Co3O4/Bi4O5I2/Bi5O7I C-scheme heterojunction for degradation of organic pollutants by light-emitting diode irradiation

Abstract

Remediation of organic pollutant matrixes from wastewater by photodegradation using different heterojunctions is extensively studied to improve performance for potential application. Brilliant black (BB) and p-nitrophenol (PNP) have been detected in the environment and implicated as directly or indirectly carcinogenic to human health. This work analyzes their elimination from aqueous solutions under visible-light irradiation with composites of cobalt(II, III) oxide and bismuth oxyiodides (Co3O4/Bi4O5I2/Bi5O7I). The synthesized nanomaterial properties were investigated using various techniques such as BET, SEM/EDS, TEM, XRD, FTIR, PL, and UV-vis. All the nanocomposites absorbed in the visible range of the solar spectrum with band gaps between 1.68 and 2.79 eV, and the specific surface area of the CB2 composite increased by 35.8% from that of Bi4O5I2/Bi5O7I. There was an observed massive reduction in the rate of electron and hole recombination, and the band gaps of the composites decreased. The mineralization of PNP and BB was followed by determination of the total organic carbon with reductions of 93.6 and 83.7%, respectively. The main active species were the hydroxyl radicals, while the superoxide anion radical and generated holes were minor as confirmed by radical trapping experiments. The optimum pHs for degradation of PNP and BB were 9.6 and 5.3, respectively. The enhanced performance of the catalyst was due to C-scheme heterojunction formation that reduced the electron and hole recombination rate and was attributed to strong adsorption of the pollutants on the photocatalyst active surface. The nanocomposite is apposite for solar energy-driven remediation of organic pollutants from environmental aqueous samples.