Dissertation > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Chemical kinetics,catalysis > Catalytic > Catalyst

Study on Durability and Poisoning Resistant Performance of Pt/C and Pt/OMC Catalysts

Author ZhangJing
Tutor ChenMeng
School Harbin Engineering University
Course Applied Chemistry
Keywords NO_x Poison Pt Mesoporous Carbon Aging
CLC O643.36
Type Master's thesis
Year 2011
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The lower power output was observed after long time operation of PEMFC, two of main reasons for that was poisoned by impurity gases in the air and self-aging of cathode catalyst in PEMFC, in this paper, Pt/C and Pt/OMC catalysts were synthesized by a microwave assisted polyol method to give studies to the issues mentioned above.In order to study the Pt/C catalyst performance at the existence of NOx in the air, rotating disk electrode (RDE) were used to investigate the catalytic activity to ORR of Pt/C catalyst in the presence of NOX. According to the experiments tests described in this article, Pt/C catalyst for ORR catalytic activity decreased to 1.5% after NOx adsorption, it proved that NOX can be strongly adsorbed on Pt surface which lead to the poisoning of catalyst. The curves which were obtained at different rotating speeds of RDE for ORR catalyst activity after Pt/C catalysts poisoned were taken to further analysis, the mechanism of Pt/C catalyst poisoned by NOx was that active sites of Pt surface were occupied by NOx which was not involved in the ORR reaction process. Subsequently, Cycle Voltammetrys (CV) were taken to study Pt/C catalyst on the adsorption of NOx at different potential, and found that more amount of NOx were tested when the surface of Pt particles were exist as metal, and less or nothing for PtOx, it proved that Pt/C catalyst on the adsorption of NOx is the process of chemical adsorption. Finally, the catalytic performance recovery of poisoned Pt/C catalyst were investigated by CV, which of potential sweep range was from OV to1.5V, 5 cycles can remove the NOX absolutely by redox reaction, and the electrochemical surface area and catalytic ability of Pt catalyst were recovered too.To study the applicability of mesoporous carbon serves as support material of cathode catalyst in PEMFC, hard template method was used to synthesize mesoporous carbon in this paper. According to the experiments about catalyst poisoned by NOX, the poisoning extents of catalysts were consistent comparing with Pt/OMC and Pt/C catalyst at the same Pt loading. Then, for the Pt/OMC catalyst aging experiments, the experimental results show that after CV1000 between 0.6-1.2V, the ESA were decreased to 30.5% and 55.8% for Pt/OMC and Pt/C catalyst respectively and for the ORR catalytic activity were 45.3% and 49.3%. Before and after aging, comparing with Pt/C catalyst, the ESA of Pt/OMC catalyst was lower, and catalytic activity toward ORR was higher. After analysis, the reason for the rapidly decreasing of ESA of Pt/OMC catalyst was the less amount of oxygen species at mesoporous carbon surface, which lead to easily aggregation of Pt particles; Higher proportion of the crystal which in favor of catalytic ORR and electronic effects between Pt and mesoporous carbon were attributed to the higher catalytic activity toward ORR.

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