提高海水电解体系中抗氯离子腐蚀性能的研究与策略

Problems such as environmental pollution and lack of fossil energy have always been important issues that have plagued the economic development and people’s lives of all countries in the world. Early, people have paid more attention and production capital to power generation from renewable energy sources such as wind, solar, and tidal energy. However, such natural energy sources are intermittent, random, and fluctuating, and thus cannot be supplied and transmitted continuously. Particularly, the regional problems have resulted in insufficient local power consumption, but long-distance power transmission is difficult and costly. Therefore, the technology and medium that can store and convert electrochemical energy are an urgent need. Hydrogen is a high-energy-density carrier with an energy density of 142 MJ·kg^-1, which is not only raw material for chemical production(such as synthetic ammonia)but also an important fuel for hydrogen fuel cells. With the advent of the hydrogen energy ear, the development of the hydrogen economy is expanding day by day. As the core foundation of the hydrogen energy industry chain, hydrogen is rich in sources and widely used, which is a green and low-carbon secondary energy and an important part of the future national energy system. Besides, combined with the electricity generated by renewable resources, the system of producing green hydrogen through water electrolysis has the characteristics of zero-carbon emission, recyclability, storage, and energy interconnection. Nowadays, many mature technologies of water electrolysis for hydrogen production are mostly based on high-purity freshwater resources. The lack of freshwater resources is one of the problems that restrict the large-scale development of such technologies, especially in coastal, central, and western regions where are abundant renewable resources such as wind, solar, and tidal energy. Thus, the electrolytic hydrogen production process using seawater as feed not only solves the shortage of freshwater resources but also contributes to the development and utilization of marine resources. However, some scientific problems need to be solved in seawater electrolysis. A large number of chloride ions in seawater can be oxidized for chorine evolution reaction and compete with the oxygen evolution reaction at the anode of the battery, which reduces the Faradaic current efficiency of the oxygen evolution reaction. Moreover, the chloride ions in seawater and the products of chorine evolution reaction (such as hypochlorous acid)could corrode the catalyst structure and equipment, thus destroying the long-term stability of the catalyst and reducing the service life of the device. Therefore, the strong corrosiveness of chloride ions in seawater is one of the bottleneck problems restricting the development of seawater electrolysis. In view of improving the corrosion resistance and oxygen evolution selectivity of the seawater electrolysis for a hydrogen production system, researchers have made more efforts and explorations. Based on the previous work, this review mainly summarized three aspects and proposed some reasonable suggestions, including: (1)The structure design of catalysts: by improving the catalytic activity of catalysts to reduce the overpotential of the oxygen evolution reaction and the probability of the chlorine evolution reaction with a higher initial voltage, so as to improve Faradaic current efficiency of the oxygen evolution reaction. A non-dense protective layer was formed on the surface of the catalyst to effectively hinder the passage of chloride ions with a larger radius(there was no obvious hindering effect on OH^- with a smaller size)according to the principle of size sieving, and the corrosion resistance of the catalyst was improved consequently. It was also possible to form an anion protective layer in situ (such as SO₄^2-), and the strong electrostatic repulsion effect between anion ions and chloride ions could reduce the diffusion movement of chloride on the surface of the catalyst, which can also improve the corrosion resistance and selectivity of catalyst. (2)The chemical reaction system was improved by replacing the high-potential oxygen evolution reaction with the low-potential oxidation reaction such as the hydrazine and sulfur oxidation reactions to improve the selectivity.(3)Adopting a multi-process coupled reaction system, such as the use of reverse osmosis membrane desalination process to reduce the concentration of chloride ions in seawater, and indirectly reduce the interference caused by chloride ions. What was more, retrofit and improvement of the reaction equipment, such as the design of membraneless electrolyzers, could also increase system life and reduce production costs and maintenance costs. When the "carbon peak" and "carbon neutrality" goals were put forward in our country, hydrogen energy, as the most promising secondary clean energy, would be further expanded in terms of development intensity and scale. Among them, seawater electrolysis of hydrogen production was a large-scale and long-term development of the hydrogen production scheme. This review not only summarizes the research results and experience of predecessors, but also proposed some corresponding strategies and suggestions from the aspects of catalyst design, chemical reaction system, and process design to provide a reference for the follow-up research and application of seawater electrolysis of hydrogen production technology.