Non-precious electrocatalysts synthesized from metal–organic frameworks

Abstract

Proton exchange membrane fuel cells (PEMFCs) are considered as clean and efficient energy conversion devices with great potential to replace currently used internal combustion engines (ICEs) in the near future. Developing high-performance and less expensive non-precious metal electrocatalysts for oxygen reduction reaction (ORR) at the cathode side is crucial for widespread application of PEMFCs. Herein an Fe-containing metal–organic framework (MOF) was employed as the sole precursor for preparing a cathode electrocatalyst. The Fe-MOF was synthesized and subsequently subjected to thermolysis under a non-reactive gas atmosphere followed by acid leaching and heat treatment under NH₃ at different temperatures between 700 and 1000 °C. Upon pyrolysis, iron–nitrogen containing carbon active sites (Fe/N/C) were formed in parallel with development of an electronically conductive carbon medium produced through pyrolytic carbonization of the organic component of the MOF material. The prepared electrocatalysts were characterized by XRD, N₂ physisorption, TEM and XPS. In a H₂SO₄ (pH = 1) electrolyte, the ORR onset potential of 0.915 V, and the half-wave potential of 0.811 V are achieved using the most promising electrocatalyst (C700/950). The membrane electrode assemblies (MEAs) made of these electrocatalysts were also tested as a cathode in a H₂/air single fuel cell. The most promising electrocatalyst (C700/950) demonstrated an open circuit voltage of 0.945 V and a maximum power density of 0.302 W cm⁻² reached at 0.391 V.