R. Imran Jafri

Nitrogen doped graphene nanoplatelets as catalyst support for oxygen reduction reaction in proton exchange membrane fuel cell

Graphene nanoplatelets have been synthesized by thermal exfoliation of graphitic oxide and nitrogen doped graphene nanoplatelets have been obtained by nitrogen plasma treatment. Graphene nanoplatelets and nitrogen doped graphene nanoplatelets have been used as a catalyst support for platinum nanoparticles for oxygen reduction reactions in proton exchange membrane fuel cells. Platinum nanoparticles were dispersed over these support materials using the conventional chemical reduction technique. The morphology and structure of the graphene based powder samples were studied using X-ray diffraction, Raman spectroscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. A full cell was constructed with platinum loaded nitrogen doped graphene nanoplatelets and the results have been compared with platinum loaded graphene nanoplatelets. A maximum power density of 440 and 390 mW cm−2 has been obtained with platinum loaded nitrogen doped graphene and platinum loaded graphene nanoplatelets as ORR catalysts respectively. Nitrogen plasma treatment created pyrrolic nitrogen defects, which act as good anchoring sites for the deposition of platinum nanoparticles. The improved performance of fuel cells with N-G as catalyst supports can be attributed to the increased electrical conductivity and improved carbon–catalyst binding.

Nanostructured Pt Dispersed on Graphene-Multiwalled Carbon Nanotube Hybrid Nanomaterials as Electrocatalyst for PEMFC

Nanostructured platinum dispersed on functionalized graphene and functionalized multiwalled carbon nanotube [Pt/(f-G-f-MWNT)] hybrid nanomaterials, a unique combination of three-, two, and one-dimensional structures, were used as an electrocatalyst for oxygen reduction reaction (ORR) in proton exchange membrane fuel cell (PEMFC). Electrochemical studies performed on Pt/(f-G-f-MWNT) composite materials by varying the ratio of the composition of f-G and f-MWNT for the investigation of the electrochemical active surface area (ECSA) have resulted in an ECSA as high as 108 m 2 /g for the Pt dispersed on nanocomposite containing equal proportions of f-G and f-MWNT. Polarization graphs for the ORR reaction in PEMFC with Pt/(f-G-f-MWNT) as an electrocatalyst resulted in the best performance of 540 mW/cm 2 for the Pt/(50 wt % f-G + 50 wt % f-MWNT) cathode catalyst, agreeing with the electrochemical active surface area of Pt, due to good accessibility and uniform dispersion of the nanostructured Pt catalyst dispersed on the f-G-f-MWNT catalyst support, making them a suitable electrocatalyst for advanced PEMFC.

Solar exfoliated graphene–carbon nanotube hybrid nano composites as efficient catalyst supports for proton exchange membrane fuel cells

Ultra thin graphene–multi walled carbon nanotube composites prepared by a solar exfoliation technique have been explored as catalyst supports for oxygen reduction reaction (ORR) in proton exchange membrane fuel cells (PEMFC). Pt nanoparticles were dispersed on a solar exfoliated graphene-functionalized multi walled carbon nanotube (sG-fMWNT) hybrid nanocomposite, which exhibits higher electrocatalytic activity for ORR than Pt dispersed functionalized solar graphene (f-sG) catalyst support. The single cell PEMFC measurements give maximum power densities of 355 mW cm−2 and 675 mW cm−2 with sG and sG-f MWNT respectively. The improved performance in the power density with the sG-f MWNT fuel cell can be ascribed to the synergistic effect of 1D MWNT and 2D graphene in sG-f MWNT as well as its high electrochemical surface area. The inclusion of MWNT bridges the defects for electron transfer besides increasing the basal spacing between graphene sheets. The good performance and possibility of high throughput production of sG-f MWNT makes this material a promising catalyst support for PEMFC.

Hydrothermal Synthesis of RuO2·xH2O/Graphene Hybrid Nanocomposite for Supercapacitor Application

Herein we report a facile approach for synthesis of well dispersed hydrated ruthenium oxide nanoparticles onto the surface of hydrogen exfoliated graphene (HEG) sheets via hydrothermal synthesis route. The as prepared hybrid nanocomposite (RuO2·xH2O/HEG) was characterized by X-ray diffraction analysis (XRD), field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). A symmetrical supercapacitor was fabricated and the electrochemical performance of this model supercapacitor cell was investigated by cyclic voltammetry (CV), chronopotentiometry (CP) and impedance spectroscopy (EIS) in 1.0 M H2SO4 solution. The hybrid nanocomposite shows a maximum specific capacitance of 154 F/g and energy density of about 11Wh/kg at a specific discharge current of 1 A/g (20 wt% Ru loading). The composite also shows a maximum power density of 5 kW/kg and coulombic efficiency of 97% for a specific discharge current of 10 A/g. KeywordsSupercapacitor; Hybrid Nanocomposite; Graphene; Hydrothermal; Pseudocapacitance