Adsorption Characteristics and Size/Shape Dependence of Pt Clusters on the CdS Surface

Motivated by recent reports on the enhanced photocatalytic activities of CdS decorated with subnanometer- and nanometer-sized noble metal clusters, we carried out first-principles density functional theory calculations to study the structure and electronic properties of Pt clusters supported on CdS surfaces. A systematic investigation of unsupported 2D bilayer and 3D Pt clusters up to 1.5 nm yielded similar trends on their structural, energetic, and electronic properties as functions of the cluster size. Detailed adsorption studies of a single Pt atom, a 2D Pt19 cluster, and a 3D Pt38 cluster on the nonpolar CdS(101̅0) surface revealed that both the cluster size/shape and the adsorption configuration have considerable influence on the surface structure, adsorption strength, and other interface characteristics. Strong bonding interactions occur at the cluster/semiconductor interface, leading to severe structural deformation of the substrate and the adsorbed clusters, as well as modification of the electronic structure. In addition, significant charge redistribution occurs at the interface and results in a shift of the local surface potential. Our work highlights the importance of explicitly treating the interface with realistic structural models to obtain an accurate picture of the structural and electronic interactions at the interface and understand the observed enhancement in photocatalytic activities.