Nitrogen-doped Reduced Graphene Oxide Nanosheets Research Articles

Mn and Co Co-Substituted Fe3O4 Nanoparticles on Nitrogen-Doped Reduced Graphene Oxide for Oxygen Electrocatalysis in Alkaline Solution

A dispersion of Mn and Co co-substituted Fe3O4 (MCF, Mn:Co:Fe=1:1:1) nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO) nanosheets was prepared by a hydrothermal method. When tested for oxygen electrocatalysis in alkaline solution, the nanoparticles displayed 80% of the oxygen reduction reaction (ORR) activity of a typical 20 wt% Pt/C catalyst (Sigma); and 61% of the oxygen evolution reaction (OER) activity of a 20 wt% RuO2/C catalyst. Extensive material characterizations by field-emission transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma mass spectrometry (ICP-MS) were carried out to provide some understanding of the good electrochemical performance. The MCF catalyst has successfully integrated the ORR activity of manganese oxide, the OER activity of cobalt oxide; and the electronic conductivity of bulk Fe3O4 into an effective bifunctional catalyst; and its good contact with the N-rGO nanosheets also reduces the external transport resistance in oxygen electrocatalysis. Hence the MCF catalyst also delivered good performance in zinc-air full cell tests where they were used in the air electrode.

Mn and Co co-substituted Fe3O4nanoparticles on nitrogen-doped reduced graphene oxide for oxygen electrocatalysis in alkaline solution

A dispersion of Mn and Co co-substituted Fe3O4 (MCF, Mn : Co : Fe = 1 : 1: 1) nanoparticles on nitrogen-doped reduced graphene oxide (N-rGO) nanosheets was prepared by a hydrothermal method. This catalyst exhibited 80% of the oxygen reduction reaction (ORR) activity of a Sigma 20 wt% Pt/C catalyst; and 61% of the oxygen evolution reaction (OER) activity of a 20 wt% RuO2/C catalyst in alkaline solution. Extensive material characterizations by field-emission transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) analysis, and inductively coupled plasma mass spectrometry (ICP-MS) were undertaken to suggest some possible reasons for the good electrochemical performance. The catalyst also delivered good performance in full zinc–air cell tests where it was used in the air electrode. The MCF catalyst has effectively combined the ORR activity of manganese oxide, the OER activity of cobalt oxide; and the electronic conductivity of bulk Fe3O4 into an integrated bifunctional catalytic system; and its good contact with the N-rGO nanosheets also reduces the external transport resistance in oxygen electrocatalysis.

Anchoring CuO nanoparticles on nitrogen-doped reduced graphene oxide nanosheets as electrode material for supercapacitors

CuO/nitrogen-doped reduced graphene oxide (CuO/N-RGO) composites are prepared by refluxing in ammonia solution and low temperature annealing. The as-prepared samples have been characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The loading of CuO has been measured by using inductively coupled plasma mass spectroscopy (ICP-MS). Results reveal that the CuO nanoparticles with ∼5nm in diameter are anchored homogeneously on the nitrogen-doped reduced graphene oxide (N-RGO) nanosheets. Their electrochemical performances for supercapacitors are investigated by cyclic voltammetry (CV), galvanostatic charge–discharge and electrochemical impedance spectroscopy (EIS). The CuO/N-RGO composite with 15.1wt% CuO loading shows a high specific capacitance of 340Fg−1 at a charge/discharge current density of 0.5Ag−1 in 6moldm−3 KOH electrolyte, and with a wide potential window of 1.4V. Importantly, 58% of capacitance is retained when the charge/discharge current density increases from 0.5Ag−1 to 5Ag−1. The capacitance retention can reach to 80% after 500 charge/discharge cycles. These findings demonstrate that the CuO/N-RGO material is a promising candidate for supercapacitor applications.