Preparation Of Direct Methanol Fuel Cell Catalysts And Their Catalytic Performance Towards Methanol Oxidation Reaction

Low temperature fuel cells include proton exchange membrane fuel cells,direct alcohol fuel cells,direct acid fuel cells,etc.Due to its simple structure,high energy conversion efficiency,portability,and environmental friendliness,the direct methanol fuel cell?DMFC?is known as the low temperature fuel cell with the most promising prospects for industrialization.However,at present,DMFC adopts platinum catalysts that are expensive and easily poisoned,which has become one of the important factors that hinder the further development of DMFC.In order to overcome this problem,researchers have conducted a lot of research on low platinum and non-platinum catalysts and achieved some positive results in the past decade.The currently developed non-platinum catalysts and low-platinum catalysts are not very satisfactory in terms of activity and stability.Therefore,how to increase the activity and stability of the catalysts and reduce the catalyst costs has very important practical significance.This thesis starts with the composition and structural design of the catalyst.Using carbon nanotubes as carriers,the titanium nitride and titanium binary nitrides are prepared by complexation nitriding treatment.Then using pulsed electrodeposition technology to load platinum on the nitrides,the low platinum core-shell catalysts with particle size of 5nm are successfully prepared.The addition of carbon nanotubes not only solves the problem of poor dispersibility of transition metal nitrides,but also provides a channel for the transport of electrons in the course of chemical reactions,which improves the performance of the catalysts.The research content of this thesis mainly includes the following aspects:?1?The carbon nanotubes were used as carriers and the transition metal nitrides were synthetized by complexation nitriding treatment.The platinum atoms were loaded by pulsed electrodeposition technology.Studies found that Pt atoms were successfully deposited on the surface of nitride nanoparticles rather than deposited on the surface of carbon nanotubes.The results showed that the nitride nanoparticles were 5 nm and have good dispersion.Compared with TiN@Pt/NCNTs the prepared Ti_0.9Cu_0.1N@Pt/NCNTs catalysts had a mass activity of 2.06A/mg Pt at 0.65V,which had about 50%higher mass activity.This shows that Cu doping has a significant impact on the catalyst which can make Pt 4f peak negative shift and weaken the combination of Pt and oxygen-containing active species.It can be seen from the dissolution voltammetry curve of CO that the initial potential of CO in the Cu-doped catalysts is the most negative,which indicates that the Ti_0.9Cu_0.1N@Pt/NCNTs catalysts has the strongest anti-poisoning ability against oxygen-containing active intermediates.The dissociation and removal of adsorbed oxygen are well balanced to have good MOR catalytic activity.?2?Secondly,Nitride nanoparticles doped with Ni and Co were prepared by hydrothermal synthesis with carbon nanotubes as carriers.Core-shell structured Ti_0.9Ni_0.1N@Pt/NCNTs and Ti_0.9Co_0.1N@Pt/NCNTs catalysts have been fabricated by pulse electrochemical deposition method usingTi_0.9Ni_0.1N/NCNTs and Ti_0.9Co_0.1N/NCNTs substrate.The resulted show that the mass activity of the prepared Ti_0.9Ni_0.1N@Pt/NCNTs and Ti_0.9Co_0.1N@Pt/NCNTs catalysts reached 2.52 A/mg Pt and 2.1 A/mg Pt at 0.65 V,which were higher than that of the previously prepared Cu doped nitrides.After the 10,000-cycle ADT scan,the ECSA still remained 82%and78%of the original,far exceeding the commercial Pt/C catalyst.The doping of Ni and Co improves the performance of the catalyst and has no negative impact on the stability.