The nanostructured BiVO₄ photoanodes were prepared by electrospinning and were further characterized by XRD, SEM, and XPS, confirming the bulk and surface modification of the electrodes attained by W addition. The role of surface states (SS) during water oxidation for the as-prepared photoanodes was investigated by using electrochemical, photoelectrochemical, and impedance spectroscopy measurements. An optimum 2% doping is observed in voltammetric measurements with the highest photocurrent density at 1.23 V_RHE under back side illumination. It has been found that a high PEC performance requires an optimum ratio of density of surface states (N_SS) with respect to the charge donor density (N_d), to give both good conductivity and enough surface reactive sites. The optimum doping (2%) shows the highest N_d and SS concentration, which leads to the high film conductivity and reactive sites. The reason for SS acting as reaction sites (i-SS) is suggested to be the reversible redox process of V⁵⁺/V⁴⁺ in semiconductor bulk to form water oxidation intermediates through the electron trapping process. Otherwise, the irreversible surface reductive reaction of VO₂⁺ to VO²⁺ though the electron trapping process raises the surface recombination. W doping does have an effect on the surface properties of the BiVO₄ electrode. It can tune the electron trapping process to obtain a high concentration of i-SS and less surface recombination. This work gives a further understanding for the enhancement of PEC performance caused by W doping in the field of charge transfer at the semiconductor/electrolyte interface.

中文翻译：

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BiVO ₄光阳极中用于水氧化的钨掺杂在表面态上的作用：调整电子俘获过程

纳米结构化的BiVO ₄光电阳极通过静电纺丝制备，并通过XRD，SEM和XPS进行了进一步表征，证实了通过添加W可获得的电极的体积和表面改性。通过使用电化学，光电化学和阻抗光谱测量，研究了所制备的光阳极在水氧化过程中表面状态（SS）的作用。在伏安法测量中，在背面照明下，在1.23 V _RHE处具有最高的光电流密度，观察到最佳的2％掺杂。已经发现，高PEC性能要求表面态密度（N _SS）相对于电荷给体密度（N _d）具有最佳比率。），以提供良好的导电性和足够的表面反应位。最佳掺杂（2％）显示出最高的N _d和SS浓度，这导致了较高的薄膜电导率和反应位点。提示SS充当反应位点（i-SS）的原因是半导体本体中V ⁵⁺ / V ⁴⁺的可逆氧化还原过程，通过电子俘获过程形成水氧化中间体。否则，尽管电子俘获过程提高了表面复合性，但VO ₂ ⁺对VO ²⁺的不可逆表面还原反应。W掺杂确实会影响BiVO ₄的表面性能电极。它可以调节电子俘获过程，以获得高浓度的i-SS和较少的表面重组。这项工作为在半导体/电解质界面处的电荷转移领域中由W掺杂引起的PEC性能增强提供了进一步的理解。