| As an efficient,clean,economic and security new a type of energy source,direct methanol fuel cell(DMFC)has a broad application prospect.But the unsatisfied performance and high costs of anode catalysts is the main obstacle to its wide commercial application.So developing new kinds of low cost and high performance anode catalysts is the main goal for researches.Currently,the vast majority of the anode catalysts used for the catalytic oxidation of methanol is Pt-based catalysts,which are usually composed by Pt-based catalysts loading on high surface area conductive carbon support.However,in the course of long-time operation of the fuel cell,the carbon is easily chemical corroded,hot corroded,and resulted in posion of Pt catalysts by the active ingredient loss or reunion.Nano-TiO2 has a high chemical stability and good optical properties.And during the electrochemical reaction,OHads over the surface of anatase TiO2 also helps to remove CO that is adsorbed on the surface of the Pt,to reduce the poisoning of the Pt catalyst.Nano-TiO2 as catalyst support of methanol fuel cell catalysts has attracted great attention.Researches on titanium dioxide nanotubes,nanoparticles,nano film as catalysts supported carrier have been developed widely,but the direct application of TiO2 nanoparticles as a catalysts support still having some difficulties.So,in this paper we select nitrogen-doped titanium dioxide(N-TiO2)as a catalyst carrier in this thesis.Pt was loaded on nano-TiO2 through ultrasonic assisted glycol reduction.The catalysts were characterized by XRD,SEM,CV,LSV,EIS and other methods to investigate the catalyst particle size,morphology,catalytic performances and stability of the catalytic oxidation of methanol.Based on my researchs,the following conclusions can be drawn:(1)Nitrogen-doped titanium dioxide was successfully synthesized by using tetrabutyl titanate as precursor,urea as the source of nitrogen,through hydrothermal methods.The composition,structure,morphology and particle size of nitrogen-doped titanium dioxide with amount of 1 wt%were characterized by XRD,TEM,SEM and other tests.The test results show that the main phase of hydrothermal synthesis of N-TiO2 was anatase structure,particle size of about 12.4nm,uniform particle size distribution,specific surface area of 124.6 m2/g was much larger than pure titanium dioxide.Characterizations of IR and XPS showed that the nitrogen was doped into the TiO2 crystal lattice,probably in the form of Ti-N-O.(2)Pt/N-Ti02(Pt content 5%,10%,15%and 20%)and Pt(10%)/TiO2 catalysts were prepared by ultrasonic assisted glycol reduction method.The composition,structure,surface morphology of the catalysts were characterized by X-ray powder diffraction(XRD),scanning electron microscopy(SEM)and other techniques,and electro-catalytic oxidation of methanol tests were carried out by cyclic voltammetry(CV),linear sweep voltammetry(LSV),impedance spectroscopy(EIS)in 1M H2SO4 +1M CH3OH solution.Results show that the structure of Pt on catalysts was the face-centered cubic.The diameter of Pt/N-TiO2 was about 14nm.Pt(10%)/N-TiO2 showed the best catalytic properties of all the catalysts.(3)The catalytic activity of Pt(10%)/N-TiO2 catalyst were examined in acid sulphric electrolyte,and the performance of different methanol concentrations and different scan rates were also studied.The results showed that high concentrations of methanol in H2SO4 electrolyte can not promote the oxidation of methanol.The oxidation of methanol in acidic electrolyte is a diffusion controlled irreversible reaction.Testing results in the alkaline solution(KOH)indicated that methanol is more easily oxidized in alkaline electrolyte,where the catalyst showed higher catalytic activity and stability. |
PDF Full Text Request