Small Molecule Oxidation Facilitated Seawater Splitting for Hydrogen Production: Opportunities and Challenges

AbstractDirect seawater splitting is an environment‐friendly and promising technology to replace freshwater electrolysis for hydrogen production. The challenge of seawater electrolysis lies in the competition between chloride oxidation reaction (CER) and oxygen evolution reaction (OER), as well as electrode corrosion and poisoning caused by chloride. Some small molecules have lower anodic electrocatalytic oxidation potentials compared to OER and CER, making them possible to substitute OER and/or CER in coupled electrolyzers not only to eliminate the electrode corrosion problem but also to significantly enhance the energy efficiency of seawater electrolysis. This article reviews the progress of such small molecule oxidation facilitated seawater electrolyzer. Starting with an overview of the key challenges in seawater electrolysis, this review introduces the fundamentals and advantages of the coupled seawater electrolyzers and discusses the strategies for anodic small molecule oxidation and cathodic hydrogen evolution reaction, including utilizing Cl− as a reactive medium, value‐added chemical synthesis, pollutants electrooxidation, and optimizing electrolyzers. Finally, the challenges and prospects of small molecule oxidation facilitated seawater splitting are summarized, aiming to provide impetus for research and development on coupled seawater electrolysis technologies.