Construction of oxygen vacancy-rich MoO3-x and NiFe-LDH p-n heterojunction for enhanced carrier separation to promote photoelectrochemical oxidation of pollutants and hydrogen precipitation

Abstract

In this work, a novel portable photoanode consisting of MoO3-x/NiFe@NF with excellent photoelectrochemical (PEC) performance and multifunctional applications was synthesized using a simple hydrothermal and electrodeposition method. In a visible-light-driven PEC system, the photoanode was able to simultaneously promote the degradation of tetracycline and the generation of hydrogen. The degradation efficiency of MoO3-x/NiFe@NF for TC (20 mg/L) was up to 99.9 %. The production of hydrogen (H2) at the cathode could be at most 32.07 μmol cm−2 within 100 min. In addition, the MoO3-x/NiFe@NF photoanode exhibited a positive bactericidal effect against Gram-negative bacteria (E. coli) which could be completely removed within 20 min under the synergistic effect of visible light and voltage. The improved photoelectrocatalytic efficiency is attributed to the built-in electric field resulting from the formation of a p-n heterojunction between MoO3-x and NiFe-LDH. Under the excitation of visible light, the built-in electric field is able to promote the separation and transmission of the photogenerated carriers. A possible mechanism of MoO3-x/NiFe@NF p-n heterojunction was proposed and discussed based on DRS, Mott-Schottky, UPS characterization and DFT theoretical calculations. Furthermore, the electrode's reusability and stability were evaluated through cycling experiments. This work provides a novel p-n heterojunction synthesis method with significant potential for wastewater treatment and future applications in ship ballast water treatment.