Palygorskite supported rare earth fluoride for photocatalytic nitrogen fixation under full spectrum

Abstract Nitrogen reduction to ammonia under mild conditions using cost-effective and full spectrum solar-driven photocatalyst is promising from an industrial perspective. Herein, sensitizer Yb3+ and activator Tm3+ co-doping LaF3 supported by palygorskite (Pal) nanocomposites (LaF3:Yb3+, Tm3+/Pal) are successfully prepared by the microwave hydrothermal method. The photocatalytic nitrogen fixation is performed using LaF3:Yb3+, Tm3+/Pal as photocatalyst. The impact of Tm3+ doping ratio and loading amount on the nitrogen fixation are explored. Results demonstrate that modified natural Pal nanorods have large surface area facilitating the immobilization of rare earth fluoride nanoparticles. The total amount of ammonia can reach the highest of 43.2 mg/L under solar light irradiation, while 5.7 mg/L can be achieved even under near infrared (NIR) light irradiation. The enhanced photocatalytic nitrogen fixation ability is ascribed to the upconversion capability of LaF3:Yb3+, Tm3+ which converts NIR into visible and UV light, improving the utilization of full solar spectrum. Meanwhile, LaF3:Yb3+, Tm3+ and modified Pal form an indirect Z-scheme heterostructure mediated by fluorine vacancy (FV), favoring the separation of the photogenerated electron-holes and preservation of high reduction–oxidation potentials. Additionally, the defective FV efficiently provides active sites beneficial for the adsorption and dissociation of N2.