Photohole Induced Corrosion of Titanium Dioxide: Mechanism and Solutions

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• 作者：Yi Yang ; Yichuan Ling ; Gongming Wang ; Tianyu Liu ; Fuxin Wang ; Teng Zhai ; Yexiang Tong ; Yat Li
• 刊名：Nano Letters
• 出版年：2015
• 出版时间：October 14, 2015
• 年：2015
• 卷：15
• 期：10
• 页码：7051-7057
• 全文大小：428K
• ISSN：1530-6992

文摘

Titanium dioxide (TiO₂) has been extensively investigated as photoanode for water oxidation, as it is believed to be one of the most stable photoanode materials. Yet, we surprisingly found that TiO₂ photoanodes (rutile nanowire, anatase nanotube, and P25 nanoparticle film) suffered from substantial photocurrent decay in neutral (Na₂SO₄) as well as basic (KOH) electrolyte solution. Photoelectrochemical measurements togehter with electron microscopy studies performed on rutile TiO₂ nanowire photoanode show that the photocurrent decay is due to photohole induced corrosion, which competes with water oxidation reaction. Further studies reveal that photocurrent decay profile in neutral and basic solutions are fundamentally different. Notably, the structural reconstruction of nanowire surface occurs simultaneously with the corrosion of TiO₂ in KOH solution resulting in the formation of an amorphous layer of titanium hydroxide, which slows down the photocorrosion. Based on this discovery, we demonstrate that the photoelectrochemical stability of TiO₂ photoanode can be significantly improved by intentionally coating an amorphous layer of titanium hydroxide on the nanowire surface. The pretreated TiO₂ photaonode exhibits an excellent photocurrent retention rate of 97% after testing in KOH solution for 72 h, while in comparison the untreated sample lost 10鈭?0% of photocurrent in 12 h under the same measurement conditions. This work provides new insights in understanding of the photoelectrochemical stability of bare TiO₂ photoanodes.