The photocatalytic CO₂ reduction technology has become a research hotspot in the field of carbon neutrality because it can simultaneously achieve "carbon fixation + solar energy conversion". CeO₂ has been widely applied in the field of photocatalysis due to the advantages of CO₂ adsorption by oxygen vacancies (Ce³⁺-O^-) and the carrier buffering capacity of the Ce³⁺/Ce⁴⁺redox couple. Bi₂S₃, due to its narrow bandgap (1.3–1.7 eV), unique layered structure, and broad light absorption range, has become an ideal candidate for broadening the spectral response. When constructing a heterojunction between Bi₂S₃ and CeO₂, the oxygen vacancies of CeO₂ can serve as CO₂ adsorption anchors, and the built-in electric field at the interface between the two can promote the directional migration of electrons and holes. In-situ introduction of metallic Bi nanoparticles can enhance the visible light absorption through the Surface Plasmon Resonance (SPR) effect and further inhibit the recombination of photogenerated carriers as electron traps. Meanwhile, one-dimensional nanofibers, because of their high aspect ratio, continuous pore structure, and mechanical stability, not only provide a three-dimensional template for the in-situ growth of Bi@Bi₂S₃, but also form microchannels through the interweaving of fibers, promoting the diffusion of CO₂ and the desorption of products, making them an ideal choice for photocatalytic carriers.

Experiment In this study, CeO₂ fibers prepared by the electrospinning technique were used as the substrate, ascorbic acid was used as the reducing agent, and deionized water, ethylene glycol, ethanol, and ethylenediamine were used as solvents respectively. Combined with the hydrothermal synthesis method, Bi@Bi₂S₃ composite CeO₂ nanofibers in the shapes of nanosheets, nanospheres, nanorods, and nanocubes were prepared. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) revealed that Bi₂S₃ was constructed on the surface of CeO₂ fibers in different morphologies, and the in-situ generated Bi nanoparticles were uniformly anchored at the interface of Bi₂S₃, forming a unique three-dimensional structure. X-ray Photoelectron Spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR) confirmed that Bi₂S₃ and CeO₂ achieved directional separation of carriers through a type-S heterojunction. Highly active electrons were retained in the conduction band of Bi₂S₃ for CO₂ reduction, and strongly oxidizing holes were retained in the valence band of CeO₂ to drive water oxidation. The SPR effect of Bi nanoparticles enhanced the visible light absorption ability, and at the same time, they served as electron bridges to shorten the charge migration path.

The photocatalytic CO₂ reduction reaction was carried out using a self-made airtight reaction device, with a 300 W Xe lamp (AM 1.5G filter, 100 mW·cm^-2) as the light source to simulate sunlight. After 3 hours of light irradiation, the Bi@Bi₂S₃/CeO₂ ternary composite fiber system showed excellent photocatalytic CO₂ activity. Among them, the nanosheet structure, with its high specific surface area and large pore volume, could form more active sites, resulting in the best photocatalytic CO₂ reduction effect. The yields of CO and CH₄ reached 14.58 μmol·g^-1·h^-1and 5.68 μmol·g^-1·h^-1respectively. Different structural characteristics such as the high light absorption efficiency of the cavity in the pompon structure, the strong local electric field at the edges of the cube structure, and the rapid separation of products in the rod-like structure all effectively improved the CO₂ reduction efficiency. The generation rates of CO were 12.26, 11.71, and 10.55 μmol·g^-1·h^-1 respectively, and the generation rates of CH₄ also reached 4.34, 4.12, and 3.38 μmol·g^-1·h^-1respectively. Meanwhile, the Bi@Bi₂S₃/CeO₂ ternary composite fibers showed good photocatalytic stability. Under the above reaction conditions, after 5 consecutive cycles (accumulated 15 hours), the yields of CO and CH₄ still remained above 90% of the initial values.

In this study, a Bi@Bi₂S₃/CeO₂ composite photocatalyst was successfully prepared using CeO₂ nanofibers as the substrate and combining the hydrothermal method. Material characterization showed that Bi₂S₃ and CeO₂ constructed a S-scheme heterojunction through interfacial interaction, achieving efficient separation of photogenerated carriers. Highly active electrons were retained in the conduction band of Bi₂S₃ for CO₂ reduction, and holes were retained in the valence band of CeO₂ to drive water oxidation. The Bi nanoparticles deposited on the surface enhanced the visible light absorption through the SPR effect, and served as electron bridges to accelerate charge migration and prolong the lifetime of photogenerated carriers. Bi@Bi₂S₃/CeO₂ showed excellent photocatalytic CO₂ reduction performance. This study provides a new idea for the design of efficient CeO₂-based photocatalysts: retaining highly active carriers through a S-scheme heterojunction and optimizing light absorption and charge transfer by combining the SPR effect of non-noble metal nanoparticles. This strategy has important reference value for the development of low-cost and highly stable CO₂ reduction catalysts and is expected to promote the practical application of photocatalytic technology in the field of carbon cycle.