Synthesis Of Graphene And Nitrogen-doped Graphene And The Development Of Graphene-Based Catalyst For Fuel Cells

Graphene has received dramatically increasing interests in the past decade due to excellent properties and application potential.The preparation of high quality graphene from exfoliation of graphite was conducted through continuous sonication with surfactant added throughout.This was accomplished through the creation and addition of a Triton X-100 surfactant solution to a graphite suspension during sonication lasting for 50 minutes,80 minutes,110 minutes,140 minutes,170 minutes,and 200 minutes respectively.It was found that the quality of graphene was improved with the sonication time increased,indicated by the reduced number of graphene layers.Solving slow kinetics of the methanol oxidation is critically important for the development of direct methanol fuel cells.In this work,Pt and Pt-Ru nanoparticles were synthesized on both graphene and nitrogen(N)-doped graphene sheets,and their effects on electrocatalytic activity for methanol oxidation were investigated using cyclic voltammetry and electrochemical impedance spectroscopy.Experimental results show that,in comparison to pure graphene as catalyst support,N-doped graphene-supported Pt and Pt-Ru nanoparticles demonstrate enhanced characteristics for methanol electro-oxidations with regard to oxidation potential,forward peak oxidation current density,and charge transfer resistance.Besides,the addition of Ru increased the IF/IR ratio,which enhanced the tolerance of Pt to carbon monoxide.Oxygen reduction reaction dominates the performance of fuel cells,graphene and nitrogen(N)-doped graphene synthesized via a solvothermal method were investigated as catalysts as well as catalyst supports for oxygen reduction reaction.In comparison to graphene,N-doped graphene demonstrated higher electrocatalytic activity in both acidic and alkaline solutions.N-doped graphene can act directly as a catalyst to facilitate four-electron oxygen reductions in alkaline solution and two-electron reductions in acidic solution.On the other hand,when used as catalyst supports for Pt and Pt-Ru nanoparticles,N-doped graphene can contribute to four-electron oxygen reductions in acidic solution,yet demonstrates much slower reaction kinetics in alkaline solution.My findings suggest the use of N-doped graphene sheets as promising catalyst supports for methanol oxidation and for oxygen reductions in acidic solutions.As for oxygen reduction reaction in alkaline solutions,N-doped graphene can be used directly as catalyst to replace the use of precious Pt catalysts.