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.

Boosting the photocatalytic performance of Bi2Fe4O9 through formation of Z-scheme heterostructure with In2S3: Applications towards water decontamination.

Design of biocompatible nano-heterostructure photocatalyst with broad UV-visible spectrum response and strong redox ability is a promising approach with potential application in micropollutant degradation and pathogen deactivation from aqueous sources. Herein, we have reported the facile fabrication of In2S3/Bi2Fe4O9 (ISxBFO) binary heterostructure by hydrothermally depositing In2S3 nanoparticles (20-40 nm) over Bi2Fe4O9 nanocuboids/nanoplates prepared by combustion synthesis route. In depth characterization study revealed broad spectrum UV-Vis absorption, large interfacial contact, improved charge carrier separation and mobility and a longer excited state life time (4.7 ns) for the ISxBFO heterostructure materials. The integration of In2S3 with Bi2Fe4O9 strongly boosts the optoelectrical and photocatalytic property of pristine Bi2Fe4O9. The ISxBFO heterostructure material exhibited enhanced photocatalytic efficiency for aqueous phase degradation of sulfamethoxazole antibiotics (kapp = 0.06 min-1) and phenyl urea herbicides (kapp = 0.028 min-1) with reaction rates 3-8 times higher than the pure BFO component. The MTT assay experiments confirmed non-cytotoxic nature of treated sulfamethoxazole and diuron solutions. The composite materials also displayed convincing antibacterial behavior towards toxigenic Vibrio cholerae pathogen. Haemagglutination assay study revealed excellent biocompatibility of the binary composite up to 200 mg L-1. Radical trapping study suggested expeditious generation of •OH and •O2- radicals over the ISxBFO surface which is nearly 3.8 and 2.3 times higher than pure BFO and In2S3 respectively. The occurrence of a direct Z-scheme mechanism is inferred from radical trapping and XPS study which accounted for the improved photocatalytic activity and strong radical generation property of the ISxBFO heterostructure material.