Study On Stability Of Platinum Carbon Orr Electrocatalyst In Alkaline System

The combustion of hydrogen does not produce greenhouse gases,no ozone layer consumption,little or no acid rain components and pollution.Hydrogen is now widely recognized as a key element of potential energy solutions for the 21st century,helping to address environmental pollution,sustainability and energy security issues.Anion exchange membrane fuel cell(AEMFC),in contrast to other acidic fuel cells,reduce the usage of platinum group metal(PGM)based catalysts,and the transfer of alkaline conditions to the electrodes opens up the potential use of a range of low cost non-precious metal catalysts.In this dissertation,the performance degradation mechanism of Pt/C in alkaline medium,the effect of anion on ORR activity and Pt/C durability in alkaline medium,and the synthesis of high ORR activity and high durability PtNi/C alloy catalyst were studied.The main contents are elaborated as follows:1.The working electrode carrying the Pt/C catalyst was subjected to cyclic voltammetry scanning aging test for 6000 cycles in 0.1 M HClO4 solution and 0.1 M KOH solution,respectively.The results show that Pt/C is less active and less durable under alkaline conditions than under acidic conditions.The durability of the Pt/C catalyst was tested by two different methods of potentiodynamic oxidation and potentiostatic oxidation.The results shows that the deactivation of the potentiostatic oxidation is less significant than that of the potentiodynamic oxidation,and the performance of the Pt/C catalyst is more attenuated to a higher potential.2.The effect of CO32-,F-,Cl-,Br-and SO42-anions on the ORR activity of Pt/C is negligible.I-,SO32-and S2-showed significant poisoning effects on the ORR kinetics of Pt/C at very low concentrations.The effect of CO32-,F-,Cl-,Br-,I-and SO42-anions on the stability of Pt/C in alkaline solutions is negligible.SO32-and S2-can still weaken the stability of Pt/C catalysts at very low concentrations.It is found that the influence of anions is related to the standard reduction potential of anions,and S2-,SO32-and I-have very low standard reduction potentials.Therefore,they have a great influence on the ORR kinetics of anions.Other anions have relatively high standard reduction potentials,so they have little effect on ORR activity under alkaline conditions.3.The PtNi/C nanoparticles were prepared using a modified polyol method.When the PtNi ratio was 1:2,the activity of the catalyst sample was the best.PtNi/C-1/2 activity is better than 20%commercial Pt/C catalyst.The PtNi/C-1/2-heat catalyst sample was prepared by dopamine coating and sintering.The dopamine coating and sintering treatment not only improved the activity of the catalyst sample,but also improved the stability of the catalyst.After 10000 cycles of potential cycle aging scanning,the half-wave potential of the PtNi/C-1/2-heat catalyst was attenuated by 25 mV.