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The main functions of the electrolyzer electrodes are to conduct electricity, serve as the site for the water electrolysis reaction, catalyze the hydrogen and oxygen evolution reactions, support and stabilize the electrolyte, and facilitate the separation of the generated gases. Their performance has a direct impact on the efficiency and cost of hydrogen production through water electrolysis. Let’s take a look at several important parameters of hydrogen production electrodes: 1. Conductivity of the electrode material – The electrode material must have good electrical conductivity, so that electricity can be transmitted efficiently from the external circuit to the electrolyte interface, thereby effectively driving the water electrolysis reaction. Electrode materials with poor electrical conductivity result in higher resistance losses, causing more energy to be lost as heat and thereby reducing the energy conversion efficiency of water electrolysis for hydrogen production. For example, platinum (Pt) electrodes possess excellent electrical conductivity, enabling them to conduct electricity effectively and reduce the contact resistance between the electrode and the electrolyte, thereby improving the efficiency of hydrogen production through water electrolysis. 2. High catalytic activity of the electrodes: Electrode materials with high activity can reduce the overpotential of the water electrolysis reaction, that is, they decrease the additional voltage required to drive the reaction. Metal oxides such as iridium oxide (IrO₂) and ruthenium oxide (RuO₂) exhibit good catalytic activity for the oxygen evolution reaction at the anode, enabling effective reduction of the anode overpotential. 3. Stability of the electrodes: The electrodes need to operate stably for a long time during the process of water electrolysis. Electrodes with poor stability are prone to corrosion, dissolution, or structural changes, which leads to a decline in their performance and affects the efficiency and sustainability of water electrolysis for hydrogen production. For example, spray-coated Reney nickel can easily peel off if not handled properly, thereby affecting the performance of the electrode. 4. Specific surface area of the electrode: The greater the specific surface area of the electrode, the larger its contact area with the electrolyte, which allows for more active sites to be available. This facilitates the progress of the water electrolysis reaction, thereby enhancing the catalytic activity of the electrode and the efficiency of hydrogen production. 5. Pore volume fraction and pore size distribution of the electrode: An appropriate pore volume fraction and pore size distribution facilitate the diffusion and penetration of the electrolyte within the electrode, allowing the electrolyte to come into full contact with the active sites on the electrode, thereby improving the efficiency of use of the electrode and its reaction efficiency. Too small a pore size may hinder the diffusion of the electrolyte, while too large a pore size may reduce the effective contact area between the electrode and the electrolyte. 6. Corrosion resistance of electrodes: During the process of water electrolysis, the electrodes need to come into contact with the electrolyte and withstand certain potentials; therefore, the electrode materials must have good corrosion resistance to prevent them from being corroded and becoming ineffective during the reaction. In alkaline electrolytic water, nickel (Ni)-based electrodes exhibit good corrosion resistance and can operate stably for a long time. 7. Degree of polarization of the electrode: The degree of polarization reflects the voltage loss of the electrode during the electrolysis of water. The lower the degree of polarization, the better the performance of the electrode, and the higher the efficiency of hydrogen production through water electrolysis. The polarization of electrodes includes aspects such as concentration polarization, resistance polarization, and activation polarization. By optimizing the material composition, structure, and surface properties of the electrodes, it is possible to reduce the degree of polarization and improve the performance of the electrodes. 8. Hydrogen production rate of the electrode: The hydrogen production rate is one of the direct indicators for evaluating the performance of an electrode. Under the same conditions, the electrode with a higher hydrogen production rate has better performance in producing hydrogen via water electrolysis. The hydrogen production rate is not only related to the catalytic activity of the electrodes, but also closely associated with factors such as the structure of the electrodes, their specific surface area, and the properties of the electrolyte. 9. Self-corrosion current density of the electrode: The self-corrosion current density indicates the degree of self-corrosion of the electrode in the electrolyte. A lower self-corrosion current density implies better stability of the electrode in the electrolyte, reducing the likelihood of self-corrosion leading to failure. 10. Number of active sites on the electrode: Active sites are the key locations where the electrolysis of water takes place; the greater the number of active sites on an electrode, the higher its catalytic activity and hydrogen production capacity. The number of active sites on an electrode is related to factors such as the material’s composition, structure, and preparation method; by optimizing these factors, the number of active sites on the electrode can be increased, thereby improving the electrode’s performance.