N-Fe-Gd co-doped TiO2/g-C3N4 nanosheet hybrid composites with superior photocatalytic dye degradation

In this study, composite consisting of thermally exfoliated g-C3N4 nanolayer/N, Gd, and Fe co-doped TiO2 (N-Gd-Fe-TiO2/g-C3N4) was successfully fabricated by a facile in situ synthetic method. The effects of nanometer heterojunction on the structure, chemical composition, light absorption property, and carrier transport of the hybrid composites were systematically studied. The amount of g-C3N4 nanosheets in the composites plays a crucial role in regulating the dispersion structure and morphology of the composites. Among the synthesized N-Fe-Gd-TiO2/g-C3N4, the sample with 3.4wt% of N-Gd-Fe-TiO2 in the composite, denoted as 3.4%GFNT/CN, exhibited an ideal heterojunction structure, and showed the highest photocatalytic rate of 98.3%, which is 1.68 and 1.42 times to that of N-Gd-Fe-TiO2 and exfoliated g-C3N4 nanosheets, respectively, and its rate constants are 5.6 and 4.4 times than that of N-Gd-Fe-TiO2 and exfoliated g-C3N4 2D nanosheets, respectively. The narrow band gap and weak photoluminescence peak intense of 3.4%GFNT/CN demonstrated the formation of well-contacted nanoscale heterojunctions in the composites. The heterojunction structure widened the light response wavelength of the catalyst, and simultaneously promoted the efficient separation of the photogenic carriers, therefore enhanced the photocatalysis performance of the resulting composite.Graphical abstractN-Gd-Fe-TiO2/g-C3N4 composite was successfully synthesized and displayed superior electron–hole separation efficiency and photocatalytic activity owing to the heterojunction structure.