A combined experimental and computational study on a nanohybrid material for potential application in NIR photocatalysis

Abstract

Complete utilization of solar light in the photocatalytic reaction is of paramount importance for efficient conversion of solar light. Although NIR constitutes almost 50% of the solar energy, there are very few efforts towards its effective utilization in photocatalysis. The difficulty of NIR usage is its associated low energetic photons, which can lead to exciton generation only for low band-gap semiconducting systems, which is sometime not enough to initiate photocatalytic process. Moreover, these type of systems have very fast charge recombination process. Assembling one low band gap semiconductor with a wide bandgap semiconductor to form a nanohybrid heterojunction could be an efficient NIR harvesting photocatalyst. Herein, we report a novel CuS-ZnO nanohybrid, bound by a cysteine ligand, to exhibit efficient photocatalytic performance using the NIR fraction of the solar light spectrum. Raman spectroscopy and picosecond resolved studies have been carried out to confirm the electronic coupling of the nanohybrid. An improved photocatalytic activity towards degradation of methyl orange (MO) was observed by the nanohybrid compared to its individual counterparts (ZnO and CuS) under NIR light illumination. First principles investigations have guided us in obtaining an insight to the photocatalytic process. Computationally predicted band alignment implies that the nanohybrid forms a type II heterojunction. An increment of significant charge separation from the conduction band of CuS to those of ZnO is the key mechanism behind the enhanced photocatalysis.