Unveiling the geometric site dependent activity of spinel Co3O4 for electrocatalytic chlorine evolution reaction

Spinel cobalt oxide (Co3O4), consisting of tetrahedral Co2+ (CoTd) and octahedral Co3+ (CoOh), is considered as promising earth-abundant electrocatalyst for chlorine evolution reaction (CER). Identifying the catalytic contribution of geometric Co site in the electrocatalytic CER plays a pivotal role to precisely modulate electronic configuration of active Co sites to boost CER. Herein, combining density functional theory calculations and experiment results assisted with operando analysis, we found that the CoOh site acts as the main active site for CER in spinel Co3O4, which shows better Cl− adsorption and more moderate intermediate adsorption toward CER than that CoTd site, and does not undergo redox transition under CER condition at applied potential. Guided by above findings, the oxygen vacancies were further introduced into the Co3O4 to precisely manipulate the electronic configuration of CoOh to boost Cl− adsorption and optimize the reaction path of CER and thus to enhance the intrinsic CER activity significantly. Our work figures out the importance of geometric configuration dependent CER activity, shedding light on the rational design of advanced electrocatalysts from geometric configuration optimization at the atomic level.