Advanced Research Lab-Thesis / Bachelor Thesis
Synthesis of layered perovskite visible light visible driven photocatalyst for water splitting
Within the past 40 years, numerous materials have been developed for photochemical water splitting. Materials able to split water absorbing visible-light with high quantum efficiencies have been increasingly been investigated in the last few decades. However, , the more efficient visible-light-driven photocatalysts, photoanodes or photocathodes are still needed to be developed to realize the necessary high efficient and cost effective photocatalyst water-splitting systems. To improve the solar to hydrogen efficiency it is required to:
i)narrow down the band gaps to harvest the visible light in the longer-wavelength regions;
ii)enhance the photogenerated charge separation during PEC water splitting to reduce recombination rate of the excitons and holes during the catalytic reaction;
and iii)large surface area to improve the catalytic efficiency, i.e., to enhance the light absorption and charge transfer.
Recently, the layered perovskite belonged to the Ruddlesden–Popper (RP) family  having the general formula, A2A′2[An−1BnO3n+1] (A′, A = alkali, alkaline earth or rare earth; B = transition metal), has attracted considerable attention due to their interesting properties, such as intercalation reactions, ionic exchange processes, electrical transport properties and excellent photocatalytic activities [3, 4]. These compounds contain a two-dimensional perovskite slab consisted of [An−1BnO3n+1] as one of the units to build a layered structure. A number (n) of corner-sharing BO6 octahedral slabs and A ions stack along the (001) direction and the alkali metal cations (A′) are sandwiched between the layers. Representative catalysts reported so far include K2Ti4O9, K4Nb6O17, K2La2Ti3O10, KLaNb2O7 [5, 6], which show potential activities for the decomposing of pure water. The relatively higher photocatalytic activity of these materials has been ascribed to its peculiar structure such as layered or tunnel structures which improves not only the solar to hydrogen efficiency but also the catalytic efficiency. These photocatalysts use their interlayer space as reactions sites, where the e—h+ recombination process could be retarded by physical separation of the electron–hole pairs generated by photo-absorption.
Within this project, the candidate will synthesize oxynitride layered perovskites by a soft urea pathway combined with solvothermal synthesis. The goal will be to assess the preparation at low temperatures (lower than 800 °C) of stable oxynitrides. The characterization of the as-prepared materials will achieve by means of XRD, spectroscopic methods such as FTIR and Raman and microscopy studies (EDX-SEM and TEM). In addition to the planned structural and microstructural investigations, extensive optical assessment will be performed to determine the band gap as well as the ration of recombination processes.
1. K. Maeda, J. Photoch. Photobio. C, 2011, 12, 237-268.
2. I. E. Castelli et al., J. Mater. Chem. A, 2015, 3, 12343-12349.
3. Y. Huang et al., Solar Energy Materials and Solar Cells, 2010, 94, 761–766.
4. M.C. Sarahan et al., J. Solid State Chem., 2008, 181 (2008), 1678–1683.
5. S. Uchida et al., J. Chem. Soc. Faraday Trans., 1997, 93, 3229–3243.
6. J.S. Wang et al., Mater. Sci. Eng. B, 2006, 126, 53–58.