Investigations of znin2s4 as a visible light responsive photocatalyst for hydrogen generation and water purification applications

Abstract

Research on semiconductor photocatalysis has been intensively focused in recent decades for variety of applications such as water disinfection and water splitting. Photocatalysis occurs when a semiconductor photocatalyst is irradiated with energy greater than or equal to its band gap value. Visible light activity of a photocatalyst is most preferred in order to harness maximum solar energy. Low cost, good photostability and ease of availability has put oxide semiconductors on a preferential list of materials for various photocatalytic applications. However their valence band comprises of deep 2p oxygen orbital lying at a potential of 3 eV making the effective band gap (Eg) to fall in the UV region. For the efficient utilization of the solar spectrum, the band gap of a photocatalyst should be in the visible region with Eglt 3 eV. This promotes the need of a material with narrow band gap having suiTable valence band positions. Metal sulfides known for their shallow valence band consisting of S3p levels at more negative potential than O2p levels of metal oxides could be an alternative to oxide semiconductors. However their stability during photocatalysis has always been a point of concern as binary sulfides easily undergo photocorrosion. Hence in view of the prospective applications, ternary semiconductor chalcogenides with hierarchical structures are emerging with greater scope in photocatalysis newline