Fe-Nx biomass-derived carbon material as efficient cathode electrocatalyst for alkaline direct methanol fuel cells

Abstract

Biomass-derived carbon materials are emerging as potential alternatives to reduce the production cost and environmental impact of electrocatalysts production. This study aims to assess two catalysts based on Fe sites over N-doped carbon materials with different textural properties towards oxygen reduction reaction (ORR) for alkaline direct methanol fuel cell (ADMFC) applications. Almond shell (AS) residues and an activated carbon (KUA) were proposed as carbon precursors for the two Fe-N-C catalysts which were obtained by similar synthesis procedures and carbonized at 900 °C in a single high-temperature treatment. Although the activity and selectivity towards the ORR of both samples evaluated in a half-cell configuration were comparable, very different performances were observed in an ADMFC device. The membrane-electrode assembly (MEA) containing the biomass-derived carbon material at the cathode side showed a high-power density, comparable to a 40 wt% Pt/C at low methanol concentration (1 M). The performance of the MEAs containing the synthesized electrocatalysts was maintained or increased in a 5 M methanol solution while Pt/C-based MEA suffered depolarization for concentrations higher than 1 M. After a 100 h durability test, high power density was maintained with the Fe-N derived biomass electrocatalyst. This work provides a first approach of applying biomass-derived catalysts as cathodes for ADMFCs and challenges in terms of stability and performance are explored.