Nanostructured NiCo<sub>2</sub>O<sub>4</sub>/BiVO<sub>4</sub> Heterojunctions for Visible-Light Photocatalytic H<sub>2</sub>O-to-H<sub>2</sub>O<sub>2</sub> Synchronized Organic Pollutant Oxidation
Ling‐Wei Wei, Shou‐Heng Liu, H. Paul Wang
Abstract
Photocatalytic H2O2 generation using unlimited solar energy for in situ oxidation of organic pollutants in wastewater has been environmentally attractive. Photocatalytic H2O-to-H2O2(aq)reaction by BiVO4, however, suffered from relatively low yields (e.g., 24 μM h–1) under visible-light irradiation, mainly due to its high recombination rate of charge carriers. Herein, nanostructured NiCo2O4/BiVO4 Z-scheme heterojunctions were prepared to increase the oxygen reduction reaction for a higher H2O2 yield rate (than BiVO4 by 16 times approximately). Additionally, highly reactive superoxide (•O2–) and hydroxyl (•OH) radicals from the photocatalytic H2O-to-H2O2 process enhanced oxidation of a representative organic pollutant (i.e., methylene blue) under visible-light irradiation. The photocatalytic oxidation rate constant was as high as 2 × 10–7 M–1 s–1. This visible-light photocatalytic H2O-to-H2O2 synchronized oxidation of an organic pollutant by the nanostructured NiCo2O4/BiVO4 heterojunctions demonstrates the possibility for a potential energy self-sufficient organic wastewater treatment process.