Synergistic Engineering of Zinc Vacancies and Er-Doping in ZnIn₂S₄ Nanosheets for Enhanced CO₂ Photoreduction via Optimized Charge Dynamics

Abstract

Although extensive research has been conducted on cation vacancies in photocatalysts, the significance of vacancy defects in photocatalytic reactions and deep-going understanding of the intrinsic mechanisms are still limited. Herein, an appropriate introduction of zinc vacancies on ZnIn₂S₄ (ZIS) is rationally designed through Er or La (Er/La)-doping. Aberration-corrected scanning transmission electron microscopy (STEM) directly demonstrates distinct zinc vacancies (V_Zn), which is also confirmed by electron spin resonance analysis. The results of experiments and density functional theory (DFT) calculations manifest that Er/La-doping not only promotes the formation of V_Zn but also enhances the built-in electric field, thus facilitating the rapid transfer of carriers. In addition, femtosecond transient absorption spectroscopy (fs-TAS) reveals that V_Zn induces a supplementary charge transfer pathway, thereby enhancing charge separation efficiency. As a result, the desired photocatalytic CO₂ reduction reaction (CO₂RR) to syngas capacity is finally achieved on Er_0.2-ZIS, with tunable H₂/CO ratios, exceeding that of untreated ZIS by over 2 times. This study not only exploits a novel avenue to develop high-activity cation vacancies photocatalysts but also provides new perspectives in regulating the photogenerated carrier dynamics.

Keywords

built-in electric field / doping / photocatalytic CO₂ reduction reaction / syngas / vacancy defects

References

[1] S. Pye, S. Bradley, N. Hughes, J. Price, D. Welsby, and P. Ekins, “An Equitable Redistribution of Unburnable Carbon,” Nature Communications 11 (2020): 3968.

[2] J. Chen, Q. Xie, M. Shahbaz, M. Song, and Y. Wu, “The Fossil Energy Trade Relations Among Brics Countries,” Energy 217 (2021): 119383.

[3] S. Wang, Y. Wang, S. L. Zhang, S. Q. Zang, and X. W. D. Lou, “Supporting Ultrathin ZnIn₂S₄ Nanosheets on Co/N-Doped Graphitic Carbon Nanocages for Efficient Photocatalytic H₂ Generation,” Advanced Materials 31 (2019): 1903404.

[4] X. Jiao, Z. Chen, X. Li, et al., “Defect-Mediated Electron–Hole Separation in One-Unit-Cell ZnIn₂S₄ Layers for Boosted Solar-Driven CO₂ Reduction,” Journal of the American Chemical Society 139 (2017): 7586–7594.

[5] D. Pakhare and J. Spivey, “A Review of Dry (CO₂) Reforming of Methane Over Noble Metal Catalysts,” Chemical Society Reviews 43 (2014): 7813–7837.

[6] X. Pan, F. Jiao, D. Miao, and X. Bao, “Oxide–Zeolite-Based Composite Catalyst Concept That Enables Syngas Chemistry Beyond Fischer–Tropsch Synthesis,” Chemical Reviews 121 (2021): 6588–6609.

[7] X. Li, S. Wang, L. Li, Y. Sun, and Y. Xie, “Progress and Perspective for In Situ Studies of CO₂ Reduction,” Journal of American Chemical Society 142 (2020): 9567–9581.

[8] K. Niu, Y. Xu, H. Wang, et al., “A Spongy Nickel-Organic CO₂ Reduction Photocatalyst for Nearly 100% Selective CO Production,” Science Advances 3 (2017): e1700921.

[9] S. Fang, M. Rahaman, J. Bharti, et al., “Photocatalytic CO₂ Reduction,” Nature Reviews Methods Primers 3 (2023): 61.

[10] J. Ran, M. Jaroniec, and S. Z. Qiao, “Cocatalysts in Semiconductor-Based Photocatalytic CO₂ Reduction: Achievements, Challenges, and Opportunities,” Advanced Materials 30 (2018): 1704649.

[11] M. Humayun, C. Wang, and W. Luo, “Recent Progress in the Synthesis and Applications of Composite Photocatalysts: A Critical Review,” Small Methods 6 (2021): 2101395.

[12] T. Hou, Y. Xiao, P. Cui, et al., “Operando Oxygen Vacancies for Enhanced Activity and Stability Toward Nitrogen Photofixation,” Advanced Energy Materials 9 (2019): 1902319.

[13] Y. Bo, H. Wang, Y. Lin, et al., “Altering Hydrogenation Pathways in Photocatalytic Nitrogen Fixation by Tuning Local Electronic Structure of Oxygen Vacancy With Dopant,” Angewandte Chemie International Edition 60 (2021): 16085–16092.

[14] F. Chen, T. Ma, T. Zhang, Y. Zhang, and H. Huang, “Atomic-Level Charge Separation Strategies in Semiconductor-Based Photocatalysts,” Advanced Materials 33 (2021): 2005256.

[15] X. Chang, T. Wang, and J. Gong, “CO₂ Photo-Reduction: Insights Into CO₂ Activation and Reaction on Surfaces of Photocatalysts,” Energy & Environmental Science 9 (2016): 2177–2196.

[16] X. Yi, S. Zhang, H. Shen, et al., “Atomic Sulfur Dissimilation Remolding ZnIn₂S₄ Nanosheets Surface to Enhance Built-Internal Electric Field for Photocatalytic CO₂ Conversion to Syngas,” Applied Catalysis B: Environmental 338 (2023): 123003.

[17] X. Wang, J. Chen, Q. Li, et al., “Light-Driven Syngas Production Over Defective ZnIn₂S₄ Nanosheets,” Chemistry – A European Journal 27 (2021): 3786–3792.

[18] J. Gao, J. Xue, S. Jia, et al., “Self-Doping Surface Oxygen Vacancy-Induced Lattice Strains for Enhancing Visible Light-Driven Photocatalytic H₂ Evolution Over Black TiO₂,” ACS Applied Materials & Interfaces 13 (2021): 18758–18771.

[19] Y. Liao, R. He, W. Pan, et al., “Lattice Distortion Induced Ce-Doped NiFe-LDH For Efficient Oxygen Evolution,” Chemical Engineering Journal 464 (2023): 142669.

[20] H. J. Lee, S. Back, J. H. Lee, S. H. Choi, Y. Jung, and J. W. Choi, “Mixed Transition Metal Oxide With Vacancy-Induced Lattice Distortion for Enhanced Catalytic Activity of Oxygen Evolution Reaction,” ACS Catalysis 9 (2019): 7099–7108.

[21] S. Xia, Z. Yuan, Y. Meng, et al., “Fabrication of Site Activated and Synergistic Double Vacancy ZnIn₂S₄ for Highly Efficient Bifunctional Photocatalysis: Nitrogen Reduction and Oxidative Degradation,” Journal of Materials Chemistry A 12 (2024): 2294–2308.

[22] Y. He, H. Rao, K. Song, et al., “3D Hierarchical ZnIn₂S₄ Nanosheets With Rich Zn Vacancies Boosting Photocatalytic CO₂ Reduction,” Advanced Functional Materials 29 (2019): 1905153.

[23] Y. Nie, T. Bo, W. Zhou, et al., “Understanding the Role of Zn Vacancy Induced by Sulfhydryl Coordination for Photocatalytic CO₂ reduction on ZnIn₂S₄,” Journal of Materials Chemistry A 11 (2023): 1793–1800.

[24] N. Wang, S. Cheong, D.-E. Yoon, et al., “Efficient, Selective CO₂ Photoreduction Enabled by Facet-Resolved Redox-Active Sites on Colloidal CdS Nanosheets,” Journal of the American Chemical Society 144 (2022): 16974–16983.

[25] H. Gu, H. Zhang, X. Wang, et al., “Robust Construction of CdSe Nanorods@Ti₃C₂ MXene Nanosheet for Superior Photocatalytic H₂ Evolution,” Applied Catalysis B: Environmental 328 (2023): 122537.

[26] S. Li, H. Rui, T. Bao, et al., ”Efficient Visible-Light-Driven CO₂ Reduction Into Tunable Syngas by Cobalt Phthalocyanine Modified Flower-Like ZnIn₂S₄ Nanosheets,” Applied Surface Science 641 (2023): 158492.

[27] W. Yang, H. J. Wang, R. R. Liu, et al., “Tailoring Crystal Facets of Metal–Organic Layers to Enhance Photocatalytic Activity for CO₂ reduction,” Angewandte Chemie International Edition 60 (2021): 409–414.

[28] K. Zhang, M. Dan, J. Yang, et al., “Surface Energy Mediated Sulfur Vacancy of ZnIn₂S₄ Atomic Layers for Photocatalytic H₂O₂ Production,” Advanced Functional Materials 23 (2023): 2302946.

[29] Y. F. Wang, M. Y. Qi, M. Conte, Z. R. Tang, and Y. J. Xu, “New Radical Route and Insight for the Highly Efficient Synthesis of Benzimidazoles Integrated With Hydrogen Evolution,” Angewandte Chemie International Edition England 135 (2023): e202304306.

[30] Y. Hu, F. Zhan, Q. Wang, et al., “Tracking Mechanistic Pathway of Photocatalytic CO₂ Reaction at Ni Sites Using Operando, Time-Resolved Spectroscopy,” Journal of the American Chemical Society 142 (2020): 5618–5626.

[31] X. Jiao, X. Li, X. Jin, et al., “Partially Oxidized SnS₂ Atomic Layers Achieving Efficient Visible-Light-Driven CO₂ reduction,” Journal of the American Chemical Society 139 (2017): 18044–18051.

[32] J. Sheng, Y. He, J. Li, et al., “Identification of Halogen-Associated Active Sites on Bismuth-Based Perovskite Quantum Dots for Efficient and Selective CO₂-to-CO Photoreduction,” ACS Nano 14 (2020): 13103–13114.

[33] L. Zhao, J. Bian, X. Zhang, et al., “Construction of Ultrathin S-Scheme Heterojunctions of Single Ni Atom Immobilized Ti-MOF and BiVO₄ for CO₂ Photoconversion of Nearly 100% to CO by Pure Water,” Advanced Materials 34 (2022): 2205303.

[34] L. Lv, Y. Liu, Y. Huang, T. Li, H. Feng, and Y. Wang, “Robust Construction of CeNi Quantum Dots/Ni-MOL Nanosheets for Superior Photocatalytic CO₂ Reduction,” Journal of Colloid and Interface Science 677 (2025): 909–917.

[35] K. Sivula, “Mott–Schottky Analysis of Photoelectrodes: Sanity Checks Are Needed,” ACS Energy Letters 6 (2021): 2549–2551.

[36] R. Yang, Z. Guo, L. Cai, et al., “Investigation into the Phase–Activity Relationship of MnO₂ Nanomaterials Toward Ozone-Assisted Catalytic Oxidation of Toluene,” Small 17 (2021): e2102744.

[37] X. Wang, X. Wang, J. Huang, S. Li, A. Meng, and Z. Li, “Interfacial Chemical Bond and Internal Electric Field Modulated Z-Scheme S_v-ZnIn₂S₄/MoSe₂ Photocatalyst for Efficient Hydrogen Evolution,” Nature Communication 12 (2021): 4112.

[38] M. Sachs, J. S. Park, E. Pastor, et al., “Effect of Oxygen Deficiency on the Excited State Kinetics of WO₃ and Implications for Photocatalysis,” Chemical Science 10 (2019): 5667–5677.

[39] C. Xing, G. Yu, J. Zhou, et al., “Solar Energy-Driven Upcycling of Plastic Waste on Direct Z-Scheme Heterostructure of V-Substituted Phosphomolybdic Acid/g-C₃N₄ Nanosheets,” Applied Catalysis B: Environmental 315 (2022): 121496.

[40] F. Liu, R. Shi, Z. Wang, Y. Weng, C. M. Che, and Y. Chen, “Direct Z-Scheme Hetero-Phase Junction of Black/Red Phosphorus for Photocatalytic Water Splitting,” Angewandte Chemie 131 (2019): 11917–11921.

[41] D. A. Wheeler and J. Z. Zhang, “Exciton Dynamics in Semiconductor Nanocrystals,” Advanced Materials 25 (2013): 2878–2896.

[42] Z. Wei, W. Wang, W. Li, et al., “Steering Electron–Hole Migration Pathways Using Oxygen Vacancies in Tungsten Oxides to Enhance Their Photocatalytic Oxygen Evolution Performance,” Angewandte Chemie International Edition 60 (2021): 8236–8242.

[43] Y. Li, Q. Wu, Y. Chen, et al., “Interface Engineering Z-Scheme Ti-Fe₂O₃/In₂O₃ Photoanode for Highly Efficient Photoelectrochemical Water Splitting,” Applied Catalysis B: Environmental 290 (2021): 120058.

[44] D. Zu, Y. Ying, Q. Wei, et al., “Oxygen Vacancies Trigger Rapid Charge Transport Channels at the Engineered Interface of S-Scheme Heterojunction for Boosting Photocatalytic Performance,” Angewandte Chemie International Edition England 63 (2024): e202405756.

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2025 The Author(s). Carbon Neutralization published by Wenzhou University and John Wiley & Sons Australia, Ltd.