Synthesis Of Graphene-based Composites With High Performances For Oxygen Reduction

The high cost of platinum (Pt) based catalysts for oxygen reduction reaction(ORR) has restricted the widespread commercialization of fuel cells. Heteroatom(N, B, P, S or Se) doped carbon materials have been regarded as the promisingcatalysts for replacing Pt based catalysts owing to their high efficiencies, goodstability and relative low cost. To realize the heteroatom doping, many methodshave been presented such as chemical vapor deposition, pyrolysis, andhydrothermal. In this paper, we prepare the heteroatom doped mesoporouscarbon/graphene (HMCG) by a hard template route and nitrogen dopedgraphene/metal nanoparticles (NG/MNPs) via a solvothermal treatment. Thedetails are as follows:(1) We present a cost-effective synthesis approach for heteroatom (N and S)doped mesoporous carbon/graphene nanosheets by using nano-casting technology.The mesoporous silica/graphene nanosheets (MSG) with sandwich structure ashard templates were firstly prepared via solution-assembly method, and fouramino acids of different composition and structure (alanine, serine, arginine andcystine) as heteroatom (N, S) and carbon precursors. A series of HMCGs ofdifferent composition were prepared by impregnation, calcification and etching ofsilica template. The resulting catalysts exhibited excellent electrocatalytic activityfor ORR in alkaline media. In particular, HMCGAlawith alanine as precursorsshowed the highest electron transfer numbers and durability. These resultsindicated the attractive potential of HMCGs as metal-free catalysts in practicalfuel cells.(2) Combining the ionic assembly with the in-situ synthesis, we report anunconventional hybrid-assembly strategy towards3D macroporous monoliths ofgraphene and metal phthalocyanines (Pcs) by using a facile solvothermaltreatment with phthalonitriles, graphene oxide (GO) and metal acetate (cobalt acetate, ferrous acetate and nickel acetate) salts as precursor. The hybrid ofgraphene/metal Pcs can be further converted to the monolithic aerogel of nitrogendoped (N-doped) graphene and metal nanoparticles (NPs) by high-temperaturepyrolysis (600and800℃). The resulting NG/MNPs have an interconnectedmacroporous framework of N-doped graphene sheets and uniform deposition ofnon-precious metal NPs including Co, Fe and Ni. These NG/MNPs showedexcellent electrochemical performance as the catalyst for ORR (4electrontransfer and outstanding stability).