| Abstract [eng] |
The thesis is related to the intensively developing research in the field of fuel cells and nanomaterials and is devoted to the search of new effective materials, that can be used for development and design of direct borohydride fuel cells (DBFCs) in order to improve the performance of existing fuel cells or create novel fuel cells with high efficiency. The aim of the work was the fabrication of efficient catalysts, their characterization and application for direct borohydride fuel cells. The AuM (M = Ni, Co, Cu) catalysts deposited on the titanium (Ti) or titania nanotube arrayed (TiO2-NTs) surfaces were fabricated by means of simple and low-cost electrochemical, electroless metal deposition and galvanic displacement techniques. With the aim of formation of effective catalysts, the immobilization of Au nanoparticles should be made on the underlayers deposited on the Ti and TiO2-NTs surfaces with the thickness of ca. 0.2-0.4 μm for Ni, ca. 0.5-1.1 μm for Co and ca. 1.5 μm for Cu. The optimal time period of immersion for Au deposition varies from 0.5 to 5 minutes. The Au(M)/Ti Au(M)/TiO2-NTs catalysts were fabricated with the Au nanoparticles sized ca. 10-100 nm and having the Au loadings from ca. 0.9 to 59.4 µgAu cm–2. The prepared Au(M)/Ti and Au(M)/TiO2-NTs catalysts have a significantly higher electrocatalytic activity towards the oxidation of sodium borohydride as compared to that of the bare Au, M/Ti and M/TiO2-NTs electrodes. The Au(M)/Ti and the Au(M)/TiO2-NTs catalysts with the Au loading ca. 0.9-57.6 and 8.2-59.4, respectively, µgAu cm–2 exhibit ca. 7-16 times higher electrocatalytic activity towards the electrooxidation reaction of sodium borohydride in an alkaline medium as compared with that of bare Au electrode. The highest mass activity (140 mA µgAu–1) towards the oxidation reaction of sodium borohydride was obtained on the Au(Ni)/Ti catalyst with the Au loading of 0.9 µgAu cm–2. Direct alkaline NaBH4-H2O2 single fuel cell tests were carried out by employing the prepared M/Ti, M/TiO2-NTs, Au(M)/Ti and Au(M)/TiO2-NTs catalysts as the anodes. It has been found that the highest peak power density up to 224 mW cm-2 was аttаined аt a temperature of 25 ºC using the Au(Co)/Ti catalyst with the Au loading of 57.6 µg cm–2 as the anode. The highest specific peak power density of 102.6 mW µgAu–1 at a temperature of 25 °C was attained using Au(Ni)/Ti with the Au loading of 0.9 µg cm–2 as an anode. The Au(M)/Ti and Au(M)/TiO2-NTs catalysts are promising materials and can be used as anodes in direct sodium borohydride fuel cells. |
