Optimizing S-scheme heterojunctions of NiCo₂O₄ and graphdiyne-Cu₃P catalysts for enhanced photocatalytic hydrogen evolution

Abstract

The development of integrated photocatalysts to enhance the charge carrier separation efficiency of bimetallic oxides is a crucial strategy for achieving photocatalytic hydrogen production. In this study, the crystalline structure and synthesis results of NiCo₂O₄ and graphdiyne-Cu₃P (G-CP) catalysts were systematically investigated using X-ray diffraction and Raman spectroscopy. The Raman spectroscopic results confirmed the presence of graphite-like carbon nitride in G-CP, further validating the successful synthesis of the catalyst. Photoelectrochemical performance tests demonstrated that the heterojunction formed between G-CP and NiCo₂O₄ effectively reduced the recombination rates of charge carriers, with NCOGCP-80 exhibiting the highest photocurrent response intensity and the lowest resistance, indicating exceptional hydrogen evolution performance. In photocatalytic hydrogen evolution experiments, NCOGCP-80 achieved a hydrogen evolution amount of 312.22 µmol (6244.4 µmol·g⁻¹·h⁻¹), representing increases of 9.83 and 4.66 times compared to the individual catalysts. Finally, the formation of the S-scheme heterojunction between G-CP and NiCo₂O₄ is verified through theoretical calculations and in situ X-ray photoelectron spectroscopy.