Abstract: 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℃ heat-treatment yielded the most active Fe-N_x/C catalyst. Fe-N_x/C catalyst with several Fe loadings(3%, 4%, 5%, 6%, 7%, 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-N_x/C catalyst. The stability of the Fe-N_x/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\5h).

Key words: Protonexchange membrane fuel cell(PEMFC), 2,6-Diaminopurine(Hdap), Fe-N_x/C electro-catalyst, Oxygen reduction reaction activity