Recent Advances in Nanoscale Engineering of Ternary Metal Sulfide-Based Heterostructures for Photocatalytic Water Splitting Applications

Ternary metal sulfides (TMSs) have been widely documented as an important subgroup of semiconducting materials in solar water splitting into hydrogen (H 2 ) fuel. Recently, interest has been rekindled in this specific branch of chalcogenide materials, particularly in the opportune integration of indium-based TMSs with emerging materials such as MXenes, metal–organic frameworks (MOFs), carbon quantum dots (CQDs), carbon nanofibers (CNFs), and metal-like Mo 2 C for various nanoscale heterojunction formations. In this mini review, recent outstanding advances of TMS-based heterostructures are concisely reviewed. Following an overview of the fundamental rationales of photocatalytic water splitting, a panorama of different indium-based TMSs (ZnIn 2 S 4, CdIn 2 S 4, and CaIn 2 S 4 ) and their heterostructures (Z-scheme, conventional heterojunction, and Schottky junction) are outlined and discussed in terms of mechanistic insights and water splitting application prospects. On top of that, investigations of other burgeoning TMS-based heterostructures are carried out, followed by recommendations on future prospects of emerging TMS-based materials and the key challenges in practical water splitting. It is believed that this critical mini review is timely to bring new advances of TMS-based heterostructures and acts as a reference toward future endeavors in developing highly efficient and stable photocatalytic systems for H 2 generation.