Construction of tetrahedral CoO4vacancies for activating the high oxygen evolution activity of Co3-xO4-δporous nanosheet arrays

This study presents low-crystalline and non-stoichiometric cobalt oxide (Co3-xO4-delta) porous nanosheet arrays (PNAs) grown on carbon fiber cloth (CFC) (Co3-xO4-delta PNAs/CFC) by a facilein situanodic oxidation strategy. We firstly verified that the above prepared low crystalline cobalt oxide contained tetrahedral CoO(4)vacancies, resulting in the creation of O vacancies at adjacent octahedral CoO(6)sites, allowing the generation of tetragonal-pyramidal CoO(5)sites which were regarded as active sites and being accessible for the oxygen evolution reaction (OER) with different reaction mechanisms compared to that of traditional CoO(6)sites in high-crystalline and stoichiometric Co3O4, thus endowing Co3-xO4-delta PNAs/CFC with significantly improved OER activity and superior stability compared to their crystalline counterparts (Co3O4PNAs/CFC), as illustrated by experiments and density functional theory (DFT) calculations. This study will open up a new approach for the synthesis of defect-rich materials and provide new insight into the structure-property relationship of OER catalysts.