Enhancing charge separation efficiency in photocatalytic hydrogen evolution via a synergistic strategy based on point/interface dual-defect engineering in Schottky heterojunctions

Abstract

Photocatalytic hydrogen evolution efficacy hinges on charge separation efficiency; dual-defect engineering markedly enhances material capabilities in this domain. This study presents an innovatively designed dual-defect heterojunction photocatalyst. It is composed of two key components: twinned Mn_0.5Cd_0.5S (T-MCS) rich in face defects and NiCo₂O₄ enriched with oxygen vacancy point defects. Experimental results demonstrate that this dual-defect heterojunction catalyst exhibits outstanding photocatalytic hydrogen evolution performance, yielding 1888 μmol of hydrogen within a 5 h reaction time. This represents 6.74 times and 2.28 times the hydrogen production of standalone WZ-MCS (280 μmol) and WZ-MCS/NiCo₂O₄ (828 μmol), respectively. An apparent quantum yield of 16.44% was achieved during monochromatic irradiation at 420 nm wavelength. Density functional theory calculations and XPS analysis suggest a Schottky junction formed at the T-MCS/Ov-NiCo₂O₄ interface, attributed to the metallic-like behavior of NiCo₂O₄. Photoelectrochemical testing revealed that the dual-defect synergistic engineering strategy significantly enhanced the carrier concentration and the built-in electric field strength of the catalyst. This substantially increased the charge separation efficiency from an initial value of 0.02% to 20.12%, thereby markedly attenuating the recombination of photogenerated electron–hole pairs. This study demonstrates a novel pathway for fabricating photocatalytic materials with superior performance through synergistic dual-defect regulation.