Solar Water Splitting on Ti-doped Hematite Nanostructured Photoanode Modified with FeOOH Electro-catalysts

Shima Farhoosh^a, Behrooz Eftekharinia^b, Naimeh Naseri^a

^aPhysics Department, Sharif University of Technology, Tehran 14588, Iran, Islamic Republic of

^bSchool of Physics, Institute for Research in Fundamental Sciences (IPM), Tehran, Iran, Iran, Islamic Republic of

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Fall Meeting19 (NFM19)

#SolFuel19. Solar Fuel Synthesis: From Bio-inspired Catalysis to Devices

Berlin, Germany, 2019 November 3rd - 8th

Organizers: Roel van de Krol and Erwin Reisner

Oral, Naimeh Naseri, presentation 228
DOI: https://doi.org/10.29363/nanoge.nfm.2019.228
Publication date: 18th July 2019

Depletion of oil and gas as hydrocarbon reservoirs and adverse effects of their combustion necessitate the use of renewable and environmentally friendly resources of energy for human societies [1,2]. Photo-assisted electrochemical water splitting into O₂ and H₂ is the most promising solution to produce solar hydrogen as a green and sustainable energy carrier [3,4]. To achieve the highest efficiency in this approach, it is vital to design proper photoanode in which high conductivity, enough hole diffusion length and active surface with a reasonable response in visible range could be provided [5].

Here, nanostructured hematite photoanodes have been synthesized in a simple hydrothermal approach and modified with FeOOH as an electrocatalyst for the water oxidation reaction. To facilitate hole transfer at the surface and prohibit charge recombination, photoanodes were doped with Ti while the molar concentration of titanium in the starting solution changed as 0.05, 0.1 and 5% of iron. Using UV-visible spectroscopy, all photoanodes obtained an optical band gap of 2.0 eV in agreement with the expected value for iron oxide. X-ray diffractometry results also revealed the formation of hematite phase of iron oxide crystalline structure with obtained 32.6 nm as an average size for nanocrystals. Field effect scanning electron microscopy illustrated the formation of multi-scale roughness on the surface with a branch like features. Photo-electrochemical measurements obtained the highest photocurrent of 0.52 mA.cm^-2 for the photoanode containing 5% Ti modified with FeOOH electrocatalyst, which provided the least charge transfer resistance of 3 kΩ.cm².

References:

[1] Davis, S. J.; Caldeira, K.; Matthews, H. D. Future CO2 emissions and climate change from existing energy infrastructure. Science 2010, 329, 1330–1333.

[2] Mazloomi, K.; Gomes, C. Hydrogen as an energy carrier: Prospects and challenges. Renewable Sustainable Energy Rev. 2012, 16, 3024–3033.

[3] Tamirat, A. G.; Rick, J.; Dubale, A. A.; Sub, W.; Hwang, B. Using hematite for photoelectrochemical water splitting: a review of current progress and challenges. Nanoscale Horiz. 2016,1, 243-267.

[4] Han, Z.; Eisenberg, R. Fuel from Water: The Photochemical Generation of Hydrogen from Water. Acc. Chem. Res.2014, 47, 2537-2544.

[5] Kment, S.; Riboni, F.; Pausova, S.; Wang, L.; Wang, L.; Han, H.; Hubicka, Z.; Krysa, J.; Schmuki, P.; Zboril, R. Photoanodes based on TiO2 and a-Fe2O3 for solar water splitting – superior role of 1D nanoarchitectures and of combined heterostructures. Chem. Soc. Rev., 2017, 46, 3716-3769.

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