Understanding the Oxygen Evolution Reaction Mechanism on CoOx using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy,Journal of the American Chemical Society

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Understanding the Oxygen Evolution Reaction Mechanism on CoOx using Operando Ambient-Pressure X-ray Photoelectron Spectroscopy
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2017-06-22 , DOI: 10.1021/jacs.7b03211
Marco Favaro _{1,

2,

3} , Jinhui Yang _{2,

3} , Silvia Nappini ₄ , Elena Magnano ₄ , Francesca M. Toma _{2,

3} , Ethan J. Crumlin ₁ , Junko Yano _{2,

3,

5} , Ian D. Sharp _{2,

3}

Affiliation

Photoelectrochemical water splitting is a promising approach for renewable production of hydrogen from solar energy and requires interfacing advanced water-splitting catalysts with semiconductors. Understanding the mechanism of function of such electrocatalysts at the atomic scale and under realistic working conditions is a challenging, yet important, task for advancing efficient and stable function. This is particularly true for the case of oxygen evolution catalysts and, here, we study a highly active Co3O4/Co(OH)2 biphasic electrocatalyst on Si by means of operando ambient-pressure X-ray photoelectron spectroscopy performed at the solid/liquid electrified interface. Spectral simulation and multiplet fitting reveal that the catalyst undergoes chemical-structural transformations as a function of the applied anodic potential, with complete conversion of the Co(OH)2 and partial conversion of the spinel Co3O4 phases to CoO(OH) under precatalytic electrochemical conditions. Furthermore, we observe new spectral features in both Co 2p and O 1s core-level regions to emerge under oxygen evolution reaction conditions on CoO(OH). The operando photoelectron spectra support assignment of these newly observed features to highly active Co4+ centers under catalytic conditions. Comparison of these results to those from a pure phase spinel Co3O4 catalyst supports this interpretation and reveals that the presence of Co(OH)2 enhances catalytic activity by promoting transformations to CoO(OH). The direct investigation of electrified interfaces presented in this work can be extended to different materials under realistic catalytic conditions, thereby providing a powerful tool for mechanism discovery and an enabling capability for catalyst design.

中文翻译：

使用 Operando 环境压力 X 射线光电子能谱了解 CoOx 上的氧气释放反应机制

光电化学水分解是一种从太阳能可再生生产氢气的有前途的方法，需要将先进的水分解催化剂与半导体连接起来。在原子尺度和现实工作条件下了解此类电催化剂的功能机制是推进高效和稳定功能的一项具有挑战性但重要的任务。对于析氧催化剂的情况尤其如此，在这里，我们通过在固体/液体带电状态下进行的操作环境压力 X 射线光电子能谱研究了 Si 上的高活性 Co3O4/Co(OH)2 双相电催化剂。界面。光谱模拟和多重拟合表明，催化剂经历了化学结构转变，作为施加的阳极电位的函数，在预催化电化学条件下，Co(OH)2 完全转化，尖晶石 Co3O4 相部分转化为 CoO(OH)。此外，我们在 CoO(OH) 上的析氧反应条件下观察到 Co 2p 和 O 1s 核心级区域中出现的新光谱特征。操作光电子光谱支持将这些新观察到的特征分配给催化条件下的高活性 Co4+ 中心。将这些结果与纯相尖晶石 Co3O4 催化剂的结果进行比较支持了这一解释，并表明 Co(OH)2 的存在通过促进转化为 CoO(OH) 来增强催化活性。这项工作中提出的带电界面的直接研究可以扩展到现实催化条件下的不同材料，

更新日期：2017-06-22

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