Synthesis of Z-schemes 0D–3D heterojunction bi-functional photocatalyst with ZnInCuS alloyed QDs supported BiOI MF for H2O2production and N2fixationElectronic supplementary information (ESI) available: The ESI file is available, which contains chemicals information; synthesis of pristine ZCIS QD and BOI MF; characterization techniques; photocatalytic experiments; fabrication of working electrodes; FESEM images of ZCIS and BOI; HRTEM image of ZCIS QD with particle size distribution curve; color-mapping images of ZCIS–BOI composites; XPS survey; H2O2/N2reaction setup; calculation of solar-to-chemical conversion efficiency (SCC%); XRD, absorbance plot before and after use; PL plot of BOI, and NBT. See DOI: https://doi.org/10.1039/d2cy02107b

Photocatalytic H2O2and NH3production are considered to be clean and encouraging technologies towards sustainable solar-to-chemical energy conversion. Exploiting the coupling of 0D–3D semiconductors, herein, we have developed a series of ZnCuInS–BiOI (ZCIS/BOI) bi-functional heterojunction composites for the first time with excellent morphological interface contact viaan in situreflux synthetic strategy. Additionally, the development of a heterojunction on the interface of two semiconductors with feasible band alignments, enriched defect sites and built-in-electric field play a pivotal role in the separation and transportation of charge carriers. The optimum Z-scheme heterojunction catalyst (ZCIS–BOI(1 : 1)) exhibits excellent activity towards H2O2and NH3generation, i.e., 2135.2 μmol h−1g−1(SSC = 0.24%) and 1610.5 μmol h−1g−1(SCC = 0.36%), respectively, with superb reusability (4 cycles). The observed enhancement in photocatalytic performance corresponds to superior photon absorption ability, feasible band alignment, greater exciton separation/transfer efficiency, and effective adsorption/activation. Furthermore, experiments investigating the influence of the sacrificial agent, pH, purging gas type, and scavenger were performed to determine the optimum conditions and mechanism. This research contributes the idea of constructing alloyed QD based Z-scheme heterojunctions with hierarchical defect sites towards robust photocatalytic hydrogen peroxide and ammonia production under ambient conditions.