Photoelectrochemical solar water splitting into hydrogen and oxygen offers an elegant and potentially efficient way to store solar energy in the chemical bonds of hydrogen, but the oxygen evolution rate is quite limited. The deposition of an oxygen evolution catalyst on the photoanode can enhance oxygen evolution, although the precise interplay between the semiconductor and the catalyst remains poorly understood and unoptimized. In this work, we use a combination of electrochemical approaches, including photoelectrochemical impedance spectroscopy and intensity modulated photocurrent spectroscopy, to unravel the nature of the interactions between different loadings of an electrocatalyst (CoFeO_x) and a hematite (α-Fe₂O₃) semiconductor. A thin layer of CoFeO_x mainly reduces surface charge recombination, while an extremely thin layer enhances charge transfer kinetics. Moreover, an interlayer of GaO_x modifies the surface state distribution and increases the charge transfer rate even further. These findings point to new opportunities for understanding and manipulating complex photoanodes for oxygen evolution.

中文翻译：

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钴铁（氧）氢氧化物（CoFeO _x）在赤铁矿光阳极上作为氧气释放催化剂的作用† ‡

分解为氢和氧的光电化学太阳能水提供了一种优雅且潜在有效的方式来将太阳能存储在氢的化学键中，但氧的释放速率非常有限。氧释放催化剂在光阳极上的沉积可增强氧释放，尽管半导体和催化剂之间的精确相互作用仍然知之甚少且未优化。在这项工作中，我们使用的电化学方法，包括光电化学阻抗光谱和强度调制光电流光谱的组合解开电极催化剂（CoFeO的不同负载量之间的相互作用的性质_X）和赤铁矿（α-的Fe ₂ ö ₃）半导体。一层薄薄的CoFeO_x主要减少表面电荷的复合，而极薄的层则增强电荷转移动力学。而且，GaO _x的中间层改变了表面状态分布并甚至进一步提高了电荷转移速率。这些发现为理解和操纵复杂的光阳极以释放氧气提供了新的机会。