Ni@Pd core-shell nanostructure supported on multi-walled carbon nanotubes as efficient anode nanocatalysts for direct methanol fuel cells with membrane electrode assembly prepared by catalyst coated membrane method

Abstract

Multi-walled carbon nanotubes supported Ni@Pd core-shell nanoparticles (Ni@Pd/MWCNTs) are successfully synthesized by two-step reduction procedure. The Ni@Pd/MWCNTs electrocatalysts are characterized by using field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. According to characterization results, nanoparticles (5–10 nm) are spread on carbon support uniformly with high porosity. Moreover, the electrocatalytic performance of Ni@Pd/CNTs towards methanol electro-oxidation are evaluated using cyclic voltammetry, electrochemical impedance spectroscopy, chronoamperometry and chronopotentiometry methods in a conventional three-electrode cell. The results show that Ni@Pd/MWCNTs electrocatalysts have a good catalytic activity towards methanol oxidation in alkaline solutions. The performance of direct methanol fuel cell (DMFC) is evaluated in a single fuel cell set-up. The Membrane Electrode Assembly used in fuel cell set-up is prepared by catalyst-coated membrane technique. The catalyst loading is fixed at 0.5 mg Pt/C cm−2 for the cathode and 1.0 mg Ni@Pd/MWCNTs cm−2 for the anode. The used anolyte and catholyte are NaOH + CH3OH and H2SO4 + H2O2, respectively. The results exhibit that the maximum power density is about 67 mW cm−2 at 60 °C. The present paper clearly demonstrates the possibility of Ni@Pd/MWCNTs nanostructure as good performance and less expensive anode catalyst for DMFCs.