Hybrid electrode obtained by sol-gel derived Ni0.3Co2.7O4 nanoparticles incorporated into polypyrrole: Electrocatalysis of O2 reduction

Abstract

A hybrid electrode was formed on glassy carbon (GC) electrode with polypyrrole (PPy) and mixed valence Ni0.3Co2.7O4 nanoparticles to study their behaviour towards the oxygen reduction reaction (ORR). The oxide nanoparticles were prepared by sol-gel route using various parameters and characterized by XRD, SEM, EDX and BET methods. The result showed that desired oxide was obtained and nanocrystallites exhibit a specific surface area ranging from 39 to 73m2/g with diameter varying from 13 to 25 nm. The hybrid electrode was then fabricated by electropolymerization of pyrrole (Py) in the presence of the smallest Ni0.3Co2.7O4 nanoparticles in KCl (0.15mol/L) at room temperature and characterized by EDX, SEM and LSV methods. Investigation of the hybrid electrode confirmed that O2 reduction mechanism changes by applying potential. Thus, at low overpotential the O2 reduction involves two electrons and provides H2O2, with cathodic transfer coefficients (β) of 0.33 and exchange current density (j0) of about 8×10-3 mA/cm2, while, at high overpotential H2O2 is further reduced into H2O. The results also show that sol-gel method led to the preparation of Ni0.3Co2.7O4 nanoparticles having a spinel structure with a desired stoichiometry which exhibits a high electrocatalytic activity for reducing oxygen mostly to H2O2.