Xu Shenzhen, Carter Emily A
Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544-5263, United States.
Office of the Chancellor and Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Box 951405, Los Angeles, California 90095-1405, United States.
J Phys Chem B. 2020 Mar 19;124(11):2255-2261. doi: 10.1021/acs.jpcb.0c01236. Epub 2020 Mar 9.
Illuminated GaP electrodes selectively reduce CO to CHOH in aqueous solution. To understand the photoelectrocatalytic mechanism, knowledge of the GaP surface atomic structure in contact with water under relevant electrochemical conditions is essential. However, there remains a debate about the oxidation state of GaP, i.e., whether oxide species are present at the surface. To address this issue, we use density functional theory to investigate the adsorption of oxide species on GaP(110), a stable and active facet for CO reduction. We predict that GaP(110) indeed could be oxidized at the standard reduction potential for CO to CHOH. However, we find that unoxidized GaP(110) is stable under illumination, as it corresponds to a highly reducing condition induced by photoexcited electrons. We conclude that an oxidized GaP electrode is very likely unstable thermodynamically under photoelectrochemical conditions for CO reduction, and therefore, the relevant GaP/water interface for catalysis is indeed the unoxidized one.
发光的GaP电极在水溶液中能将CO选择性还原为CHOH。为了理解光电催化机理，了解在相关电化学条件下与水接触的GaP表面原子结构至关重要。然而，关于GaP的氧化态仍存在争议，即表面是否存在氧化物物种。为了解决这个问题，我们使用密度泛函理论研究氧化物物种在GaP(110)上的吸附，GaP(110)是用于CO还原的稳定且活性的晶面。我们预测，在将CO还原为CHOH的标准还原电位下，GaP(110)确实会被氧化。然而，我们发现未氧化的GaP(110)在光照下是稳定的，因为这对应于光激发电子诱导的高还原条件。我们得出结论，在光电化学条件下用于CO还原时，氧化的GaP电极在热力学上很可能是不稳定的，因此，催化相关的GaP/水界面实际上是未氧化的界面。
