Nanostructured NiCo₂O₄/BiVO₄ Heterojunctions for Visible-Light Photocatalytic H₂O-to-H₂O₂ Synchronized Organic Pollutant Oxidation

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.