Enhanced Charge Separation through ALD-Modified Fe2O3/Fe2TiO5 Nanorod Heterojunction for Photoelectrochemical Water Oxidation

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• 作者：Chengcheng Li ; Tuo Wang ; Zhibin Luo ; Shanshan Liu and Jinlong Gong
• 刊名：Small
• 出版年：2016
• 出版时间：July 6, 2016
• 年：2016
• 卷：12
• 期：25
• 页码：3415-3422
• 全文大小：1571K
• ISSN：1613-6829

文摘

Hematite suffers from poor charge transport and separation properties for solar water splitting. This paper describes the design and fabrication of a 3D Fe₂O₃/Fe₂TiO₅ heterojunction photoanode with improved charge separation, via a facile hydrothermal method followed by atomic layer deposition and air annealing. A highly crystallized Fe₂TiO₅ phase forms with a distinct interface with the underlying Fe₂O₃ core, where a 4 nm Fe₂TiO₅ overlayer leads to the best photoelectrochemical performance. The favorable band offset between Fe₂O₃ and Fe₂TiO₅ establishes a type-II heterojunction at the Fe₂O₃/Fe₂TiO₅ interface, which drives electron–hole separation effectively. The Fe₂O₃/Fe₂TiO₅ composite electrode exhibits a dramatically improved photocurrent of 1.63 mA cm⁻² at 1.23 V versus reversible hydrogen electrode (RHE) under simulated 1 sun illumination (100 mW cm⁻²), which is 3.5 times that of the bare Fe₂O₃ electrode. Decorating the Fe₂O₃/Fe₂TiO₅ heterojunction photoanode with earth-abundant FeNiO_x cocatalyst further expedites surface reaction kinetics, leading to an onset potential of 0.8 V versus RHE with a photocurrent of 2.7 mA cm⁻² at 1.23 V and 4.6 mA cm⁻² at 1.6 V versus RHE. This sandwich photoanode shows an excellent stability for 5 h and achieves an overall Faradaic efficiency of 95% for O₂ generation. This is the best performance ever reported for Fe₂O₃/Fe₂TiO₅ photoanodes.