Solar-Driven Plasmon-Enhanced Photocatalysis: Co2+-doped ZnFe2O4 Nanospheres embedded ZnO Nanosheets for Effective Degradation of Dyes and Antibiotics

Abstract

To ensure sustainable management and availability of water and sanitation for all, a UN Sustainable Development Goals(SDGs) promising methods to eliminate aqueous pollutants is urgently required. Solar-photocatalysis, driven by freely available sunlight using low-cost, reusable photocatalysts is a promising approach. In this context, we present a novel full-solar-spectrum photocatalyst with promising efficiency attributed to the laddered heterojunction and the Ag-based plasmon enhanced activity. It comprises of Co2+-doped zinc-ferrite nanoparticles embedded on to zinc-oxide sheets that are later conformally coated with small weight fraction(2.5%) of Ag under sunlight. The photocatalyst was optimized for different synthesis methods, post-synthesis temperatures, and different compositions with Orange G as a model pollutant. Unlike reports so far without any scavengers the photocatalyst was effective for highly polluted water of ~740 ppm chemical oxygen demand(COD) and eliminated 66% of it within an hour. We have coined a new term called the Solar Photo-Oxidation Efficiency(SPOE) of the photocatalyst. SPOE was directly dependent on the pollutant concentration and it is found to be 72% for 400 ppm ciprofloxacin with apparent quantum yield of 36%. Promising activity of our photocatalyst continued even after several reuses. The generation of hydroxyl and superoxide radicals were confirmed by respective confirmatory tests, the scavenging tests indicated highest contribution of superoxide radicals and holes in photodegradation. Our photocatalyst is promising and has enormous potential for use in the treatment of diverse pollutants.