Preparation Of Anode Catalysts For Direct Methanol Fuel Cells And Research On Its Electrocatalytic Performance

In order to cope with global energy tensions and deteriorating environmental pollution and climate change and other ecological issues,it is necessary to find more environmentally friendly alternative energy sources and efficient energy conversion devices.Direct methanol fuel cell is one of the energy systems with broad development prospects because of its high energy conversion efficiency,low use temperature,clean product,safe fuel transportation,modular structure,flexibility and convenience.At present,the main factors restricting the development of methanol fuel cells are concentrated on the high cost of catalysts,which usually use precious metal catalysts such as Pt and Pd catalysts are easily poisoned.The preparation of anode catalysts with high activity,stability and low cost is the current research hotspot.In this paper,active metals were deposited on the prepared carbon nanotube and titanium dioxide composite support by cyclic voltammetric electrodeposition,and Pt-based and Au-based catalysts were prepared respectively,and their characterization and performance were carried out.（1）The sol-gel method was used to obtain titanium dioxide,and then the specific surface area of the composite carrier obtained under different ratios of carbon nanotubes and titanium dioxide was characterized by BET,and the optimal ratio for preparing the composite carrier was obtained.Is 5%.The mass ratio is 5%,the p H is adjusted to 3 with nitric acid,and the catalyst carrier with a specific surface area of 268.706 m2/g is obtained after aging,calcination and grinding.The morphology and thermal stability of the catalyst were characterized by XRD,SEM,TEM and other characterization methods.（2）Using cyclic voltammetric electrodeposition method,successfully prepared Pt-CNT@TiO₂,Pt Co-CNT@TiO₂ catalyst.The research results show that the addition of Co makes the catalyst exhibit higher catalytic activity and better stability than single-metal catalysts.The optimal preparation ratio of the two metals in the bimetallic catalyst was explored,and it was found that when Pt:Co=1:3,Pt Co-CNT@TiO₂ had the best catalytic effect,and the peak current density of methanol oxidation peak reached 98.9 mA·cm^-2,the oxidation peak current density shows that it decreases with the increase of the metal ratio.（3）Au-CNT@TiO₂,Au Co-CNT@TiO₂ catalysts were prepared by electrodeposition method.The effect of different metal ratios on the performance of the catalyst was also investigated,and it was found that there is also a synergistic effect between the metals between Au and Co.The introduction of Co can improve the catalytic performance of the catalyst.Among them,when Au:Co=1:2,the bimetallic catalyst Au Co-CNT@TiO₂ shows the best catalytic performance,and the peak current density of methanol oxidation is 5.49 mA·cm^-2.With the increase of the metal ratio,the methanol oxidation peak current density also showed a trend of first increasing and then decreasing.Comparing the catalytic effects of platinum-based and gold-based catalysts,it is found that the effect of Au-based catalysts is far inferior to that of platinum-based catalysts prepared under the same conditions.（4）The structure and morphology of the composite support and the four catalysts were characterized by SEM,TEM,XRD and other methods.Cyclic voltammetry was used to investigate the catalytic ability of the catalyst to methanol at different temperatures,different scan rates,and different alkaline conditions.The electrochemical performance of the catalyst was investigated by CA and electrochemical impedance（EIS）.The results showed that the peak current of Pt Co-CNT@TiO₂ catalyzing methanol in 1M KOH methanol solution at 60℃reached 220 mA·cm^-2;Au Co-CNT@TiO₂ catalyzes methanol oxidation peak current density of11.9 mA·cm^-2 at 65°C,both of which show better catalytic performance than single metal catalysts.