Eco-Materials and Renewable Energy Research Center (ERERC), Collaborative Innovation Center of Advanced Microstructures, College of Engineering and Applied Sciences, Nanjing University , No. 22, Hankou Road, Nanjing, Jiangsu 210093, P. R. China.
Jiangsu Key Laboratory for Nano Technology, National Laboratory of Solid State Microstructures, Department of Physics, Nanjing University , No. 22, Hankou Road, Nanjing, Jiangsu 210093, P. R. China.
ACS Appl Mater Interfaces. 2017 Oct 4;9(39):33887-33895. doi: 10.1021/acsami.7b09827. Epub 2017 Sep 21.
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 TiO nanotube photoanodes after using hydrogen peroxide (HO) 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 TiO 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, HO 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 HO 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.
添加电荷清除剂通常比水更不稳定，这是一种有效方法，可以量化光电化学分解水反应中电荷分离、转移和注入过程中光电极的量子效率损失。在这里，我们在使用过氧化氢（HO）作为空穴清除剂的 TiO 纳米管光阳极上检测到，在碱性电解质中饱和光电流下降了近 40%，而在酸性电解质中饱和光电流几乎没有差异。我们发现，光电子被 TiO 的表面态捕获，在从 1.0 到 13.6 的宽 pH 值范围内，电子的存储容量几乎相同。然而，被表面态捕获的光电子的逆反应（HO 还原）在碱性电解质中的动力学比在酸性电解质中快约 10 倍。因此，HO 还原的 pH 依赖性动力学差异对饱和光电流产生了负面影响。我们的结果为理解电子返移对表面态和电荷清除剂电化学行为的影响提供了新的认识。
