Charge separation engineering via CoAl2O4/ZnCdS heterojunction and d-band center modulation for synergistically enhanced photocatalytic hydrogen evolution

Abstract

In response to the bottleneck of traditional photocatalysts, this study innovatively constructed a nanoflower-structured CoAl₂O₄-loaded ZnCdS solid solution (CZ15) composite photocatalyst, achieving an improvement in the performance of solar-driven hydrogen production. The hydrogen production rate of CZ15 under visible light is as high as 7388.72 μmol g⁻¹ h⁻¹, which is nearly 5.24 times higher than that of single ZnCdS, and its activity does not decline after 4 cycles. The improvement of performance stems from the synergistic effect of multiple mechanisms: a type-II heterojunction formed at the interface between CoAl₂O₄ and ZnCdS effectively drives the migration of photogenerated electrons from ZnCdS to CoAl₂O₄, thereby significantly suppressing electron–hole recombination; meanwhile, the introduction of CoAl₂O₄ regulates the electronic structure of the composite catalyst. DFT calculations confirmed that the center of its d-band was closer to the Fermi level, which optimizes the adsorption energy of the reaction intermediates and accelerates the surface reaction kinetics. In addition, the unique CoAl₂O₄ nanoflower structure effectively increases the specific surface area and provides more active sites.