Simple fabrication of Fe3O4/C/g-C3N4 two-dimensional composite by hydrothermal carbonization approach with enhanced photocatalytic performance under visible light

The construction of a multifunctional two-dimensional (2D) composite photocatalyst is of great significance because such a composite can exhibit enhanced catalytic performance and improved practical usability in contrast to a single component catalyst. Herein, a ternary photocatalyst composed of g-C3N4, a carbon layer (C), and Fe3O4 nanoparticles was successfully synthesized by a facile one-pot hydrothermal carbonization (HTC) method from g-C3N4, glucose, and FeCl3. The resultant composite, Fe3O4/C/g-C3N4, had an ordered 2D heterostructure and exhibited enhanced visible-light-driven photocatalytic performances and good magnetic recyclability. The kobs for Cr(VI) photoreduction (or dimethoate photodegradation) over Fe3O4/C/g-C3N4 was 20.9-fold (or 2.1-fold) of that over g-C3N4. Comparative study of Fe3O4/C/g-C3N4, C/g-C3N4, and g-C3N4 on their optoelectronic properties revealed that this enhanced photocatalytic activity was mainly due to rapid photogenerated electron transport from the g-C3N4 component to carbon and/or Fe3O4, which effectively suppressed the recombination of photogenerated electrons and holes. In addition, the good surface adsorption capacity of the carbon component towards Cr(VI) also contributed to Cr(VI) photoreduction over Fe3O4/C/g-C3N4. Finally, a reasonable photocatalytic reaction mechanism of Fe3O4/C/g-C3N4 was proposed based on the results of trapping experiments. This study is not only limited to developing a high-performance g-C3N4 based photocatalyst, but also expected to provide a green, facile, and cost-efficient strategy to combine 2D materials with a carbonaceous layer and other functional components for a multifunctional system.