Icosahedron kernel defect in Pt₁Ag series of bimetallic nanoclusters enhances photocatalytic hydrogen evolution

Developing high-efficiency photocatalysts for photocatalytic hydrogen production and understanding the structure-property relationships is much desired. In this study, a family of Pt₁Ag (x = 9, 11, 13 and 14) nanoclusters (NCs), including a new Pt₁Ag₁₁(SR)₅(P(Ph-OMe)₃)₇ NC, were designed and synthesized via ligand engineering (SR = 2,3,5,6-tetrafluorothiophenol, P(Ph-OMe)₃ = tris(4-methylphenyl)phosphine). The positive effect of the kernel structural defect on photocatalytic activity was investigated using the photocatalytic water-splitting reaction as a model, and the mechanistic relationship between the defect structure and catalytic activity was clarified. In this series of Pt₁Ag bimetallic NCs, the Pt₁Ag₁₁ NC, which exhibits a distinctive defect-containing icosahedral kernel structure, displayed excellent catalytic performance for photocatalytic hydrogen evolution, with the hydrogen production rate reaching 1780 μmol g^-1 h^-1. The experimental results revealed that the superior catalytic activity of Pt₁Ag₁₁/g-C₃N₄ may originate from the formation of Z-scheme heterojunction between Pt₁Ag₁₁ and the g-C₃N₄, facilitating efficient electron-hole separation and charge transfer. Furthermore, density-functional theory (DFT) calculations reveal the critical role of the defect-containing icosahedron-kernel on photocatalytic activity, which is favourable for the formation of the most stable nanocomposites and the easy absorption of H* intermediates on the Ag sites in Pt₁Ag₁₁/g-C₃N₄. This paper provides insights into the effect that the defects have on the mechanism of the photocatalytic hydrogen evolution reaction at the atomic level and promotes the rational design of high-efficiency photocatalysts.