Views: 2
The electrolytic hydrogen production industry has a long history, and the electrolytic cell generally adopts a filter-press type bipolar structure, or a box-type single-pole structure.
Water electrolysis is to pass direct current in the water to produce hydrogen and oxygen. Fuel cells use hydrogen as fuel. In order to optimize the environment and reduce pollution, hydrogen will be used as energy for automobiles in the future. Water electrolysis is the only industrial way to make hydrogen from water. In water electrolysis, oxygen is precipitated on the cathode and oxygen is precipitated on the anode. The reaction equation is: H2O——(electrolysis)H2+(1/2)O2 In the electrolytic cell voltage, the anode overpotential and cathode overpotential account for a large proportion. The size of the overpotential has a lot to do with the electrode material used.
The electrolytic cell of water electrolysis is basically composed of four elements: anode, cathode, electrolyte and diaphragm. The voltage loss varies widely by the combination of electrode material and electrolyte. In general water electrolyzers, the electrolyte uses 20-30% KOH or NaOH aqueous solution, and the operating temperature is 50-70 degrees. Nickel-plated steel sheet is used for the insoluble anode and carbon steel is used for the cathode. Various surface treatment methods have been considered in order to reduce the hydrogen overpotential. Sulfur-containing nickel electroplating is widely used in Japan. Adding NaCNS to a common aqueous solution can obtain sulfur-containing black-gray nickel plating. Compared with carbon steel, its hydrogen overpotential is 250-300mv lower. Compared with the nickel-plated steel sheet, the oxygen overpotential is also about 100mv lower. Japan has developed a solid polymer water electrolysis process, which can use a fluororesin-based ion exchange membrane as a solid electrolyte for proton conductors. Due to the thinning of the solid polymer electrolyte, the electrolyte resistance is reduced, which is beneficial to the electrolysis operation at a high current density. If a solid oxide electrolyte is used, it is possible to apply a high-temperature water electrolysis process using water vapor. The theoretical decomposition voltage of this process is small, the amount of electric energy must be reduced, and especially the overpotential, which is the resistance of the electrolysis reaction, is reduced. Electrolysis method that operates electrolysis at the highest and lowest cell voltages. In alkaline water electrolysis, nickel-plated steel is used for the anode, nickel of the same shape, or nickel-plated mild steel, and mild steel is used for the cathode. As a new cathode material, a porous nickel electrode with a large surface area should be tried. In solid polymer type water electrolysis, since a strong acid electrolyte is used, the electrode material is required to be resistant to acid corrosion, so inexpensive materials such as nickel and iron cannot be used, and expensive platinum group metal materials must be used.
1. The surface is polished and polished,
2. First acetone cleaning, then chromic acid lotion immersion
3. Pretreatment of electrode: ①Small sandpaper to smooth the surface
② Grind to a mirror surface with alumina slurry
③ Wash with dichromic acid mixture, hot nitric acid (Pt Au), aqua regia (Pt), etc.
④ Rinse with water
⑤ Pre-scan
4. First wash with organic solvent, and then soak with dilute nitric acid. This is the cleaning method of platinum electrode used as Karl Fischer titration sensor. After a long time to measure the moisture of organic matter, the surface of the Pt electrode is covered with an organic matter film, which makes the reaction passivated, the end point is delayed, and the solution turns brown-red. However, if it is a precision conductivity electrode, it is generally a platinum black electrode, not a bright electrode. If the accuracy deteriorates, it needs to be re-plated with platinum.
5. Generally use acetone or ethanol to remove oil, do not clean with alkaline solution.
6. Ultrasonic oscillation
7. ORP measuring electrode platinum or gold, its surface should be bright, rough or contaminated surface will affect the potential mV of the electrode. The following methods can be used for cleaning and activation: ① For inorganic pollution, the electrode can be immersed in 0.1mol/L dilute hydrochloric acid for 30 minutes, washed with pure water, and then immersed in the immersion solution for 6 hours before use. ② For organic oil stains and oil film contamination, the platinum or gold surface can be cleaned with detergent, then washed with pure water, and then immersed in soaking solution for 6 hours before use. ③ The surface of platinum is seriously polluted and an oxide film is formed. Toothpaste can be used to polish the surface of platinum or gold (it is important that when polishing,
Fine marks should be avoided), then wash with pure water, and then immerse in soaking solution for 6 hours before use.
8. First use small sandpaper to smooth the surface, then wash with dichromic acid mixture, hot nitric acid, or aqua regia, rinse with water, and do several potential scans in the same solution as the electrolyte used for measurement
9. Soak in chromic acid solution for half an hour
10. Use water, acetone, ethanol, and water for ultrasonic treatment in sequence
11. ① Newly purchased or manufactured electrodes can be directly soaked in chromic acid solution for 30 minutes. Remove the oil stains on the surface, and then clean them with deionized water; ②Insert the electrode into 0.5 M H2SO4 as a research electrode, in the potential range of -0.25~1.2V vs SCE, scan cyclically until the cyclic voltammetry curve no longer changes, then it can be used as an auxiliary or research electrode . However, if used as an auxiliary electrode, platinum black plating is performed at the end to reduce electrode polarization.
