In-situ synthesis and characterization of metal free heteroatom doped graphene based oxygen reduction reaction catalyst from pyrolysed Assam silk cocoons

Abstract

The fuel cell and electrolyzer together may be an important alternative source for clean energy production. The oxygen-hydrogen produced in the water splitting reaction in an electrolyzer may also be used in any conventional combustion engines with a little or no modification of the existing engines. The sluggish oxygen reduction reaction (ORR) in these devices necessitates higher loading of catalysts in the cathode. However, the best catalyst used in fuel cell and electrolyzer is platinum and/or its derivatives. The use of metal free graphene based heteroatom doped ORR catalyst may be a promising alternative for conventional platinum electrocatalyst. In particular, nitrogen-doped Graphene synthesized from natural carbon based biomass material has the potential to be a sustainable, green and economical ORR. In this study, Assam silk cocoons was used to synthesize nitrogen doped graphene based catalyst via one step in-situ pyrolysis. The morphological and chemical characterization of the synthesized catalyst was carried out with the help of XRD, Raman, FTIR, TEM, EDS and XPS. The X-Ray diffractograms of the catalyst revealed presence of defect induced broad peaks at graphitic 002 and 004 peaks at 24.5° and 43°, respectively. The Raman spectra showed the presence of D-band, G-band and D′ band with an ID/IG ratio of 0.86. The EDS analysis confirmed the presence of 21.55 At% in-situ nitrogen in the synthesized catalyst. The morphological analysis through TEM showed the presence of multilayer graphene. The formation of in-situ nitrogen doped graphene catalyst was confirmed through X-ray photoelectron spectroscopy, which showed the presence of pyridinic and graphitic nitrogen. The synthesized electrocatalyst was later analyzed with the help of a rotating disk electrode for its catalytic activity in ORR.