Yang Chi-Ta, Wood Brandon C, Bhethanabotla Venkat R, Joseph Babu
Department of Chemical and Biomedical Engineering, University of South Florida, Tampa, FL 33620, USA.
Phys Chem Chem Phys. 2015 Oct 14;17(38):25379-92. doi: 10.1039/c5cp03674g.
Using density functional theory calculations, we investigate the influence of size-dependent cluster morphology on the synergistic catalytic properties of anatase TiO2(101) surfaces decorated with subnanometer Pt clusters. Focusing on the formation of the key precursor in the CO2 photoreduction reaction (bent CO2(-)), we find that flatter (2D-like) Pt clusters that "wet" the TiO2 surface offer significantly less benefit than 3D-like Pt clusters. We attribute the differences to three factors. First, the 3D clusters provide a greater number of accessible Pt-TiO2 interfacial sites with geometries that can aid CO2 bond bending and charge transfer processes. Second, binding competition among each Pt-CO2 bonding interaction mitigates maximum orbital overlaps, leading to insufficient CO2 binding. Third and also most interestingly, the 3D clusters tend to possess higher structural fluxionality than the flatter clusters, which is shown to correlate positively with CO2 binding strength. The preferred morphology adopted by the clusters depends on several factors, including the cluster size and the presence of oxygen vacancies on the TiO2 surface; this suggests a strategy for optimizing the synergistic effect between Pt clusters and TiO2 surfaces for CO2 photocatalysis. Clusters of ∼6-8 atoms should provide the largest benefit, since they retain the desired 3D morphology, yet are small enough to exhibit high structural fluxionality. Electronic structure analysis provides additional insight into the electronic motivations for the enhanced binding of CO2 on TiO2-supported 3D Pt clusters, as well as suppressed binding on flattened, 2D-like clusters.
通过密度泛函理论计算，我们研究了尺寸依赖的团簇形态对用亚纳米铂团簇修饰的锐钛矿型TiO2(101)表面协同催化性能的影响。聚焦于CO2光还原反应中关键前驱体（弯曲的CO2(-)）的形成，我们发现“浸润”TiO2表面的更扁平（类似二维）的铂团簇所带来的益处远不如类似三维的铂团簇。我们将这些差异归因于三个因素。首先，三维团簇提供了更多可及的Pt-TiO2界面位点，其几何结构有助于CO2键弯曲和电荷转移过程。其次，每个Pt-CO2键合相互作用之间的结合竞争减轻了最大轨道重叠，导致CO2结合不足。第三且最有趣的是，三维团簇往往比更扁平的团簇具有更高的结构流动性，这与CO2结合强度呈正相关。团簇所采用的优选形态取决于几个因素，包括团簇尺寸和TiO2表面氧空位的存在；这为优化Pt团簇与TiO2表面之间在CO2光催化中的协同效应提供了一种策略。约6-8个原子的团簇应能带来最大益处，因为它们保留了所需的三维形态，但又足够小以表现出高结构流动性。电子结构分析为CO2在TiO2负载的三维铂团簇上增强结合以及在扁平的类似二维团簇上结合受抑制的电子动机提供了额外的见解。
