title: Revealing the Role of TiO2 Surface Treatment of Hematite Nanorods Photoanodes for Solar Water Splitting.
abstract: Ultrathin TiO2 is deposited on conventional hydrothermal grown hematite nanorod arrays by atomic layer deposition (ALD). Significant photoelectrochemical water oxidation performance improvement is observed when the ALD TiO2-treated samples are annealed at 650 °C or higher temperatures. The electrochemical impedance spectroscopy (EIS) study shows a surface trap-mediated charge transfer process exists at the hematite-electrolyte interface. Thus, one possible reason for the improvement could be the increased surface states at the hematite surface, which leads to better charge separation, less electron-hole recombination, and hence, greater improvement of photocurrent. Our Raman study shows the increase in surface defects on the ALD TiO2-coated hematite sample after being annealed at 650 °C or higher temperatures. A photocurrent of 1.9 mA cm(-2) at 1.23 V (vs RHE) with a maximum of 2.5 mA cm(-2) at 1.8 V (vs RHE) in 1 M NaOH under AM 1.5 simulated solar illumination is achieved in optimized deposition and annealing conditions.
authors.affiliation: †Energy Research Institute @ NTU, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, X-Frontier Block, Level 5, Singapore 637553.
authors.forename: Xianglin
authors.initials: X
authors.lastname: Li
authors.affiliation: ‡School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798.
authors.forename: Prince Saurabh
authors.initials: PS
authors.lastname: Bassi
authors.affiliation: †Energy Research Institute @ NTU, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, X-Frontier Block, Level 5, Singapore 637553.
authors.forename: Pablo P
authors.initials: PP
authors.lastname: Boix
authors.affiliation: †Energy Research Institute @ NTU, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, X-Frontier Block, Level 5, Singapore 637553.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Fang
authors.affiliation: †Energy Research Institute @ NTU, Nanyang Technological University, 50 Nanyang Drive, Research Techno Plaza, X-Frontier Block, Level 5, Singapore 637553.|‡School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798.
authors.forename: Lydia Helena
authors.initials: LH
authors.lastname: Wong
keywords: TiO2; atomic layer deposition (ALD); hematite; nanorods; photoelectrochemical cells (PEC); surface treatment