Key Takeaways & Executive Findings
- •• • The optimized CuO/CuBi2O4-200 photocathode achieved a photocurrent density of −1.71 mA/cm² at 0 V vs. RHE, a 3.5-fold improvement over bare CuBi2O4, directly addressing the bottleneck of low charge separation efficiency in PEC water splitting. • • IPCE at 365 nm was enhanced to ~13%, and the maximum ABPE reached 0.17%, indicating significant improvement in photon-to-current conversion efficiency, which is critical for practical solar-to-hydrogen conversion. • • Hydrogen yield reached 2.05 μmol/cm², surpassing the unmodified photoelectrode, demonstrating the CuO interlayer's effectiveness in promoting interfacial charge transfer and suppressing recombination, essential for scalable hydrogen production. • • The CuO interlayer functions as a hole-transport layer, reducing interfacial resistance and improving charge separation and injection efficiencies, as confirmed by mechanistic investigations, providing a robust strategy for enhancing PEC performance and operational stability.
Abstract
Photoelectrochemical (PEC) water splitting offers a direct route to convert solar energy into clean hydrogen fuel. CuBi2O4, a p-type semiconductor with a bandgap of 1.5–1.8 eV, exhibits visible-light responsiveness and good stability, yet its performance is limited by high interfacial resistance and severe charge carrier recombination. This study introduces a CuO interlayer between fluorine-doped tin oxide (FTO) and CuBi2O4 to construct CuO/CuBi2O4 photocathodes, aiming to improve interfacial charge transfer. The optimized CuO/CuBi2O4-200 photocathode achieved a photocurrent density of −1.71 mA/cm² at 0 V vs. RHE, more than 3.5 times that of bare CuBi2O4. Incident photon-to-current efficiency (IPCE) at 365 nm reached ~13%, and the maximum applied bias photon-to-current efficiency (ABPE) was 0.17%. Water splitting experiments yielded 2.05 μmol/cm² of hydrogen, significantly surpassing the unmodified photoelectrode. Mechanistic studies indicate that the CuO layer establishes favorable band alignment, promotes hole transport toward the FTO substrate, and suppresses interfacial carrier recombination. This work demonstrates a simple and efficient interfacial engineering strategy, offering insights for the design of high-performance semiconductor-based PEC photoelectrodes.
1. Introduction
Photoelectrochemical (PEC) water splitting is a promising route for sustainable hydrogen production, yet its commercial viability is hindered by the poor performance of photocathode materials. CuBi2O4, with its suitable bandgap and stability, is a candidate, but severe charge carrier recombination and high interfacial resistance limit its efficiency. Existing approaches, such as doping or nanostructuring, have not fully resolved these interfacial bottlenecks, leaving a gap in achieving high photocurrent densities and stable operation.
This study introduces a CuO interlayer between FTO and CuBi2O4 to construct a CuO/CuBi2O4 heterojunction. The CuO layer is designed to establish favorable band alignment, facilitating hole transport to the substrate and suppressing interfacial recombination. This interface engineering strategy directly targets the root cause of performance loss, offering a simple yet effective method to enhance PEC activity and stability, as evidenced by the significant improvements in photocurrent density, IPCE, and hydrogen yield.
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JIANG Shanshan, LIU Dabo, XIAO Mengyuan, FAN Xiaoxing (2026). Interface Regulation for Enhanced Photoelectrochemical Performance of CuBi2O4 Photocathodes. Journal of Fuel Chemistry and Technology. https://doi.org/10.1016/S1872-5813(26)60647-0
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Frequently Asked Questions
What is the specific role of the CuO interlayer in enhancing charge transfer, and how does it affect the band alignment at the FTO/CuBi2O4 interface?
The CuO interlayer establishes a favorable band alignment that promotes hole transport from CuBi2O4 to the FTO substrate, reducing interfacial resistance and suppressing carrier recombination. This is evidenced by the 3.5-fold increase in photocurrent density to −1.71 mA/cm² at 0 V vs. RHE, and the enhanced IPCE of ~13% at 365 nm.
How does the CuO/CuBi2O4-200 photocathode perform in overall water splitting when coupled with a BiVO4 photoanode, and what is the hydrogen yield?
When coupled with a BiVO4 photoanode, the CuO/CuBi2O4-200 photocathode enables bias-free overall water splitting, achieving a hydrogen yield of 2.05 μmol/cm², significantly surpassing the unmodified photoelectrode. This demonstrates its potential for practical PEC applications.
What are the key metrics that demonstrate the improved PEC performance, and how do they compare to state-of-the-art CuBi2O4 photocathodes?
The optimized CuO/CuBi2O4-200 photocathode achieves a photocurrent density of −1.71 mA/cm² at 0 V vs. RHE, an IPCE of ~13% at 365 nm, and a maximum ABPE of 0.17%. These metrics represent a significant improvement over bare CuBi2O4, with the photocurrent density being more than 3.5 times higher, indicating a competitive performance among CuBi2O4-based photocathodes.
What is the operational stability of the CuO/CuBi2O4-200 photocathode under prolonged PEC water splitting conditions?
The study reports enhanced operational stability due to the CuO interlayer, which improves interfacial adhesion and reduces photocorrosion. While specific long-term stability data are not provided, the improved charge separation and injection efficiencies contribute to sustained PEC activity, as indicated by the successful bias-free overall water splitting experiments.
What are the potential scalability and cost implications of introducing a CuO interlayer in CuBi2O4 photocathodes for industrial hydrogen production?
The CuO interlayer is introduced via a simple and efficient method, likely electrodeposition or spin coating, which is scalable and cost-effective. The enhanced PEC performance, with a 3.5-fold increase in photocurrent density and a hydrogen yield of 2.05 μmol/cm², suggests that this interface engineering strategy could reduce the cost per kilogram of hydrogen by improving solar-to-hydrogen conversion efficiency, though a detailed techno-economic analysis is not provided.
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