Dual-template strategy synthesis of hierarchically porous electrocatalysts for oxygen reduction reaction

Abstract

Metal organic frameworks derived M-N-C catalysts have been discovered as promising alternatives to Pt-based catalysts in oxygen reduction reaction (ORR). However, the dominated micropores in their porous structures strongly restrain the mass transfer and lead to insufficient utilization of active sites. Here, we proposed a dual-template strategy to improve the catalytic performance of ZIF-8 derived M-N-C catalysts. Both the silica and sodium chloride templates created mesopores, which may intensified the mass transfer. Moreover, the molten sodium chloride connected the individual ZIF-8 crystals form highly graphitized carbon structure which had better stability and conductivity. The as-synthesized (FeCo)HPNC@NaCl catalyst exhibited similar ORR activity to commercial Pt/C under acidic conditions with half-wave potential of 0.808 V. The catalyst expressed high stability with 12 mV decrease of half-wave potential after 5000 cycles and 80% remained activity after 100000 s operation. Moreover, we tested the catalyst in fuel cell for practical application, achieving a high peak power density of 427 mW cm⁻².