Development status of electrolyzers

The distance between the cathode and the anode is one of the important factors affecting the cell voltage. As the pole spacing increases, the ohmic voltage drop in the tank increases and the tank voltage increases. Especially when working with high current, this voltage loss is more serious. Modern electrolyzers adopt various measures to reduce the pole spacing, such as using diffused anodes and modified separators to create zero pole spacing electrolytic cell structures. The residence time of the electrolyte in the electrolytic cell not only affects the production capacity of the equipment, but also, in some cases, affects the current efficiency of the electrolysis process. For example, in the production of sodium chlorate by electrolysis, the intermediate product hypochlorous acid (HClO) and hypochlorous acid are The chemical reaction between chlorate ions (ClO3) is very slow. If left in the electrolytic cell for a long time, it will not only reduce the utilization rate of the electrolytic cell, but also the hypochlorite ions will be oxidized on the anode surface or reduced on the cathode surface, reducing the current efficiency. . Therefore, modern electrolyzer designs strive to reduce the volume and allow the electrolyte to flow quickly along the electrodes. If further reactions are required, an independent chemical reactor can be installed outside the electrolyzer.
The electrodes in the electrolytic cell are installed vertically to be more compact, the conductive plates are easy to connect, and it is helpful to reduce the bubble effect. Because there are often bubbles on the surface of the electrode where gas is released, it will reduce the working surface area of the electrode. In addition, the solution near the electrode will also be filled with bubbles, increasing the solution resistance. This phenomenon is called the "bubble effect". However, near the vertical electrode surface, the characteristics of high aeration, low solution density, and fast rising speed in the solution can be used to form a natural circulation of the electrolyte, accelerate the bubbles to leave the electrode surface, and reduce the bubble effect. When the vertical electrode is used as a gas electrode, the shape of the electrode is mostly mesh, which not only increases the working surface area, but also facilitates the escape of bubbles.
Electrolytic cell materials can be steel, cement, ceramics, etc. Steel is alkali resistant and is the most widely used. For highly corrosive electrolytes, the inside of the steel tank should be lined with lead, synthetic resin or rubber.
At present, electrolyzers are developing in the direction of large capacity and low energy consumption. The bipolar electrolyzer is suitable for large-scale production and has been used by the water electrolysis and chlor-alkali industries.
Most electrolytic cells for hydrogen production through water electrolysis use iron as the cathode surface and nickel as the anode surface in a series electrolytic cell (looking like a filter press) to electrolyze aqueous solutions of caustic potassium or caustic soda. Oxygen comes out of the anode and hydrogen comes out of the cathode. This method is more expensive, but the product has high purity and can directly produce hydrogen with a purity of more than 99.7%.