Investigation On The Support And Supported Electrocatalyst For Reversible Fuel Cells

United regenerative fuel cells (URFCs) use hydrogen as the medium, combine two functions of the proton exchange membrane fuel cell (PEMFC) and proton exchange membrane water electrolyser (PEMWE) in one unit, and are considered as promising one of the competing technologies for utility-scale energy storage in the future. The performances of it mainly depend on the electrochemical characteristics of the oxygen electrodes. That is the improvement in the performance and stability of active catalysts for the oxygen electrodes under the less loading of the noble metal.The paper investigated the physical structure and electrochemical performance of the supports and supported electrocatalysts of the oxygen electrodes of the URFCs by physical and electrochemical characterization from the view in the active components, ratio of active catalyst, and supports of the catalyst.The supported Pt/C electrocatalysts were prepared by three different systems. The experimental results confirmed that the supported electrocatalysts which are prepared by the microemulsion method are well separated, and good electrocatalysts activity, and the size of the particle is about 5～10nm. Four different proportions of the PtIr/C electrocatalysts were prepared by the microemulsion method, and the Pt85Ir15But during the long-term operation of fuel cell, the stability of carbon materials is not good enough due to their oxidation and corrosion. Used nano-sized titanium carbide (TiC) as the precursor, and controlled oxidation process to prepare the three-phase compositions by fluidized-bed micro-reactor. The influence of temperature, the ratio of oxygen and reaction time are studied experimentally on the phase. In this process temperature is the key factor. With the temperature increasing, TiC is gradually changed into Anatase Syn-TiO/C showed the highest comprehensive electrochemical activity in URFC. 2 and Rutile Syn-TiO₂, the surface of the supports is from smooth to rough. And when N₂ : Air=200 ml min^-1:100 ml min^-1 , reaction time is 3min and temperature reaches to above 610℃, the BET surface area and pore volumes is higher than the other. Additional, the supported electrocatalysts on the different supports were prepared by micromulsion method. The average diameter of the electrocatalysts particle size is about 10nm. Comprehensive analysis experiments show that supported electrocatalysts of the modified TiC at 610℃has greater electrochemical activity by the CV, and it is shown that the TiC-TiO2 composites are a good support for the electrocatalysts in the URFC. Additional, this paper investigated the corrosion resistance of the supports by the potentiodynamic method. It can be seen that the corrosion potential of TiC is 0.435V (vs. SCE), and the modified supports have increased. So through controlled oxidation process to modify supports arises to the antiseptic efficiency of supports. This is because the surface of supports is oxidized to TiO2 to protect TiC, which improve the corrosion resistance.In conclusion, nano-size TiC and modified TiC is a promising support material of the catalysts for the oxygen electrode of URFCs. The active components Ir improved the performance of catalyst at some extent.