Deep Reconstruction of Transition Metal MolybdateHydroxide Heterostructure Triggered by Anion-Exchange Reaction as High Efficiency Water Oxidation Electrocatalyst

Developing an efficient strategy to facilitate deep reconstruction of precatalysts to generate more active sites is crucial for fabricating efficient OER-catalysts but remains challenging. Here, an anion-exchange strategy was developed to achieve the complete reconstruction of cobalt molybdate (CoMoO4·nH2O) by engineering the ultrathin and amorphous Co(OH)2 nanosheets to in situ growing on CoMoO4·nH2O. The leaching of molybdate during anion-exchange reaction favors the formation of the loose hierarchical nanostructure, which facilitates deep reconstruction of precatalyst under electro-oxidation conditions. In-situ and ex-situ techniques demonstrate that CoMoO4·nH2O@Co(OH)2 undergoes four stages of reconstruction, and the reconstruction degree depend on the electrolyte and the bias voltage. After reconstruction, more CoOOH species were generated in the reconstructed CoMoO4·nH2O@Co(OH)2 compared with the reconstructed CoMoO4·nH2O, which was ascribed to the preferential conversion of amorphous Co(OH)2 to b-Co(OH)2 and CoOOH under alkaline conditions. As a result, the reconstructed CoMoO4·nH2O@Co(OH)2 catalyst exhibits the significantly enhanced OER activity and long-term durability. This study provided an effective strategy to construct the highly efficient OER electrocatalyst, and investigated the origin of catalytic activity through deep self-reconstruction