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

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 degrees C are obtained for Pd-Ni/N-rGO and Pd-Co/N-rGO, respectively.