Ultra-efficient and durable photoelectrochemical water oxidation using elaborately designed hematite nanorod arrays

• Published in: Nano energy Vol. 39; pp. 211 - 218
• Main Authors: Jeon, Tae Hwa, Moon, Gun-hee, Park, Hyunwoong, Choi, Wonyong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-09-2017
• Subjects: Artificial photosynthesis; Solar fuel; Stable photoanode; Surface passivation; Water splitting; Water splitting; Surface passivation; Artificial photosynthesis; Solar fuel; Stable photoanode
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2017.06.049

Ultrahigh-efficiency photoelectrochemical water oxidation using modified hematite (α-Fe2O3) nanorod arrays is reported. The hematite nanorod arrays are synthesized using chemical bath deposition and further modified by hydrogen treatment, loading of a ~ 3.5-nm-thick TiO2 overlayer, and deposition of a cobalt phosphate (CoPi) catalyst. Although each modification method is well known, an elaborate optimization of the combined modification methods achieves a stable photocurrent density of ~ 6mAcm−2 at 1.23V vs. RHE over 100h under AM 1.5G irradiation (100mWcm−2) with the stoichiometric O2 and H2 evolutions at ~ 95% of Faradaic efficiency. To the best of our knowledge, this is the highest photocurrent density obtained using a hematite-based photoanode, and such long-term durability coupled with this level of efficiency has been rarely reported. The modified-hematite photoanodes are thoroughly characterized using various spectroscopic and electrochemical techniques. While the hydrogen treatment enhances the electrical conductivity, the ultrathin TiO2 overlayer reduces the surface charge recombination and effectively preserved the integrity of the hydrogen-treated hematite electrode.
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•Hematite nanorod arrays doped with hydrogen and coated with an ultrathin TiO2 layer are synthesized.•An optimized hematite exhibits unprecedented photocurrents of ~ 6mAcm−2 at 1.23V over 100h.•O2 is linearly produced from water with a current efficiency of 100% without deactivation for 100h.•A stoichiometric amount of H2 was simultaneously produced.