In situ activation of Br-confined Ni-based metal-organic framework hollow prisms toward efficient electrochemical oxygen evolution.

Fundamental insights into the structural evolution of oxygen electrocatalysts under operating conditions are of substantial importance for designing efficient catalysts. Here, on the basis of operando x-ray absorption fine structure spectroscopy, we probe the in situ activation of Br-confined conductive Ni-based metal-organic framework (Br-Ni-MOF) hollow prisms toward an active oxygen electrocatalyst during the oxygen evolution reaction (OER) process. The successive structural transformations from pristine Br-Ni-MOF to a β-Ni(OH) analog then subsequently to a γ-NiOOH phase during OER are observed. This post-formed γ-NiOOH analog manifests high OER performance with a superior overpotential of 306 mV at 10 mA cm and a high turnover frequency value of 0.051 s at an overpotential of 300 mV, making Br-Ni-MOF one of the most active oxygen electrocatalysts reported. Density functional theory calculations reveal that the strong electronic coupling between Br and Ni atoms accelerates the generation of the key *O intermediate toward fast OER kinetics.