title: Photohole Induced Corrosion of Titanium Dioxide: Mechanism and Solutions.
abstract: 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 10-20% 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.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz , Santa Cruz, California 95064, United States.
authors.forename: Yi
authors.initials: Y
authors.lastname: Yang
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz , Santa Cruz, California 95064, United States.
authors.forename: Yichuan
authors.initials: Y
authors.lastname: Ling
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz , Santa Cruz, California 95064, United States.
authors.forename: Gongming
authors.initials: G
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz , Santa Cruz, California 95064, United States.
authors.forename: Tianyu
authors.initials: T
authors.lastname: Liu
authors.affiliation: School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, People's Republic of China.
authors.forename: Fuxin
authors.initials: F
authors.lastname: Wang
authors.affiliation: School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, People's Republic of China.
authors.forename: Teng
authors.initials: T
authors.lastname: Zhai
authors.affiliation: School of Chemistry and Chemical Engineering, Sun Yat-Sen University , Guangzhou 510275, People's Republic of China.
authors.forename: Yexiang
authors.initials: Y
authors.lastname: Tong
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz , Santa Cruz, California 95064, United States.
authors.forename: Yat
authors.initials: Y
authors.lastname: Li
mesh_terms: D003343:Corrosion; D008855:Microscopy, Electron, Scanning; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium
keywords: TiO2; photocorrosion; photoelectrochemical stability; water oxidation