Noble-metal-free Electrocatalysts for Oxygen Reduction Reaction in Alkaline Media: Efficient Oxygen Reduction Reaction by NiO/Reduced Graphene Oxide Composite Synthesized Using Molecular Level Mixing

Abstract

For commercial use and large-scale applications of proton exchange membrane (PEM) fuel cells, using Pt as an electrocatalyst is a significant hindrance due to its low abundance and high cost. To make the PEM fuel cells commercially viable, cost-effective materials with performance comparable to that of Pt are required. In this work, a NiO/reduced graphene oxide (rGO) composite is synthesized and tested as an efficient electrocatalyst for the oxygen reduction reaction (ORR). The ORR activity of NiO/rGO composite, in terms of onset potential (i.e., ∼−0.04 V at −0.1 mA/cm²), half-wave potential (i.e., ∼−0.3 V), and limiting current density (∼4 mA/cm²-geo) are excellent for a non-noble metal containing electrocatalyst for ORR. The efficient ORR activity of the NiO/rGO composite is attributed to the presence of Ni²⁺/Ni³⁺ redox couples and oxygen defects in the material, as revealed by different characterization results.