Cobalt compounds-based hollow structure electrocatalysts for water splitting: a review

Electrocatalytic water dissociation consists of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is an efficient process to create valuable fuels. But the slow OER reaction kinetics attributed to the multiple proton-coupled electron transport reaction and a high theoretical potential to a big challenge in industrial application. Hollow structures of cobalt-based electrocatalysts were considered a promising solution because of their inexpensiveness, low toxicity, large surface area, abundant exposed active sites, and adjustable elemental components. Also, hollow architectures could be used as ideal platforms for coating electrocatalysts to create beneficial effects. This study presented various strategies for generating hollow electrocatalysts, including template-assisted and template-free campaigns. Also, we summarized recent studies of Co-based electrocatalyst's hollow architectures for water splitting, which involves cobalt oxides, cobalt phosphides, cobalt selenides, cobalt sulfides, and cobalt-layered double hydroxides. Finally, the challenges and application prospects of hollow structural electrocatalysts for water dissociation are discussed.