Key Laboratory of Magnetic Molecules & Magnetic Information Materials Ministry of Education, The School of Chemical and Material Science, Shanxi Normal University, Taiyuan, 030000, China.
Phys Chem Chem Phys. 2022 Dec 21;25(1):768-777. doi: 10.1039/d2cp03757b.
Density functional theory (DFT) calculations are executed to investigate the effect of a potassium (K) promoter on the activity of the water gas shift reaction (WGSR) over an Ag(111) surface. It is found that the WGSR proceeds mainly through the OH(O)-assisted carboxy pathway in which HO dehydrogenation is the rate-controlling step on both Ag(111) and K/Ag(111) surfaces. Energetic span model analysis shows that K addition can enhance the activity of the WGSR by reducing the apparent activation energy of the whole reaction since it can promote HO dissociation and stabilize the adsorption of the reactants (CO and HO). Importantly, the K adatom can stabilize the binding of all oxygenates by direct K-O bonding and the stabilizing effect of K on OH adsorption of the transition state (TS) plays a leading role in promoting HO dissociation. Moreover, the K-O distance and K coverage are two key factors affecting HO activation, that is, the shorter the K-O distance (2-3 Å) the more the K coverage (25%) contributes to the stronger promotion effect. For various metals catalyzing the WGSR, K promotes HO dissociation on inert metals like Ag, Au and Cu better than those on reactive metals (Pd and Ni) since the more inert metal surfaces would weaken the K and O binding and accordingly strengthen the interaction between them, resulting in a higher promotion effect.
采用密度泛函理论（DFT）计算研究了钾（K）助剂对 Ag（111）表面上水煤气变换反应（WGSR）活性的影响。结果表明，WGSR 主要通过 OH（O）辅助的羧基途径进行，其中 HO 脱氢是在 Ag（111）和 K/Ag（111）表面上的速率控制步骤。能垒跨度模型分析表明，K 的添加可以通过降低整个反应的表观活化能来增强 WGSR 的活性，因为它可以促进 HO 的解离并稳定反应物（CO 和 HO）的吸附。重要的是，K 原子可以通过直接的 K-O 键合稳定所有含氧物的结合，并且 K 对过渡态（TS）中 OH 吸附的稳定作用在促进 HO 解离方面起着主导作用。此外，K-O 距离和 K 覆盖率是影响 HO 活化的两个关键因素，即 K-O 距离越短（2-3 Å），K 覆盖率越高（25%），促进作用越强。对于各种金属催化 WGSR，K 促进 HO 在惰性金属（如 Ag、Au 和 Cu）上的解离比在活性金属（Pd 和 Ni）上的解离更好，因为更惰性的金属表面会削弱 K 和 O 的结合，并因此增强它们之间的相互作用，从而产生更高的促进作用。
