Decoupling the charge collecting and screening effects in piezotronics-regulated photoelectrochemical systems by using graphene as the charge collector
Decoupling the charge collecting and screening effects in piezotronics-regulated photoelectrochemical systems by using graphene as the charge collector
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DOI：
10.1016/j.nanoen.2018.03.066
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发表时间：
2018-06-01
期刊：
影响因子：
17.6
通讯作者：
Wang, Xudong
中科院分区：
文献类型：
--
作者：
Chen, Xiaobo;German, Lazarus;Wang, Xudong
压电学在提高光电化学(PEC)反应效率方面显示出巨大的潜力，但其全速功能受到半导体电荷收集和极化材料屏蔽效应之间长期存在的矛盾的制约。在这份报告中，我们通过使用石墨烯作为电荷收集器来分离收集和筛选轨迹来解决这个问题。石墨烯的中等电荷密度确保了对相邻电极化的最小屏蔽，并同时将光生自由载流子输送到对电极。基于PMN-PT/石墨烯/TiO2PEC体系，通过铁电极化来调节界面电子能级，获得了显著的性能提升。正向极化可以使1V时的光电流密度比RHE提高50%，并且起始电位发生了有利的漂移。计算和实验结果都表明，这一结果是由于石墨烯的低屏蔽效应所致。相反，无论极化条件如何，金电极都能完全屏蔽PMN-PT的极化，并产生类似的PEC性能。这项工作揭示了石墨烯可能是一种理想的导电电极，可以将压电PEC器件从载流子收集和电荷屏蔽之间的权衡中解脱出来。
Piezotronics have shown great promises in promoting the efficiency of photoelectrochemical (PEC) reactions, while their full-gear functionalities are constrained by the longstanding contradiction between the charge collection of semiconductors and the screening effect of polarization materials. In this report, we tackle this issue by decoupling the collecting and screening trajectories using graphene as the charge collector. The moderate charge density of graphene ensures minimal screen of the adjacent electrical polarizations and concurrently delivers photogenerated free carriers toward the counter electrode. Based on a PMN-PT/graphene/TiO2 piezotronic PEC system, substantial performance gains were received through tuning the interfacial electronic energy level via ferroelectric polarizations. Forward poling could lead to a 50% improvement of photocurrent density at 1 V vs. RHE and a favorably shifted onset potential. Both calculation and experimental results suggest this outcome was beneficial from the low screening effect from graphene. In contrast, gold electrode will fully screen the polarization from PMN-PT and yield similar PEC performance despite of the poling conditions. This work reveals graphene could be an ideal conductive electrode selection for freeing piezotronic PEC devices from the performance capstone imposed by the trade-off between carrier collecting and charge screening.