The minimum thickness of titanium fiber felt is 0.25mm, the porosity is 50-70%, and the structure is more conducive to gas-liquid mass transfer. In order to maintain its conductivity, platinum and iridium need to be plated on the surface. There are problems such as large amount of precious metals and high prices; there are problems such as poor coating stability and shedding of the anode catalyst layer.
(1) When using titanium sintered felt as a fuel cell gas diffusion layer, carbon fiber is easily corroded;
(2) Titanium sintered felt coating methods include coating-baking method and pulse electroplating;
1. Titanium felt anode gas diffusion layer
Sintered titanium felt is used as a substrate for platinum catalyst deposition. The sample used is round, 30mm in diameter, 1mm thick, and has a porosity of more than 70%. The specific processing steps are as follows:
(1) Deoxidation film: Titanium felt is in an electrolytic pickling solution based on nitric acid and hydrofluoric acid with a pH of 0.5 at room temperature; then a voltage of 2.5V is applied to the felt to cause anodic dissolution of the titanium/titanium dioxide surface. Titanium expanded mesh plated with platinum based counter electrodes has been used for this purpose as a preparatory step.
(2) Argon cleaning: After rinsing with deionized water, the titanium workpiece surface was subjected to plasma treatment in argon to remove the contaminants still remaining on the titanium surface.
(3) Plating: Following a continuous plasma physical cleaning process and further rinsing with deionized water, the titanium fibers were immediately electrochemically plated with platinum under argon. During the electroplating process, the titanium electrode was placed between two connected counter electrodes. Subsequently, in order to increase the electrochemical activity of the catalyst to deposit micro- and nano-sized platinum particles on the surface area, the electroplating mode was switched to pulse electroplating of the counter electrode at a cathode voltage of -3.0 V without interrupting the process. The on time was set to 10 ms and the off time to 56.7 ms, resulting in a duty cycle of 15%. The second part of the electroplating process was carried out for another 10 min.
(4) MEA assembly: The electrodes have been impregnated with 0.5 ml Nafion® proton conducting ionomer solution (5 wt.% in ethanol) and subsequently plated with platinum. The solution has been applied by air brushing, while the titanium-based electrodes are connected to a heated sample holder. The air temperature is set to 60 °C to accelerate the evaporation of ethanol from the electrode surface.
(5) and bipolar plates form a stack, 20 groups.
2. Platinum coating on titanium felt
The micrographs below show sintered titanium fibers with platinum coating. The fibers located on the outside of the felt protect the entire coating, an effect that can be explained by the electric field distribution within the galvanic cell (the working electrode is located between and parallel to the two counter electrodes). The coating is sufficient to allow long-term stable adhesion of the platinum nanoparticles.
Contact us for more information. Thank you
Nicole
Company: Baoji Jimiyun Dynamic Co., Ltd
Country:China
Add:Baoti road,Jintai,Baoji city,Shaanxi,China
Cel:+86 13369210920
Gmail:nicole@jmyunti.com
Website:www.jm-titanium.com
