Rational Design of Ag Nanoparticles Modified LaFeO ₃ /g-C ₃ N ₄ Heterojunction to Boost Z-Scheme Charge Transfer and Photocatalytic Redox Activity

Photocatalysis holds great potential in sustainable environmental purification and carbon dioxide transformation. Nevertheless, the performance of semiconductor photocatalysts is significantly hampered by fast charge recombination. In this study, LaFeO3 nanospheres were synthesized via a simple hydrothermal method and were subsequently combined with g-C3N4 nanosheets that had undergone mechanical activation and thermal condensation processes. Furthermore, Ag nanoparticles were homogeneously introduced into the composite through photodeposition and impregnation methods, to successfully construct a LaFeO3/Ag/g-C3N4 Z-scheme heterostructure. Composition, microstructure, and photoelectrochemical properties of the photocatalysts were thoroughly investigated using X-ray analysis, microscopy, UV–vis absorption spectroscopy, and photoluminescence (PL) spectroscopy. The LaFeO3/Ag/g-C3N4 composite exhibited outstanding photocatalytic CO2 reduction performance, with CO and CH4 yields of 7.55 and 1.90 μmol·g–1·h–1, respectively, which are 17.9 and 15.8 times higher than those of pure LaFeO3. Additionally, the composite sample with 1% Ag loading demonstrated favorable degradation kinetics for rhodamine B (RhB) and tetracycline (TC) under visible light irradiation, with a remarkable RhB degradation rate of 98.58% within 75 min. Finally, the reduction of CO2 to intermediate products such as *COOH was analyzed using in situ diffuse reflectance infrared Fourier transform spectroscopy (In-situ DRIFTs), and a plausible reaction pathway was proposed.