Abstract: Against the backdrop of continuously rising global CO₂ emissions, this study constructs Ce³⁺,Tb³⁺ co-doped LaPO₄/CeO₂ composite fibers via the combination of electrospinning and solvothermal methods, and reveals their synergistic mechanism in photocatalytic CO₂ reduction. XRD and TEM characterizations show that LaPO₄ nanosheets are uniformly constructed on the surface of CeO₂ fibers, forming an S-scheme heterojunction with atomic-level close contact. The built-in electric field at the interface effectively drives the reverse migration of photogenerated carriers, preserving the highly active electrons in the conduction band of LaPO₄ and the strong oxidizing holes in the valence band of CeO₂. The co-doping of Ce³⁺ and Tb³⁺ introduces discrete energy levels into the forbidden band of LaPO₄ through 4f→5d transitions, expanding the light response range to the visible light region of 400~600 nm, and enhances carrier separation efficiency via lattice distortion. Fluorescence spectroscopy and photocurrent experiments demonstrate a significant reduction in carrier recombination rate. Photocatalytic performance tests show that Ce³⁺, Tb³⁺:LaPO₄/CeO₂ achieves CO and CH₄ yields of 12.31 and 9.66 μmol·g⁻¹·h⁻¹ under simulated sunlight, which are 13 and 17 times higher than those of pure LaPO₄, and the yield decay rate is less than 10% after 10 cycles. EPR experiments confirm that the S-scheme heterojunction interface significantly enhances the generation of ·OH and ·O₂⁻ radicals by selectively recombining low-activity carriers. Combined with energy band matching analysis, this system achieves efficient CO₂ reduction through a triple mechanism of "broadened spectral response-strengthened charge separation-activated active sites", providing a new idea for the design of rare earth-based photocatalysts.