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.

中文翻译：

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MgAlTi-LDH/g-C3N4 的 2D/2D 异质结与氧空位工程可增强自然阳光下的光催化活性

半导体光催化是一种理想的废水处理方法。然而，光生电子-空穴对的快速复合限制了光催化效率的提高。通过不同能带匹配的半导体构建异质结构和表面缺陷工程被认为是抑制光生电子空穴对复合的有效策略。在此，首次通过在超薄-CN纳米片上生长富含氧空位的MgAlTi-LDH来制备新型MgAlTi-LDH/-CN异质结，用于在自然阳光下降解亚甲蓝（MB）。随后通过 XRD、FT-IR、UV-vis DRS、TEM、BET 和 XPS 对所制造材料的光学吸收特性、晶相、微观结构和形态分析进行表征。由于Ti掺杂，富含氧空位的MgAlTi-LDH表现出优异的MB降解光催化活性，是MgAl-LDH的5.5倍。此外，MgAlTi-LDH/-CN异质结构在可见光照射下表现出更高的光催化活性，分别是MgAl-LDH、MgAlTi-LDH和-CN的5.9、4.9和3.2倍。在自然阳光照射下，MgAlTi-LDH/-CN在照射130分钟后可降解95%的MB。 MgAlTi-LDH/-CN光催化活性的提高归因于MgAlTi-LDH和-CN、表面氧空位和异质结构界面的协同作用。这项工作提出了一种通过构建具有表面缺陷的异质结来合成高效光催化剂以去除废水中有机污染物的新策略。