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.

Palladium-Nickel Electrocatalysts on Nitrogen-Doped Reduced Graphene Oxide Nanosheets for Direct Hydrazine/Hydrogen Peroxide Fuel Cells

“…00-04-0850), it is concluded that all the peaks for synthesized catalysts are placed between the peaks of Pd and Ni metal NPs. These results reveal the successful preparation of the Pd-Ni/NrGO nanostructure in good accordance with those reported in the literature [39,[47][48][49][50].…”

“…Moreover, a new peak appears at 1187 cm −1 which can be related to the C-N bonds. These observations provide valuable information in regard to the existence of nitrogen-containing groups in the synthesized catalyst support in close agreement with reports in the literature [39][40][41]. Figure 1b presents XRD patterns of GO, NrGO, and Pd-Ni/NrGO samples; the existence of sharp peaks in these XRD patterns characterize a crystalline structure for the synthesized materials.…”

“…Such a peak is also observed in the XRD spectra of NrGO and Pd-Ni/NrGO but moving to a higher 2θ value of 26.45 • than that of GO [43,44]. The interlayer spacing of NrGO samples was about 0.340 nm, which is a somewhat smaller than that in the bare rGO (0.37 nm), which is ascribed to the more compact graphitic structure created after nitrogen doping [39,45,46].…”

“…The functional groups of the catalyst support can simplify the incorporation of metal nanoparticles on surfaces. According to recent work [39], FT-IR was conducted to qualify the GO functional groups and their changes in NrGO support after simultaneous nitrogen atom doping of the GO skeleton and reduction of oxygenated species, as shown in Figure 1a. In both spectra (in the range of 400-4000 cm −1 ), the band at 3400 cm −1 demonstrates the O-H stretch of the -OH group.…”

“…The CV method has been used recently for the investigation of borohydride oxidation reaction kinetics that occurred on the bimetallic Pd-based nanocatalysts and also for the calculation of their electrochemical active surface area (ECSA), which determines the electrode kinetics for various redox reactions taking place at the electrode surface. Following on from previous work [39], we decided here to record again the CVs of the Pd-Ni/NrGO and Pd/NrGO in NaOH 1.0 mol L −1 with a sweep rate of 100 mV s −1 , as seen in Figure 3b. In both plots, hydrogen desorption and adsorption peaks (a 1 and C 1 ) are observed from the −0.75 to −0.3 V potential range in the forward and backward sweeps, respectively.…”