Synthesis of Cu9S8/carbon nanotube nanocomposites with high electrocatalytic activity for the oxygen reduction reaction

Abstract

We have synthesized Cu₉S₈/carbon nanotube (CNT) nanocomposites (NCs) with high electrocatalytic activity for direct methanol fuel cells (DMFCs). Cu₉S₈/CNT NCs are prepared from Cu(NO₃)₂, CNTs, and thioacetamide in the presence of poly(vinylpyrrolidone) under alkaline conditions. There are Cu₉S₈ nanoparticles (diameter: 50 ± 6 nm) and aggregates on the surfaces of CNTs. The as-prepared Cu₉S₈/CNT NC modified electrodes provide a four-electron pathway for the oxygen reduction reaction (ORR) in alkaline media. Three representative Cu₉S₈/CNT electrodes (mass loading: 1.63 mg cm⁻²) provide a mean limiting current density of 3.43 ± 0.03 mA cm⁻² (each with three measurements) at a constant scan rate of 1 mV s⁻¹ and a rotation rate of 3600 rpm. At a constant potential of −0.5 V, the kinetic rate constant for the Cu₉S₈/CNT is 2.82 × 10⁻² cm s⁻¹, revealing higher activity of the Cu₉S₈/CNT electrodes in the ORR. The Cu₉S₈/CNT relative to Pt/C electrodes is more tolerant against methanol and carbon monoxide poisoning. These low-cost, stable, and highly active Cu₉S₈/CNT electrodes have great potential for use in DMFCs.