Understanding the Role of Oxygen Vacancy Defects in Iridium-Leveraged MOFs-Type Catalyst

Engineering oxygen vacancies (Vo) in metal–organic framework (MOF) is considered as an effective strategy to improve the hydrazine oxidation reaction (HzOR) performance. However, the role of Vo and the metal sites for HzOR is still not fully understood. Herein, this study reports the synthesis of a well-defined bimetallic V_O-rich benzene dicarboxylic acid-based MOF (NiIr_0.03-BDC) as a model to clarify the intricate catalytic mechanism. Operando characterizations demonstrate that the Vo-rich environment favors the adsorption of OH⁻ on the catalyst surface during the HzOR process, leading to the formation of Ni(OH)_x active species. Theoretical calculations reveal that the introduced Ir at metal nodes not only boosts the HzOR activity of the Ni sites by tuning their electronic structure but also serves as the active sites for hydrogen evolution. As a result, the two-electrode electrolyzer with NiIr_0.03-BDC || NiIr_0.03-BDC configuration achieved 10 mA cm⁻² at an ultralow cell voltage of 0.046 V. This work provides new insights into oxygen vacancy defect engineering of MOFs and paves a solid step for low-energy consumption hydrogen production.