Recent Advances in High-Performance Direct Seawater Electrolysis for “Green” Hydrogen

Abstract

Electrocatalytic water splitting through the electrolyzer is the most promising strategy for hydrogen production. Recently, water electrolysis is mainly based on high-purity freshwater, which not only consumes a large number of freshwater resources but also improves the overall cost due to the extra water purification system. Hence, direct electrolysis of seawater is more desirable for large-scale hydrogen generation. As is known, the dominant rate-determining step of overall water splitting is the anodic oxygen evolution reaction (OER), which involves four-electron transfer and owns a much larger overpotential than cathodic hydrogen evolution reaction. The large challenge for the design of OER catalysts in the seawater media is the competition reaction between OER and chloride oxidation reaction, which greatly influences energy efficiency. Hence, except for the activity and stability, selectivity is another key point for seawater splitting. Herein, after a brief introduction of two half reactions for water splitting, the latest metal hydr(oxide) electrocatalysts with different crystalline structures are summarized according to the previous reports. Moreover, the advantages and disadvantages of three common water electrolyzers are compared. Finally, the perspectives of seawater electrolysis for hydrogen production are outlined for practical applications.