Multi-scaled porous Fe-N/C nanofibrous catalysts for the cathode electrodes of direct methanol fuel cells

In the present work, a nanofibrous Fe-N/C catalyst with a multi-scaled porous structure is proposed and prepared via electrospinning a polyacrylonitrile (PAN) solution containing Fe3+incorporated graphitic carbon nitride (Fe-g-C3N4). Physical and chemical characterizations confirm that micropores, mesopores and hollow-out macropores are co-existed in the Fe-N/C nanofibrous catalysts. The abundant micropores are beneficial for accommodating active sites, while the mesopores and hollow-out macropores can facilitate the supply of oxygen to the active surfaces. Moreover, due to the fibrous morphology of the catalyst, a 3D highly-porous electrode with well-established networks can be formed for facile transport of electrons and oxygen. The experimental results show that the Fe-N/C catalyst delivers a good activity toward oxygen reduction reaction (ORR) in acid media with a half-wave potential of 740 mV and an almost four-electron transfer process, high stability and excellent methanol tolerance. Furthermore, the as-prepared catalyst is used to fabricate the cathode of a direct methanol fuel cell, which yields a peak power density of 14.9 mW cm-2with 1 M methanol solutions, dry air and an operating temperature of 70°C.