Zeolitic imidazolate framework-67 derived ultra-small CoP particles incorporated into N-doped carbon nanofiber as efficient bifunctional catalysts for oxygen reaction

Abstract

Herein ultra-small CoP nanoparticles incorporated into nitrogen-doped carbon nanofibers derived from zeolitic imidazolate framework-67 (ZIF-67) are found active as a bifunctional catalyst for oxygen electrocatalysis. The composite nanofibers of polyacrylonitrile-cobalt acetate are firstly prepared by the electrostatic spinning and then immersed into 2-methylimidazole ethanol solution for the growth of restricted ZIF-67. The hybrid is further annealed and phosphided to obtain the ultra-small CoP nanoparticles incorporated into nitrogen-doped carbon nanofibers (CoP/NC). The degree of carbonization and retention of the nanofiber topology structure are determined by the annealing temperature. Excellent bifunctional oxygen electrocatalysis performance is observed on CoP/NC and the performance improvement can be attributed to the more active site exposure, good conductivity and co-action of CoP and N-doped carbon nanofiber. An overpotential of 290 mV is required to drive 10 mA cm−2 for oxygen evolution reaction, and an onset potential of 0.90 V and half-wave potential of 0.78 V are obtained for the oxygen reduction reaction in the alkaline electrolyte. A strong application in Zn-air battery is also demonstrated compared with the device configured by Pt/C catalyst. The current work demonstrates a significant technique to boost the catalytic performance of MOF derived catalysts for energy-relevant catalytic reactions.