Steam activation of Fe-N-C catalyst for advanced power performance of alkaline hydrazine fuel cells

Abstract

Alkaline hydrazine liquid fuel cells (AHFC) have been highlighted in terms of high power performance with non-precious metal catalysts. Although Fe-N-C is a promising non-Pt electrocatalyst for oxygen reduction reaction (ORR), the surface density of the active site is very low and the catalyst layer should be thick to acquire the necessary number of catalytic active sites. With this thick catalyst layer, it is important to have an optimum pore structure for effective reactant conveyance to active sites and an interface structure for faster charge transfer. Herein, we prepare a Fe-N-C catalyst with magnetite particles and hierarchical pore structure by steam activation. The steam activation process significantly improves the power performance of the AHFC as indicated by the lower IR and activation voltage losses. Based on a systematic characterization, we found that hierarchical pore structures improve the catalyst utilization efficiency of the AHFCs, and magnetite nanoparticles act as surface modifiers to reduce the interfacial resistance between the electrode and the ion-exchange membrane.