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Ultrathin space charge layer in hematite photoelectrodes: A theoretical investigation
The Journal of Chemical Physics ( IF 4.4 ) Pub Date : 2021-09-15 , DOI: 10.1063/5.0060417
P A Delcompare-Rodriguez 1 , N Seriani 2
Affiliation  

The space charge layer in hematite photoelectrodes has been analyzed by means of Poisson–Boltzmann equations, the Stern model, and density functional theory, in view of its application for photoelectrochemical water oxidation. The width of the space charge layer can be smaller than ∼10 Å under experimental conditions. In this regime, a substantial part of the potential drop takes place in the Helmholtz layer, leading to important corrections to the Mott–Schottky behavior of the space charge layer capacitance. These results shed light on an unexpected regime of high photoelectrocatalytic efficiency, different from the classical picture of the electrochemical interface of a semiconducting photocatalyst, which is also amenable to direct study by quantum-mechanical atomistic simulations. Density functional theory has been used to calculate the band bending (BB) in the space charge layer in atomistic models of pristine stoichiometric and hydroxylated surfaces. These surface terminations display BBs of 0.14 and 0.49 eV, respectively, with an increasing width of the space charge layer, however still in the sub-nanometer regime. This work shows that, at high doping, the width of the space charge layer of a hematite photoelectrode can become comparable with interatomic distances.

中文翻译:

赤铁矿光电极中的超薄空间电荷层:理论研究

鉴于赤铁矿光电极中的空间电荷层在光电化学水氧化中的应用,已通过泊松-玻尔兹曼方程、斯特恩模型和密度泛函理论分析了赤铁矿光电极中的空间电荷层。在实验条件下,空间电荷层的宽度可以小于~10 Å。在这种情况下,很大一部分电位降发生在亥姆霍兹层中,导致对空间电荷层电容的莫特-肖特基行为进行重要修正。这些结果揭示了一种意想不到的高光电催化效率,不同于半导体光催化剂电化学界面的经典图片,这也可以通过量子力学原子模拟进行直接研究。在原始化学计量和羟基化表面的原子模型中,密度泛函理论已被用于计算空间电荷层中的能带弯曲 (BB)。这些表面终端分别显示 0.14 和 0.49 eV 的 BB,随着空间电荷层的宽度增加,但仍处于亚纳米范围内。这项工作表明,在高掺杂下,赤铁矿光电极的空间电荷层的宽度可以与原子间距离相媲美。
更新日期:2021-09-21
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