Fe-N/C-TsOH催化剂应用碱性介质催化氧还原的电催化活性(英文)

Electrocatalytic Activity of Fe-N/C-TsOH Catalyst for the Oxygen Reduction Reaction in Alkaline Media

通过溶剂分散热处理方法制备了一种吡咯和对甲苯磺酸(TsOH)共同修饰的碳载非贵金属复合催化剂(Fe-N/C-TsOH),并采用扫描电子显微镜(SEM)、X射线衍射(XRD)和X射线光电子能谱(XPS)对催化剂的形貌和组成成分进行表征.借助循环伏安法(CV)和旋转圆盘技术研究了TsOH对催化剂在0.1 mol·L-1KOH介质中催化氧还原性能的影响.结果表明:TsOH的存在对催化剂催化氧还原反应(ORR)的活性影响很大.以其制备的气体扩散电极在碱性电解质溶液中催化氧还原过程时转移的电子数为3.899,远比不含TsOH修饰的催化剂催化氧还原的电子数(3.098)高.此外,研究发现600°C热处理过的Fe-N/C-TsOH催化剂表现出最佳的氧还原催化性能.相比未经热处理过的Fe-N/C-TsOH催化剂,起峰电位和-1.5 mA·cm-2电流密度对应的电压分别向正方向移动30和170 mV.XPS研究结果表明吡咯氮是催化剂主要活性中心,提供氧还原活性位,而TsOH加入形成的C―Sn―C和―SOn―有利于催化剂催化氧还原活性的提高,从而使该催化剂对氧还原表现出很好的电催化性能和选择性.

Pyrolyzed carbon supported ferrum polypyrrole （Fe-N/C） catalysts were synthesized with and without the dopant p-toluenesulfonic acid （TsOH） through a solvent-grinding method followed by heat-treatment at the desire temperature. Both the catalysts were characterized using electrochemical techniques, such as cyclic voltammetry （CV）, as well as the rotating disk electrode （RDE） technique. It was found that the catalysts doped with TsOH showed significantly better oxygen reduction reaction （ORR） activity than the undoped catalysts. The average electron transfer numbers for the catalyzed ORR were 3.899 and 3.098 for the TsOH-doped and undoped catalysts, respectively. Thermal treatment was found to be a necessary step for catalyst activity improvement. The catalyst pyrolyzed at 600 ℃ showed the best ORR activity： the onset potential and the potential at the current density of-1.5 mA·cm^-2 for the TsOH-doped catalyst were 30 and 170 mV more positive than those for the un-pyrolyzed TsOH-doped catalyst, respectively. To clarify the effects of TsOH doping and pyrolyzation, scanning electron microscopy （SEM）, Xo ray diffraction （XRD）, and X-ray photoelectron spectroscopy （XPS） were used to analyze the morphology,structure, and composition of the catalysts. The XPS results suggest that the pyrrolic-N groups are the most active sites and sulfur species are structurally bound to carbon in the form of C-Sn-C and oxidized-SOn-bonds, which is an additional beneficial factor for the ORR.