Investagation On Graphene-based Support For Anode Catalyst Of PEMFC

Proton exchange membrane fuel cell (PEMFC) has received worldwideattention because of its low temperature operation, high energy density, faststart-up, and the potential application in automotive and portable electronics. Thecommercial application of the PEMFC is expected to lead to furtherimprovements in performance, durability, and cost. The paper outlines thereseach on current status of fuel cell and summarizes the reason for thedegradation of catalyst as well as the methods to enhance the stability of thecatalyst. The dissertation is mainly focus on the development of facile and rapidmethod for preparation of high catalytic activity and stability of anode graphenebased catalyst.Firstlyt, Pt/graphene-TiO2hybrid catalyst was synthesized by a facileone-pot solvothermal method with ethylene glycol (EG) and isopropyl alcohol(IPA) as mixed solvent. TiO2and fine Pt nanoparticles (NPs) disperse uniformlyon the graphene and form unique “triple junction structure”. Pt/graphene-TiO2hybrid catalyst has methanol electro-oxidation reaction (MOR) activity of423.3A·g-1, which is1.46times higher than that of Pt/graphene (synthesized byone-pot solvothermal method,289.5A·g-1) and stability is also increased bynearly15%after1000cycles of accelerated potential cycling test (APCT). Theresults above can be ascribed to the strong metal-support interaction (SMSI)between Pt and TiO2, and the unique triple junction structure that is conducive toplay the synergetic effect between Pt, graphene and TiO2. The effects of contentsof TiO2, solvothermal temperature and solvothermal reaction time on theperformance of Pt/graphene-TiO2catalyst have also been systematically studied.When TiO2content existed in the mixed support is40mass%, theelectrochemical activity is best, and the stability is14.4%higher than that ofPt/graphene. Considering the factors of the activity and stability comprehensively,the optimized solvothermal temperature is140oC. When solvothermal reactiontime is4h, the catalyst has the best electrochemical activity, and stabilityenhanced two times more than2h.Different structured Pt-based catalyst was prepared with graphene as basematerial. Pt/graphene was in-situ composited with graphene to synthesizesandwich-structured graphene-Pt-graphene (G-P-G) hybrid catalyst. G-P-Ghybrid catalyst has MOR activity of462.8A·g-1, which is1.27times higher thanthat of Pt/graphene (synthesized by microwave assisted polyol process,363.1 A·g-1) and stability is also increased by nearly20%after the APCT. Thesignificantly enhanced electrochemical performance is ascribed to the uniquesandwich sheet-like structure. The effect of content of composited graphene isexamined on the performance of G-P-G hybrid catalyst. The study found with theincrement of the content of composited graphene, ESA decrease gradually, butthe specific activity for MOR and the stability gradually increases. Consideringthe factors of the activity and stability comprehensively, the optimal content ofcomposited graphene is50%.Then Pt/C was composited with graphene to prepare the Pt/C/graphenehybrid catalyst. Pt NPs appeared on the “clean” graphene surface during theripening process after the APCT and the stability of Pt/C/graphene hybridcatalyst increases by12%. In order to further improve the stability, Pt/C andPt/graphene catalyst is composited with nitrogen doped graphene (NG). Theresearch found the stability of Pt/C and Pt/graphene composited with NG hasimproved further, however, ESA of catalyst drops more apparent. Finally,N-Pt/C/graphene hybrid catalyst was synthesized by one-step hydrothermalreaction with Pt/C catalyst, urea and graphite oxide (GO) as raw materials. TEMreveals Pt NPs not only load on carbon, but uniform distribution on the nitrogendoped graphene. Compared with the Pt/C, the mean size of Pt NPs does notincrease evidently and the stability increases by14%.