【作者】 李健；

【导师】 黄成德；

【作者基本信息】 天津大学 ， 应用化学， 2015， 硕士

【摘要】 直接硼氢化钠燃料电池（DBFC）作为一种新型的化学电源,具有燃料易储存与运输、无阳极催化剂的CO中毒现象、理论开路电压高、较高的功率密度和工作温度低等优点,受到了研究人员的广泛关注。DBFC在便携式电源领域有着广阔的应用前景,然而要实现其商业实用化还需进一步的深入研究。如何开发设计高催化活性、低成本和高选择性的阳极催化剂,从而提高NaBH₄电氧化反应动力学速度,同时降低水解反应程度,是DBFC阳极催化剂研究的主要目标,也是实现DBFC商业化的关键问题。针对DBFC存在的问题,本论文制备了不同原子比的Pd-Ag/C和Pd-Fe/C催化剂,并研究了它们在硼氢化钠电氧化反应中的电化学行为。主要研究内容如下:1.采用化学还原法制备了Pd/C催化剂,并通过循环伏安和计时电流法分别研究了扫描速度、电解液的组成、温度、载体及催化剂制备方法对硼氢化钠在Pd/C上的电化学行为的影响,结果表明它们对硼氢化钠电氧化反应动力学速度和反应机理均有不同程度的影响。2.室温下采用化学还原法分别制备了Pd/C、Pd₆₇Ag₃₃/C、Pd₅₀Ag₅₀/C和Pd₃₃Ag₆₇/C催化剂,并考察了它们对硼氢化钠电氧化反应行为的影响。研究结果表明适量Ag的掺杂可以有效降低催化剂的成本,并且具有较高的催化活性和转移电子数,有利于燃料效率的提高。同时所制备的催化剂金属纳米颗粒均匀地分散在载体碳黑的表面,金属Ag进入到Pd的晶格中与Pd形成了合金,使得Pd的晶体结构发生了变化,并且晶粒尺寸和PdOads含量是影响催化剂活性的重要因素。3.在80℃下采用化学还原法分别制备了Pd/C、Pd₆₇Fe₃₃/C、Pd₅₀Fe₅₀/C、Pd₃₃Fe₆₇/C、Fe/C催化剂。研究结果表明在硼氢化钠电氧化反应中Pd-Fe/C单位质量Pd的峰电流均显著高于Pd/C,其中Pd₃₃Fe₆₇/C催化剂的活性和稳定性都较高,适量Fe的掺杂有利于表观转移电子数的提高。所制备的Pd-Fe/C催化剂中有一定量的Fe₃O₄,Pd₃₃Fe₆₇/C催化剂金属纳米颗粒均匀地分散在载体碳黑表面,它含有Pd、Fe、O和C四种元素,其中Fe与Pd的原子比为2.02:1,该比例与实验时的投料比基本吻合,其中Pd主要以零价态存在。更多还原

【Abstract】 Direct borohydride fuel cell（DBFC） as a new type of chemical power source is received extensive attention of the researchers for many advantages, such as easy storage and transportation of fuel, no CO poisoning of anode catalyst, high theoretical open circuit voltage, higher power density and low operating temperature. DBFC has broad application propects in the field of portable power supply, however it need further study to achieve the commercialization. How to anode catalyst with high catalytic activity, low cost and high selectivity, thereby increasing the sodium borohydride electrooxidation reaction kinetic speed and reducing the extent of the hydrolysis reaction, is main goal of DBFC anode catalyst research and is also the key issue to achieve DBFC commercialization. Aiming at the existing problems of DBFC, Pd-Ag/C and Pd-Fe/C catalysts with different atomic ratio were prepared and their electrochemical behaviors of sodium borohydride electrooxidation reaction were studied. The main contents are as follows:1. Pd/C catalyst was prepared using chemical reduction method. The effects of scan rate, the composition of electrolyte, temperature, catalyst carrier, and preparation method of catalyst on the electrochemical behavior of sodium borohydride electrooxidation at Pd/C electrode were investigated by cyclic voltammetry and chronoamperometry. It showd that their effects on the sodium borohydride electrooxidation reaction kinetic speed and the mechanism of sodium borohydride electrooxidation reaction in varying degrees.2. Pd/C, Pd₆₇Ag₃₃/C, Pd₅₀Ag₅₀/C and Pd₃₃Ag₆₇/C catalysts were prepared respectively by chemical reduction method at room temperature, and their effects on the electrochemical behavior of sodium borohydride electrooxidation were investigated. The results showed that the Ag doping with an appropriate amount could effectively reduce the cost of catalysts, have higher catalytic activity and the number of transferred electron, which was beneficial to the improvement of the fuel efficiency. The metal nanoparticles of prepared catalysts evenly dispersed on the surface of carbon black. Pd-Ag alloy was formed with the metallic Ag getting into the crystal lattice of Pd, which made the crystal structure of Pd changed. The grain size and the content of PdOads were important factors that can affect the catalytic activity of Pd-Ag/C.3. Pd/C, Pd₆₇Fe₃₃/C, Pd₅₀Fe₅₀/C, Pd₃₃Fe₆₇/C and Fe/C catalysts were prepared respectively by chemical reduction method at 80℃. It showed that the peak current per unit Pd mass of Pd-Fe/C were significantly higher than that of Pd/C. the activity and stability of Pd₃₃Fe₆₇/C catalyst were high, and the Fe doping with a moderate amount was beneficial to increase the number of transferred electrons. There was a certain amount of Fe₃O₄ in prepared Pd-Fe/C catalysts. The metal nanoparticles of prepared Pd₃₃Fe₆₇/C catalyst evenly dispersed on the surface of carbon black. it contained Pd, Fe, O and C four elements, and the Fe to Pd ratio was 2.02:1, which was basic coincident with the theoretic value. The Pd of prepared Pd₃₃Fe₆₇/C catalyst mainly existed in Pd⁰.更多还原