Defect-engineered TiO2/Zn0.5Cd0.5S S-Scheme heterojunction for photocatalytic H2 evolution

H₂, as a renewable source of energy, is regarded as an ideal alternative to traditional fossil fuels due to its excellent density of energy, sustainability, and ecological friendliness. Solar-driven semiconductor photocatalytic technology is a potential approach for H₂ evolution. Importantly, it is significant to explore the efficient photocatalysts to strengthen photocatalytic H₂ evolution. TiO₂ has been extensively studied as a water-splitting photoanode for its excellent chemical durability, relatively inexpensive cost, and harmlessness. However, the inadequate light-harvesting ability, quick photogenerated carrier recombination, and inferior redox capacity of TiO₂ restrict the photocatalytic activity. To address these problems, designing and constructing a defect‐engineered TiO₂-based S-scheme heterojunction is of considerable significance for achieving high-efficiency photocatalytic activity. Zn_0.5Cd_0.5S, a ternary metal sulfide with excellent visible light absorption and stability, matches TiO₂ well for S-scheme heterojunction construction. Yet, the synergistic integration of defect engineering with the S-scheme heterojunction in TiO₂/Zn_0.5Cd_0.5S remains unexplored. Therefore, constructing a defect-engineered TiO₂/Zn_0.5Cd_0.5S S-scheme heterojunction would be valuable for advancing the progress of photocatalysis.

Recently, a research team led by Dr. Bin Sun and Prof. Guowei Zhou from Qilu University of Technology (Shandong Academy of Sciences), China presents a defect-engineered TiO₂/Zn_0.5Cd_0.5S S-Scheme heterojunction for photocatalytic H₂ evolution. An oxygen vacancy-rich TiO₂-Ov/Zn_0.5Cd_0.5S S-scheme heterojunction photocatalyst with dual charge transfer pathways achieves high-efficiency photocatalytic H₂ evolution activity. Meanwhile, the S-scheme charge transfer pathway, dynamic behavior, and surface reaction active sites are systematically analyzed. The results were published in Chinese Journal of Catalysis (DOI: 10.1016/S1872-2067(25)64909-6).

The defect-engineered S-scheme heterojunction is designed and constructed through a hydrothermal method, achieved by in situ growth of Zn_0.5Cd_0.5S nanoparticles onto oxygen vacant TiO₂ flower-like microspheres to establish TiO₂-Ov/Zn_0.5Cd_0.5S heterojunction. Remarkably, the optimal heterojunction achieves a superior H₂ evolution rate of 15.31 mmol g^–1 h^–1, surpassing those of TiO₂, TiO₂-Ov, Zn_0.5Cd_0.5S, and defect-free TiO₂/Zn_0.5Cd_0.5S. Meanwhile, TiO₂-Ov/Zn_0.5Cd_0.5S S-scheme heterojunction also exhibits excellent cycling stability. Furthermore, the H adsorption free energy of S site approaching zero indicates an optimal adsorption-desorption equilibrium for H₂ evolution.

Within the photocatalytic system, the synergistic effects of oxygen vacancy and S-scheme heterojunction endow excellent light absorption ability, effective spatial separation and transfer of photo-induced charge, and superior redox capacity. In particular, the presence of dual photo-induced charge transfer pathways significantly enhances the trapping efficiency of photo-induced electrons in TiO₂-Ov and effectively promotes the combination of photo-induced electrons in TiO₂-Ov with holes in Zn_0.5Cd_0.5S. Furthermore, the in-situ characterization and DFT calculation further verify the S-scheme charge transfer mechanism in TiO₂-Ov/Zn_0.5Cd_0.5S heterojunction. This work provides a feasible strategy for constructing high-performance S-scheme heterojunction photocatalyst with defect engineering for solar to H₂ energy conversion. The results were published in Chinese Journal of Catalysis (DOI:10.1016/S1872-2067(25)64909-6)

About the journal

Chinese Journal of Catalysis is co-sponsored by Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Chinese Chemical Society, and it is currently published by Elsevier group. This monthly journal publishes in English timely contributions of original and rigorously reviewed manuscripts covering all areas of catalysis. The journal publishes Reviews, Accounts, Communications, Articles, Highlights, Perspectives, and Viewpoints of highly scientific values that help understanding and defining of new concepts in both fundamental issues and practical applications of catalysis. Chinese Journal of Catalysis ranks among the top six journals in Applied Chemistry with a current SCI impact factor of 17.7.

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