Intermetallic Differences at CdS–Metal (Ni, Pd, Pt, and Au) Interfaces: From Single-Atom to Subnanometer Metal Clusters

Metal co-catalysts tipped at a photocatalyst surface form a crucial component in the nanoheterostructures designed for the photocatalytic hydrogen evolution reaction. To examine the intermetallic differences and size effects at these interfaces, we use spin-polarized density functional theory to study single-atom, 13-atom, and 55-atom cluster depositions of Ni, Pd, Pt, and Au on the CdS(101̅0) surface. For the single metal atoms, the ground-state configuration was the same site for all of the elements. Analysis of the metal–CdS bonding and of the charge transfers revealed a Ni–Cd bonding complex leading to depletion of electronic charge at the Ni single atom and at deposited Ni clusters, in contrast to charge accumulation observed for the other three metals Pd, Pt, and Au. For scaling up sizes of the metal deposition, six subnanometer cluster types were selected over a wide range of cluster’s effective coordination number, and their interfaces were differentiated by charge redistributions, structure and adhesion energies, highest occupied molecular orbital–lowest occupied molecular orbital (HOMO-LUMO) gaps, and Schottky barrier heights. Although all considered clusters are semiconducting in the gas phase, 9 out of 28 clusters became (semi)­metallic after deposition on the CdS semiconductor surface. Intermetallic differences and common trends are discussed.负载于光催化剂表面的金属助催化剂，是为光催化析氢反应（Photocatalytic Hydrogen Evolution Reaction）设计的纳米异质结构的关键组成部分。为探究此类界面处的金属间差异与尺寸效应，我们采用自旋极化密度泛函理论（Spin-polarized Density Functional Theory），研究了Ni、Pd、Pt及Au在CdS(101̅0)表面的单原子、13原子及55原子团簇沉积行为。对于单金属原子而言，四种元素的基态构型均占据同一吸附位点。通过对金属-CdS键合过程与电荷转移行为的分析，我们发现Ni-Cd键合复合物会导致Ni单原子及沉积Ni团簇处出现电子电荷耗竭，而Pd、Pt、Au这另外三种金属则表现出电荷积累现象。为拓展金属沉积的尺寸范围，我们在覆盖宽泛有效配位数区间的范围内选取了6种亚纳米团簇类型，并通过电荷再分布、结构与粘附能、最高占据分子轨道-最低未占据分子轨道（HOMO-LUMO）能隙以及肖特基势垒高度（Schottky Barrier Heights）对这些团簇与CdS表面形成的界面进行区分。尽管所有被研究的团簇在气相中均呈半导体特性，但28个团簇中有9个在沉积至CdS半导体表面后转变为（半）金属性。本文还对金属间差异与共性趋势展开了讨论。