Fe₃C/C nanoparticles encapsulated in N-doped graphene aerogel: an advanced oxygen reduction reaction catalyst for fiber-shaped fuel cells

Flexible fuel cells directly convert the chemical energy to electricity, and represent one of the most promising power generators using in bendable electronic equipments such as curved displays and wearable devices. The ambient oxygen is the most acceptable oxidant, and therefore the design of highly actived and low cost oxygen reduction reaction (ORR) catalysts is extremely important for future commercialization. Here we report a facile process to fabricate the catalyst by encapsulating the Fe₃C/C nanoparticles on the nitrogen-doped graphene aerogel scaffolds. Benefitting from the meso-porous structure and presence of Fe–N–C functionalities that serve as the catalytic sites, the conductivity and active-site accessibility in the composites are significantly improved. The resulting hybrid electrocatalysts show a comparable catalytic performance with 20 wt% commercial Pt/C powder, but possess a much lower capital cost and higher tolerance to fuel in the durability test. Consequently, the fiber-shaped fuel cell delivers a high-power density of 4.57 W m⁻² and current density of 22.5 A m⁻², outperforming many flexible fuel cells reported previously. Such a non-noble-metal ORR catalyst opens new avenue to trigger the electricity generation by fiber-shaped fuel cell under the folded and rolled-up conditions.