Carbon supported Fe–Co nanoparticles with enhanced activity and BH4− tolerance used as a cathode in a passive air breathing anion exchange membrane direct borohydride fuel cell

Abstract

The performance and borohydride-tolerance of a non-noble metal cathode nanocatalyst, Hypermec™K14, were investigated in an anion-exchange membrane direct borohydride fuel cell (DBFC). Cell polarization curves in the passive air breathing DBFC indicate that the DBFC equipped with a non-noble metal cathode catalyst exhibit a higher open circuit voltage and peak power density compared to a DBFC, which uses commercial 10 wt% Pt/C at the cathode side; 0.970 V and 138 mW cm⁻² vs. 0.752 V and 48 mW cm⁻². Data on the performance of the active DBFC using Hypermec™K14 gives power densities of 890 mW cm⁻² using an oxidant and fuel flow rate of 250 and 6 mL min⁻¹, respectively, at 75 °C. Further electrochemical investigations were carried out by a driven-cell mode to compare the NaBH₄-tolerance of Hypermec™K14 and 10 wt% Pt/C in a DBFC. Hypermec™K14 exhibits excellent tolerance towards NaBH₄ electrooxidation compared to 10 wt% Pt/C catalyst; tolerance is 10 times higher according to the produced current density from the oxidation of crossed-over fuel. Separation of the anode and cathode polarizations in both membrane electrode assemblies (MEAs) confirms that the difference in the cathode polarization is responsible for the difference in the obtained cell power densities. Electrochemical impedance spectra of both cells also demonstrate the lower charge and mass transfer resistances for DBFC equipped with Hypermec™K14, which is consistent with the obtained performance. The layered microstructure of the catalyst was also investigated by N₂ adsorption (BET) study and scanning electron microscopy (SEM).