When direct current is applied to some electrolyte aqueous solutions, the decomposed substances have nothing to do with the original electrolyte. What is decomposed is water as a solvent, and the original electrolyte remains in the water. For example, sulfuric acid, sodium hydroxide and potassium hydroxide all belong to this electrolyte.
In proton exchange membrane water electrolysis, pure water is a typical weak electrolyte because of its low ionization degree and low conductivity, so it is necessary to add the above electrolyte to increase the conductivity of the solution, so that water can be successfully electrolyzed into hydrogen and oxygen. In chlor-alkali industry, a large amount of pure hydrogen is produced by-product, which can not only be used to synthesize hydrochloric acid, but also be purified to produce ordinary hydrogen or pure hydrogen. For example, the hydrogen used in the second chemical plant is a by-product of electrolytic brine.
Problems needing attention in hydrogen production by electrolysis of water
1. Safety: Hydrogen production by electrolysis of water involves electrolysis process, so safety is the primary consideration. Ensure the use of equipment and materials that meet relevant safety standards to avoid fire, explosion and other safety accidents.
2. Choose the appropriate electrolyte: electrolyte is the key factor to promote water decomposition. Commonly used electrolytes include alkaline solution (such as sodium hydroxide or potassium hydroxide solution) and acidic solution (such as sulfuric acid solution). Choosing appropriate electrolyte can improve hydrogen production efficiency and reduce energy consumption.
3. Controlling current density: Controlling current density can adjust the speed and efficiency of hydrogen production by electrolysis of water. Excessive current density may lead to overheating of electrolyzer, increase energy consumption and even cause equipment damage. Therefore, it is very important to select and control the current density reasonably.
4. Control the electrolysis time: The time for producing hydrogen by electrolyzing water depends on the required hydrogen output and equipment performance. Too long electrolysis time will increase energy consumption, and too short electrolysis time may not produce enough hydrogen. According to the actual demand, reasonably control the electrolysis time.
5. Pay attention to corrosion protection: Hydrogen production by electrolysis of water involves the contact between materials and solutions, and some materials are easily corroded by solutions. Choosing corrosion-resistant materials can prolong the service life of equipment and reduce the maintenance cost.
Refer to the above content: Baidu Encyclopedia-Hydrogen production by water electrolysis