N-Doped Carbon Nanofibers and Carbon Nanotubes-Encapsulated CoNi Alloy as Highly Active Oxygen Reduction Catalysts for Direct Methanol Fuel Cells

The slow oxygen reduction kinetics of direct methanol fuel cell (DMFCs) are one of the limiting factors affecting its application. Therefore, exploring nonprecious catalysts with high activity and methanol resistance is urgently needed. Herein, zeolitic imidazolate framework-8 particles are first blended with different proportions of metal salts (Ni as well as Co) and further electrospun to obtain a nanofiber precursor. After pyrolysis treatment, a composite catalyst (CoNi@N-CNFs) with a highly dispersed CoNi alloy phase supported by porous N-doped carbon nanofiber and carbon nanotube is prepared. The surface electronic structure can be reasonably adjusted by optimizing the doping ratio of Ni and Co. The CoNi@N-CNFs shows high oxygen reduction activity and methanol resistance. Half-wave potential and the onset potential of Co1Ni1@N-CNFs (Co: Ni mole ratio = 1:1) are 0.79 and 0.87 V. Additionally, Co1Ni1@N-CNF-modified DMFC endows a high power density (24.07 mW cm-2), which is close to Pt/C-based DMFC (27.59 mW cm-2). Rich active sites, large specific surface area, and synergy between CoNi alloy and N configuration of CoNi@N-CNFs effectively accelerate electron transfer, resulting in the superior catalytic activity. This work provides a new strategy to design effective 1D oxygen reduction reaction catalysts in fuel cells. Herein, a novel N-doped carbon nanofiber catalyst loaded with CoNi alloy nanoparticles is synthesized through a simple electrospinning and pyrolysis process. The synergistic effect between CoNi alloy and N doping promotes oxygen reduction reaction (ORR) performance. CoNi@NCNF/carbon nanotube (CNT) exhibits high ORR activity and methanol tolerance. Direct methanol fuel cells modified with CoNi@NCNF/CNT provides high power (24.07 mW cm-2).image (c) 2024 WILEY-VCH GmbH