Recent Advancements in Electrochemical Hydrogen Production via Hybrid Water Splitting

As one of the most promising approaches to producing high‐purity hydrogen (H2), electrochemical water splitting powered by the renewable energy sources such as solar, wind, and hydroelectric power has attracted considerable interest over the past decade. However, the water electrolysis process is seriously hampered by the sluggish electrode reaction kinetics, especially the four‐electron oxygen evolution reaction at the anode side, which induces a high reaction overpotential. Currently, the emerging hybrid electrochemical water splitting strategy is proposed by integrating thermodynamically favorable electro–oxidation reactions with hydrogen evolution reaction at the cathode, providing a new opportunity for energy–efficient H2 production. To achieve highly efficient and cost–effective hybrid water splitting toward large–scale practical H2 production, much work has been continuously done to exploit the alternative anodic oxidation reactions and cutting–edge electrocatalysts. This review will focus on recent developments on electrochemical H2 production coupled with alternative oxidation reactions, including the choice of anodic substrates, the investigation on electrocatalytic materials, and the deep understanding of the underlying reaction mechanisms. Finally, some insights into the scientific challenges now standing in the way of future advancement of the hybrid water electrolysis technique are shared, in the hope of inspiring further innovative efforts in this rapidly growing field. Replacing the anodic oxygen evolution reaction with thermodynamically more favorable oxidation reactions is regarded as a promising strategy to radically reduce the energy required for H2 production from water electrolysis. Here the recent progress of some major types of alternative oxidation reactions for hybrid water splitting has been comprehensively summarized.