First Author: Wanwan Wu
Corresponding Authors: Haiyan Li and Dongbin Dang
DOI: 10.1016/j.apsusc.2026.166174
This study successfully constructed a stable Cs₃Bi₂Br₉/Ta₂O₅ type-II heterojunction through an in-situ growth strategy. The material demonstrated excellent performance in photocatalytic CO₂ conversion, achieving a reaction rate of up to 413.45 μmol g-1 h-1 with 100.00% selectivity. Its outstanding performance is attributed to the type-II heterojunction, which promotes spatial charge separation and effectively suppresses charge-carrier recombination. In addition, the system completely avoids the use of toxic metals and requires no organic sacrificial agents, highlighting its environmentally friendly advantages.
In February 2026, Applied Surface Science published online the latest research achievement in photocatalysis from Professor Dongbin Dang’s team at Henan University. The study reports the construction of a lead-free Cs₃Bi₂Br₉/Ta₂O₅ electrostatic heterojunction through an in-situ assembly strategy for highly efficient photocatalytic CO₂ conversion. The first author of the paper is Wanwan Wu, and the co-corresponding authors are Haiyan Li and Dongbin Dang.
Photocatalytic reduction of CO₂ into high-value-added hydrocarbon fuels is a promising green strategy for addressing the energy crisis and advancing carbon-neutrality goals. However, this technology faces several challenges, including the strong chemical inertness of CO₂ molecules, the high dissociation energy of carbon–oxygen bonds, the narrow solar-spectrum response of existing photocatalytic systems, rapid charge-carrier recombination, and insufficient surface active sites. Lead-free Cs₃Bi₂Br₉ perovskite has attracted considerable attention as a candidate material because of its low toxicity, high stability, and strong reduction capability. However, it suffers from a relatively high charge-carrier recombination rate. Constructing a heterojunction by combining halide perovskites with high-surface-area metal oxides such as Ta₂O₅ can not only promote efficient charge separation but also optimize the surface adsorption behavior of reactants. The staggered band structures of Ta₂O₅ and Cs₃Bi₂Br₉ provide a theoretical basis for constructing an efficient heterojunction with enhanced charge-separation properties.
Figure 1
Figure 2
Morphological and Structural Characteristics (Figures 1 and 2): Porous Ta₂O₅ was prepared by a sol-gel method, after which Cs₃Bi₂Br₉ was grown in situ on its surface to form the composite photocatalyst. Zeta-potential measurements showed that Cs₃Bi₂Br₉ was positively charged at +16.7 mV, while Ta₂O₅ was negatively charged at −12.9 mV. This complementary charge distribution promoted the close self-assembly of the composite through electrostatic interactions. HRTEM images clearly revealed characteristic lattice fringes corresponding to the Cs₃Bi₂Br₉ (200) plane and the Ta₂O₅ (012) plane, confirming the successful construction of the heterojunction composite.
Figure 3
Surface Chemistry and Interfacial Interactions (Figure 3): High-resolution XPS analysis revealed significant chemical shifts. In the optimized T2 composite, the binding energies of Cs 3d and Br 3d shifted toward lower values, whereas the Ta 4f and O 1s orbitals shifted toward higher values. These systematic shifts in binding energy indicate substantial interfacial charge redistribution, with electrons transferring from Ta₂O₅ to Cs₃Bi₂Br₉.
Figure 4
Figure 5
Band Structure and Gas-Adsorption Capacity (Figures 4 and 5): Diffuse reflectance spectroscopy (DRS) showed that the composite retained the optical properties of Cs₃Bi₂Br₉ and significantly red-shifted the photoresponse edge to approximately 500 nm. Gas-adsorption measurements demonstrated that, owing to the introduction of porous Ta₂O₅, the T2 composite exhibited a larger specific surface area of 16.35 m2/g and enhanced CO₂ adsorption capacity compared with pure Cs₃Bi₂Br₉. EPR measurements further confirmed the presence of both Bi and O vacancy defects, which facilitate CO₂ adsorption and activation.
Figure 6
Photocatalytic Activity and Stability Tests (Figure 6): In a pure gas-solid reaction system without any sacrificial agent or cocatalyst, the optimized T2 sample achieved a photocatalytic CO-production rate of 413.45 μmol g-1 h-1, which was 4.7 times and 22.3 times higher than those of pure Cs₃Bi₂Br₉ and Ta₂O₅, respectively. The reaction exhibited 100% selectivity toward CO. After six consecutive cycles totaling 24 hours, the CO production rate remained stable, and no obvious changes were observed in the material structure based on XRD and XPS analyses, demonstrating the excellent reaction stability of the catalyst.
Figure 7
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Photoelectrochemical Properties and Mechanistic Investigation (Figures 7, 8, and 9): The enhanced transient photocurrent response, reduced electrochemical impedance spectroscopy response, and shortened lifetime observed in time-resolved photoluminescence spectroscopy strongly demonstrate that the heterojunction greatly promotes the separation and transfer of photogenerated electron-hole pairs. Based on in-situ XPS measurements and DFT calculations, including work-function differences and differential charge-density analysis, the authors proposed a type-II heterojunction mechanism. Under light irradiation, electrons transfer from the conduction band of Cs₃Bi₂Br₉ to the conduction band of Ta₂O₅, while holes transfer from the valence band of Ta₂O₅ to the valence band of Cs₃Bi₂Br₉, thereby enabling efficient spatial charge-carrier separation.
In this study, a Cs₃Bi₂Br₉/Ta₂O₅ heterojunction photocatalyst with strong electrostatic interactions was successfully prepared through a simple and efficient in-situ growth strategy. Experimental results and theoretical calculations jointly confirmed that the introduction of porous Ta₂O₅ not only increased the specific surface area but also introduced surface defects, including Bi and O vacancies, thereby significantly enhancing the capture and activation of CO₂ molecules. Under a pure gas-solid reaction environment, the system exhibited excellent catalytic performance, with a CO production rate of 413.45 μmol g-1 h-1, 100% selectivity, and outstanding long-term stability. This research not only demonstrates the great potential of lead-free bismuth-based perovskites in artificial photosynthesis but also provides important theoretical guidance and practical references for the design of highly efficient and environmentally friendly semiconductor composites through interface engineering.
Dongbin Dang is a professor, doctoral supervisor, and Distinguished Professor at Henan University. He is a Distinguished Young Scholar in Science and Technology Innovation of Henan Province, an Academic and Technical Leader of the Henan Provincial Department of Education, and a Young Backbone Teacher at a higher-education institution in Henan Province. He has led and completed more than ten research projects, including two projects funded by the National Natural Science Foundation of China and one Distinguished Young Scholar Fund project for Science and Technology Innovation in Henan Province. He has published more than 120 SCI-indexed papers, holds two authorized invention patents, and has received more than 20 scientific and technological awards, including the Second Prize of the Henan Provincial Science and Technology Progress Award.
Haiyan Li is an associate professor and master’s supervisor. Her research focuses on the preparation of semiconductor nanomaterials and their photocatalytic and electrocatalytic properties.
Wanwan Wu, Haiyan Li, Dongbin Dang et al. In-situ grown lead-free perovskite Cs3Bi2Br9 on porous Ta2O5 for boosted gas-solid phase CO2 photocatalytic conversion. Applied Surface Science 2026, 729, 166174.
https://doi.org/10.1016/j.apsusc.2026.166174
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