CIS QDs nucleated on oxygen vacancy rich BOI microplates: a hybrid photocatalyst with enhanced green energy production via mediator free Z-scheme dynamics

Abstract

Designing a promising and environmentally benign semiconductor photocatalyst for photocatalytic H₂ and O₂ production with a benchmark solar to chemical energy conversion efficiency is a challenging task. In this regard, CuInS₂ (CIS) quantum dots (QDs) coupled with oxygen vacancy rich BiOI (BOI) microplates (MPs) were fabricated via an in situ reflux technique, resulting in the formation of a CIS–BOI heterostructure. Additionally, the oxygen vacancies (Ov) in the binary hybrid, as evidenced from Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) analyses, play a vital role in enhancing the water splitting reaction via a lower activation energy barrier. Further, the nucleation of OD CIS QDs on the 2D BOI MPs resulted in strong interfacial contact, encouraging effective exciton separation that resulted in improved water-splitting activity. The 15% CIS–BOI composite shows tremendous improvement in H₂ and O₂ production activity, i.e., 615.5 μmol h⁻¹ (ACE = 9.84%) and 570.8 μmol h⁻¹ (ACE = 9.16%) with 9.44 × 10¹⁶ and 8.76 × 10¹⁶ number of H₂ and O₂ molecules per s, respectively. This increment can be attributed to mediator-free Z-scheme charge transfer dynamics, where highly reducing electrons reside on the CIS QDs and powerful oxidizing holes are present on the BOI surface. This investigation gives a new perspective on designing cocatalyst free, direct Z-scheme oriented oxygen vacancy rich hybrid systems for photocatalytic water redox reactions.