Tailoring porosity and diameter into carbon nanofiber membrane: freestanding electrodes with mechanical flexibility and catalytic functionality in direct methanol fuel cell.

Engineering free-standing electrodes that combine mechanical flexibility with electrocatalytic activity is pivotal for motivating fuel cell development. Here, A binder-free, flexible, and porous free-standing PCNF-15-250 catalyst was fabricated via electrospinning, effectively eliminating the requirement for traditional binder components in alkaline direct methanol fuel cells (DMFC). Notably, the diameter and porous structure of the nanofibers are meticulously tailored by modulating the concentration of polyvinylpyrrolidone in the polymer blend and the pre-oxidation temperature. The stress-strain curve and characterization techniques unveil that the suitable diameter coupled with internal porosity synergistically mitigate stress concentration, thereby endowing PCNF-15-250 with excellent mechanical flexibility. Concurrently, the porous architecture facilitates mass/electron transfer, accelerating reaction kinetics. Oxygen reduction activity is augmented by pyridinic-N, pyrrolic-N and graphitic-N formed during pyrolysis, as reflected by a half-wave potential of 0.67 V. As anticipated, PCNF-15-250 is deployed directly as a binder-free cathode in DMFC, effectively decreasing the interfacial impedance of the membrane electrode and delivering a peak power density of 8.74 mW cm-2. This work delineates a cost-effective synthesis strategy for flexible self-supporting electrodes, offering a novel insight to conquer interfacial impedance and mechanical fragility associated with traditional electrodes.