The electro-oxidation of water to oxygen is expected to play a major role in the development of future electrochemical energy conversion and storage technologies. However, the slow rate of the oxygen evolution reaction remains a key challenge that requires fundamental understanding to facilitate the design of more active and stable electrocatalysts. Here, we probe the local geometric ligand environment and electronic metal states of oxygen-coordinated iridium centres in nickel-leached IrNi@IrO_x metal oxide core–shell nanoparticles under catalytic oxygen evolution conditions using operando X-ray absorption spectroscopy, resonant high-energy X-ray diffraction and differential atomic pair correlation analysis. Nickel leaching during catalyst activation generates lattice vacancies, which in turn produce uniquely shortened Ir–O metal ligand bonds and an unusually large number of d-band holes in the iridium oxide shell. Density functional theory calculations show that this increase in the formal iridium oxidation state drives the formation of holes on the oxygen ligands in direct proximity to lattice vacancies. We argue that their electrophilic character renders these oxygen ligands susceptible to nucleophilic acid–base-type O–O bond formation at reduced kinetic barriers, resulting in strongly enhanced reactivities.

预期水到氧气的电氧化将在未来电化学能量转换和存储技术的发展中发挥重要作用。然而，氧释放反应的缓慢速率仍然是关键挑战，需要基本了解以促进更活性和稳定的电催化剂的设计。在这里，我们探究了镍浸出的IrNi @ IrO _x中氧配位铱中心的局部几何配体环境和电子金属态使用操作X射线吸收光谱，共振高能X射线衍射和差分原子对相关分析，在催化氧逸出条件下形成金属氧化物核-壳纳米粒子。催化剂活化过程中的镍浸出会产生晶格空位，进而产生独特缩短的Ir–O金属配体键和异常大量的d。氧化铱壳上的带孔。密度泛函理论计算表明，形式铱氧化态的这种增加驱使氧配体上的空穴直接靠近晶格空位形成。我们认为，它们的亲电子特性使这些氧配体易于以降低的动力学势垒形成亲核酸碱型O-O键，从而大大增强了反应性。