We identify the function of CuO impurities in CuBi₂O₄ photocathodes significantly improving the photoelectrochemical water reduction efficiency. Spectroelectrochemical photo/voltage-induced absorption spectroscopies are employed to investigate the charge carrier dynamics of pure, CuO-impure, and CuO-covered CuBi₂O₄ photocathodes during photoelectrochemical water reduction, in comparison with the CuO/FTO for electrochemical water reduction. Electrons after photoexciation are found to accumulate at the surface CuO in both CuO-covered and impure CuBi₂O₄ photocathodes, rather than directly reducing water from the CuBi₂O₄ conduction band. A rate law analysis is employed to compare the kinetics of water reduction in CuO/FTO electrochemically and CuBi₂O₄ photoelectrochemically, showing a faster water reduction rate constant in CuO than CuBi₂O₄. The kinetic comparison demonstrates that the CuO impurity functions as a cocatalyst on the surface of CuBi₂O₄ during water reduction due to the faster kinetics. Our results demonstrate the importance of considering the catalytic function of surface impurities responsible for the enhancement of water reduction efficiency.

中文翻译：

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CuBi2O4 光电阴极催化水还原过程中 CuO 杂质的光谱电化学鉴定

_{我们确定了CuBi 2} O ₄光电阴极中CuO杂质的作用，显着提高了光电化学减水效率。采用光谱电化学光/电压诱导吸收光谱研究纯、CuO 杂质和 CuO 覆盖的 CuBi ₂ O ₄光阴极在光电化学水还原过程中的载流子动力学，并与电化学水还原过程中的 CuO/FTO 进行比较。发现光激发后的电子在CuO覆盖的和不纯的CuBi ₂ O ₄光电阴极中积聚在表面CuO上，而不是直接从CuBi ₂ O ₄导带还原水。采用速率定律分析比较了CuO/FTO电化学和CuBi ₂ O _{4光电化学减水动力学，结果表明CuO比CuBi 2} O ₄具有更快的减水速率常数。动力学比较表明，由于动力学较快，CuO杂质在水还原过程中在CuBi ₂ O ₄表面上起到助催化剂的作用。我们的结果证明了考虑表面杂质的催化功能对于提高减水效率的重要性。