Anomalous electronic conductivity in polycrystalline hematite ceramic electrodes modified with SnO2: the existence of preferential pathways
| Reference | Presenter | Authors (Institution) | Abstract |
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| 06-201 | Mario Rodrigo dos Santos Soares | Soares, M.R.(Federal University of Sao Carlos); Leite, E.R.(Centro Nacional de Pesquisa em Energia e Materiais); | A photoelectrochemical (PEC) cell is an elegant and feasible way to convert solar energy in useful fuel [1]. In this system, a photocatalyst capture the solar light and use for splits water into O2 and H2. Hematite (?-Fe2O3) is considered the most promising material to photoanode of a PEC cell. However, to use this ionic semiconductor is a huge challenge, due the poor intrinsic electronic and optical properties. In a previous work [2], we showed that SnO2 addition (as impurity in sintered hematite ceramics) decreased the resistance of grain boundary those samples, due to segregation of the contaminant to this solid-solid interface. Now, we performed a deep investigation on the role of SnO2 segregation at the grain boundary, and the effect of this phenomenon on the electronic transport. For this, we prepare a high-density pellet of hematite modified with 2.0 wt.% SnO2 and this sample was sliced and polished until to obtain thickness about 1000 µm, 400 µm and 200 µm. With a characterization by current density vs. electric field and solid-state impedance spectroscopy measurements, we observed a strong and non-conventional dependence of the electrical behavior with the sample thickness, consequently of number of grain boundaries (n value), suggesting the preferential pathways for electronic conduction. We can confirm this by AFM/EFM analysis, where we demonstrated grain boundaries with different electronic charges storage capacity. The existence of preferential grain boundary conductivity can have a direct impact in the hematite photoanode performance and this discovery can revolutionize the design of development of photoanodes. ACKNOWLEDGEMENTS: FAPESP (CEPID - 2013/07296-2 and 2017/03135-5), FINEP, CAPES, CNPq (project 401452/2017-4, process 168295/20017-2) and CNPEM-LNNano. REFERENCES: [1] M. G. Walter, et al., Chem. Rev. 110, 6446 (2010) [2] M. R. S. Soares, et al., Phys. Chem. Chem. Phys. 18, 21780 (2016)
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