Department of Chemistry, University of Southampton, Southampton, United Kingdom.
Johnson Matthey Technology Centre, Blounts Court, Sonning Common, Reading RG4 9NH, United Kingdom.
J Chem Phys. 2019 Sep 21;151(11):114702. doi: 10.1063/1.5120571.
Metal oxide supports often play an active part in heterogeneous catalysis by moderating both the structure and the electronic properties of the metallic catalyst particle. In order to provide some fundamental understanding on these effects, we present here a density functional theory (DFT) investigation of the binding of O and CO on Pt nanoparticles supported on titania (anatase) surfaces. These systems are complex, and in order to develop realistic models, here, we needed to perform DFT calculations with up to ∼1000 atoms. By performing full geometry relaxations at each stage, we avoid any effects of "frozen geometry" approximations. In terms of the interaction of the Pt nanoparticles with the support, we find that the surface deformation of the anatase support contributes greatly to the adsorption of each nanoparticle, especially for the anatase (001) facet. We attempt to separate geometric and electronic effects and find a larger contribution to ligand binding energy arising from the former. Overall, we show an average weakening (compared to the isolated nanoparticle) of ∼0.1 eV across atop, bridge and hollow binding sites on supported Pt for O and CO, and a preservation of site preference. Stronger effects are seen for O on Pt, which is heavily deformed by anatase supports. In order to rationalize our results and examine methods for faster characterization of metal catalysts, we make use of electronic descriptors, including the d-band center and an electronic density based descriptor. We expect that the approach followed in this study could be applied to study other supported metal catalysts.
金属氧化物载体通常通过调节金属催化剂颗粒的结构和电子性质在多相催化中发挥积极作用。为了对这些效应提供一些基本的了解，我们在这里使用密度泛函理论（DFT）研究了负载在二氧化钛（锐钛矿）表面的铂纳米颗粒上的 O 和 CO 的结合。这些系统很复杂，为了开发出现实的模型，在这里，我们需要进行多达 ∼1000 个原子的 DFT 计算。通过在每个阶段进行全几何弛豫，我们避免了“冻结几何”近似的任何影响。就铂纳米颗粒与载体的相互作用而言，我们发现锐钛矿载体的表面变形对每个纳米颗粒的吸附有很大贡献，特别是对锐钛矿（001）面。我们试图分离几何和电子效应，并发现前者对配体结合能的贡献更大。总的来说，我们发现与孤立的纳米颗粒相比，在负载的 Pt 上， atop、bridge 和 hollow 结合位点上的 O 和 CO 的配体结合能平均减弱了 ∼0.1 eV，并且保持了位点偏好。在被锐钛矿载体严重变形的 Pt 上，O 的影响更强。为了使我们的结果合理化，并研究更快地表征金属催化剂的方法，我们使用了电子描述符，包括 d 带中心和基于电子密度的描述符。我们希望在这项研究中采用的方法可以应用于研究其他负载金属催化剂。
