No abstract

The development of hydrogen carriers that are free from safety risks such as explosivity, volatility and toxicity is essential for safe hydrogen storage. In this study, we synthesize a safe and hydrophilic isopropanol/acetone‐substituted polymeric hydrogen carrier by a facile synthetic procedure that is conducted in water and only requires dialysis with water for purification. A simple nucleophilic substitution of poly(allylamine) and 2‐bromoacetone produces a hydrophilic acetone‐substituted poly(allylamine) derivative, facilitating control over the hydrophilicity of the polymer according to the degree of substitution. The polymer is readily hydrogenated using NaBH4 to obtain a hydrophilic isopropanol‐substituted poly(allylamine). The high density of the repeating units and high hydrophilicity of the amine groups enable the maximization of the mass hydrogen storage density of the redox polymer to ca 1.5 wt%. Reversible hydrogen gas fixation/release from the polymeric hydrogels via chemical bond formation/disconnection is realized with complete conversion, with dehydrogenation occurring at 65–95 °C in the presence of an iridium complex catalyst. © 2021 Society of Industrial Chemistry.

The cover image is based on the Research Article Hydrophilic isopropanol/acetone‐substituted polymers for safe hydrogen storage by Kouki Oka et al., https://doi.org/10.1002/pi.6337. image

A novel quaternized polymer was synthesized by introducing butanediol into poly(allylamine) and converting the remaining amino groups into quaternary ammonium cations. The polymer accelerated the dehydrogenation of butanediol due to...

Redox-active polymers with electrochemical reversibility and rapid electrode reaction rates are employed to develop organic electrode-active materials employed in organic batteries, based on their selfexchange reactions in polymer layers. Negative charging of the electroneutral redox polymers results in a signifi cant increase in basicity to allow protonation of each redox-active site in the polymer. Since most of the hydrogenated products are no longer redox-active, aprotic battery electrolytes are employed to avoid the hydrogenation in organic batteries. On the other hand, organic compounds that undergo reversible hydrogenation, such as toluene to yield methylcyclohexane, have been studied as hydrogen storage materials. However, the hydrogenation with hydrogen gas usually proceeds via a highly energy consuming process. We anticipated that electrolytic hydrogenation of the redox-active molecules would provide a much simpler process. We have found that ketone-containing polymers stored hydrogen via the electrolytic process in the presence of water at room temperature. The resulting alcohol polymer evolved hydrogen gas by warming under mild conditions with an iridium catalyst. The hydrogenation/dehydrogenation cycle was accomplished throughout the polymer layer, meaning that all of the ketone groups in the polymer were equilibrated with the hydrogen gas according to > C = O + H 2 ⇄ > CH-OH in the presence of the iridium catalyst. The reversible hydrogenation/dehydrogenation was extended to various types of organic groups in the polymer, providing many types of the hydrogen carrier polymers as a new class of energy-related functional polymers. The easy handling and moldable nature of the organic polymers indicate the feasibility of applying them as pocketable hydrogen carriers.