titanium fiber felt
titanium felt
(1) Using titanium felt sintered as the fuel cell gas diffusion layer, carbon fiber is easy to corrosion;
(2) Titanium sintering felt coating method includes coating-baking method, pulse electroplating;
The lowest titanium fiber felt thickness is 0.25mm, the porosity is 50-70%, and the structure is more conducive to air-liquid mass transfer.To maintain its conductivity, coat platinum and iridium on the surface.High precious metal consumption, poor coating stability and falling anode catalytic layer.
1. Titanium felt anode gas diffusion layer
Sintered titanium felt serves as a substrate for platinum catalyst deposition.The samples used were circular, 30mm in diameter, 1 mm thick, and had a porosity higher than 70%.Specific processing steps are as follows:
(1) Demembrane: the titanium felt has been used in an electrolytic pickling solution from , based on nitric acid and hydrofluoric acid, pH 0.5 at room temperature; then 2.5V voltage has been applied to the felt, causing the anode of the titanium / Ti 2 surface dissolution.A titanium expansion mesh based on the electrode plated from Wieland Edelmetalle platinum has been used for preparation steps for this purpose.
(2) Argon gas cleaning: after washing with deionized water, the surface of the titanium workpiece is plasma treated in argon gas to remove the remaining pollutants on the titanium surface.The plasma reactor used the Pink V 15-G model of TopTiTech with parameters set to an argon flow rate of 100 ml min-1, and was treated at 60 Pa for 30 min with a microwave power of 400 W.
(3) Plating: the continuous plasma physical cleaning process is further washed with deionized water, and the titanium fiber is immediately coated with platinum by electrochemistry under argon gas.The commercially available electroplating bath type Galvatron Platinbad from TopTiTech has been used based on hexachloroplatin acid.The bath parameters were set to pH and temperature of 50 C.The plating process was performed at a constant cathode voltage for 10 min, -3.2 V with the opposite electrode (titanium / platinum from Wieland Edelmetalle).During this plating process, the titanium electrodes were placed electrically between the two connected paired electrodes.Subsequently, to increase the electrochemical activity of the catalyst by depositing micron and nanoscale platinum particles in the surface area, the plating mode was switched to pulse plating the paired electrode at a cathode voltage of-3.0 V without disrupting the process.The on time was set to 10 ms and the off time to 56.7 ms, so the duty cycle is 15% cycles.The second part of the plating process was performed for another 10 minutes.
(4) MEA assembly: The electrode has been impregnated with a 0.5 ml proton-conducting ionization solution (5 wt.% in ethanol) and then plated with platinum.The solution has been cast by a gas brush smear and the titanium-based electrode is connected to a heated sample holder.The air temperature was set to 60 C to accelerate the evaporation of ethanol from the electrode surface.
(5) And the bipolar plate to form a power stack, 20 groups.
2. Platinum coating on the titanium felt
The following microscopic images show the sintered titanium fibers with platinum coating. Fibers located outside of the felt protect the entire coating, an effect that can be explained by the electric field distribution of the primary cell (the working electrode is located between and parallel to the two counter electrodes). The coating is sufficient to allow for a long-term stable adhesion of platinum nanoparticles. The following below shows micrographs of platinum particles deposited on titanium plated fibers by a pulse plating process.
