Alkanes are a type of hydrocarbon, with a molecular structure of straight or circular chains. Due to the covalent bond connection between carbon atoms and hydrogen atoms, alkanes are saturated and do not contain double or circular bonds. Alkanes can be divided into methane, ethane, propane, etc. based on the number of carbon atoms, with the general formula CnH2n+2. Polyalkanes are high polymers composed of several alkane molecules, each of which is an organic compound composed of carbon and hydrogen. Polyalkanes are a very common type of polymer, with common polyalkanes such as polyethylene and polypropylene. Polyalkanes have many excellent properties, such as low density, corrosion resistance, and excellent insulation performance, and are widely used in plastic products, packaging materials, wire and cable insulation, and other fields.
Electrolytic water production of green hydrogen gas is one of the most promising technologies in the future, which is expected to achieve large-scale renewable energy and efficient utilization of decarbonization. Among various electrolysis water technologies, emerging anion exchange membrane water electrolyzers (AEMWEs) combine the advantages of alkaline water electrolysis cells and proton exchange membrane water electrolysis cells, and have enormous commercial application potential. Membrane electrode assemblys (MEAs) are the fundamental units of AEMWEs electrochemical reactions. The structure, composition, and preparation process of membrane electrodes play a crucial role in hydroelectric electrolysis cells, determining the hydrogen production rate and energy consumption of the cells. Alkaline ionomers are key components in membrane electrodes. Compared with anion exchange membranes, researchers have paid relatively less attention to alkaline ionomers, and the impact of alkaline ionomers on the performance of AEMWEs electrolytic cells has been severely underestimated.
Recently, researchers have proposed a new strategy for using ionized self contained microporous polymers as alkaline ionomers, utilizing their high free volume properties. A series of self porous alkaline ionomers were obtained using electron rich aromatic monomers and p-trifluoromethylbenzaldehyde/p-cyanobenzaldehyde as co monomers. It was found that introducing twisted spiral ring structures and trifluoromethyl functional groups into the ionomer skeleton can promote the formation of microporous structures, improve the performance and durability of AEMWE. This work systematically explores the relationship between the structure and performance of self porous alkaline ionomers, indicating that ionic self porous polymers are ideal candidates for high-performance AEMWE alkaline ionomers.
Researchers studied the microporous properties of the material through carbon dioxide adsorption desorption experiments. Compared with ionomer materials with similar IEC (QP1-CF3-1, QP1-CN-1, QP2-CF3-1, and QP2-CN-1), materials with spiral ring structures have higher specific surface area. The specific surface area of ionomer materials increases with the increase of spiro monomer content.
The conductivity of these alkaline ionomers was studied by electrochemical impedance spectroscopy, and the Cl - conductivity of QP2-CF3-3 reached 90.7 mS cm-1 at 80 ℃; Without excluding the influence of carbon dioxide on the test results, its OH conductivity can still reach 144.4 mS cm-1 at 80 ℃, indicating that QP2-CF3-3 has a high level of ion conductivity.
Various experiments have also demonstrated that introducing spiral ring structures and trifluoromethyl substituents into ionomer materials is beneficial for constructing microporous structures, increasing free volume, and constructing effective ion transport channels, thereby improving ion conductivity and gas diffusion ability, and achieving excellent AEMWEs electrolytic cell performance.
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Reference
- Application of Ionized Intrinsic Microporous Poly(phenyl-alkane)s as Alkaline Ionomers for Anion Exchange Membrane Water Electrolyzers
Macromolecules, 2023, 56, 6037–6050
