Orbital-Tailored Pt Sites via Atomic-Level Carrier Pre-Design for Enhanced Photocatalytic Hydrogen Evolution

Modulating the coordination geometry of single atoms (SAs) is crucial for overcoming the limitations in catalytic activity. This study aims to construct a clear relationship between the coordination geometry of Pt SAs and their catalytic activity to guide the synthesis of targeted high-activity SA catalysts. An interesting atomic-level predesign strategy for SA carriers is proposed, enabling precise atomic regulation of N2c coordination sites. Seven distinct SA carriers were synthesized: pristine CN, Nv-CN (1, 2, 3) with N2c vacancies and Od-CN (1, 2, 3), in which N2c sites are substituted by oxygen doping, thereby achieving the controlled synthesis of four Pt coordination geometries: Pt–N4 in pristine CN, Pt–N2Cl4 (reconstructed to Pt–N2) in Nv-CN, and Pt–N3O in Od-CN. Among these, Od-CN–Pt exhibited exceptional photocatalytic hydrogen evolution performance (66.4 mmol g–1 h–1), which is 3.75 and 2.7 times higher than that of CN–Pt and Nv-CN–Pt, respectively. By combining in-situ KPFM-SPV, X-ray photoelectron spectroscopy, femtosecond transient absorption, and density functional theory calculations, a volcano-type relationship model was established between activity and three descriptors Bader charge, Pt 5d intensity, and ΔE (from PDOS to the Fermi level)─to elucidate the correlation between the coordination geometry and catalytic activity of SA-based catalysts. Such a descriptor may guide the predesign of high-performance SA catalysts.