Photocatalytic technology, which has the advantages of energy conservation and environmental protection, has shown broad application prospects in the field of energy and environment. Over the past few decades, researchers have been working on the development of low-cost, high-performance, and environmentally friendly photocatalysts. As a stable polymer semiconductor material containing only carbon and nitrogen, G-C3N4 is considered to be a photocatalyst with practical application potential due to its simple synthesis method, stable structure and suitable bands.
At the same time, metal dichalphides (such as CDS and Bi2S3) are considered to be one of the best candidates for the design of highly active heterojunction catalysts due to their unique electronic structure, narrow bandgap and excellent light response. Therefore, the combination of G-C3N4 with Bi2S3 and CDS to construct a ternary heterojunction photocatalyst is expected to promote charge separation, improve light absorption and utilization, alleviate photocorrosion and improve catalyst lifetime.
Recently,Wang Yude, Yunnan UniversityOur research group designed a three-dimensional self-supporting B-G-C3NX Bi2S3 CDS (BDCN BS CS) double-S heterojunction photocatalytic system to achieve multi-channel fast charge transfer. The experimental results showed that the H2 production rate of the prepared BDCN BS CS photocatalyst was as high as 478 mmol1 g1, which is 25 times that of pure DCN;And the degradation rate of geotetracycline (OTC) within 150 min was as high as 986%, which is 156% higher than DCN, which can be attributed to the synergistic effect of the double-S heterojunction and the photothermal effect to promote charge separation and increase the rate of chemical reactions.
More importantly, the structure and morphology of the BDCN BS CS photocatalyst did not change significantly after 5 cycles, indicating that it had excellent stability.
Spectral characterization and theoretical calculations show that the Fermi level difference leads to the redistribution of charges on the contact surface between BS, CS and BDCN, forming a dual built-in electric field pointing to BDCN. Under light conditions, the photogenerated electrons on the CB of BDCN are driven by the built-in electric field and transfer to the VB of BS and CS along two different paths. In addition, in the double-S-type charge transfer mechanism, the photogenerated electrons with weak redox ability and holes are recombined, while the photogenerated carriers with strong redox ability complete the spatial separation.
More importantly, the electrons on the Cb of BS and CS can react with hydrogen protons to form H2 and reduce the surface adsorbed O2 to O2;The photogenerated holes on the VB of BDCn react with water to form OH, which is able to co-degrade pollutants with O2. In addition, the introduction of BS and CS broadens the spectral response of the photocatalyst and produces a strong photothermal effect, which further improves the charge transfer and catalytic reaction rate.
In conclusion, this work elucidates the mechanism of charge spatial separation promoted by double S-type heterojunctions, and provides theoretical guidance for the construction of high-performance S-type photocatalysts with multi-channel charge transfer characteristics.
multi-channel charge transfer in self-supporting b-g-c3nx/bi2s3/cds dual s-scheme heterojunction toward enhanced photothermal-photocatalytic performance. nano energy, 2023. doi: 10.1016/j.nanoen.2023.109164