Copper nanoparticles immobilized on a hybrid chitosan derivative-graphite substrate as a novel electrocatalyst for the oxygen reduction reaction

Abstract

In this study, abundant and cheap graphite support (G) was modified with chitosan (Chit) and amine groups to obtain N-Chit-G and subsequently decorated with copper nanoparticles (CuNPs). The nanocomposites thus obtained were characterized at different stages of the synthesis using various techniques such as transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller, carbon-hydrogen nitrogen sulfur analyzer, cyclic voltammetry, and electrochemical impedance spectroscopy. Results showed that CuNPs had been uniformly and finely decorated on the N-Chit-G support, in which copper was in the predominant form of Cu(Ⅰ). The Randles–Sevcik equation revealed the high active surface area of Cu@N-Chit-G compared to the remaining composites obtained. Oxygen reduction reaction (ORR) at Cu@N-Chit-G was evaluated by linear sweep voltammetry using a rotating disk electrode in a KOH solution (0.1 mol L−1) saturated with O2 and O2 plus MeOH (1.0 mol L−1) to find the good electrocatalytic capability of Cu@N-Chit-G for ORR with a small onset potential of 0.74 V (vs. RHE). A KOH solution, saturated with MeOH (1.0 mol L−1), revealed good 10000 s durability of Cu@N-Chit-G electrocatalyst with a slow drop in the current (91%). Finally, ORR kinetic investigations were conducted using the Koutecky–Levich (K-L) plot to find the ORR progress through a 4e– pathway.