Robust direct Z-scheme exciton transfer dynamics by architecting 3D BiOI MF-supported non-stoichiometric Cu0.75In0.25S NC nanocomposite for co-catalyst-free photocatalytic hydrogen evolution

Abstract

Designing promising photocatalytic systems with wide photon absorption and better exciton separation ability is a cutting-edge technology for enhanced solar-light-driven hydrogen production. In this context, non-stoichiometric Cu_0.75In_0.25S nanocrystals (CIS NCs) coupled with three-dimensional (3D) BiOI micro-flowers (BOI MFs) were synthesized through an ultra-sonication strategy forming a CIS–BOI heterojunction, which was well supported by XRD, photocurrent, XPS and Mott–Schottky analyses. Further, the co-catalyst-free CIS–BOI binary hybrid shows improved hydrogen evolution, i.e., 588.72 μmol h⁻¹, which is 3.2 times greater than the pristine CIS NC (183.97 μmol h⁻¹). Additionally, the binary composite confers an apparent conversion efficiency (ACE) of 9.44% (8.90 × 10¹⁶ number of H₂ molecule per sec), which is extensively attributed to the robust charge carrier separation and transfer efficiency via the direct Z-scheme mechanism (proved through superoxide and H₂ evolution activity). Moreover, the broad photon absorption range and productive exciton separation over the CIS–BOI composite are substantially justified by UV-Vis DRS, PL, EIS and photocurrent measurements.