Direct Oxidation Of Sodium Borohydride With Au Catalyst

As a novel type of fuel cell using sodium borohydride (NaBH4) alkaline solution as the anode fuel, the direct sodium borohydride fuel cell (DBFC) has higher theoretical open circuit voltage (1.64V) and theoretical energy density (9.30kWh/kg). There are two kinds of catalytic materials for the direct oxidation of sodium borohydride. The one is precious metal and its alloy. These catalytic materials make direct oxidation of sodium borohydride generate higher number of electrons but cause serious polarization. Another is non-precious metal catalysts and its alloy, such as metal Ni. The slight polarization but lower number electrons of direct oxidation of sodium borohydride are found on these metal catalysts. However, there are still several problems such as high cost and complicated production process for the appropriate precious catalysts on the direct oxidation of borohydride because of the necessity of Nanotechnology. The previous research showed that direct oxidation of sodium borohydride using precious metal catalysts can be improved by adding appropriate additive. This method has advantages such as easy and cheap. In the thesis, the direct oxidation of sodium borohydride using Au catalysts and the effects of additives on that were researched.Firstly, the effects of experiment conditions on direct oxidation of sodium borohydride using Au catalysts was studied by cyclic voltammetry. The results showed that the hydrolysis of sodium borohydride were inhabited and the direct oxidation improved when CNaOH/CNaBH4 was 30:1. In electrolyte consisted of 0.1mol/L NaBH4 and 3.0mol/L NaOH, the direct oxidation of sodium borohydride using Au catalysts could be carry out well with the range of temperature from 283K to 343K. The direct oxidation of sodium borohydride using Au catalysts was controlled by diffusion.Furthermore, the effects of additives on the direct oxidation of sodium borohydride using Au catalysts catalyst was studied by cyclic voltammetry, electrochemical impedance spectroscopy and open circuit potential, the influence of temperature and time was also researched, too. The results showed that the number of BH4- on the surface of the electrode was reduced due to the absorption of triethylene tetramine, aminobenzene and melamine and resulted in the increase of the number H atoms of each BH4- oxidated on the catalytic spots of the electrode. So the direct oxidation of sodium borohydride using Au catalysts was improved by adding triethylene tetramine, aminobenzene and melamine. The optimal concentration of three additives was 1.6μmol/L, 160μmol/L and 20μmol/L, respectively, and triethylene tetramine was the best additives among them. Lastly, it was found that the improvement of the direct oxidation of sodium borohydrideusing Au catalysts could be contribution to adding additives with amidocyanogen in molelcular structure and medium size.