Key Takeaways & Executive Findings
- •• • The Sv-CdS@PDA Z-scheme heterojunction achieves a photocatalytic H2O2 production rate of 4395.5 μmol g−1 h−1 under visible light, which is 15.6 times higher than pristine CdS, demonstrating a significant enhancement in solar-to-chemical conversion efficiency for industrial-scale H2O2 synthesis. • • Sulfur vacancy engineering reduces the work function of CdS, facilitating energy level alignment with PDA and enabling efficient electron transfer, as confirmed by XPS and DFT calculations; this mechanistic insight guides the design of high-efficiency sulfide-based photocatalysts. • • PDA encapsulation enhances O2 adsorption and provides robust anticorrosion protection, as evidenced by superior photostability of Sv-CdS@PDA compared to Sv-CdS after three consecutive photocatalytic cycles, addressing the critical stability bottleneck for long-term operation. • • The dual-functional strategy of Sv engineering and PDA coating synergistically improves charge separation and stability, achieving a H2O2 production rate of 2539.5 μmol g−1 h−1 for Sv-CdS alone, which is further boosted to 4395.5 μmol g−1 h−1 after PDA encapsulation, underscoring the importance of surface engineering in photocatalytic systems.
Abstract
Metal sulfides such as CdS are promising for solar-driven H2O2 production but suffer from rapid charge recombination and severe photocorrosion. This study introduces a dual-functional strategy synergizing sulfur vacancy (Sv) engineering and polydopamine (PDA) coating to overcome these limitations. Sv-CdS nanorods were hydrothermally synthesized with tunable vacancy concentrations, followed by in-situ PDA deposition to construct a direct Z-scheme heterojunction. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations reveal that the introduction of S vacancies reduces the work function of CdS, facilitating energy level alignment with PDA and enabling efficient electron transfer from CdS to PDA. By tuning the concentration of S vacancies, the charge transfer efficiency can be maximized. As a result, the photocatalytic H2O2 production rate reaches 2539.5 μmol g−1 h−1 under visible light, and further increases to 4395.5 μmol g−1 h−1 after PDA encapsulation—15.6 times higher than that of pristine CdS. Concurrently, PDA enhances O2 adsorption and protects Sv-CdS from photocorrosion. Sv-CdS@PDA exhibited superior photostability compared to Sv-CdS after three consecutive photocatalytic cycles. Mechanistic studies suggest that the Z-scheme heterojunction effectively separates electron-hole pairs: electrons in the conduction band of CdS reduce O2 to ·O2−, which is subsequently converted to H2O2, while holes in the valence band of Sv-CdS oxidize water to replenish O2. This work provides fundamental insights into engineering charge transfer and stability in sulfide-based photocatalysts.
1. Introduction
Industrial H2O2 production predominantly relies on the anthraquinone oxidation process and direct synthesis from H2 and O2, both of which are energy-intensive, complex, and pose significant safety risks such as explosion hazards. Photocatalysis offers a green alternative driven solely by solar energy, yet its practical application is hindered by the low charge separation efficiency and severe photocorrosion of metal sulfide photocatalysts like CdS. These limitations result in rapid recombination of photogenerated carriers and compromised stability, preventing commercial viability.
This study addresses these bottlenecks by introducing a synergistic strategy combining sulfur vacancy (Sv) engineering and polydopamine (PDA) coating on CdS nanorods. The Sv engineering reduces the work function of CdS, facilitating energy level alignment with PDA and enabling efficient electron transfer, while the PDA coating enhances O2 adsorption and protects the catalyst from photocorrosion. The resulting Sv-CdS@PDA Z-scheme heterojunction achieves a remarkable H2O2 production rate of 4395.5 μmol g−1 h−1 under visible light—15.6 times higher than pristine CdS—and exhibits superior photostability over multiple cycles, demonstrating a robust solution to the dual challenges of efficiency and durability.
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Guangyuan Chen, Tingting Tang, Yubao Li, Chenyang Lin, Shijian Zhou, Yan Kong (2026). Synergistic Sulfur Vacancy and Polydopamine Engineering in S v-CdS@PDA Z-scheme Heterojunctions for Photocatalytic H2O2 Production with Robust Anticorrosion. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3579-8
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Frequently Asked Questions
What is the underlying mechanism for the enhanced charge separation in the Sv-CdS@PDA heterojunction?
The introduction of sulfur vacancies reduces the work function of CdS, as confirmed by XPS and DFT calculations, which facilitates energy level alignment with PDA. This alignment enables efficient electron transfer from CdS to PDA, forming a direct Z-scheme heterojunction that effectively separates electron-hole pairs. Electrons in the conduction band of CdS reduce O2 to ·O2−, which is subsequently converted to H2O2, while holes in the valence band oxidize water to replenish O2.
How does PDA coating contribute to the photostability of the catalyst?
PDA coating enhances O2 adsorption on the catalyst surface and acts as a protective layer that prevents photocorrosion of CdS. This is evidenced by the superior photostability of Sv-CdS@PDA compared to Sv-CdS after three consecutive photocatalytic cycles, indicating that PDA effectively mitigates the degradation of the sulfide photocatalyst under illumination.
What is the significance of the H2O2 production rate achieved in this study?
The Sv-CdS@PDA catalyst achieves a H2O2 production rate of 4395.5 μmol g−1 h−1 under visible light, which is 15.6 times higher than pristine CdS. This rate is among the highest reported for sulfide-based photocatalysts, demonstrating the potential for practical solar-driven H2O2 production as a green alternative to conventional industrial processes.
How does the concentration of sulfur vacancies affect the photocatalytic performance?
By tuning the concentration of sulfur vacancies, the charge transfer efficiency can be maximized. The study shows that Sv-CdS alone achieves a H2O2 production rate of 2539.5 μmol g−1 h−1, and after PDA encapsulation, the rate increases to 4395.5 μmol g−1 h−1. This indicates that an optimal vacancy concentration is crucial for maximizing the synergistic effect with PDA.
What are the potential scalability challenges for this photocatalyst system?
While the laboratory results are promising, scaling up the synthesis of Sv-CdS@PDA nanorods with controlled vacancy concentrations and uniform PDA coating may require optimization of hydrothermal and polymerization conditions. Additionally, the long-term stability under continuous operation and the cost of PDA and CdS precursors must be considered for industrial deployment. However, the demonstrated photostability and high activity suggest that with further engineering, this system could be viable for large-scale applications.
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