Tailoring CoNi Alloy-Embedded Carbon Nanofibers by Coaxial Electrospinning for an Enhanced Oxygen Reduction Reaction

A flexible CoNi@CNF electrochemical catalyst was developed using coaxial electrostatic spinning technology. The distribution and content of CoNi alloy nanoparticles on the surface of carbon fibers were adjusted by regulating the feed speed ratio of the outer and inner axes of coaxial electrostatic spinning. The results indicate that the content of the CoNi alloy distributed on the carbon fiber surface increased from 26.7 wt.% to 38.4 wt.% with an increase in the feed speed of the inner axis. However, the excessive precipitation of the CoNi alloy on the carbon fiber surface leads to the segregation of the internal CoNi alloy, which is unfavorable for the exposure of active sites during the electrolytic reaction. The best electrocatalytic performance of the composite was achieved when the rate of the outer axis feed speed was constant (3 mm/h) and the rate of the inner axis was 1.5 mm/h. The initial oxygen reduction potential and half-slope potential were 0.99 V and 0.92 V (VS RHE), respectively. The diffusion-limited current density was 6.31 mA/cm−2 and the current strength retention was 95.2% after the 20,000 s timed current test.