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Combined Experimental and Theoretical Investigations of n-Type BiFeO3 for Use as a Photoanode in a Photoelectrochemical Cell
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-04-02 , DOI: 10.1021/acs.chemmater.0c00545 Andjela Radmilovic 1 , Tyler J. Smart 2 , Yuan Ping 3 , Kyoung-Shin Choi 1
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-04-02 , DOI: 10.1021/acs.chemmater.0c00545 Andjela Radmilovic 1 , Tyler J. Smart 2 , Yuan Ping 3 , Kyoung-Shin Choi 1
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Combined experimental and theoretical investigations were performed to evaluate the potential of n-type BiFeO3 as a photoanode. While previous experimental and theoretical studies on BiFeO3 mainly focused on its ferroelectric properties, several studies have reported the advantages of BiFeO3 as a photoelectrode for solar water splitting (e.g., bandgap energy and band-edge positions relative to water reduction and oxidation potentials). However, the photoelectrochemical properties of n-type BiFeO3 have not yet been thoroughly investigated. In our experimental investigation, we developed an electrodeposition-based synthesis to prepare uniform n-type BiFeO3 thin-film electrodes. Furthermore, using a heat treatment under a N2 environment, we intentionally introduced additional oxygen vacancies into the pristine n-type BiFeO3 electrodes to increase the majority carrier density. The bandgaps, flatband potentials, photocurrent onset potentials, photocurrent generation, and photoelectrochemical stabilities of the pristine and N2-treated BiFeO3 photoanodes were investigated comparatively to improve our understanding of BiFeO3 photoanodes and to examine the effect of oxygen vacancies on the photoelectrochemical properties of BiFeO3. In our theoretical investigation, we performed first-principles calculations and demonstrated the formation of a small polaron when an extra electron was introduced into the BiFeO3 lattice. Changes in electronic states caused by the small polaron formation were carefully investigated. We also examined the effects of oxygen vacancies on electron-polaron formation and carrier concentration in BiFeO3. Using charge formation energy calculations and referencing charge transition levels to the free electron-polaron level instead of to the conduction band minimum, we showed that the oxygen vacancy is capable of serving as a donor to enhance the carrier concentration of BiFeO3. Our theoretical results agree well with our experimental findings. Together, the new experimental and theoretical results and discussion provided in this study have considerably improved our understanding of n-type BiFeO3 as a photoanode.
中文翻译：
在光电电化学电池中用作光阳极的n型BiFeO 3的联合实验和理论研究
结合实验和理论研究，以评估n型BiFeO 3作为光阳极的潜力。尽管先前对BiFeO 3的实验和理论研究主要集中在其铁电特性上，但一些研究报告了BiFeO 3作为用于太阳能水分解的光电极的优势（例如，相对于水还原和氧化电势的带隙能和带边缘位置） 。然而，尚未完全研究n型BiFeO 3的光电化学性质。在我们的实验研究中，我们开发了一种基于电沉积的合成方法来制备均匀的n型BiFeO 3薄膜电极。此外，通过在N 2环境下进行热处理，我们有意将额外的氧空位引入原始的n型BiFeO 3电极中，以增加多数载流子密度。比较研究了原始和N 2处理的BiFeO 3光电阳极的带隙，平带电势，光电流起始电势，光电流生成和光电化学稳定性，以增进我们对BiFeO 3光电阳极的了解，并研究氧空位对光电化学性能的影响。的BiFeO 3。在理论研究中，我们进行了第一性原理计算，并证明了将额外的电子引入BiFeO 3晶格后会形成小的极化子。仔细研究了由小极化子形成引起的电子态变化。我们还检查了氧空位对BiFeO 3中电子极化子形成和载流子浓度的影响。使用电荷形成能的计算并将电荷跃迁能级转换为自由电子-极化子能级而不是导带最小值，我们表明氧空位能够用作施主来提高BiFeO 3的载流子浓度。我们的理论结果与我们的实验结果非常吻合。总之，这项研究中提供的新的实验和理论结果以及讨论大大改善了我们对n型BiFeO 3作为光阳极的理解。
更新日期：2020-04-23
中文翻译：
在光电电化学电池中用作光阳极的n型BiFeO 3的联合实验和理论研究
结合实验和理论研究，以评估n型BiFeO 3作为光阳极的潜力。尽管先前对BiFeO 3的实验和理论研究主要集中在其铁电特性上，但一些研究报告了BiFeO 3作为用于太阳能水分解的光电极的优势（例如，相对于水还原和氧化电势的带隙能和带边缘位置） 。然而，尚未完全研究n型BiFeO 3的光电化学性质。在我们的实验研究中，我们开发了一种基于电沉积的合成方法来制备均匀的n型BiFeO 3薄膜电极。此外，通过在N 2环境下进行热处理，我们有意将额外的氧空位引入原始的n型BiFeO 3电极中，以增加多数载流子密度。比较研究了原始和N 2处理的BiFeO 3光电阳极的带隙，平带电势，光电流起始电势，光电流生成和光电化学稳定性，以增进我们对BiFeO 3光电阳极的了解，并研究氧空位对光电化学性能的影响。的BiFeO 3。在理论研究中，我们进行了第一性原理计算，并证明了将额外的电子引入BiFeO 3晶格后会形成小的极化子。仔细研究了由小极化子形成引起的电子态变化。我们还检查了氧空位对BiFeO 3中电子极化子形成和载流子浓度的影响。使用电荷形成能的计算并将电荷跃迁能级转换为自由电子-极化子能级而不是导带最小值，我们表明氧空位能够用作施主来提高BiFeO 3的载流子浓度。我们的理论结果与我们的实验结果非常吻合。总之，这项研究中提供的新的实验和理论结果以及讨论大大改善了我们对n型BiFeO 3作为光阳极的理解。
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