The development of low-cost and safe hydrogen storage systems is a priority when creating new energy sources. Storing hydrogen in chemical compounds in which it occurs naturally is the only ...alternative. Aromatic hydrocarbons, capable of reversible hydrogenation–dehydrogenation reactions, are of the greatest interest among regenerated hydrogen-containing compounds and can be used for hydrogen storage. Naphthalene, its methyl derivatives and the products of hydrogenation have the high storage density among the aromatic hydrocarbons (up to 7.3 wt%) which make it the extremely perspective as liquid hydrogen storage carriers. Therefore, the synthesis of the compounds with the higher added value (as decalin) is a highly important from scientific point of view. However, for the building up of “ideal” chemical system of hydrogen storage the development of effective catalytic systems with the composition and morphology adopted to the structure of aromatic substrate is highly needed. This review discusses the role of the metal in the catalytic hydrogenation of naphthalene and its derivatives for hydrogen storage.
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•Chemical hydrogen storage in liquid organic hydrogen carriers is studied.•The supported metal role in the hydrogenation of naphthalene's is discussed.•The non-noble metal doped with small amounts of noble metal are promising catalysts.
Future energy systems will be determined by the increasing relevance of solar and wind energy. Crude oil and gas prices are expected to increase in the long run, and penalties for CO
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emissions will ...become a relevant economic factor. Solar- and wind-powered electricity will become significantly cheaper, such that hydrogen produced from electrolysis will be competitively priced against hydrogen manufactured from natural gas. However, to handle the unsteadiness of system input from fluctuating energy sources, energy storage technologies that cover the full scale of power (in megawatts) and energy storage amounts (in megawatt hours) are required. Hydrogen, in particular, is a promising secondary energy vector for storing, transporting, and distributing large and very large amounts of energy at the gigawatt-hour and terawatt-hour scales. However, we also discuss energy storage at the 120-200-kWh scale, for example, for onboard hydrogen storage in fuel cell vehicles using compressed hydrogen storage. This article focuses on the characteristics and development potential of hydrogen storage technologies in light of such a changing energy system and its related challenges. Technological factors that influence the dynamics, flexibility, and operating costs of unsteady operation are therefore highlighted in particular. Moreover, the potential for using renewable hydrogen in the mobility sector, industrial production, and the heat market is discussed, as this potential may determine to a significant extent the future economic value of hydrogen storage technology as it applies to other industries. This evaluation elucidates known and well-established options for hydrogen storage and may guide the development and direction of newer, less developed technologies.
Mesoporous alumina (MA) materials with outstanding textural properties have been synthesized by a facile approach, and were evaluated as supports of Pt-based catalyst for methylcyclohexane ...dehydrogenation. At 300 °C, the resultant catalyst demonstrates a much higher activity with a maximum hydrogen evolution rate of 2081 mmol/gPt/min in comparison with the state-of-the-art alumina supported Pt catalysts. Interestingly, even after a long-time reaction of 100 h or regeneration, more than 80% of original activity was still maintained. The superior catalytic performance of the obtained catalyst is associated with the high specific surface area and large mesoporous size of support MA, thus benefiting the increase in the number of Pt active sites and efficiently inhibiting the formation of coke deposition during the reaction. Our contribution has provided a rational design strategy for highly efficient and stable dehydrogenation catalysts, which is a key for the utilization of methylcyclohexane-toluene system in hydrogen storage technology.
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•A confined hydrolysis-condensation approach.•Mesoporous alumina with excellent textural properties.•Pt-based catalyst with highly homogenous dispersion of Pt.•Improved catalytic performance for dehydrogenation of methylcyclohexane at low temperature.
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•The features and utilization of diverse hydrogen storage technologies are compared.•Various systems for Liquid Organic Hydrogen Carriers (LOHCs) are investigated.•The catalysts, ...reactors, and projects of LOHCs technology are discussed.•Concept and roadmap to prepare LOHCs by the conversion of biomass are proposed.•The feasibility and challenges for biomass-based LOHCs are analyzed.
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.
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•High-loading Co-Al2O3-SiO2 was synthesized using the co-precipitation method.•Al incorporation modifies metal-carrier interaction and promotes Co dispersion.•The as-prepared ...Co70/Al4Si1O catalyst displayed the optimized catalytic performance.•The inherent reasons for the enhanced catalytic hydrogenation activity were revealed.•DFT calculations provide deep understanding for the catalytic hydrogenation process.
We developed a series of high-loading Co-Al2O3-SiO2 catalysts to enhance the hydrogenation of N-propylcarbazole (NPCZ) by fine-tuning the Al/Si ratio. Our research reveals that adjusting this ratio can significantly modify the electronic structure of Co nanoparticles, as confirmed by XPS, H2-TPD, and CO-DRIFT analyses, thereby affecting the adsorption of hydrogen species and their interaction with unsaturated π-bonds of NPCZ intermediates. Optimal Al concentration promotes Co nanoparticles dispersion, while excessive Al leads to increased acidity and reduced surface area. The Co70/Al4Si1O catalyst, with an Al/Si ratio of 4, demonstrated superior hydrogenation efficiency by enabling fast and stable hydrogenation of NPCZ, achieving an activation energy of 64.53 kJ/mol and maintaining high performance over 10 cycles. Through DFT calculations, we explored the d-band center and Bader charge across 6 different Co10/Al-Si-O models and assessed the adsorption energies of NPCZ intermediates, along with the energetics of three stepwise reactions. The initial hydrogenation step from NPCZ to 4H-NPCZ is predominantly influenced by the catalyst's acidity/basicity, whereas the subsequent deeper hydrogenation steps of 4H-NPCZ and 8H-NPCZ are governed by the d-π feedback interaction between the metal and the adsorbate. This research offers critical guidance on selecting optimal supports for Co-based catalysts in LOHC hydrogenation.
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•Series of La-Ni/Al2O3 catalysts were synthesized by a facile co-precipitation method.•La-Ni/Al2O3 catalysts exhibited superior catalytic hydrogenation activity for LOHCs.•The ...ultrafine nanoparticles were formatted with balanced dispersion of acid sites.•The temperature significantly influenced the Ni and NiO content of as-prepared catalysts.•DFT calculations revealed a significant charge accumulation at the Ni-NiO interface.
The development of cost-effective, efficient and stable catalysts for liquid organic hydrogen carriers (LOHC) is crucial for large-scale hydrogen storage. Herein, we introduced La species into Ni/Al2O3 via co-precipitation method, yielding La-Ni/Al2O3 catalysts. Such catalysts demonstrated exceptional performance and durability in hydrogenating various LOHC candidates. Their hydrogenation capabilities surpassed most state-of-the-art and commercial catalysts, attributing to the homogenous formation of ultrafine nanoparticles induced by La species, prevention of producing unfavorable components, optimal microstructural distributions and balanced dispersion of acid sites. DFT calculations indicated that Ni-NiO(002) interface played crucial roles in modulating the electron deficiency of surface Ni atoms. The synergistic effect of Ni0-Niδ+ shifts the d-band center of Ni closer to the Fermi level, enhancing the catalyst’s adsorption capacity of intermediates and achieving higher activity toward activation of benzene and pyrrole ring, therefore leading to rapid and deep LOHC hydrogenation. The resultant catalysts exhibited great potentials for industrial applications.
One option to transport hydrogen over longer distances in the future is via Liquid Organic Hydrogen Carriers (LOHC). They can store 6.2 wt% hydrogen by hydrogenation. The most promising LOHCs are ...toluene and dibenzyltoluene. However, for the dehydrogenation of the LOHCs – to release the hydrogen again – temperatures above 300 °C are needed, leading to a high energy demand. Therefore, a Life Cycle Assessment (LCA) and Life Cycle Costing are conducted. Both assessments concentrate on the whole life cycle rather than just direct emissions and investments. In total five different systems are analysed with the major comparison between conventional transport of hydrogen in a liquefied state of matter and LOHCs. Variations include electricity supply for liquefaction, heat supply for dehydrogenation and the actual LOHC compound. The results show that from an economic point of view transport via LOHCs is favourable while from an environmental point of view transport of liquid hydrogen is favourable.
•Life Cycle Assessment and Life Cycle Costing of hydrogen transport.•Comparison of transport in liquid organic hydrogen carriers and in a liquefied form.•Liquid transport is environmentally more benign.•Transport in liquid organic hydrogen carriers is cheaper than in a liquefied stage.•System variations can improve single environmental impacts, e.g. heat source.
Perhydro-dibenzyltoluene (18H-DBT) have been paid more attention as liquid organic hydrogen carriers (LOHCs) because of its high hydrogen storage, easy transportation, low price and other advantages. ...The 18H-DBT dehydrogenation reaction rate is the key point of the hydrogen storage. In this work, the relationship between the Pt dispersion, the average coordinated number and the total catalyst activity for 18H-DBT dehydrogenation reaction was studied. Al2O3 with the large specific surface area was synthesized by the sol–gel method and Pt/Al2O3 catalysts were prepared by incipient wetness impregnation. Their catalytic performance was tested by 18H-DBT dehydrogenation reaction. It was found that the relationship between the Pt dispersion and the catalytic performance is a volcano curve. The optimal dispersion of Pt for dehydrogenation reaction is 11.16 %. That's because that there exists a balance between the Pt dispersion and the average coordinated number in order to obtain the best total catalyst activity. The experiments and characterization results show that the increasing of Pt dispersion will increase the active site number but the average coordinated number will decrease. DFT calculation results further confirm that the catalytic activity of the single active site would decline with the decreasing average coordinated number.
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•Al2O3 with a large specific surface area (436 m2 g−1) was successfully synthesized.•The highest degree of dehydrogenation and TOF for 18H-DBT dehydrogenation is 63.84 % and 1.31 min−1, respectively.•When the Pt dispersion increase, the average coordinated number of active sites will decrease.•The catalytic activity of the single active site will decrease with the average coordinated number decreasing.
Liquid organic hydrogen carriers (LOHCs) have been attractive as the technology to decarbonize the mobility sector. In this work, the dehydrogenation of 1,1,6,6-tetracyclohexylhexane (7.29 wt% H2) ...was explored using various DFT-based approaches. The effect of BN substitution on the dehydrogenation was explored based on the changes in the dehydrogenation energies in response to BN substitution. The BN substitution was shown to clearly lower the dehydrogenation energy. The energy barrier for dehydrogenation was also found to be influenced by the BN substitution. The dehydrogenated system was found to possess a lower HOMO-LUMO gap than the hydrogenated one, showing the chemical reactivity of the dehydrogenated form of the studied LOHC.
•Dehydrogenation of 1,1,6,6-tetracyclohexylhexane was elucidated based on first-principles.•Reduction in dehydrogenation energy upon BN substitution was found.•BN substitution was effective in lowering activation energies for dehydrogenation of the LOHC.•H2-lean state of the LOHC was also found to be reactive for hydrogenation.
Dodecahydro-N-ethylcarbazole (12H-NEC) is considered as a highly promising liquid organic hydrogen carrier, but its commercial application is constrained by the requirement of large amounts of ...precious metal catalysts for dehydrogenation. Herein, Pd nanoclusters with an average particle size of 1.1 nm supported on amine groups modified carbon blacks (Pd/N–CHNO3) are developed to efficiently catalyze the dehydrogenation of 12H-NEC with a low loading of Pd (2.2 wt%, 0.12 mol%). Induced by the nitrogen doping in the carbon black, the d-band center of the Pd (111) surface shifts from −1.64 eV to −1.53 eV, resulting in the electron-deficient structure of thus-formed Pd nanoclusters owing to the electron transfer from Pd to N atoms and uniform distribution of Pd nanoclusters inside of carbon blacks. This electron transfer effectively tunes Pd0:Pdδ+ ratio for enhancing the adsorption of reactant species of 12H-NEC on the surface of Pd nanoclusters and hence facilitates the catalytic role of Pd nanoclusters in enhancing the hydrogen desorption performance of 12H-NEC. As a result, every step of the dehydrogenation of 12H-NEC under the catalysis of Pd nanoclusters on the nitrogen-doped support exhibits lower ΔG values compared to the non-doped support, which provides direct evidence to the important role of the nitrogen doping of the catalyst support in improving the dehydrogenation performance of 12H-NEC on the Pd surface. Therefore, a hydrogen release capacity of 5.60 wt% with 100% conversion and a selectivity of 90% could be obtained for 12H-NEC under the catalysis of Pd nanoclusters supported on amine-functionalized carbon black at 453 K with a low precious metal dosage (0.12 mol%).
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•Pd nanoclusters with an average particle size of 1.1 nm supported on amine groups modified carbon blacks are developed.•A hydrogen release capacity of 5.60 wt% is obtained for 12H-NEC with an ultralow Pd dosage (0.12 mol%).•A H2 release amount of 5.49 wt% with a capacity retention of 96% is achieved for 12H-NEC after five cycles for 40 h.•The d-band center of the Pd (111) surface shifts from −1.64eV to −1.53eV upon nitrogen doping.•DFT calculations reveal that ΔG for the dehydrogenation of 12H-NEC by the catalyst is decreased upon nitrogen doping.
