Fe-Nx/C电催化剂的氧还原性能及配体结构对催化活性的影响

摘要

以2,6-二氨基嘌呤(Hdap)为配体合成了Fe-Nx/C氧还原催化剂,并优化了热处理温度和Fe含量.对催化剂组成和结构进行了表征,分析了配体Hdap在热处理过程中随温度的变化情况,通过循环伏安法和线性扫描伏安法测试了催化剂的氧还原催化性能.结果表明,热处理温度为800℃,Fe质量分数为5％时,催化剂活性最高.吡啶N含量较高的配体有利于提高催化剂的活性,配体中含S元素会增加催化剂的活性.%2,6-Diaminopurine was used as a ligand to prepare Fe-Hdap complexes for the development of a new oxygen reduction reaction (ORR) catalyst. The prepared Fe-Hdap complexes were heat-treated at 600, 700, 800 and 900 ℃ to optimize their activity for ORR. It was found that the 800 V. heat-treatment yielded the most active Fe-Nx/C catalyst. Fe-Nx/C catalyst with several Fe loadings(3% , 4% , 5% , 6% , 1% , mass fraction) were also synthesized and a 5% Fe loading yielded the best catalytic ORR activity. XRD, TG, TEM, XPS and line-scan voltammograms techniques were used to characterize the structural changes in these catalyst after heat-treatment, including the catalyst composition, structure, morphologe and the electrochemical activity. As observed by XRD, when the heat-treatment temperature or Fe content was too high, Fe3O4 could be produced. This would lead to a decrease in ORR activity. XPS analysis revealed that the catalyst surface consisted of 0. 61% (mass fraction) N(largely pyrrolic-like). The ORR activities of/catalysts synthesized using ligands with different structures were studied. The result indicated that the catalyst prepared using the compound containing more pyridinic N as ligand had enhanced activity, and the S element in ligand can improve the activity of Fe-Nx/C catalyst. The stability of the Fe-Nx/C catalyst in the voltage region having ORR kinetic limiting was tested by fixing a electrode potential to record the change in current density with time. The obtained degradation rates for this catalyst is 0. 0048 mA/ ( cm2·h).