p-Type CuBi₂O₄ is considered a promising metal oxide semiconductor for large-scale, economic solar water splitting due to the optimal band structure and low-cost fabrication. The main challenge in utilizing CuBi₂O₄ as a photoelectrode for water splitting, is that it must be protected from photo-corrosion in aqueous solutions, an inherent problem for Cu-based metal oxide photoelectrodes. In this work, several buffer layers (CdS, BiVO₄, and Ga₂O₃) were tested between CuBi₂O₄ and conformal TiO₂ as the protection layer. RuO_x was used as the co-catalyst for hydrogen evolution. Factors that limit the photoelectrochemical performance of the CuBi₂O₄/TiO₂/RuO_x, CuBi₂O₄/CdS/TiO₂/RuO_x, CuBi₂O₄/BiVO₄/TiO₂/RuO_x and CuBi₂O₄/Ga₂O₃/TiO₂/RuO_x heterojunction photoelectrodes were revealed by comparing photocurrents, band offsets, and directed charge transfer measured by modulated surface photovoltage spectroscopy. For CuBi₂O₄/Ga₂O₃/TiO₂/RuO_x photoelectrodes, barriers for charge transfer strongly limited the performance. In CuBi₂O₄/CdS/TiO₂/RuO_x, the absence of hole traps resulted in a relatively high photocurrent density and faradaic efficiency for hydrogen evolution despite the presence of pronounced deep defect states at the CuBi₂O₄/CdS interface. Hole trapping limited the performance moderately in CuBi₂O₄/BiVO₄/TiO₂/RuO_x and strongly in CuBi₂O₄/TiO₂/RuO_x photoelectrodes. For the first time, our results show that hole trapping is a key factor that must be addressed to optimize the performance of CuBi₂O₄-based heterojunction photoelectrodes.

中文翻译：

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揭示CuBi2O4异质结光电极中光电化学性能与界面空穴俘获之间的关系

由于具有最佳的能带结构和低成本的制造工艺，p型CuBi ₂ O ₄被认为是用于大规模，经济的太阳能水分解的有前景的金属氧化物半导体。利用CuBi ₂ O ₄作为用于水分解的光电极的主要挑战是必须保护它免受水溶液中的光腐蚀，这是基于铜的金属氧化物光电极固有的问题。在这项工作中，在CuBi ₂ O ₄和保形TiO ₂作为保护层之间测试了几个缓冲层（CdS，BiVO ₄和Ga ₂ O ₃）。的RuO _X用作氢气析出的助催化剂。限制CuBi ₂ O ₄ / TiO ₂ / RuO _x，CuBi ₂ O ₄ / CdS / TiO ₂ / RuO _x，CuBi ₂ O ₄ / BiVO ₄ / TiO ₂ / RuO _x和CuBi ₂ O ₄的光电化学性能的因素/ Ga ₂ O ₃ / TiO ₂ / RuO _x通过比较光电流，能带偏移和通过调制表面光电压光谱法测量的定向电荷转移来揭示异质结光电极。对于CuBi ₂ O ₄ / Ga ₂ O ₃ / TiO ₂ / RuO _x光电电极，用于电荷转移的势垒极大地限制了性能。在CuBi ₂ O ₄ / CdS / TiO ₂ / RuO _x中，尽管在CuBi ₂ O ₄处存在明显的深缺陷状态，但没有空穴陷阱导致了相对较高的光电流密度和法拉第效率的析氢作用。/ CdS接口。空穴俘获在CuBi ₂ O ₄ / BiVO ₄ / TiO ₂ / RuO _x中适度限制了性能，而在CuBi ₂ O ₄ / TiO ₂ / RuO _x光电极中强烈限制了性能。我们的结果首次表明，空穴陷阱是优化基于CuBi ₂ O ₄的异质结光电电极性能所必须解决的关键因素。