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

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 MgAlTiLDH/g-C3N4 heterojunction was fabricated by in-situ growth of oxygen vacancy rich MgAlTi-LDH on ultrathin gC3N4 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/g-C3N4 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 g-C3N4, respectively. Upon natural sunlight irradiation, MgAlTi-LDH/g-C3N4 can degrade 95 % of MB after 130 min of irradiation. The improvement of photocatalytic activity of MgAlTi-LDH/g-C3N4 was attributed to the synergistic effect of MgAlTi-LDH and g-C3N4, 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.