Novel Bimetallic Pd–X (X = Ni, Co) Nanoparticles Assembled on N-Doped Reduced Graphene Oxide as an Anode Catalyst for Highly Efficient Direct Sodium Borohydride–Hydrogen Peroxide Fuel Cells

Abstract

Bimetallic Pd–X (X = Ni, Co) nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO) are fabricated through a thermal solid-state technique followed by polyol reduction to be used as anode electrocatalysts for direct sodium borohydride–hydrogen peroxide fuel cells. The physical characterization of synthesized materials is investigated using Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The results confirm the uniform distribution of nanoparticles on nitrogen-doped reduced graphene oxide with a size of 11–13 nm. The electrochemical half-cell tests are used to study their electrocatalytic properties toward borohydride oxidation in an alkaline solution. Although perfect performance is observed for both catalysts, Pd–Ni/N-rGO indicates a higher current density, better stability, more negative onset potential, lower activation energy, and smaller charge-transfer resistance than the other. Kinetic studies suggest a first-order reaction with 6.83 and 6.06 electrons exchanged during the borohydride oxidation reaction for Pd–Ni/N-rGO and Pd–Co/N-rGO electrocatalysts, respectively. Finally, a direct sodium borohydride–hydrogen peroxide fuel cell is assembled using Pt/C as a cathode and Pd–X (X = Ni, Co)/N-rGO as an anode. Maximum power density values of 353.84 and 275.35 mW cm^–2 at 60 °C are obtained for Pd–Ni/N-rGO and Pd–Co/N-rGO, respectively.