Hetero-metal oxides have been used in photoelectrochemical (PEC) water splitting systems, but synthetic-originating defects and charge recombination process degrades PEC cell performance. Herein, we studied intrinsic physical properties of pure-phase copper bismuth oxide (CuBi2O4, CBO) photocathode through controlling defects and band edge alignment. Preparation of pure-phase CBO film with large grain sizes (average ∼290 nm) enabled to investigate the correlation between CBO’s crystal structure and charge carrier transport efficiency. The Cu1+-Vo point defects were regulated through electrochemical oxidation or thermal oxygenation under argon, air, and O2 atmosphere. The thermal treatment in an O2-saturated environment significantly reduced Cu1+-Vo defects, increasing charge carrier density, thereby reducing band gap, which eventually facilitated the charge transport. Moreover, electrochemical oxidation produced similar band structure to thermal oxygenation under O2, demonstrating a high level of Cu1+ defect control could be achieved through electrochemical oxidation as well as thermal oxygenation, showing systematic adjustment of the CBO band edge. Additionally, the hole-transfer heterojunction at the CBO film’s back side was engineered using copper oxide (CuO) thin film for interfacial band alignment. As a result, band edge-aligned FTO|CuO|CBO heterojunction exhibited a remarkably increased photocurrent density up to 2.63 mA/ cm2 at 0.4 V vs. RHE in alkaline electrolyte.

中文翻译：

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大块结晶 CuBi2O4 薄膜的电化学缺陷控制和光电化学减水的带边对准


杂金属氧化物已用于光电化学 （PEC） 分解水系统，但合成产生的缺陷和电荷复合过程会降低 PEC 电池的性能。在本文中，我们通过控制缺陷和带边对齐研究了纯相氧化铜铋氧化物 （CuBi2O4， CBO） 光阴极面的本征物理性质。制备具有大晶粒尺寸（平均 ∼290 nm）的纯相 CBO 薄膜，能够研究 CBO 的晶体结构与电流子传输效率之间的相关性。Cu1+-Vo 点缺陷在氩气、空气和 O 2 气氛下通过电化学氧化或热氧合进行调控。在 O2 饱和环境中的热处理显着减少了 Cu1+-Vo 缺陷，增加了电荷载流子密度，从而降低了带隙，最终促进了电荷传输。此外，电化学氧化产生与O2下热氧合相似的能带结构，表明通过电化学氧化和热氧合可以实现高水平的Cu1+缺陷控制，表明CBO带边缘的系统调整。此外，CBO 薄膜背面的空穴转移异质结是使用氧化铜 （CuO） 薄膜进行界面带对准的工程设计。因此，带边对齐的 FTO|CuO |与碱性电解质中的 RHE 相比，CBO 异质结在 0.4 V 时的光电流密度显著提高，最高可达 2.63 mA/cm2。