Photoelectrocatalytic and photocorrosion behavior of MoS2- and rGO-containing TiO2 bilayer photocatalyst immobilized by plasma electrolytic oxidation

Abstract

TiO2-based bilayer photocatalysts including MoS2 light-absorbing and rGO conductive layers were immobilized on titanium supports using the plasma electrolytic oxidation process. Their properties were studied to find out the photoelectrocatalytic activity and photocorrosion stability. Investigating the immobilization process revealed that the formation of the bilayer structure increased the photocatalyst's surface porosity, thickness, and roughness. The preparation of the MoS2/TiO2 and rGO/TiO2 layers synergistically enhanced the light-harvesting capability of the photocatalyst in the visible region and slowed down the recombination of the photoinduced charge carriers. The bilayer photocatalyst improved the photoelectrodegradation kinetics of methylene blue pollutant by 1.6 times under 100 W xenon irradiation and 5 V applied bias. Evaluating the photocorrosion stability in sulfate medium by potentiodynamic polarization and electrochemical impedance spectroscopic analysis confirmed that the polarization resistance of the bilayer photocatalyst improved by 4.5 and 3.8 times compared to the pure TiO2 photocatalyst under dark and xenon light, respectively. Moreover, the Mott-Schottky experiment denoted that the corrosive ion adsorption was reduced in the bilayer photocatalyst.