DOI: https://doi.org/10.9767/bcrec.20798

SnO2-x/TiO2 Photocatalysts for Dye Removal Under Visible Light: Effect of Sn2+:Sn4+ Ratio on Defect Formation

1Chemical Engineering Department, Faculty of Engineering, Universitas Sultan Ageng Tirtayasa, Cilegon, 42435, Indonesia

2Research Center for Environmental and Clean Technologies, National Research and Innovation Agency (BRIN), KST Samaun Samadikun, Bandung 40135, Indonesia

3Process Integration and Sustainable Systems Research Group, University of Sultan Ageng Tirtayasa, Cilegon 42435, Indonesia

Received: 15 Jul 2026; Revised: 24 Sep 2026; Accepted: 25 Sep 2026; Available online: 1 Oct 2026; Published: 26 Dec 2026.
Editor(s): Istadi Istadi
Open Access Copyright (c) 2026 by Authors, Published by BCREC Publishing Group
Creative Commons License This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
Fulltext View|Download

Citation Format:
Cover Image
Abstract
Sn2+ self-doping of Sn-based photocatalysts is a promising route to visible-light-active photocatalysts, since Sn2+ incorporation narrows the band gap and generates oxygen vacancies that extend light absorption beyond the UV region. However, the Sn2+:Sn4+ molar ratio, which directly controls defect formation, has not been systematically varied in this heterostructure system, so its effect on defect density, band structure, and photocatalytic performance remains unclear. This study investigates that effect. SnO2-x/TiO2 with Sn2+:Sn4+ ratios of 2:1 (ST-2:1) and 1:1 (ST-1:1) were synthesized via a sol-hydrothermal method, characterized by XRD, Raman, XPS, and UV-Vis, and tested for methyl orange (MO) photodegradation under UV-A and visible light. XRD confirmed cassiterite SnO2 as the dominant phase; Raman detected short-range TiO2 ordering. XPS detected Sn2+, Sn4+, Ti3+, Ti4+ in both samples, with oxygen vacancies rising from 12.71% to 17.64% and the valence band maximum shifting upward by 0.54 eV as the Sn2+:Sn4+ ratio increased. Tauc plots gave Eg = 2.21 eV (ST-2:1) and 2.41 eV (ST-1:1), both narrower than pristine SnO2 (3.29 eV) and TiO2 (3.14 eV). ST-2:1 achieved near-complete MO degradation in 10 min under UV-A and 65% in 60 min under visible light, versus only 39% and 10% for ST-1:1, with rate constants 138 and 28 times higher, attributed to its higher defect density and narrower band gap. This study demonstrates that the Sn2+:Sn4+ ratio is an effective, tunable defect-engineering parameter for SnO2-x/TiO2 heterostructures.
Keywords: Photocatalysis; SnO2-x/TiO2; Sn2+:Sn4+; oxygen vacancy; defect engineering
Funding: Ministry of Higher Education, Science, and Technology of the Republic of Indonesia under contract 269/C3/DT.05.00/PL-BARU/2026; National Research and Innovation Agency (BRIN) under contract 62/III.5/HK/2025.

Article Metrics:

Article Info
Section: Original Research Articles
Language : EN
Recent articles
Recent Development in the Synthesis of 1,2,3-Triazole Derivatives Using Nanocatalysts Microwave-Assisted Synthesis of Bismuth Silicate (Bi2SiO5) from Natural Tunisian Sand for Efficient Solar Photocatalytic Degradation of Rhodamine B Potential Conversion of Chicken Bone Waste into Fe2O3-Functionalized Hydroxyapatite Photocatalyst SnO2-x/TiO2 Photocatalysts for Dye Removal Under Visible Light: Effect of Sn2+:Sn4+ Ratio on Defect Formation More recent articles
  1. Rajput, R.B., Jamble, S.N., Kale, R.B. (2022). A review on TiO2/SnO2 heterostructures as a photocatalyst for the degradation of dyes and organic pollutants. Journal of Environmental Management, 307, 114533. DOI: 10.1016/j.jenvman.2022.114533
  2. Zarrin, S., Heshmatpour, F. (2020). Facile preparation of new nanohybrids for enhancing photocatalytic activity toward removal of organic dyes under visible light irradiation. Journal of Physics and Chemistry of Solids, 140, 109271. DOI: 10.1016/j.jpcs.2019.109271
  3. Jorgetto, A.D.O., Boldrin Zanoni, M.V., Orlandi, M.O. (2023). Assessment of the superior photocatalytic properties of Sn2+-containing SnO2 microrods on the photodegradation of methyl orange. Scientific Reports, 13(1), 14774. DOI: 10.1038/s41598-023-40659-8
  4. Yang, G., Yan, Z., Xiao, T. (2012). Preparation and characterization of SnO2/ZnO/TiO2 composite semiconductor with enhanced photocatalytic activity. Applied Surface Science, 258(22), 8704–8712. DOI: 10.1016/j.apsusc.2012.05.078
  5. Zhao, W., He, M., Chen, F., Jin, X., Duan, H., Long, M., Wu, Z., Cao, B., Yu, Y. (2022). One-pot synthesis of flower-like SnS2/SnO2 heterojunction with enhanced visible light photocatalytic performance. Optical Materials, 123, 111934. DOI: 10.1016/j.optmat.2021.111934
  6. Yang, L., Yang, Y., Liu, T., Ma, X., Lee, S.W., Wang, Y. (2018). Oxygen vacancies confined in SnO2 nanoparticles for glorious photocatalytic activities from the UV, visible to near-infrared region. New Journal of Chemistry, 42(18), 15253–15262. DOI: 10.1039/C8NJ00668G
  7. Murugadoss, G., Venkatesh, N., Vijayakumar, B., Panneerselvam, V., Sakthivel, P., Kannappan, T. (2026). Synthesis of Mn(II)-doped SnO2 quantum dots as high-performance photocatalysts for rapid degradation of textile dyes. Chemical Physics Impact, 12, 100998. DOI: 10.1016/j.chphi.2025.100998
  8. Rimoldi, L., Meroni, D., Pargoletti, E., Biraghi, I., Cappelletti, G., Ardizzone, S. (2019). Role of the growth step on the structural, optical and surface features of TiO2 /SnO2 composites. Royal Society Open Science, 6(1), 181662. DOI: 10.1098/rsos.181662
  9. Etshindo, L.A., Sousa, C., Tamiasso-Martinhon, P., Colaço, M.V., Camara, A.R., Rocha, A.S. (2025). SnO2-TiO2 materials for photocatalytic degradation of cationic dye under UV and visible light and a chitosan composite film investigation. Catalysis Today, 444, 114995. DOI: 10.1016/j.cattod.2024.114995
  10. Sadik, W., M. El-Demerdash, A., Nashed, A.W., Mostafa, A.A., Lamie, E. (2024). Synthesis and investigation of optical properties and enhancement photocatalytic activity of TiO2–SnO2 semiconductor for degradation of organic compounds. Scientific Reports, 14(1), 27846. DOI: 10.1038/s41598-024-78755-y
  11. Long, J., Xue, W., Xie, X., Gu, Q., Zhou, Y., Chi, Y., Chen, W., Ding, Z., Wang, X. (2011). Sn2+ dopant induced visible-light activity of SnO2 nanoparticles for H2 production. Catalysis Communications, 16(1), 215–219. DOI: 10.1016/j.catcom.2011.10.002
  12. Manikandan, M., Tanabe, T., Li, P., Ueda, S., Ramesh, G.V., Kodiyath, R., Wang, J., Hara, T., Dakshanamoorthy, A., Ishihara, S., Ariga, K., Ye, J., Umezawa, N., Abe, H. (2014). Photocatalytic Water Splitting under Visible Light by Mixed-Valence Sn3 O4. ACS Applied Materials & Interfaces, 6(6), 3790–3793. DOI: 10.1021/am500157u
  13. Madani, H., Saepurahman (2025). Low-energy light-activated Sn2+-SnO2/TiO2 photocatalyst for water pollutant removal. Journal of Water Process Engineering, 77, 108425. DOI: 10.1016/j.jwpe.2025.108425
  14. Zhu, X., Han, S., Feng, W., Kong, Q., Dong, Z., Wang, C., Lei, J., Yi, Q. (2018). The effect of heat treatment on the anatase–rutile phase transformation and photocatalytic activity of Sn-doped TiO2 nanomaterials. RSC Advances, 8(26), 14249–14257. DOI: 10.1039/C8RA00766G
  15. Ohsaka, T., Izumi, F., Fujiki, Y. (1978). Raman spectrum of anatase, TiO2. Journal of Raman Spectroscopy, 7(6), 321–324. DOI: 10.1002/jrs.1250070606
  16. Kelly, S., Pollak, F.H., Tomkiewicz, M. (1997). Raman Spectroscopy as a Morphological Probe for TiO2 Aerogels. The Journal of Physical Chemistry B, 101(14), 2730–2734. DOI: 10.1021/jp962747a
  17. Liu, L.Z., Li, T.H., Wu, X.L., Shen, J.C., Chu, P.K. (2012). Identification of oxygen vacancy types from Raman spectra of SnO2 nanocrystals. Journal of Raman Spectroscopy, 43(10), 1423–1426. DOI: 10.1002/jrs.4078
  18. Vázquez-López, A., Maestre, D., Ramírez-Castellanos, J., Cremades, A. (2021). In Situ Local Oxidation of SnO Induced by Laser Irradiation: A Stability Study. Nanomaterials, 11(4), 976. DOI: 10.3390/nano11040976
  19. Kwoka, M., Ottaviano, L., Passacantando, M., Santucci, S., Czempik, G., Szuber, J. (2005). XPS study of the surface chemistry of L-CVD SnO2 thin films after oxidation. Thin Solid Films, 490(1), 36–42. DOI: 10.1016/j.tsf.2005.04.014
  20. Furukawa, M., Iwamoto, D., Inamori, K., Tateishi, I., Katsumata, H., Kaneco, S. (2023). Synthesis of Tungsten-Modified Sn3O4 through the Cetyltrimethylammonium Bromide-Assisted Solvothermal Method for Dye Decolorization under Visible Light Irradiation. Catalysts, 13(8), 1179. DOI: 10.3390/catal13081179
  21. Joy, S., Atapattu, H.R., Sorensen, S., Pruett, H., Olivelli, A.B., Huckaba, A.J., Miller, A.-F., Graham, K.R. (2022). How additives for tin halide perovskites influence the Sn4+ concentration. Journal of Materials Chemistry A, 10(25), 13278–13285. DOI: 10.1039/D2TA01429G
  22. Guan, S., Cheng, Y., Hao, L., Yoshida, H., Tarashima, C., Zhan, T., Itoi, T., Qiu, T., Lu, Y. (2023). Oxygen vacancies induced band gap narrowing for efficient visible-light response in carbon-doped TiO2. Scientific Reports, 13(1), 14105. DOI: 10.1038/s41598-023-39523-6
  23. Fan, C.-M., Peng, Y., Zhu, Q., Lin, L., Wang, R.-X., Xu, A.-W. (2013). Synproportionation Reaction for the Fabrication of Sn2+ Self-Doped SnO2-x Nanocrystals with Tunable Band Structure and Highly Efficient Visible Light Photocatalytic Activity. The Journal of Physical Chemistry C, 117(46), 24157–24166. DOI: 10.1021/jp407296f
  24. Carey, J.J., McKenna, K.P. (2019). Screening Doping Strategies To Mitigate Electron Trapping at Anatase TiO2 Surfaces. The Journal of Physical Chemistry C, 123(36), 22358–22367. DOI: 10.1021/acs.jpcc.9b05840
  25. Zhao, Y., Zhang, M., Wang, W., Song, W., Jiang, K., Zhang, X. (2021). Preparation of Ti3+/N-co-doped TiO2 by one-step hydrothermal synthesis method with high photocatalytic degradation performance under visible light. Journal of Materials Science: Materials in Electronics, 32(18), 22910–22920. DOI: 10.1007/s10854-021-06768-8
  26. Mao, C., Zuo, F., Hou, Y., Bu, X., Feng, P. (2014). In Situ Preparation of a Ti3+ Self‐Doped TiO2 Film with Enhanced Activity as Photoanode by N2 H4 Reduction. Angewandte Chemie International Edition, 53(39), 10485–10489. DOI: 10.1002/anie.201406017
  27. Luo, Y., Zhou, X., Zhang, J., Qi, Y., Li, Z., Zhang, F., Li, C. (2021). Development of Sn2+-based oxyfluoride photocatalyst with visible light response of ca. 650 nm via strengthened hybridization of Sn 5s and O 2p orbitals. Journal of Energy Chemistry, 63, 385–390. DOI: 10.1016/j.jechem.2021.07.028
  28. Uddin, Md.T., Hoque, Md.E., Chandra Bhoumick, M. (2020). Facile one-pot synthesis of heterostructure SnO2 /ZnO photocatalyst for enhanced photocatalytic degradation of organic dye. RSC Advances, 10(40), 23554–23565. DOI: 10.1039/D0RA03233F
  29. Makuła, P., Pacia, M., Macyk, W. (2018). How To Correctly Determine the Band Gap Energy of Modified Semiconductor Photocatalysts Based on UV–Vis Spectra. The Journal of Physical Chemistry Letters, 9(23), 6814–6817. DOI: 10.1021/acs.jpclett.8b02892
  30. Chen, S., Luo, Y., Xu, Y., Chen, Y., Jiang, Y., Li, Z., Tian, L., Wang, F., Liu, Y., Li, J. (2024). Conjugated Polyvinyl Alcohol Modified SnO2 for Efficient Visible Light Photocatalytic Reduction of Cr(VI). Bulletin of Chemical Reaction Engineering & Catalysis, 19(4), 609-621. DOI: 10.9767/bcrec.20226
  31. Kadem, A.J., Tan, Z.M., Suntharam, N.M., Pung, S.Y., Ramakrishnan, S. (2023). Synthesis of CuO, ZnO and SnO2 Coupled TiO2 Photocatalyst Particles for Enhanced Photodegradation of Rhodamine B Dye. Bulletin of Chemical Reaction Engineering & Catalysis, 18(3), 506-520. DOI: 10.9767/bcrec.19532

Last update:

No citation recorded.

Last update:

No citation recorded.