Organic small molecule oxidation as a substitute for oxygen evolution reaction in water electrolysis: Mechanisms, catalyst design, and future challenges

Hydrogen production by water electrolysis faces challenges such as high over-potential of oxygen evolution reaction (OER), low economic value of oxygen, and generation of harmful reactive oxygen species (ROS). In recent years, replacing OER with the oxidation of organic small molecules to construct hybrid electrolysis systems coupled with hydrogen evolution reaction (HER) has emerged as a key strategy for achieving low-energy-consumption of high-value-added chemicals and H₂ production. This review systematically summarized the reaction mechanisms, catalyst design strategies, and research progress of our group and other researchers in recent three years on alternative oxidation reactions, such as urea, hydrazine, ammonia, alcohols, and biomass platform molecules, in water electrolysis for H₂ production. This approach not only significantly reduces energy consumption and improves H₂ purity, but also enables the simultaneous synthesis of high-value chemicals or wastewater treatment, offering advantages in energy, environment, and economy. We also discussed the key issues that need to be addressed in the future, providing directional guidance for advancing the sustainable development of hybrid water electrolysis technology and the green production of high-value-added chemicals.