Recent progress of cobalt-based electrocatalysts for water splitting: Electron modulation, surface reconstitution, and applications

Electrocatalytic water splitting is an essential and effective means to produce green hydrogen energy structures, so it is necessary to develop non-precious metal catalysts to replace precious metals. Cobalt-based catalysts present effective alternatives due to the diverse valence states, adjustable electronic structures, and plentiful components. In this review, the catalytic mechanisms of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) for electrocatalytic water splitting are described. Then, the synthesis strategies of various cobalt-based catalysts are systematically summarized, followed by the relationships between the structure and performance clarified. Subsequently, the effects of d-band center and spin regulation for cobalt-based catalysts are also discussed. Furthermore, the dynamic electronic and structural devolution of cobalt-based catalysts are elucidated by combining a series of in-situ characterizations. Finally, we highlight the challenges and future developed directions of cobalt-based catalysts for electrocatalytic water splitting.