Platinum-modified Hydroxy Titanium Dioxide To Methanol And Co Electro-catalytic Oxidation

In the recent years, the direct methanol fuel cell (DMFC), in which methanol is directly used as the fuel in the proton exchange membrane fuel cell (PEMFC) instead of hydrogen, has been paid more and more attention due to its special advantages. Especially, it can be used as the mobile power sources. However, there are some key problems in DMFC. One of them is that most used Pt catalyst has the low electrocatalytic activity for the methanol oxidation and is easy to be poisoned with the intermediate of the methanol oxidation. At present, two ways are suggested for solving the problem. Firstly, the components of the Pt alloys are studied to increase in the resistant ability to poisoning. Secondly, the preparation methods are investigated to increase in the electrocatalytic activity of Pt based catalysts. Our group has reported for the first time that the Pt/C catalysts prepared with the solid phase reaction method and the organic sol method exhibit the high electrocatalytic activities for methanol oxidation. In addition, it was found with our group that the complex catalyst of Pt and TiO2 has the good electrocatalytic activity and resistant ability to poisoning for the methanol oxidation. The results obtained are as follows:1. It is reported for the first time that the Pt/C catalyst was prepared with organic sol method and then the TiO2 particles were deposited on the Pt/C catalyst with hydrolysis of Ti(OBu)4 to obtain the Pt-TiO2/C catalyst. It was found that after the heat treatment at 500癈, the Pt-TiO2/C catalyst with 2:1 molar ratio of Pt and TiO2 exhibits the high electrocatalytic activity and stability for methanol oxidation. It is mainly due to that the close combination of Pt and TiO2 is occurred after the heat treatment and thus the synergetic effect between Pt and TiO2 is increased. In addition, when molar ratio of Pt to TiO2 is small, the effect of the heat treatment on the size of the TiO2 particles and the amount of TiOH on the surface is small.2. It is reported also for the first time that the Pt/C catalyst were prepared by solid phase reaction method and then the TiO2 particles were deposited on the Pt/C catalyst with hydrolysis of Ti(OBu)4. After the heat treatment at 500 C, the Pt-TiO2/C catalystobtained with 1:1 molar ratio of Pt and TiO2 exhibits the high electrocatalytic activity and stability for methanol oxidation. The peak potential of the methanol oxidation at the Pt-TiO2(l:l)/C catalyst prepared with this method shifts negatively 70mV, comparing with that at the Pt/C catalyst. While the peak potential of the methanol oxidation at the Pt-TiO2(l:l)/C catalyst prepared with the organic sol method does not shift. It is mainly due to that the roughness of the Pt surface in the catalyst prepared with the solid phase reaction is higher than that prepared with the organic sol method, so that the TiO2 particles are not easy to be aggregated.3. It was found that beginning potential of the electrocatalytic oxidation of CO at the Pt-TiO2/C catalyst prepared with the solid phase reaction also shifts negatively, comparing with the Pt/C catalyst. It is also due to the synergetic effect of Pt and TiO2. It further demonstrated that the high electrocatalytic activity and stability of the Pt-TiO2/C catalysts for methanol oxidation is due to the synergetic effect of Pt and TiO2.