Influence of Fe-N-C morphologies on the oxygen reduction reaction in acidic and alkaline media

The development of nonnoble metal oxygen reduction reaction (ORR) catalysts for fuel cells has been motivated by the high cost and limited supply of noble metals, as well as the desire to improve the performance and durability of this type of energy conversion device. In this study, nonnoble Fe-N-C catalyst was synthesized using a zeolitic imidazole framework (ZIF-8), poly (aniline), and 10,10 & PRIME;-dibromo-9,9 & PRIME;-bianthry as precursors to produce Fe-N-C with hollow sphere (HS), amorphous bulky structure (B), and sheet-like thin sheet (N) structure. The Fe-N-C catalyst was analysed in terms of their shape, crystal structure, pore characteristics, and elemental composition. Among all the Fe-N-C catalysts, Fe-N-C_HS had the highest total surface area, followed by Fe-N-C_B and Fe-N-C_N. To evaluate their ORR catalytic activity, a half-cell electrochemical experiment with .1 M KOH and .1 M HClO4 as the alkaline and acidic electrolytes was conducted. This study revealed that Fe-N-C_HS exhibited the highest onset potential but the Fe-N-C_B has the highest limiting current density in alkaline medium; meanwhile, in acidic media, Fe-N-C_HS shows the best ORR performance with the highest onset potential and limiting current. This highly porous Fe-N-C_HS catalyst also demonstrated active site activation and excellent stability compared with the other samples as well as commercial Pt/C in acidic electrolyte, which suggests its potential for application in proton exchange membrane fuel cells (PEMFCs).