Inorganic / polymeric assemblies as catalysts for water splitting
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Splitting water with sunlight is an attractive and promising research topic over the last two decades since it produces a non-carbon-based resource, hydrogen, which is a suitable energy carrier due to its high energy output and for being environmentally friendly. A great deal of research in this eld has been centered on the development of e cient water oxidation and reduction catalysts. The rst part of the thesis focuses on a novel photosensitizer-water oxidation catalyst (PS-WOC) dyad. A Ru metal coordinated pyridine-based ligand and a cobalt-iron pentacyanoferrate have been used as the photosensitizer and water oxidation catalyst, respectively. In this assembly, poly(4-vinylpyridine) serves as the bridging group between two units mainly to enhance the performance and stability of the system compared to its analogous intermolecular system. A 5-fold improvement on the catalytic activity has been achieved with a turnover frequency (TOF) of 5:6 10-4 s-1 under 1 hour light illumination and a turnover number (TON) of 11 in a 6-hour catalytic study. Evolved oxygen was quanti ed with gas chromatography. Structural characterization was carried out by Fourier Transform Infrared Spectroscopy (FTIR), Ultraviolet-Visible Spectroscopy (UV-Vis), X-Ray Photoelectron Spectroscopy (XPS), X-Ray Powder Di raction (XRD), Scanning Electron Microscopy (SEM), and Energy-dispersive X-Ray Spectroscopy (EDX) techniques. Comparative XPS and FTIR studies were performed on pristine and post-catalytic samples to con rm the stability of the dyad. In the second part of the study, a facile synthetic pathway using poly(4- vinylpyridine) as a polypyridyl platform has been reported for the formation of a cobalt-based metallopolymer. Electrochemical studies indicate that the metallopolymer acts as an e cient H2 evolution catalyst similar to cobalt-polypyridyl complexes. Furthermore, metallopolymer can be transformed to cobalt particles when a cathodic potential is applied in the presence of an acid. It has been found that these cobalt particles also serve as e cient hydrogen evolution catalysts. Approximately 80 µmoles of H2 gas can be collected during 2 h of electrolysis at -1.5 V (vs. Fc+/0) in the presence of 60 mM of acetic acid. A comprehensive study of the electrochemical and electrocatalytic behavior of cobalt-poly(4-vinylpyridine) was discussed in detail.
KeywordsWater Reduction Catalyst
Hydrogen Evolution Catalyst
Light-Driven Water Oxidation Catalyst
Light-Driven Oxygen Evolution Catalyst
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Mishra, R.; Ülker, E.; Karadas, F. (Wiley-VCH Verlag, 2017)Although cobalt-based heterogeneous catalysts are the central focus in water oxidation research, interest in copper-based water oxidation catalysts has been growing thanks the great abundance of copper and its biological ...
Carbon supported nano-sized Pt-Pd and Pt-Co electrocatalysts for proton exchange membrane fuel cells Kadirgan, F.; Kannan, A. M.; Atilan, T.; Beyhan, S.; Ozenler, S. S.; Süzer, Şefik; Yörür, A. (2009)Nano-sized Pt-Pd/C and Pt-Co/C electrocatalysts have been synthesized and characterized by an alcohol-reduction process using ethylene glycol as the solvent and Vulcan XC-72R as the supporting material. While the Pt-Pd/C ...
Nune, S. V. K.; Basaran, A. T.; Ülker, E.; Mishra, R.; Karadas, F. (Wiley Blackwell, 2017)Non-oxide cobalt-based water-oxidation electrocatalysts have received attention recently for their relative ease of preparation, they are stable both in acidic and basic media, and they have higher turnover frequencies ...