A unique oxygen ligand environment facilitates water oxidation in hole-doped IrNiOx core-shell electrocatalysts
A unique oxygen ligand environment facilitates water oxidation in hole-doped IrNiOx core-shell electrocatalysts
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DOI：
10.1038/s41929-018-0153-y
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发表时间：
2018-11-01
期刊：
影响因子：
37.8
通讯作者：
Strasser, Peter
中科院分区：
文献类型：
--
作者：
Hong Nhan Nong;Reier, Tobias;Strasser, Peter
预计电氧化水制氧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，放氧反应的缓慢速度仍然是一个关键的挑战，需要对其进行基本的了解，以促进更活跃和更稳定的电催化剂的设计。在本文中，我们利用X-射线吸收光谱、共振高能X射线衍射和差示原子对相关分析，研究了镍浸出的IrNi@LRO(X)金属氧化物核壳纳米粒子在催化析氧条件下氧配位的Ir中心的局域几何配位环境和电子金属状态。催化剂活化过程中的镍浸出会产生晶格空位，进而产生独特的缩短的Ir-O金属配位键，并在氧化Ir壳层中形成异常多的d带空穴。密度泛函理论计算表明，这种形式Ir氧化态的增加促使氧配体上直接靠近晶格空位的空穴的形成。我们认为，它们的亲电性使得这些氧配体容易在降低的动力学势垒下形成亲核酸碱型O-O键，从而导致强烈增强的反应活性。
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@lrO(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.