Research On Electrochemical Hydrogen Storage Properties Of Nitrogen Heterocyclic Organic Compounds

Due to its high energy density and cleanliness,hydrogen energy is considered as an alternative to non-renewable energy sources such as coal,oil and natural gas,which can alleviate the severe pollution situation.However,the widespread use of hydrogen energy is limited by the high production cost and the difficulty of storage.Therefore,suitable hydrogen storage carriers and green hydrogen storage solutions need to be explored.Electrochemical hydrogenation and dehydrogenation of nitrogen-containing organic compounds with low enthalpy change are investigated in this paper from the perspectives of dehydrogenation,hydrogenation,and hydrogenation/dehydrogenation cycles.The aim of this paper is to explore a green and recyclable hydrogen storage scheme.An electrochemical dehydrogenation scheme was explored using 2,2,6,6-tetramethylpiperidine-N-oxyl（TEMPO）as a dehydrogenation catalyst.The electrochemical dehydrogenation reactivity of nitrogen heterocycles（including pyrazine,1,2,3,4-tetrahydrocarbazole,1,2,3,4-tetrahydroquinoline,1,2,3,4-tetrahydroquinolone,and 2,3-dihydroindole）in the TEMPO system is investigated by linear sweep voltammetry（LSV）.The oxidation potentials of 1,2,3,4-tetrahydroquinoline,1,2,3,4-tetrahydroquinolone,and 2,3-dihydroindole are found.Subsequently,nitrogen heterocycles are shown to undergo electrochemical dehydrogenation in the TEMPO system after dehydrogenation attempts and gas chromatography-mass spectrometry（GC-MS）analysis of the products.The influencing factors of the electrochemical dehydrogenation of 1,2,34-tetrahydroquinoline are also investigated.The effects of three factors,including reaction ratio,temperature,and current,on the quinoline yield are analyzed using single-factor experiments and orthogonal experiments.The results showed that the order of their importance was reaction ratio>temperature>current.The optimal reaction conditions were a current of 7 m A,a temperature of 25℃,and a reaction ratio of 0.75/0.375/0.3.The maximum quinoline yield is 78%,indicating that the electrochemical dehydrogenation reaction of 1,2,3,4-tetrahydroquinoline have been significantly improved.In order to make the nitrogen heterocycles hydrogen storage recyclable and sustainable,low-cost catalytic electrode is prepared and the electrochemical addition/dehydrogenation reaction of nitrogen heterocycles is investigated.A Ni²⁺metal ion organic complex is synthesized by a solvothermal method,and then the catalyst Ni is obtained by reducing the complex under H₂ atmosphere.subsequently,a nickel-based bifunctional electrode（denoted as Ni@NF）is prepared by loading Ni onto nickel foam（nickel foam,NF）via an ionic copolymer.Using Ni@NF as the catalytic electrode,the largest current difference was found for quinoxaline by LSV when V _acetonitrile:V _KOH（aq）is 1:4.Moreover,nitrogen heterocycles（quinoline,quinoxaline and indole）could all be electrochemically hydrogenated on the Ni@NF surface.And the yields of the hydrogenated products are above 50%,indicating that the electrochemical hydrogenation catalytic ability of Ni@NF is still relatively considerable.In addition,1,2,3,4-tetrahydroquinoline,1,2,3,4-tetrahydroquinoxaline and 2,3-dihydroindole can also be dehydrogenated on the Ni@NF surface,but the dehydrogenation efficiency is low.The hydrogenation and dehydrogenation reactions can be repeated if the products under different systems are separated and purified.Therefore,superhydrophobic filter membranes are applied for the removal of water from organic matter in this paper.Hydrophobic filter membranes are prepared after spraying fluorine-modified Si O₂ nanoparticles onto the substrate.The static contact angle test reveals that the contact angle between the hydrophobic filter membrane and water is larger than 120o.And the filter paper is modified to obtain superhydrophobic filter membrane.The superhydrophobic filter paper is used for acetonitrile water removal because of its strength and optimal hydrophobicity.When the superhydrophobic filter paper is used as a filter membrane,the removal of water from acetonitrile has a significant effect.The water content in acetonitrile is decreased to 1.3%from 5%.Since the water content meets the requirements of the TEMPO system,liquid organic hydrogen storage model with separate hydrogenation and dehydrogenation is possible.