【作者】 王丽；

【导师】 陈昌国；

【作者基本信息】 重庆大学 ， 物理化学， 2007， 硕士

【摘要】 硼氢化钠直接燃料电池(DBFC)理论开路电压达到1.64V而引起人们的广泛关注,且其高能量密度可达到9.3Wh/g,高于甲醇燃料电池(6.1 Wh/g)。在硼氢化钠直接燃料电池的工作过程中,硼氢化钠在阳极进行直接氧化反应,但同时硼氢根的水解反应也在进行,而氢气的生成不仅会降低燃料的利用率,且会降低电池的性能。因此,在研究BH4-阳极氧化过程中,如何改善BH4-直接氧化反应,抑制BH4-水解反应具有重要的意义。论文首先采用循环伏安法研究了NaBH4碱性溶液在铂、微盘铂、金、铜、银、泡沫镍、玻碳等电极上的电化学行为。结果表明:在以金、铂电极作工作电极时,硼氢化钠直接氧化反应可以很好的发生;微盘铂电极不宜用于研究浓度较大的硼氢化钠溶液的电化学性能;银和铜电极活性高,但对硼氢化钠直接氧化的研究干扰较大;泡沫镍也显示了一定的活性,但稳定性不好;玻碳不宜作为研究硼氢化钠直接氧化的电极材料。论文进一步采用线性伏安法对铂电极和金电极上的氧化过程进行了详细研究。结果表明:当硼氢化钠浓度大于0.135mol/L且[NaOH]∕[NaBH4]比值在3～7内,铂电极能较好地抑制硼氢化钠水解反应;在金电极上,[NaOH]∕[NaBH4]比值在10～40内,增大氢氧化钠浓度能抑制水解反应,但同时直接氧化电流会随之下降。在硼氢化钠浓度相同,用金电极比用铂做工作电极时,氢氧化钠的需用量要大;铂电极上的硼氢化钠直接氧化过程为非氧化-还原催化,金电极上的硼氢化钠直接氧化过程为扩散控制。但硼氢化钠浓度一定而氢氧化钠量未到所需时,扫描速度增大,溶液对流对电极反应的响应影响减少,有利于电流峰的测定;在303K～353K范围,铂电极上的直接氧化反应电流随温度升高先增大后降低,而金电极上的直接氧化反应电流随温度的升高而升高;添加适量的硫酸钠和硝酸钠,都能使铂和金电极上的直接氧化反应电流增大,但硫酸钠的加入还能促进硼氢化钠的水解反应且过量时会导致氧化反应电流降低,硝酸钠能抑制硼氢化钠水解反应。更多还原

【Abstract】 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.更多还原