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Synthesis of first row transition metal oxide nanomaterials for electrocatalytic water oxidation reaction

Çetin, Asude
Environmental concerns associated with the use of fossil fuels have elevated the demand for safe, clean and renewable energy sources. Hydrogen is an outstanding energy carrier because of the high amount of energy stored in its bond, and an excellent alternative to fossil fuels. Therefore, production of hydrogen from readily available and abundant sources such as water through electrochemical water splitting has gained increasing attention in the last couple of decades. However, water oxidation step of overall water splitting process has large energy barrier and thus, requires application of overpotential and use of highly stable and active catalysts for the efficient formation of hydrogen. A great number of nano-sized metal oxide materials have been proven to be very active catalysts for electrochemical water oxidation. In addition to their unique properties, their large surface area and thus, large active sites make such nanomaterials promising candidates as electrocatalysts. This dissertation covers the preparation and characterization of bimetallic oxide nanomaterials composed of various combinations of earth abundant, transition metals as well as their electrochemical activities towards water oxidation reaction. Firstly, metal oxide nanomaterials in CuCr2O4, FeMnO3, NiFe2O4-NiO and NiCo2O4-NiO structures with various morphologies were synthesized via simple and reproducible methods. Synthesized nanomaterials were then characterized using a combination of analytical techniques including XRD, SEM, EDX, TEM, XPS, ICP- OES and BET. Conductive electrode surfaces were modified with these nanomaterials, and finally their electrochemical behavior in water oxidation reaction were investigated. The overall water oxidation activity of the synthesized materials was observed to be comparable to benchmark RuO2 or superior to some of the water oxidation catalysts having similar structures.