The Preparation Of Heteroatom Doped Graphene Aerogels As Efficient Electrocatalyst For Oxygen Reaction

Direct methanol fuel cells(DMFCs) have been paid intensive attentions attributed to their low operating temperature, eco-friendly nature, high energy density and good stability. However, the sluggish kinetics of the cathodic ORR is one of the most important factors hindering the performance of DMFCs. So far, platinum(Pt)-based catalysts are widely applied as effective catalysts due to their relative lower overpotential and higher current density. Nevertheless, Pt-based catalysts still encounter several problems, such as the high price, intolerance to poisonous substance, and instability. These disadvantages have tremendously hindered fuel cells widespread commercialization.In recent years, heteroatom-doped carbons are regard as high active catalysts for ORR. Herein, in this essay, three kinds of heteroatom-doped graphene aerogels are prepared through hydrothermal synthesis and high temperature pyrolysis two-step process. Firstly, 5-amino-1,3,4-thiadiazole-2-thiol(C2H3N3S2) was used for sulfur and nitrogen sources, poly 5-amino-1,3,4-thiadiazole-2-thiol(PATT) modified graphene hydrogels(PATT-GHs) were prepared by hydrothermally assembled method, then, the as-prepared hydrogels were directly dehydrated via a freeze-drying process for 48 h to gain PATT modified graphene aerogels(PATT-GAs). Following, The catalyst pyrolyzed at different temperatures was denoted as N-S-GAs X; Secondly, 2,6-aminopyridine was chosen for nitrogen source, poly 2,6-aminopyridine modified graphene hydrogels(PAP-GHs) were synthesized by hydrothermal method, the as-prepared hydrogels were directly dehydrated via a freeze-drying process, then the catalyst which was pyrolyzed at different temperatures at Ar atmosphere was denoted as N-GAs X; In order to improve the catalytic performance of the N-GAs, ferric nitrate was introduced into the PAP-GHs by in-situ way, the as-prepared hydrogels were directly dehydrated via a freeze-drying process, following, the catalyst that pyrolyzed at different temperatures was denoted as Fe-N-GAs. After pyrolyzing, Fe3+ was transformed to Fe3 C nanoparticles, which can improve the ORR performance obviously in both alkiane and acid media. The prepared catalysts are characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), nitrogen adsorption and desorption isotherms, Raman spectra and X-ray photoelectron spectroscopy. Rotating disk electrode(RDE) and rotating ring-disk electrode(RRDE) techniques were employed to study the catalytic activity of the oxygen reduction reaction on the as-synthesised catalysts in an alkaline medium. The heteroatom-doped graphene aerogels demonstrate higher electrocatalytic activity and diffusion-limiting current density, better stability and methanol tolerance. The excellent performance of heteroatom-doped graphene aerogels for ORR is attributed to in replace the Pt/C widespread commercialization.