Study On The Electrochemical Behavior Of Sodium Borohydride

In recent years, the rapid social and economic development request having brought forward height to chemistry power source. Among the many chemical power, the theoretical open-circuit voltage of direct sodium borohydride fuel cell (DBFC) is up to 1.64V and have a high energy density 9.3Wh/g, which is higher than methanol fuel cell (6.1 Wh/g). So it is a cause for concern. In the fuel cell course of work, the sodium borohydride carries out direct oxide reaction in the positive electrode. While borohydride hydrolysis reaction is in progress, hydrogen generation will not only reduce fuel efficiency but also reduce battery performance. Therefore, in the study of BH4- anodizing process, how to improve BH4- direct oxidation reaction and inhibit BH4- hydrolysis reaction are of great significance.In this dissertation, the electrochemical behavior of NaBH4 alkaline solution on gold, silver, copper, platinum, glassy carbon, nickel foam and Micro-platinum is studied by cyclic voltammetry. The results have shown that the sodium borohydride direct oxidation reaction on gold and platinum electrode can be well happening, Micro-disc platinum electrode is inappropriate for studying electrochemical behavior of sodium borohydride with larger concentration. Silver and copper's activity are too high to disturb the direct oxidation of the sodium borohydride. Nickel foam also show a certain activity, but its stability is bad. Glassy carbon can not be the electrode material of sodium borohydride direct oxidation.Furthermore, linear scan voltammetry is used for the study of the oxide process on the platinum and the gold electrode. The results have shown that the platinum with sodium borohydride concentrations is greater than 0.135mol/L and [NaOH]/[NaBH4] is 3～7, inhibit sodium borohydride hydrolysis. While [NaOH]/[NaBH4] is 10～40 on gold and increasing the concentration of sodium hydroxide will fall the direct oxidation current. Sodium borohydride in the same concentration, compared to uses with the golden electrode when the platinum makes the work electrode ,the sodium hydroxide needs the amount used to have to be big. The direct oxidation process of sodium borohydride as platinum dose working electrode is not oxidation-reduction catalysis. The scanning velocity is increased , the influence of the solution convection to the response of the electrode reaction reduce. The direct oxidation process of sodium borohydride as gold dose working electrode is controlled by proliferation. The direct oxidation current on platinum increases at first and then drops with changing temperature from 303K to 353K, which is different to increase at all times on gold. Adding appropriate amount of sodium sulfate and sodium nitrate can increase the direct oxidation current on platinum and gold electrode. The addition of sodium sulfate can promote the hydrolysis reaction of sodium borohydride and excessive sodium sulfate will lead to lower oxidation current. However, sodium nitrite can inhibit sodium borohydride hydrolysis.