Graphene Incorporation as a Propitious Approach for Improving the Oxygen Reduction Reaction (ORR) Activity of Self-assembled Polycrystalline NiCo2O4–NiO

Abstract

Electrocatalytic activity of a new, pristine and graphene-modified NiCo2O4–NiO catalysts towards oxygen reduction reaction (ORR) was gauged. Linear sweep voltammetry attests that NiCo2O4–NiO (NCO) catalyst, obtained by a facile synthesis route based on a self-assembling co-templated by diethanolamine (DEA) and tripropylamine (TPA), shows conspicuous catalytic activity towards ORR. The catalytic activity of NCO was tentatively ascribed to the presence of the cubic spinel NiCo2O4 and of a small amount of NiO, as a secondary phase (evidenced by XPS and XRD) which most likely enables the formation of efficient active sites and enhances the conductivity of the material. After mixing the NCO with reduced graphene oxide (rGO), the catalytic activity of the new composite NiCo2O4–NiO-rGO (NCO-rGO) was significantly improved. Electrochemical results reveal that the presence of graphene facilitates a more efficient mass transport, supplies more accessible active sites, and provides higher stability and better resistance to deactivation during ORR. The synthesis route herein developed for preparing NCO material might be successfully used for large-scale applications due to its outstanding features, such as low cost, easy availability, and straightforward control of the phase composition.