Reversible Hydrogen Releasing and Fixing with Poly(Vinylfluorenol) through a Mild Ir‐Catalyzed Dehydrogenation and Electrochemical Hydrogenation

Abstract

The radical polymerization of 2‐vinylfluorenol, an alcohol derivative of vinylfluorene, gives poly(vinylfluorenol), which quantitatively releases hydrogen gas (≈110 mL per gram polymer at standard temperature and pressure) by simply warming at 100 °C with an iridium catalyst. A high population of fluorenol units in the polymer accomplishes a large formula‐weight‐based theoretical hydrogen density (1.0 wt%). The dehydrogenated ketone derivative, poly(vinylfluorenone), exhibits reversible negative‐charge storage with a high density of 260 mAh g−1. The electrolytically reduced poly(vinylfluorenone) is momentarily hydrogenated in the presence of an electrolyte with water as the hydrogen source to be converted to the original poly(vinylfluorenol). The formed poly(vinylfluorenol) almost quantitatively evolves hydrogen gas similar to the starting poly(vinylfluorenol). Both hydrogen and charge storage with the organic fluorenol/fluorenone polymer suggest a new type of energy‐storage configuration.

Facile reversible hydrogenation of a poly(6‐vinyl‐2,3‐dimethyl‐1,2,3,4‐tetrahydroquinoxaline) gel‐like solid

“…The gel‐like solid of poly(6‐vinyl‐1,2,3,4‐tetrahydroquinoxaline) (PVHQX) was dehydrogenated with a small amount of γ‐butyrolactone (GBL) and Ir cat. For 5 h under 120°C and air, and was reversibly hydrogenated under 60°C and ambient hydrogen pressure 23‐28 . This study also shows a new aspect of polymer gels 29,30 as a hydrogen storage material.…”

“…On the other hands, we have demonstrated polymers bearing hydrogen storage units as hydrogen carriers. These polymers have exhibited with inherent advantages as a sheet‐ or gel‐like solids, including ease of handling and high safety 23,24 . The gel‐like solid of poly(6‐vinyl‐1,2,3,4‐tetrahydroquinoxaline) (PVHQX) was dehydrogenated with a small amount of γ‐butyrolactone (GBL) and Ir cat.…”

Hydrophilic isopropanol/acetone‐substituted polymers for safe hydrogen storage

“…Recently, we reported hydrogen storage using alcohol/ketone‐substituted polymers by means of a hydrogenation/dehydrogenation cycle 19–22 . These polymers act as highly safe hydrogen carriers and have inherent advantages such as moldability and ease of handling.…”

“…Furthermore, owing to the high population of the hydrogenation/dehydrogenation sites in the bulk of the polymer, the proton‐ and hydrogen‐exchange reactions occur efficiently. Furthermore, these polymers can be fully hydrogenated and dehydrogenated even in their solid states 15,20,23–31 . Most recently, we reported the reversible hydrogen storage capability of isopropanol/acetone‐substituted vinyl polymers swollen with ethylene glycol containing an Ir cat 31 .…”

Charge- and Proton-Storage Capability of Naphthoquinone-Substituted Poly(allylamine) as Electrode-Active Material for Polymer–Air Secondary Batteries

“…Redox polymers bear a redox-active group in their repeat units. Their densely populated redox sites enable them to feature high charge-transport and charge-storage capabilities. − The utilization of organic redox polymers as anodes and acidic aqueous solutions as electrolytes resolved the detrimental dendrite problem and the carbonate clogging, respectively. The polymer–air secondary battery composed of a redox polymer bearing 2,5-dihydroxy-1,4-benzoquinone as anode, Pt/C electrode as conventional cathode, and H 2 SO 4 aqueous solution as electrolyte displayed a high cyclability of >500 cycles and high rate capability (full capacity even at 10 C) with a voltage of 0.40 V during discharging.…”