CoOOH: Synthesis and Application in Alkaline Electrochemical Oxygen Evolution Reaction

Oxygen evolution reaction (OER) is the bottleneck for electrochemical water splitting due to its sluggish 4-electron kinetics and high formation energy of O═O bond. Multiple kinds of Co-based compounds such as oxides, hydroxides, sulfides, phosphides and so on are demonstrated to possess excellent OER activity. However, these materials will partially or fully convert to CoOOH after OER, and therefore CoOOH receive extensive research interests as the true active species for Co-based OER catalyst in the past decade. Herein, the OER mechanism and synthesis of CoOOH and the strategies are reviewed for enhancing the OER performance of this kind of catalyst. The synthetic methods for CoOOH, including wet-chemical oxidation method, electrochemical oxidation method, molten-salt-assisted synthesis and hydrothermal method will be reviewed and compared. Moreover, the strategies will be summarized for design active CoOOH-based OER catalysts such as element doping and construction of hybrid catalysts in detail. Finally, an outlook is provided about the remaining challenges and future opportunities in this area.