减少的铜表面态对CuBi 2 O 4的光电化学性能的影响,ACS Applied Energy Materials

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减少的铜表面态对CuBi ₂ O ₄的光电化学性能的影响
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2019-08-23 00:00:00 , DOI: 10.1021/acsaem.9b01333
Freddy E. Oropeza , Benjamin T. Feleki , Kelvin H. L. Zhang ₁ , Emiel J. M. Hensen , Jan P. Hofmann

Affiliation

首次报道了表面光还原对铋酸铜光响应的有益作用。详细光电子能谱学（PES）揭示CUBI的照射₂ ö ₄与ħ ν ≥为2.7eV在惰性气氛中导致降低表面的Cu的形成。与减少的Cu种类相关的表面状态会引起0.35 eV的向下带弯曲，这可以通过测量所测得的特征表面光电压（SPV）从0.07 V增加到0.27 V来改善这种材料的电荷载流子传输性能。研究表明，CuBi ₂ O ₄的光响应提高了30％在使用H ₂ O ₂作为电子清除剂进行光电化学性能测试之前，已经在氩气中进行了可见光辐照（100 mW / cm ²白色LED）的光阴极。通过在接近环境压力的PES下进一步研究了在相关反应条件下还原的表面态和相关SPV的稳定性。结果表明，在氩气和甲醇的存在下，还原的表面态保持稳定，但是在氧气的存在下，表面铜的再氧化会发生，这会降低测得的SPV。因此，这项工作建立了表面上还原的Cu的存在与CuBi ₂ O _4的SPV之间的直接关系。对其光伏性能具有重要意义。在CuBi ₂ O ₄和通过物理气相沉积沉积的Cu薄膜之间的界面处观察到类似的向下带弯曲，这进一步突出了Cu / CuBi ₂ O ₄掩埋界面在光电极中的重要性。

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Influence of Reduced Cu Surface States on the Photoelectrochemical Properties of CuBi2O4

The beneficial effect of surface photoreduction on the photoresponse of copper bismuthate is reported for the first time. A detailed photoemission spectroscopy study (PES) reveals that irradiation of CuBi₂O₄ with hν ≥ 2.7 eV in an inert atmosphere leads to the formation of reduced surface Cu. Surface states associated with reduced Cu species induce a 0.35 eV downward band bending, which improves the charge carrier transport properties of this material as judged by a measured increase of the characteristic surface photovoltage (SPV) from 0.07 to 0.27 V. In connection with this PES study, improvements of up to 30% in the photoresponse are observed for CuBi₂O₄ photocathodes that have been subjected to a visible light irradiation (100 mW/cm² white LED) in argon prior to photoelectrochemical performance testing using H₂O₂ as an electron scavenger. The stability of reduced surface states and associated SPV under relevant reaction conditions has been further studied by near-ambient pressure PES. Results indicate that reduced surface states remain stable in the presence of Ar and methanol, but reoxidation of surface Cu occurs in the presence of oxygen, which decreases the measured SPV. Hence, this work establishes a direct relationship between the presence of reduced Cu at the surface and SPV of CuBi₂O₄, having important implications on its photovoltaic properties. A similar downward band bending is observed at the interface between CuBi₂O₄ and a Cu thin film deposited by physical vapor deposition, which further highlights the importance of the Cu/CuBi₂O₄ buried interface in photoelectrodes.

更新日期：2019-08-23

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