Srtucture Optimization Of Low Platinum Catalysts For Fuel Cells And Design Of New Catalyst Support

The fuel cell is a kind of energy conversion device,which can directly convert chemical energy to electric energy.The fuel cell has been extensively studied due to its high energy conversion efficiency,low environmental pollution,high specific energy,low noise,wide applicability and other advantages,Direct methanol fuel cells?DMFCs?and direct dimethyl ether fuel cells?DDFCs?,are the most promising candidates for hydrogen based proton exchange membrane fuel cells?PEMFC?because of their advantages of high theoretical energy density,wide source of raw materials,easy storage and transportation.Platinum is the most widely used anode catalyst for DMFCs and DDFCs,However,the commercialization of DMFCs and DDFCs has been seriously hindered by the high price and small reserves of platinum,which is also easily poisoned by intermediate products.Therefore,efficient,low-platinum anode catalysts and non-noble metal catalysts need to be developed urgently.This thesis aimed to solve the problems of low activity,poor stability and high cost of traditional fuel cell anode catalysts.The electrocatalytic properties of PtPd/C and PtNi/C alloy catalysts on for methanol and dimethyl ether in different electrolyte solutions were systematically studied.Furthermore,we chose different preparation method to optimize the application of TiO2 in the anode catalyst support.The concrete results are listes in the following.?1?The ethylene glycol method was used to prepare PtPd/C alloy catalysts of different proportions.The structure and morphology of the prepared PtPd/C catalyst were characterized by XRD and TEM.The activity and stability of PtPd/C catalysts were systematically studied for the electrocatalytic oxidation of methanol and dimethyl ether in acid and alkaline electrolytes with different low platinum alloy catalysts.The electrochemical results showed that the catalytic oxidation performance of PtPd/C?1:1?catalyst was the best for dimethyl ether in the both acid and alkaline systems,and the peak mass ratio activity in the corresponding acid andalkaline systems was 2 times and 5.4 times higher than that of commercial Pt/C catalysts,respectively.On the other hand,PtPd/C?1:1?catalyst had the best catalytic oxidation performance for methanol,and its peak mass ratio activity was 3 times higher than that of commercial Pt/C catalyst in the acid system.In the alkaline system,PtPd/C?1:4?catalyst has the best electrocatalytic oxidation and stability performance for methanol,and the highest catalytic efficiency.The peak current density was 3 times higher than that of commercial Pt/C catalyst,and the corresponding peak mass ratio activity was 10 times higher than that of commercial Pt/C catalyst.Moreover,it was found that PtPd/C catalysts in alkaline system has better electrocatalytic performance for methanol and dimethyl ether compared with that in acid system,and lower platinum was needed in the alkaline system.?2?The ethylene glycol method was applied to prepare PtNi/C alloy catalysts of different proportions.The structure of the prepared PtNi/C catalyst were characterized by XRD.And the electrocatalytic activity and stability of the PtNi/C catalysts for methanol and dimethyl ether were studied in both acid and alkaline systems of different pH.The results showed that PtNi/C?5:1?catalysts in acid systems had the best catalytic activity for methanol and dimethyl ether compared with commercial Pt/C catalysts,and their current density for oxidation of dimethyl ether and methanol was 2.5 times and 2 times higher than that of commercial Pt/C catalysts,respectively.In the alkaline system,the catalytic activity of PtNi/C?2:1?catalyst to dimethyl ether was the best,while the catalytic activity and stability of PtNi/C?3:1?catalyst to methanol were the best.It was also found that the electrocatalytic performance of PtNi/C catalysts for methanol and dimethyl ether in alkaline system was significantly higher than that in acid system.Because of the advantages of large reserves and low prices,PtNi/C alloy catalysts have a wider foreground of applications in the process of future commercialization of fuel cells.?3?We studied the effects that different preparation paths were used for the application of TiO2 was optimized by different methods in the graphene-supported platinum catalysts.The Pt/RGO-TiO2 catalyst with RGO-TiO2 as composite support was prepared by ethylene glycol method,and TiO2@Pt/rGO core-shell catalysts with different proportions was prepared by photocatalysis method.Different experimental conditions were discussed such as the influence of the experimental conditions such as the addition of capture agent,nitrogen and material composition ratio,and the addition sequence on the performance of the catalysts.The structure and morphology of the prepared catalyst were characterized by XRD and SEM.By comparing the properties of two catalysts,the performance of the catalyst prepared by photocatalytic method is better than that by glycol method.TiO2@Pt/rGO core-shell catalysts of different proportions were prepared.The electrocatalytic performance of methanol and dimethyl ether was tested respectively,and the catalytic activity of TiO₂@Pt/rGO-20%was the best under the alkaline conditions.