Unveiling the role of surface P–O group in P-doped Co3O4 for electrocatalytic oxygen evolution by On-chip micro-device

Transition metal phosphides or partially phosphatized oxides usually suffer from surface reconstruction during oxygen evolution reaction (OER), but still possess enhanced catalytic activity than directly synthesized oxides, which has aroused great interest in exploring the causes of such high catalytic activity. To monitor electronic property of catalyst during the OER can provide crucial insights into catalytic ability. Here we design a planar electrochemical microdevice based on individual thin-film catalyst, and for the first time explore the continuous electric conductance evolution of lattice P-doped oxides during the electrochemical activation process. Moreover, combining on-chip electrochemical impedance spectra measurements, in situ I-V measurements, and theoretical simulations of reconstructed lattice P-doped oxides, the effect of P–O groups on new-formed oxides is clarified. The induced electronic coupling between new-formed oxides and P-O groups has been studied and demonstrated. The coupled P–O groups effectively promote the metal–oxygen covalency of new-formed oxides, which accelerates electron transfer between active metallic center and oxygen adsorbates, thus leading to the enhanced electrocatalytic activity. Our study highlights the role of surface P–O groups in Co3O4 during the OER, and such unique on-chip electrochemical microdevice platform can also be applied in other related fields to understand the dynamic behavior of energy materials at nanoscale.