Liquid organic hydrogen carriers

The development of efficient hydrogen storage materials is one of the biggest technical challenges for the coming ＂hydrogen economy＂. The liquid organic hydrogen carriers （LOHCs） with high hydrogen contents, reversibilities and moderate dehydrogenation kinetics have been considered as an alternative option supplementing the extensively investigated inorganic hydride systems. In this review, LOHCs for long distance H2 transport and for onboard application will be discussed with the focuses of the design and development of LOHCs and their hydrogenation ＆ dehydrogenation catalyses.

Hydrogen storage by liquid organic hydrogen carriers:Catalyst,renewable carrier,and technology--A review

Hydrogen has attracted widespread attention as a carbon-neutral energy source,but developing efficient and safe hydrogen storage technologies remains a huge challenge.Recently,liquid organic hydrogen carriers(LOHCs)technology has shown great potential for efficient and stable hydrogen storage and transport.This technology allows for safe and economical large-scale transoceanic transportation and long-cycle hydrogen storage.In particular,traditional organic hydrogen storage liquids are derived from nonrenewable fossil fuels through costly refining procedures,resulting in unavoidable environmental contamination.Biomass holds great promise for the preparation of LOHCs due to its unique carbon-balance properties and feasibility to manufacture aromatic and nitrogen-doped compounds.According to recent studies,almost 100%conversion and 92% yield of benzene could be obtained through advanced biomass conversion technologies,showing great potential in preparing biomass-based LOHCs.Overall,the present LOHCs systems and their unique applications are introduced in this review,and the technical paths are summarized.Furthermore,this paper provides an outlook on the future development of LOHCs technology,focusing on biomass-derived aromatic and N-doped compounds and their applications in hydrogen storage.

Nonstoichiometric Yttrium Hydride–Promoted Reversible Hydrogen Storage in a Liquid Organic Hydrogen Carrier

N-Ethylcarbazole(NEC)is one of the most promising liquid organic hydrogen carriers(LOHCs),but its application is limited by sluggish kinetics due to lack of high-efficiency,low-cost catalysts.This work reports a cobalt(Co)-based catalyst promoted by nonstoichiometric yttrium hydride(YH_(3−x))to achieve high-efficiency,reversible hydrogen storage in NEC,with>5.5 wt%reversible hydrogen storage capacity could be achieved below 473 K,and with good kinetics.The YH_(3−x)-promoted Co-based catalyst is the first non-noble metal catalyst with high activity for NEC hydrogenation and 12H-NEC dehydrogenation reactions.A mechanistic study suggests that YH_(3−x)facilitates the reversible hydrogen transfer both in the hydrogenation and the dehydrogenation reactions.The nonstoichiometric YH_(3−x)contained both lattice H and H vacancies with tunable H chemical potential serve as the H donor and H acceptor for reversible hydrogen transfer.Our results support the practical application of LOHCs and inspire new approaches for the utilization of conventional metal hydrides to promote versatile H transfer reactions.

Bimetallic Ru-Ni/TiO2 catalysts for hydrogenation of N-ethylcarbazole:Role of TiO2 crystal structure

Hydrogenation of N-ethylcarbazole(NEC),the hydrogen lean form of a liquid organic hydrogen carrier,on TiO2 supported Ru-Ni bimetallic catalysts is investigated.Crystal structure of TiO2 plays a critical role on the hydrogenation activity and selectivity towards fully hydrogenated product.Ru/anatase catalyst exhibits higher selectivity but lower reactivity compared to Ru/rutile catalyst.Ni addition significantly promotes the performance of Ru/anatase catalyst while causes severe performance deterioration of Ru/rutile catalyst.Commercial P25,a mixture of anatase and rutile phases in approximate ratio A/R1/4,is found to be the best TiO2 support for NEC hydrogenation.Ru/P25 catalyst outperforms both Ru/rutile and Ru/anatase and its activity can be further slightly improved by Ni addition.The unexpected synergism between the two different TiO2 phases for Ru based NEC hydrogenation catalysts is related to metal-support interaction and Ru-Ni interaction.

Highly efficient hydrogen production from methanol by single nickel atoms anchored on defective boron nitride nanosheet

Exploiting inexpensive and effective nickel-based catalysts that produce hydrogen from liquid organic hydrogen carriers(LOHCs)is crucial to alleviating the global energy and environmental crisis.In this study,we report a rational strategy that can realize atomically dispersed Ni atoms anchored on vacancy-abundant boron nitride nanosheets(Ni1/h-BNNS)with high specific surface area(up to 622 m^(2)·g^(-1))and abundant hydroxyl groups for high efficient hydrogen production.Methanol dehydrogenation results show an excellent hydrogen production performance catalyzed by this Ni1/h-BNNS,as evidenced by a remarkably high H_(2) yield rate(1684.23 mol·mol_(Ni)^(-1)·h^(-1)),nearly 100%selectivity toward hydrogen and CO,and high anti-coking performance.Density functional theory(DFT)calculations reveal that the outstanding catalytic performance of Ni1/h-BNNS primarily originates from the unique coordinated environment of atomically dispersed Ni(Ni-B_(2)O_(2))and the synergistic interaction between Ni single atoms and the h-BNNS support.Specifically,the coordinated O atoms play a decisive role in promoting the activity of Ni,and the neighboring B sites significantly decrease the energy barriers for the adsorption of key intermediates of methanol dehydrogenation.This study offers a novel strategy for developing high-performance and stable single-atom Ni catalysts by precisely controlling single-atom sites on h-BN support for sustainable hydrogen production.