Langhammer David, Kullgren Jolla, Österlund Lars
Department of Materials Science and Engineering, The Ångström Laboratory, Uppsala University, P.O. Box 35, SE-751 03 Uppsala, Sweden.
Department of Chemistry, The Ångström Laboratory, Uppsala University, P.O. Box 538, SE-751 21 Uppsala, Sweden.
J Am Chem Soc. 2020 Dec 30;142(52):21767-21774. doi: 10.1021/jacs.0c09683. Epub 2020 Dec 17.
Adsorption of molecules is a fundamental step in all heterogeneous catalytic reactions. Nevertheless, the basic mechanism by which photon-mediated adsorption processes occur on solid surfaces is poorly understood, mainly because they involve excited catalyst states that complicate the analysis. Here we demonstrate a method by which density functional theory (DFT) can be used to quantify photoinduced adsorption processes on transition metal oxides and reveal the fundamental nature of these reactions. Specifically, the photoadsorption of SO on TiO(101) has been investigated by using a combination of DFT and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). The combined experimental and theoretical approach gives a detailed description of the photocatalytic desulfurization process on TiO, in which sulfate forms as a stable surface product that is known to poison the catalytic surface. This work identifies surface-SO as the sulfate species responsible for the surface poisoning and shows how this product can be obtained from a stepwise oxidation of SO on TiO(101). Initially, the molecule binds to a lattice O ion through a photomediated adsorption process and forms surface sulfite, which is subsequently oxidized into surface-SO by transfer of a neutral oxygen from an adsorbed O molecule. The work further explains how the infrared spectra associated with this oxidation product change during interactions with water and surface hydroxyl groups, which can be used as fingerprints for the surface reactions. The approach outlined here can be generalized to other photo- and electrocatalytic transition metal oxide systems.
分子吸附是所有多相催化反应的基本步骤。然而，光子介导的吸附过程在固体表面发生的基本机制却鲜为人知，主要是因为它们涉及激发态催化剂，这使得分析变得复杂。在此，我们展示了一种方法，通过该方法密度泛函理论（DFT）可用于量化过渡金属氧化物上的光致吸附过程，并揭示这些反应的基本性质。具体而言，通过结合DFT和原位漫反射红外傅里叶变换光谱（DRIFTS）研究了SO在TiO(101)上的光吸附。实验与理论相结合的方法详细描述了TiO上的光催化脱硫过程，其中硫酸盐作为一种稳定的表面产物形成，已知其会使催化表面中毒。这项工作确定表面 - SO为导致表面中毒的硫酸盐物种，并展示了该产物如何通过SO在TiO(101)上的逐步氧化获得。最初，分子通过光介导的吸附过程与晶格O离子结合形成表面亚硫酸盐，随后通过吸附的O分子转移中性氧将其氧化为表面 - SO。该工作还进一步解释了与这种氧化产物相关的红外光谱在与水和表面羟基相互作用期间如何变化，这可作为表面反应的指纹。这里概述的方法可推广到其他光催化和电催化过渡金属氧化物体系。
