Simultaneously mastering operando strain and reconstruction effects via phase-segregation strategy for enhanced oxygen-evolving electrocatalysis

Material strain and reconstruction effects are critical for catalysis reactions, but current insights into operando strain effects during reaction and means to master catalyst reconstruction are still lacking. Here, we propose a facile thermal-induced phase-segregation strategy to simultaneously master material operando strain and reconstruction effects for enhanced oxygen-evolving reaction (OER). Specifically, self-assembled and controllable layered LiCoO₂ phase and Co₃O₄ spinel can be generated from pristine Li₂Co₂O₄ spinel via Li and O volatilization under different temperatures, realizing controllable proportions of two phases by calcination temperature. Combined operando and ex-situ characterizations reveal that obvious tensile strain along (003) plane appears on layered Li_xCoO₂ phase during OER, while low-valence Co₃O₄ phase transforms into high-valence CoOOH_x, realizing simultaneous operando strain and reconstruction effects. Further experimental and computational investigations demonstrate that both strained Li_xCoO₂ phase and reconstructed CoOOH_x compound contribute to the beneficial adsorption of important OH⁻ reactants, while respective roles in activity and stability are uncovered by exploring their lattice-oxygen participation mechanism. This work not only reveals material operando strain effects during OER, but also inaugurates a new thermal-induced phase-segregation strategy to artificially master material operando strain and reconstruction effects, which will enlighten rational material design for many potential reactions and applications.