Introduction Hematite is attractive materials for photoelectrohemical water splitting because of its high chemical stability in aqueous solution, suitable valance band position, low cost and photoactivity under the visible light. However, the drawbacks of short diffusion length, high electron-hole recombination rate and low rate constant for water oxidation. These drawbacks limit the photoelectrochemical conversion efficiency of hematite. Recent work reports that introducing thin under layer can lead dramatic enhancement of solar water splitting efficiency of hematite thin film.[1] The thickness of under layer is critical for the efficiency of hematite films. So, we introduce thin silica layer between fluorine doped tin oxide (FTO) and hematite film getting high photoelectrochemical water splitting efficiency. Results We introduced thin silica layer between FTO substrate and hematite thin film by deposition and annealing (DA) method.[2] Photoelectrochemical study showed that the enhanced photocurrent density depends on thickness of introduced silica layer, and approximately 1 nm thick under layer led to the highest photocurrent density. Electrochemical impedance spectroscopy (EIS) study also showed reduced impedance value when introduced thin silica under layer between FTO substrate and hematite thin film. The transient photocurrent measurement showed that back electron transfer from FTO substrate to hematite thin film was suppressed when ultra-thin silica under layer was inserted. By suppressing back electron transfer, visible light water splitting of hematite thin film showed enhanced efficiency with absorbed light to current conversion efficiency (APCE). Conclusions This work thus reports that inserting silica thin layer as under layer between FTO substrate and hematite thin film can lead to increase of solar water splitting efficiency of hematite film, by suppressing back electron transfer from FTO substrate to hematite thin film. Acknowledgement This work is financially supported by Korea Center for Artificial Photosynthesis (KCAP) located at Sogang University funded by the Ministry of Science, ICT and Future Planning (MISP) trough the National Research Fund of Korea and Brain Korea 21 Project 2014. References (1) Hisatomi, T.; Dotan, H.; Stefik M.; K. Sivula; A. Rothschild; M. Gratzel; N. Mathews Adv. Mat. 2012, 24, 2699 (2) Wang, G.; Ling Y.; Wheeler, D.-A.; George, K.-E.-N.; Horsley, K.; Heske, C.; Zhang, J.-Z.; Li Y. Nano Lett. 2011, 11, 3503.

Enhanced photoelectrochemical water splitting on hematite thin film with ultrathin SiO2 underlayer

249th National Meeting (2015)

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