Visible Light-Active Ternary Heterojunction Photocatalyst for Efficient CO 2 Reduction with Simultaneous Amine Oxidation and Sustainable H 2 O 2 Production.

The present work described a unique approach for CO 2 reduction to methanol along with the oxidation of various amines to the corresponding imines and photocatalytic H 2 O 2 production from H 2 O and molecular O 2 using a heterojunction photocatalyst made up of ZnIn 2 S 4 /Ni 12 P 5 /g-C 3 N 4 (NCZ) under visible light irradiation. The photocatalysts were synthesized via a high-temperature treatment of nickel and phosphorous precursors with g-C 3 N 4 followed by decoration of ZnIn 2 S 4 . 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 Ni 12 P 5 and the conduction band maximum (CBM) from ZnIn 2 S 4 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-C 3 N 4 to that of ZnIn 2 S 4 using Ni 12 P 5 as an electron bridge. Moreover, the reduced band gap of the ternary heterojunction played a key role in its higher efficiency.