Unraveling the Impact of Electrochemically Created Oxygen Vacancies on the Performance of ZnO Nanowire Photoanodes
2019; American Chemical Society; Volume: 7; Issue: 21 Linguagem: Inglês
10.1021/acssuschemeng.9b05442
ISSN2168-0485
AutoresShifang Duan, Yongfei Ji, Wei Wang, Dongfang Han, Haoyu Wang, Qiu-Yu Wei, Chunfeng Li, Fei Jia, Dongxue Han, Li Niu, Dongdong Qin, Chun‐Lan Tao,
Tópico(s)Copper-based nanomaterials and applications
ResumoOxygen vacancy engineering is effective for improving the photoelectrochemical (PEC) performance of electrodes. However, such a protocol has not yet shown impressive success for ZnO photoanodes due to the unstable nature of ZnO under a reducing atmosphere. In this work, an electrochemical method is explored to create oxygen vacancies in ZnO with a controllable concentration. Unlike the successful example of other materials with chemical treatment, such a mild electrochemical method seems unable to evidently extend the working spectrum of ZnO by generating isolated trap states or upshifting the conduction band edge, but it dramatically improves the light absorption in the UV region. Importantly, we find that the created oxygen vacancies act as water oxidation intermediate species facilitating charge transfer rather than recombination sites. The origin of this merit is explained by the lowered overpotential for water oxidation on the ZnO surface. Moreover, it is also found that a balance among the density of oxygen vacancy, charge separation, and charge transfer is required to maximize the efficiency of ZnO by giving enough surface reactive sites and efficient bulk charge separation. The optimized ZnO achieves a photocurrent density of 1.2 mA cm–2 at 1.23 V vs reversible hydrogen electrode, 3.0 times greater than that of the pristine sample (0.4 mA cm–2). Without doubt, the electrochemical treatment affords a new avenue for enhancing the PEC performance of ZnO and may hold huge potential applications in other semiconductors for large-scale manufacturing.
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