Synthesis of Graphene, and Nitrogen-Doped Graphene as Catalysts and Catalyst Supports for Oxygen Reduction Reaction

Solving slow kinetics of the oxygen reduction reaction is critically important for the development of hydrogen fuel cells and direct methanol/ethanol fuel cells. In this study, graphene and nitrogen (N)-doped graphene were synthesized via a solvothermal method and 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. Additionally, 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. My findings conclude that N-doped graphene can be developed as an efficient catalyst for oxygen reductions to replace the use of precious Pt catalysts in alkaline solution but not in acidic solution. In addition, quality of graphene was improved with the sonication time increased, indicated by the reduced number of graphene layers