Hagiwara Satoshi, Kuroda Fumiaki, Kondo Takahiro, Otani Minoru
Center for Computational Sciences, University of Tsukuba, 1-1-1 Ten-nodai, Tsukuba, Ibaraki 305-8577, Japan.
Department of Materials Science and Tsukuba Research Center for Energy Materials Science, Institute of Pure and Applied Sciences and R&D Center for Zero CO2 Emission with Functional, Tsukuba, Ibaraki 305-8573, Japan.
ACS Appl Mater Interfaces. 2023 Nov 1;15(43):50174-50184. doi: 10.1021/acsami.3c10548. Epub 2023 Oct 19.
Rhombohedral boron monosulfide (r-BS) with a layer stacking structure is a promising electrocatalyst for an oxygen evolution reaction (OER) within an alkaline solution. We investigated the catalytic mechanisms at the r-BS electrode/alkaline medium interface for an OER using hybrid solvation theory based on the first-principles method combined with classical solution theory. In this study, we elucidate the activities of the OER at the outermost r-BS sheet with and without various surface defects. The Gibbs free energies along the OER path indicate that the boron vacancies at the first and second layers of the r-BS surface (V and V) can promote the OER. However, we found that the V is easily occupied by the oxygen atom during the OER, degrading its electrocatalytic performance. In contrast, V is suitable for the active site of the OER due to its structure stability. Next, we applied a bias voltage with the OER potential to the r-BS electrode. The bias voltage incorporates the positive excess surface charge into pristine r-BS and V, which can be understood by the relationship between the OER potential and potentials of zero charge at the r-BS electrode. Because the OH ions are the starting point of the OER, the positively charged surface is kinetically favorable for the electrocatalyst owing to the attractive interaction with the OH ions. Finally, we qualitatively discuss the flat-band potential at a semiconductor/alkaline solution interface. It suggests that p-type carrier doping could promote the catalytic performance of r-BS. These results explain the previous measurement of the OER performance with the r-BS-based electrode and provide valuable insights into developing a semiconductor electrode/water interface.
具有层状堆叠结构的菱方硼单硫化物（r-BS）是一种在碱性溶液中用于析氧反应（OER）的有前景的电催化剂。我们基于第一性原理方法结合经典溶液理论，使用混合溶剂化理论研究了r-BS电极/碱性介质界面上OER的催化机制。在本研究中，我们阐明了在有无各种表面缺陷的情况下，最外层r-BS薄片上OER的活性。沿OER路径的吉布斯自由能表明，r-BS表面第一层和第二层的硼空位（V和V）可以促进OER。然而，我们发现V在OER过程中很容易被氧原子占据，从而降低其电催化性能。相比之下，V由于其结构稳定性，适合作为OER的活性位点。接下来，我们向r-BS电极施加具有OER电位的偏置电压。该偏置电压将正过量表面电荷引入原始r-BS和V中，这可以通过r-BS电极上OER电位与零电荷电位之间的关系来理解。由于OH离子是OER的起始点，带正电的表面由于与OH离子的吸引相互作用，在动力学上对电催化剂有利。最后，我们定性地讨论了半导体/碱性溶液界面处的平带电位。这表明p型载流子掺杂可以提高r-BS的催化性能。这些结果解释了先前对基于r-BS的电极的OER性能的测量，并为开发半导体电极/水界面提供了有价值的见解。
