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.
In the present work, nitrogen-doped reduced graphene oxide-supported (NrGO) bimetallic Pd–Ni nanoparticles (NPs), fabricated by means of the electrochemical reduction method, are investigated as an anode electrocatalyst in direct hydrazine–hydrogen peroxide fuel cells (DHzHPFCs). The surface and structural characterization of the synthesized catalyst affirm the uniform deposition of NPs on the distorted NrGO. The electrochemical studies indicate that the hydrazine oxidation current density on Pd–Ni/NrGO is 1.81 times higher than that of Pd/NrGO. The onset potential of hydrazine oxidation on the bimetallic catalyst is also slightly more negative, i.e., the catalyst activity and stability are improved by Ni incorporation into the Pd network. Moreover, the Pd–Ni/NrGO catalyst has a large electrochemical surface area, a low activation energy value and a low resistance of charge transfer. Finally, a systematic investigation of DHzHPFC with Pd–Ni/NrGO as an anode and Pt/C as a cathode is performed; the open circuit voltage of 1.80 V and a supreme power density of 216.71 mW cm−2 is obtained for the synthesized catalyst at 60 °C. These results show that the Pd–Ni/NrGO nanocatalyst has great potential to serve as an effective and stable catalyst with low Pd content for application in DHzHPFCs.
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