Indirect hydrogen storage in metal ammines

Vegge, Tejs; Sørensen, Rasmus Zink; Klerke, Asbjørn; Hummelshøj, Jens Strabo; Johannessen, Tue; Nørskov, Jens K.; Christensen, Claus H.

doi:10.1533/9781845694944.4.533

Cited by 28 publications

(23 citation statements)

References 43 publications

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“…Since SrCl 2 binds 7 out of 8 ammonia molecules with low binding energy (1-7: 41.4 kJ/mol, 8: 48.1 kJ/mol) compared to 6 out of 8 for CaCl 2 (1-4: 41.0 kJ/mol, 5-6: 42.3 kJ/mol, 7: 63.2 kJ/mol, 8: 69.1 kJ/mol), SrCl 2 is often the chosen material for practical applications. 7 The stable ammines of SrCl 2 are the monoammine Sr(NH 3 )Cl 2 , the di-ammine Sr(NH 3 ) 2 Cl 2 , and the octa-ammine Sr(NH 3 ) 8 Cl 2 . Depending on temperature and pressure, transitions can go between mono-, di-, and octaammine or directly between mono-and octa-ammine.…”

Section: Introductionmentioning

confidence: 99%

Surface adsorption in strontium chloride ammines

Ammitzbøll¹,

Lysgaard

Klukowska³

et al. 2013

The Journal of Chemical Physics

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An adsorbed state and its implications on the ab-and desorption kinetics of ammonia in strontium chloride ammine is identified using a combination of ammonia absorption measurements, thermogravimetric analysis, and density functional theory calculations. During thermogravimetric analysis, ammonia desorption originating from the adsorbed state is directly observed below the bulk desorption temperature, as confirmed by density functional theory calculations. The desorption enthalpy of the adsorbed state of strontium chloride octa-ammine is determined with both techniques to be around 37-39 kJ/mol. A simple kinetic model is proposed that accounts for the absorption of ammonia through the adsorbed state. © 2013 AIP Publishing LLC. [http://dx

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Section: Introductionmentioning

confidence: 99%

Surface adsorption in strontium chloride ammines

Ammitzbøll¹,

Lysgaard

Klukowska³

et al. 2013

The Journal of Chemical Physics

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“…[1][2][3] To date,the dominant industrial route for NH 3 synthesis is the Haber-Bosch process using N 2 and H 2 as the feeding gases,b ut this process operates at high temperature and high pressure,a nd consumes al arge amount of energy while emitting CO 2 . One of the cheapest and most abundant metals on earth, iron, is an effective dopant for greatly improving the nitrogen reduction reaction (NRR) performance of TiO 2 nanoparticles in ambient N 2 -to-NH 3 conversion.…”

mentioning

confidence: 99%

“…[1][2][3] To date,the dominant industrial route for NH 3 synthesis is the Haber-Bosch process using N 2 and H 2 as the feeding gases,b ut this process operates at high temperature and high pressure,a nd consumes al arge amount of energy while emitting CO 2 . [1][2][3] To date,the dominant industrial route for NH 3 synthesis is the Haber-Bosch process using N 2 and H 2 as the feeding gases,b ut this process operates at high temperature and high pressure,a nd consumes al arge amount of energy while emitting CO 2 .…”

mentioning

confidence: 99%

Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping

Zhu

Xing

et al. 2019

Angewandte Chemie

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Titanium-based catalysts are needed to achieve electrocatalytic N 2 reduction to NH 3 with alarge NH 3 yield and ahigh Faradaic efficiency (FE). One of the cheapest and most abundant metals on earth, iron, is an effective dopant for greatly improving the nitrogen reduction reaction (NRR) performance of TiO 2 nanoparticles in ambient N 2 -to-NH 3 conversion. In 0.5 m LiClO 4 ,F e-doped TiO 2 catalyst attains ah igh FE of 25.6 %a nd al arge NH 3 yield of 25.47 mgh À1 mg cat À1 at À0.40 Vv ersus ar eversible hydrogen electrode.This performance compares favorably to those of all previously reported titanium-and iron-based NRR electrocatalysts in aqueous media. The catalytic mechanism is further probed with theoretical calculations.Asanessential activated nitrogen source,NH 3 is extensively used to manufacture dyes,p olymers,f ertilizers,a nd explosives,and it also serves as carbon-neutral energy carrier with high energy density. [1][2][3] To date,the dominant industrial route for NH 3 synthesis is the Haber-Bosch process using N 2 and H 2 as the feeding gases,b ut this process operates at high temperature and high pressure,a nd consumes al arge amount of energy while emitting CO 2 . [4] Electrochemical N 2 reduction offers an attractive alternative in an environmentally benign and sustainable manner,b ut the strong N N bond is fairly inert and thus difficult to break in ac hemical reaction, underlying the need for electrocatalysts with high activity in the nitrogen reduction reaction (NRR). [5][6][7][8] Noble metals perform the NRR efficiently;however, their scarcity and high cost limits their application in large-scale N 2 reduction. [8][9][10][11] NRR research has thus shifted to development of noble-metal-free alternatives. [12][13][14][15][16][17][18][19][20][21][22][23][24] TiO 2 is highly adaptable as asemiconductor catalyst because of its long-term thermodynamic stability,n atural abundance,a nd nontoxicity. [25] Recent studies have demonstrated that TiO 2 with oxygen defects has good electrocatalytic activity for the NRR, [26,27] and heteroatoms (B, [28] C, [29] V, [30] and Zr, [31] )a re effective dopants to enhance the NRR performances of TiO 2 catalysts. However,T i-based catalysts that simultaneously achieve al arge NH 3 yield with ah igh Faradaic efficiency (FE) are not available thus far.As one of the cheapest and most abundant metals on the earth, [32] Fe also exists in biological nitrogenases for natural N 2 fixation. [33] Fe compounds have been widely utilized as catalysts for artificial N 2 fixation in the Haber-Bosch [4] and electrochemical [34][35][36][37][38][39] processes.I ti st hus natural for us to explore use of Fe as ad opant for TiO 2 ,w hich has not been reported before.Herein, we report on our recent experimental results that Fe-doped TiO 2 is superior in performances for electrocatalytic N 2 reduction under ambient conditions.I n 0.5 m LiClO 4 ,t his catalyst achieves ah igh FE of 25.6 %a nd al arge NH 3 yield of 25.47 mgh À1 mg cat À1 at À0.40 Vv ersus ar eversible hydrogen electrode (...

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“…13 The metal halide ammines often display good kinetics 14,15 , but most of the pure metal halides release the ammonia at high temperatures and in multiple steps spread over broad temperature ranges. 8,16 Therefore, new materials with optimized release patterns are needed if ammonia should be used as a future energy carrier for transportation. A number of mixed metal halide ammines have already been investigated, both mixing the cations and the anions [17][18][19] , resulting in materials performing better than their individual components, encouraging the search for other mixed materials.…”

Section: Introductionmentioning

confidence: 99%

“…Both octa-and hexa ammines are investigated as smaller cations would normally form compact and relatively light hexa ammines, whereas larger cations form structures allowing the uptake of more ammonia to form the octa ammine structure, possibly resulting in higher energy densities. 4,12,16,19 It is therefore expected that either the octa or hexa ammine would be observed, but mixtures thereof passing through both the hexa and octa ammine are also allowed. To determine whether the release is a multi-step reaction, the stability of possible intermediate di-and mono ammines are checked.…”

Section: Introductionmentioning

confidence: 99%

Accelerated DFT-Based Design of Materials for Ammonia Storage

Jensen

Bialy

Blanchard³

et al. 2015

Chem. Mater.

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Future energy carriers are needed in order to lower the CO2 emissions resulting from the burning of fossil fuels. One possible energy carrier is ammonia, which can be stored safely and reversibly in metal halide ammines; however, the release often occurs in multiple steps at too high temperatures. Therefore, there is a need for new materials, releasing the ammonia in a narrow temperature interval. To search for new mixed metal halide chlorides, we use DFT calculations guided by a genetic algorithm (GA) to expedite the search, as the defined search space allowing up to three different metals contains more than 100,000 different structures. Here, we search for materials releasing the ammonia between 0 and 100 °C, a temperature range suitable for system integration with low-temperature polymer electrolyte membrane fuel cells (PEMFC). The efficiency of the implemented algorithm is verified by three trial runs capable of finding the same optimal mixtures starting from different random populations, testing < 5% of the candidates. Some of the best candidates are already confirmed experimentally and others offer a record high, accessible hydrogen capacity exceeding 9 wt%. Among the identified materials is the first known high-capacity ternary metal halide ammine, which we have subsequently synthesized and confirmed the ammonia storage properties using temperature programmed desorption (TPD). IntroductionAmmonia is a widely used chemical with many different applications; most importantly as the main component in fertilizers, sustaining the growth of the world's population. 1 A major drawback of ammonia is, however, its toxicity, requiring careful handling and storage. 2 It is well-known that pure metal halide ammines have the ability to store ammonia, and release it when heat is supplied. 3,4 These solid storage materials have been proposed as energy carriers for transportation usage 5-12 and for on-board reduction of NOX gases from combustion processes. 13 The metal halide ammines often display good kinetics 14,15 , but most of the pure metal halides release the ammonia at high temperatures and in multiple steps spread over broad temperature ranges. 8,16 Therefore, new materials with optimized release patterns are needed if ammonia should be used as a future energy carrier for transportation. A number of mixed metal halide ammines have already been investigated, both mixing the cations and the anions 17-19 , resulting in materials performing better than their individual components, encouraging the search for other mixed materials.

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Indirect hydrogen storage in metal ammines

Cited by 28 publications

References 43 publications

Surface adsorption in strontium chloride ammines

Surface adsorption in strontium chloride ammines

Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping

Accelerated DFT-Based Design of Materials for Ammonia Storage

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Indirect hydrogen storage in metal ammines

Cited by 28 publications

References 43 publications

Surface adsorption in strontium chloride ammines

Surface adsorption in strontium chloride ammines

Greatly Improving Electrochemical N2 Reduction over TiO2 Nanoparticles by Iron Doping

Accelerated DFT-Based Design of Materials for Ammonia Storage

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Greatly Improving Electrochemical N₂ Reduction over TiO₂ Nanoparticles by Iron Doping