Hierarchical UiO-66(−NH2)/CuInS2 S-Scheme Photocatalyst with Controlled Topology for Enhanced Photocatalytic N2 Fixation and H2O2 Production

The fabrication of defect rich S-scheme binary heterojunction system with enhanced space charge separation and mobilization is a pioneering approach for improving photoreduction efficiency towards the production of value added chemicals. Herein, we have rationally fabricated an atomic sulfur defect-rich hierarchical UiO-66(-NH2)/CuInS2 n-p heterojunction system by uniform dispersion of UiO-66(-NH2) (UN66) nanoparticles over the surface of hierarchical CuInS2 nanosheets under mild conditions. The designed heterostructures are characterized by using different structural, microscopic, and spectroscopic techniques. The hierarchical CuInS2 (CIS) component shows surface sulfur defects leading to creation of more surface exposed active sites with improved absorption of visible light and augmented diffusion of charge carriers. The photocatalytic performance of prepared UiO-66(-NH2)/CuInS2 heterojunction materials is explored for N2 fixation and O2 reduction reactions (ORR). The optimal UN66/CIS20 heterostructure photocatalyst exhibited outstanding N2 fixation and O2 reduction performances with yields of 398 and 4073 μmol g-1 h-1 under visible light illumination, respectively. An S-scheme charge migration pathway coupled with improved radical generation ability accounted for the superior N2 fixation and H2O2 production activity. This research work furnishes a new perspective on the synergistic effect of atomic vacancy and an S-scheme heterojunction system toward enhanced photocatalytic NH3 and H2O2 production using a vacancy-rich hierarchical heterojunction photocatalyst.