Investigation of n-GaAs Photoanode Corrosion in Acidic Media with Various Thin Ir Cocatalyst Layers
Investigation of n-GaAs Photoanode Corrosion in Acidic Media with Various Thin Ir Cocatalyst Layers
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DOI：
10.1021/acsaem.1c01768
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发表时间：
2021-10
影响因子：
6.4
通讯作者：
Sahar Pishgar;Matthew C. Mulvehill;Saumya Gulati;G. Sumanasekera;Joshua M. Spurgeon
中科院分区：
文献类型：
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作者：
Sahar Pishgar;Matthew C. Mulvehill;Saumya Gulati;G. Sumanasekera;Joshua M. Spurgeon
n-GaAs是一种开发良好的III-V族半导体，具有优异的光吸收和电荷传输特性，使其成为高效光阳极的有希望的候选者。然而，在阳极偏压下，在水性电解质中的强光腐蚀阻止该半导体具有持久的以及有效的光电化学性能。在这项工作中，n-GaAs在酸性介质中的光腐蚀过程进行了监测，通过在溶液中的溶解元素的原位紫外-可见光谱分析，与SEM成像和XPS表面分析提供了额外的洞察力。电流密度与电位行为和相关的光腐蚀的强烈依赖性与n型掺杂密度相关，过渡到简并样行为产生明显不同的光电化学和腐蚀行为。在酸中的光阳极行为也进行了研究与薄的表面层的酸稳定的水氧化催化剂Ir。电流位移用于产生共形薄膜的Ir的n-GaAs，这是比较的薄膜的Ir旋涂从化学前体。原位紫外-可见光谱表明，短期内减少的腐蚀法拉第效率从Ir膜，但没有提供足够的保护，以防止GaAs光刻最终成为主导的电化学途径。每个Ir膜的不同性质进行了讨论，以解释所观察到的表面化学和形态的差异后，光阳极操作。
n-GaAs is a well-developed III–V semiconductor with excellent light absorption and charge-transport properties, making it a promising candidate for an efficient photoanode. However, strong photocorrosion under anodic bias in aqueous electrolyte prohibits this semiconductor from having durable as well as efficient photoelectrochemical performance. In this work, the photocorrosion process of n-GaAs in acidic media was monitored via in situ UV–vis spectroscopic analysis of the dissolved elements in solution, with additional insight provided by SEM imaging and XPS surface analysis. A strong dependence of the current density vs potential behavior and associated photocorrosion was correlated to the n-type doping density, with the transition into degenerate-like behavior yielding distinctly different photoelectrochemical and corrosion behavior. The photoanode behavior in acid was also investigated with thin surface layers of the acid-stable water oxidation catalyst Ir. Galvanic displacement was used to produce conformal thin films of Ir on n-GaAs, which was compared to films of Ir spin-coated from chemical precursors. In-situ UV–vis spectroscopy showed short-term decreases in the corrosion faradaic efficiency from the Ir films, but none provided sufficient protection to prevent GaAs photoetching from eventually becoming the dominant electrochemical pathway. The disparate nature of each Ir film is discussed to explain the observed differences in surface chemistry and morphology after photoanodic operation.