Solvothermal synthesis of Ag2WO4/Sb2WO6 heterostructures for enhanced charge transfer properties and efficient visible-light-driven photocatalytic activity and stability

Abstract Visible-Light-Driven (VLD) photocatalysis for the dye waste water treatment is impeded by the immediate recombination effect and weak redox potential of the charge carriers. Here, we report the synthesis of silver and antimony tungstate-based novel hybrid composite (Ag2WO4/Sb2WO6) with significant charge carrier partition and strong redox potential for superior photocatalysis in an aqueous medium. The synthesized composite has a matching electronic band structure and synergistic effect—wherein, Ag2WO4 operates as an electron acceptor for Sb2WO6 which in return promotes photoelectron transfer; consequently, leading to charge partition and mitigation of electron-hole recombination. Relying upon the solvothermal approach, a fresh hertojunction was obtained via in-situ development of Sb2WO6 hierarchical structures on Ag2WO4 rods. Samples prepared were tested for their photocatalytic evaluation by degradation of non-azo dye rhodamine B (RhB) under visible-light subjection. The Ag2WO4/Sb2WO4 composite materials (comprising type 2 hetero-junction), displayed enhanced photocatalytic performance in comparison to the pristine Sb2WO6. In addition, the effect of the Ag2WO4 amount on photocatalytic activity was investigated. Among the four different compositions—9 wt%, 12 wt%, 15 wt%, and 18 wt% of Ag2WO4 in the composite (i.e., Ag2WO4/Sb2WO6), the composite with a 15 wt% composition of Ag2WO4 illustrated superior performance. In the case of the composite with 15-wt% of Ag2WO4, the photocatalytic degradation of RhB exhibits kapp value of 3.3x10-2 min-1 which is 5.4 times greater than kapp values of pristine Sb2WO6 (6.1x10-3 min-1). In the radical scavenger tests, ·OH and h+ were identified as the main reactive species—for which a possible photocatalytic mechanism is sketched to display the charge transfer and partition in Ag2WO4/Sb2WO6. Lastly, the composite catalyst revealed an excellent photostability with 86 % retention of photocatalytic efficiency after four catalytic cycles.