Zagalskaya Alexandra, Alexandrov Vitaly
J Phys Chem Lett. 2020 Apr 2;11(7):2695-2700. doi: 10.1021/acs.jpclett.0c00335. Epub 2020 Mar 23.
Understanding the mechanistic interplay between the activity and stability of water splitting electrocatalysts is crucial for developing efficient and durable water electrolyzers. Ir-based materials are among the best catalysts for the oxygen evolution reaction (OER) in acidic media, but their degradation mechanisms are not completely understood. Here, through first-principles calculations we investigate iridium dissolution at the IrO(110)/water interface. Simulations reveal that the surface-bound IrOOH species formed upon iridium dissolution should be thermodynamically stable in a relatively wide potential window undergoing transformations into Ir (as IrO) at high anodic potentials and Ir (as Ir(OH)) at low anodic potentials. The identified high-valence surface-bound dissolution intermediates of Ir are determined to display greater OER activities than the pristine IrO(110) surface in agreement with the experimentally observed high activity of an amorphous hydrated IrO surface layer. Combined with recent experimental results, our simulations illuminate the mechanistic details of the degradation mechanism of IrO and how it couples to electrocatalytic OER.
了解析水电催化剂活性与稳定性之间的机制相互作用对于开发高效耐用的水电解槽至关重要。铱基材料是酸性介质中析氧反应（OER）的最佳催化剂之一，但其降解机制尚未完全明确。在此，我们通过第一性原理计算研究了IrO(110)/水界面处铱的溶解情况。模拟结果表明，铱溶解时形成的表面结合IrOOH物种在相对较宽的电位窗口内应该是热力学稳定的，在高阳极电位下会转变为Ir（以IrO形式），在低阳极电位下会转变为Ir（以Ir(OH)形式）。已确定的高价表面结合铱溶解中间体被认为比原始的IrO(110)表面表现出更高的OER活性，这与实验观察到的非晶态水合IrO表面层的高活性一致。结合最近的实验结果，我们的模拟阐明了IrO降解机制的详细机理以及它与电催化OER的耦合方式。
