogen production. Therefore, replacing OER with a lower potential anodic oxidation reaction is an important strategy to reduce energy consumption. While review articles on anode substitution have proliferated in recent years, few offer a systematic examination integrating mechanistic insights, energy requirements, and economic viability. This review summarizes recent research progress on anodic OER replacement via the electrooxidation of biomass, small-molecule reagents, and pollutants. Furthermore, it emphasizes the recovery and reuse of high-value-added products from anodic replacement reactions. Finally, this review presents a comprehensive assessment of the strengths, weaknesses, and technoeconomic viability of different replacement strategies, along with a forward-looking perspective on the future development paths and key challenges in electrocatalytic hydrogen production.