氮/硫双杂化非贵金属碱性阴离子膜燃料电池阴极非铂催化剂

摘要

N/S co-doped non-precious metal material for the oxygen reduction reaction( ORR) was prepared with ferrous sulfate heptahydrate(FeSO4·7H2O), pyrrole and p-toluenesulfonic acid(TsOH) as Fe, N and S precursors supported on vulcan XC 72R, and followed by heat treatment in an inert atmosphere at 600℃. The electrochemical techniques such as cyclic voltammetry( CV) and rotating disk electrode( RDE) were employed with the Koutechy-Levich theory to make clear the ORR kinetical constants and the reaction mechanism. It is found that the catalysts dual-doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The overall electron transfer numbers for the catalyzed ORR are determined to be 3. 899 and 3. 098, respectively, for the catalysts with and without TsOH-doping. And these catalysts exhibit superior methanol tolerance to commercial 40%Pt/C catalyst. The XRD results demonstrate the decomposition of the precursors because of pyrolysis and formation of Fe-Nx-C active surface groups and some less active species. XPS analysis indicate that the pyrrolic-N groups are the most active sites and sulfur species are also structurally bonded to carbon in the forms of C—Sn—C and oxidized —SOn— bonds, which are beneficial for ORR.%以吡咯和对甲苯磺酸( TsOH)作为碳载过渡金属催化剂的掺杂剂，经溶剂分散及600℃热处理制备了一种高效催化氧还原反应( ORR )的碳载双杂化过渡金属催化剂( Fe-N/C-TsOH-600).利用 X 射线衍射( XRD)和X射线光电子能谱( XPS)对催化剂的结构进行表征.运用旋转圆盘电极( RDE)技术研究了该催化剂在碱性介质中催化氧还原的电化学催化活性和稳定性，探讨了不同浓度甲醇溶液对Fe-N/C-TsOH-600催化剂催化氧还原活性的影响.结果表明，以Fe-N/C-TsOH-600制备的气体扩散电极在0.1 mol/L KOH电解质溶液中对氧具有很高的选择催化还原活性和稳定性.当电极经过4800圈循环伏安( CV)扫描测试后，催化剂催化氧还原的性能基本保持稳定，并以4电子途径将氧气催化还原.此外，研究还发现， Fe-N/C-TsOH-600在混有甲醇的碱性电解质溶液中对氧的催化还原选择性比商业Pt/C催化剂高. XPS结果表明，吡咯氮是催化剂高效催化氧还原的主要活性中心，提供氧还原的活性位，而TsOH作为供硫掺杂剂对提高催化剂的活性具有重要作用，其加入后形成的C-S-C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.