Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA, Leiden, The Netherlands.
Nat Chem. 2017 Jan 9;9(5):457-465. doi: 10.1038/nchem.2695.
Understanding how materials that catalyse the oxygen evolution reaction (OER) function is essential for the development of efficient energy-storage technologies. The traditional understanding of the OER mechanism on metal oxides involves four concerted proton-electron transfer steps on metal-ion centres at their surface and product oxygen molecules derived from water. Here, using in situ O isotope labelling mass spectrometry, we provide direct experimental evidence that the O generated during the OER on some highly active oxides can come from lattice oxygen. The oxides capable of lattice-oxygen oxidation also exhibit pH-dependent OER activity on the reversible hydrogen electrode scale, indicating non-concerted proton-electron transfers in the OER mechanism. Based on our experimental data and density functional theory calculations, we discuss mechanisms that are fundamentally different from the conventional scheme and show that increasing the covalency of metal-oxygen bonds is critical to trigger lattice-oxygen oxidation and enable non-concerted proton-electron transfers during OER.
了解催化氧气析出反应 (OER) 的材料的作用机制对于开发高效储能技术至关重要。传统观点认为，金属氧化物的 OER 机制涉及表面金属离子中心的四个协同质子-电子转移步骤，以及来自水分子的产物氧分子。在这里，我们使用原位 O 同位素标记质谱，提供了直接的实验证据，证明在一些高活性氧化物的 OER 过程中生成的 O 可以来自晶格氧。能够进行晶格氧氧化的氧化物在可逆氢电极尺度上也表现出 pH 依赖性的 OER 活性，表明 OER 机制中存在非协同质子-电子转移。基于我们的实验数据和密度泛函理论计算，我们讨论了与传统方案有根本区别的机制，并表明增加金属-氧键的共价性对于引发晶格氧氧化和在 OER 过程中实现非协同质子-电子转移至关重要。
