Back Electron Transfer at TiO2 Nanotube Photoanodes in the Presence of a H2O2 Hole Scavenger,ACS Applied Materials & Interfaces

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Back Electron Transfer at TiO2 Nanotube Photoanodes in the Presence of a H2O2 Hole Scavenger
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2017-09-21 00:00:00 , DOI: 10.1021/acsami.7b09827
Heng Zhu ₁ , Shicheng Yan ₁ , Zhaosheng Li ₁ , Zhigang Zou _{1,

2}

Affiliation

Adding charge scavengers, which usually are more unstable than water, is an effective method to quantify the quantum efficiency loss of photoelectrode during the charge separation, transfer, and injection processes of the water splitting reaction. Here, we detected, on TiO₂ nanotube photoanodes after using hydrogen peroxide (H₂O₂) as a hole scavenger, a nearly 40% saturated photocurrent decrease in alkaline electrolyte and a negligible saturated photocurrent difference in acid electrolyte. We found that the photoelectrons were trapped in the surface states of TiO₂ with nearly the same storage capacity of electrons in a wide range of pH values from 1.0 to 13.6. However, kinetics of a back reaction, H₂O₂ reduction by the photoelectrons trapped in surface states, is about 10 times higher for that in alkaline electrolyte than in acid electrolyte. As a result, the pH-dependent kinetic difference in H₂O₂ reduction induced the negative effects on the saturated photocurrent. Our results offer a new insight into understanding the effects of back electron transfer on electrochemical behaviors of surface states and charge scavengers.

中文翻译：

H ₂ O ₂空穴清除剂的存在下TiO ₂纳米管光阳极的反向电子转移

添加电荷清除剂（通常比水更不稳定）是量化水分离反应的电荷分离，转移和注入过程中光电极量子效率损失的有效方法。在这里，我们检测到在使用过氧化氢（H ₂ O ₂）作为空穴清除剂后的TiO ₂纳米管光阳极上，碱性电解质中的饱和光电流降低了近40％，而酸性电解质中的饱和光电流差可忽略不计。我们发现，在1.0至13.6的宽pH值范围内，光电子被捕获在TiO ₂的表面态中，具有几乎相同的电子存储容量。但是，H ₂ O的逆反应动力学由表面状态中捕获的光电子引起的₂还原，在碱性电解质中的还原度比在酸性电解质中的高约10倍。结果，H ₂ O ₂还原中pH依赖性的动力学差异引起了对饱和光电流的负面影响。我们的结果为了解反向电子转移对表面态和电荷清除剂的电化学行为的影响提供了新的见解。

更新日期：2017-09-21

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