2D/2D heterojunction of MgAlTi-LDH/g-C3N4 with oxygen vacancy engineering for enhanced photocatalytic activities under natural sunlight

Abstract

Semiconductor photocatalysis is an ideal method for wastewater treatment. However, the rapid recombination of photogenerated electron-hole pairs limits the improvement of photocatalytic efficiency. Constructing heterostructures by different energy band-matched semiconductors and surface defect engineering are considered as effective strategies to inhibit the recombination of photogenerated electron-hole pairs. Herein, a novel MgAlTi-LDH/-CN heterojunction was fabricated by growth of oxygen vacancy rich MgAlTi-LDH on ultrathin -CN nanosheets first time for the degradation of methylene blue (MB) under natural sunlight. The optical absorption properties, crystalline phase, microstructure, and morphological analysis of the fabricated materials are subsequently characterized by XRD, FT-IR, UV–vis DRS, TEM, BET and XPS. Owing to Ti-doping, oxygen vacancy rich MgAlTi-LDH exhibited superior photocatalytic activity for MB degradation, which was 5.5 times of that of MgAl-LDH. Furthermore, MgAlTi-LDH/-CN heterostructures showed a higher photocatalytic activity under visible light irradiation, which was 5.9, 4.9, and 3.2 times of that of MgAl-LDH, MgAlTi-LDH and -CN, respectively. Upon natural sunlight irradiation, MgAlTi-LDH/-CN can degrade 95 % of MB after 130 min of irradiation. The improvement of photocatalytic activity of MgAlTi-LDH/-CN was attributed to the synergistic effect of MgAlTi-LDH and -CN, surface oxygen vacancies, and heterostructure interface. This work promotes a new strategy to synthesize high-efficiency photocatalysts for the removal of organic pollutants from wastewater by constructing heterojunctions with surface defects.