g-C3N4 modified with non-precious metal Al with LSPR as an efficient visible light catalyst

Abstract

The issue of water pollution has emerged as a formidable challenge, prompting a pressing need for solutions. The utilization of metal nanoparticles with surface plasmon resonance and semiconductor composite photocatalysts is regarded as a highly effective approach to solve this problem. g-C₃N₄ is an effective catalyst for the degradation of organic pollutants. Its photocatalytic performance is usually enhanced by the use of the noble metal Au Ag. However, the high cost of these materials limits their application. In this study, we present the synthesis of Al NPs/g-C₃N₄ nanocomposites using the bridging effect of ligands. The characterized of transmission electron microscopy (TEM), X-ray diffractometer (XRD) and ultraviolet-visible spectroscopy (UV-Vis) proved that Al NPs/g-C₃N₄ with a wider light absorption range were successfully synthesized. The effects of ligands, (glutathione (GSH), glutamic acid (GAG), and cysteine (CYS)), Al diameter (40 to 200 nm) and the ratio of Al to g-C₃N₄ (1:1 to 5:1) on the photocatalytic degradation of methylene blue (MB) by Al NPs/g-C₃N₄ were also evaluated. The results showed that the optimum degradation efficiency of Al NPs/g-C₃N₄ for MB at 5 mg/L reached 100% within 60 min, which was 11 times higher than that of pure g-C₃N₄. The principal analysis of Al enhancing the photocatalytic performance of g-C₃N₄ was studied through transient photocurrent spectroscopy (TPC), electrochemical impedance spectroscopy (EIS), and steady-state transient fluorescence spectroscopy (PL). The results confirmed that hot carriers generated by localized surface plasmon resonance (LSPR) of Al nanoparticles increase the carrier concentration. In addition, the Schottky barrier generated by Al and g-C₃N₄ could also improve the carrier separation rate and increase the carrier lifetime. This work is expected to solve the problem of organic wastewater treatment and lay the foundation for subsequent research on photocatalysis.

Keywords: Al nanoparticles; LSPR; Photocatalytic; Water pollution; g-C3N4.