HYBRID ELECTRODE FORMED BY 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 and characterized by XRD method. The result showed that the desired oxide was obtained and the nanocrystallites exhibit a diameter about 13 nm. The hybrid electrode was then fabricated by the electropolymerization of pyrrole (Py) in the presence of Ni0.3Co2.7O4 nanoparticles in KCl (0.15 mol/L) at room temperature and characterized by 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 an exchange current density (j0) of about 8×10-3 mA/cm2, while, at high overpotential H2O2 is further reduced into H2O. Also, the result shows that the 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