Visible Light-Active Ternary Heterojunction Photocatalyst for Efficient CO2 Reduction with Simultaneous Amine Oxidation and Sustainable H2O2 Production

The present work described a unique approach for CO₂ reduction to methanol along with the oxidation of various amines to the corresponding imines and photocatalytic H₂O₂ production from H₂O and molecular O₂ using a heterojunction photocatalyst made up of ZnIn₂S₄/Ni₁₂P₅/g-C₃N₄(NCZ) under visible light irradiation. The photocatalysts were synthesized via a high-temperature treatment of nickel and phosphorous precursors with g-C₃N₄ followed by decoration of ZnIn₂S₄. The synthesized photocatalysts were characterized using various spectroscopic and microscopic techniques. The density functional theory (DFT) studies suggested the participation of the valence band maximum (VBM) from Ni₁₂P₅ and the conduction band maximum (CBM) from ZnIn₂S₄ in the ternary NCZ heterojunction. The ternary composite exhibited superior photocatalytic activity compared to that of its individual components due to the formation of a heterojunction, thereby enhancing the transfer efficiency of electrons from the conduction band of g-C₃N₄ to that of ZnIn₂S₄ using Ni₁₂P₅ as an electron bridge. Moreover, the reduced band gap of the ternary heterojunction played a key role in its higher efficiency.