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d-p orbital hybridization; Work-function gradient; Photocatalytic H2 evolution; DFT calculation
ABSTRACT
Efficient photocatalytic hydrogen evolution demands precise orchestration of charge separation and hydrogen adsorption/desorption kinetics. Here we tackle this challenge by synergistically integrating a work-function gradient with d-p orbital hybridization in a ternary Ag-NiOx-g-C3N4 architecture. Pronounced work function mismatch, confirmed by synchronous illumination X-ray photoelectron spectroscopy and density functional theory calculations, drives a directional electron cascade from Ag to NiOx via the g-C3N4 bridge, enforcing unidirectional charge migration. Concurrently, experimental and theoretical analyses reveal strong Ni 3d-N 2p orbital hybridization, which broadens Ni 3d band and downshifts its center to -2.12 eV. Compared with the control models, orbital hybridization induced Ni 3d band modulation fine-tunes hydrogen adsorption/desorption free energy to a near optimal -1.28 eV and concomitantly lowers interfacial charge transfer barrier. Consequently, the optimized 2%Ag-1.5% NiOx-g-C3N4 delivers an outstanding H2 evolution rate of 3594 μmol h-1 g-1, outperforming pristine g-C3N4 (25 μmol h-1 g-1), 2%Ag-g-C3N4 (284 μmol h-1 g-1) and 1.5% NiOx-g-C3N4 (1391 μmol h-1 g-1) by factors of 143.8, 12.6 and 2.6, respectively. This work establishes a general paradigm that couples macroscopic charge steering with microscopic orbital engineering for solar-to-hydrogen conversion.