Operando Unveiling Structural Evolution of Br-Ni-MOF for Highly Efficient Oxygen Evolution Electrocatalysis

Operando Unveiling Structural Evolution of Br-Ni-MOF for Highly Efficient Oxygen Evolution Electrocatalysis

Understanding the structural evolution of oxygen electrocatalysts under operating conditions is crucial for designing efficient catalysts. This study investigates the in-situ activation of a Br-confined conductive Ni-based metal-organic framework (Br-Ni-MOF) hollow prism during the oxygen evolution reaction (OER) using operando X-ray absorption fine structure spectroscopy.

We observed a series of structural transformations from the pristine Br-Ni-MOF to a β-Ni(OH)2 analog, and subsequently to a γ-NiOOH phase during the OER process. This post-formed γ-NiOOH analog exhibits exceptional OER performance, achieving a superior overpotential of 306 mV at 10 mA cm−2 and a high turnover frequency value of 0.051 s−1 at an overpotential of 300 mV. This performance ranks Br-Ni-MOF among the most active oxygen electrocatalysts reported to date.

Density functional theory calculations provide further insights, revealing that the strong electronic coupling between Br and Ni atoms accelerates the generation of the key *O intermediate, significantly boosting the OER kinetics.

Key Findings:

• Operando XAFS reveals the dynamic structural evolution of Br-Ni-MOF during the OER.* A highly active γ-NiOOH phase is identified as the active species for OER.* Br-Ni-MOF exhibits superior OER performance, outperforming many reported catalysts.* DFT calculations highlight the crucial role of Br-Ni electronic coupling in enhancing OER kinetics.

This work provides valuable insights into the dynamic behavior of MOF-based electrocatalysts under operating conditions and offers guidance for the rational design of high-performance OER catalysts.