A model of hydrogen absorption by metals

Dergachev, Yu. M.

doi:10.1134/s002016850908007x

Cited by 9 publications

(6 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figure 7 a,b shows computational models of the hydrogen deficient LaH 3 (110) and LaH 2.5 O 0.25 (100) with and without Ru cluster. The work functions (WFs) for both LaH 3 [ 15 ] and LaH 2.5 O 0.25 decreased from 3.5 eV to 1.8 eV. When a Ru cluster is loaded on each support, electrons at hydride vacancy ( V H ) sites are transferred to Ru, leading to that the charges (Qs) of Ru on LaH 3− x V H x and LaH 2.5− x V H x O 0.25 are determined to be −0.33 and −0.26, respectively.…”

Section: Resultsmentioning

confidence: 99%

Ruthenium Catalysts Promoted by Lanthanide Oxyhydrides with High Hydride‐Ion Mobility for Low‐Temperature Ammonia Synthesis

Ooya

Jiang

Fukui

et al. 2020

Advanced Energy Materials

View full text Add to dashboard Cite

Haber-Bosch process requires harsh condition, that is, high temperature (400-500 °C) and high pressure (10-30 MPa) to dissociate strong NN bonds (945 kJ mol −1) over Fe-based catalyst effectively, [2] resulting in the enlargement of ammonia synthesis plant to meet the production cost. The ruthenium (Ru) catalysts are known to work as efficient catalysts under milder conditions than iron-based catalyst used in the industrial process, because Ru has an optimum N 2 adsorption energy. [3] However, hydrogen atoms tend to be adsorbed strongly on the active sites of Ru surface at low reaction temperatures (<350 °C), preventing nitrogen adsorption on the Ru surface which is requisite for N 2 dissociation. [4] This is known as a hydrogen poisoning effect. For this reason, high N 2 activation ability and suppression of hydrogen poisoning are two major requirements for Ru catalysts especially for lowtemperature ammonia synthesis. We have previously reported that electride and hydride materials such as C12A7:e − , Ca 2 NH, CaH 2 , LnH 2+x (Ln = La, Ce, Y), and Ca(NH 2) 2 promote the catalytic activity of Ru catalysts significantly at low reaction temperatures when these materials are used as catalyst supports. [5] In these catalyst systems, the high catalytic performance is realized by two unique properties of the support material. First, electrons are located at crystallographic interstitial void Lanthanum oxyhydrides were recently reported to be fast hydride ion conductors with the highest conductivity at 100-400 °C. Here, the relationship between the hydride-ion conduction and the ammonia synthesis activity of ruthenium-loaded lanthanum oxyhydrides (Ru/LaH 3−2x O x) is investigated. The onset ammonia formation temperature by the Ru/LaH 3−2x O x is lower by 100 °C when compared to the Ru-loaded lanthanum oxides. The apparent activation energy of ammonia synthesis over Ru/LaH 3−2x O x is 64 kJ mol −1 , which is much smaller than that of hydride-ion conductivity (≈100 kJ mol −1), indicating no direct relationship between the catalytic activity and the bulk hydride-ion conductivity. However, the catalytic performance is strongly correlated with the surface H − ion mobility of Ru/LaH 3−2x O x , which gives rise to the formation of low work function electrons at H − ion vacancies near the Ru-support interface and high resistance for H 2 poisoning on the Ru catalyst. Moreover, LaH 3−2x O x has high nitridation resistance as compared with lanthanum hydride (LaH 3) under ammonia synthesis condition. As a result, the high surface H − concentration of Ru/LaH 3−2x O x is preserved during ammonia synthesis, exhibiting more robust activity than Ru/LaH 3. Almost the same results are obtained for Ru/CeH 3−2x O x implicating the common characteristics of rare-earth oxyhydride support.

show abstract

Section: Resultsmentioning

confidence: 99%

Ruthenium Catalysts Promoted by Lanthanide Oxyhydrides with High Hydride‐Ion Mobility for Low‐Temperature Ammonia Synthesis

Ooya

Jiang

Fukui

et al. 2020

Advanced Energy Materials

View full text Add to dashboard Cite

show abstract

“…The Fermi energy is located at ∼5 eV below the vacuum level for Cu, 4.8 eV for ZnO, and 4.7 eV for Al 2 O 3 ; therefore, efficient electron transfer cannot be expected for the interface between ZnO or Al 2 O 3 and Cu. The situation is distinctly different for LaH 3 , in which the Fermi level is ∼3.5 eV from the vacuum level.…”

Section: Requirements For An Efficient Catalystmentioning

confidence: 89%

Low-Temperature Methanol Synthesis by a Cu-Loaded LaH_2+xElectride

et al. 2022

View full text Add to dashboard Cite

Methanol is a key chemical in C1 chemistry and energy carrier. The industrial synthesis of methanol uses a heterogeneous catalyst, Cu/ZnO/Al2O3, under harsh conditions of high temperature and high pressure. Here, we propose a design concept for a catalyst to achieve low-temperature synthesis of methanol and report that Cu-loaded rare-earth hydrides (Cu/REH2+x ) work as effective catalysts for methanol synthesis from CO and H2 at temperatures below 100 °C, where the conventional Cu/ZnO/Al2O3 industrial catalyst does not work well. This catalytic activity is due to negatively charged Cu sites that originate from the highly electron-donating support material and hydride ions directly reactive with CO. The activation energy and turn over frequency for the catalyst are less than half and ∼20 times higher than that for conventional Cu-based catalysts, respectively. The present work demonstrates that anionic electrons with a low work function, the metallic nature of the support material, and hydride ions in the support play key roles for low-temperature methanol synthesis.

show abstract

“…Recently, Dergachev [41] has noticed the relationship between the hydrogen-to-metal atomic ratio x in crystal and the Fermi energy of solid transition metals. However, with great difficulty of defining and calculating the Fermi energy of liquid metals, it should not directly correlate the hydrogen solubility with the Fermi energy of metals, which is similar to electron-to-atom ratio (e/ a), whose effect on the structure of alloys is a result of the Fermi energy.…”

Section: The Calculating Model and Discussionmentioning

confidence: 99%

A Model for Calculating Hydrogen Solubility in Liquid Transition Metals

Jiang

2010

Metall Mater Trans A

View full text Add to dashboard Cite

The documented experimental results of hydrogen solubility in different liquid metals were summarized according to the periodic table. It is found that the hydrogen solubility in liquid transition metals is much higher than in others and it changes regularly with the atomic number to form a V-shaped curve. It is supposed that the electron interaction between the hydrogen and metal atoms of the liquid is the major factor in determining hydrogen solubility in the liquid metal. Based on this consideration, a model was proposed for characterizing electron interaction and calculating the hydrogen solubility in various liquid metals according to the nearly freeelectron theory. The calculated hydrogen solubility in liquid transition metals agrees well with the documented experimental results, and some undocumented results could be predicted.

show abstract

A model of hydrogen absorption by metals

Cited by 9 publications

References 1 publication

Ruthenium Catalysts Promoted by Lanthanide Oxyhydrides with High Hydride‐Ion Mobility for Low‐Temperature Ammonia Synthesis

Ruthenium Catalysts Promoted by Lanthanide Oxyhydrides with High Hydride‐Ion Mobility for Low‐Temperature Ammonia Synthesis

Low-Temperature Methanol Synthesis by a Cu-Loaded LaH_2+xElectride

A Model for Calculating Hydrogen Solubility in Liquid Transition Metals

Contact Info

Product

Resources

About

A model of hydrogen absorption by metals

Cited by 9 publications

References 1 publication

Ruthenium Catalysts Promoted by Lanthanide Oxyhydrides with High Hydride‐Ion Mobility for Low‐Temperature Ammonia Synthesis

Ruthenium Catalysts Promoted by Lanthanide Oxyhydrides with High Hydride‐Ion Mobility for Low‐Temperature Ammonia Synthesis

Low-Temperature Methanol Synthesis by a Cu-Loaded LaH2+xElectride

A Model for Calculating Hydrogen Solubility in Liquid Transition Metals

Contact Info

Product

Resources

About

Low-Temperature Methanol Synthesis by a Cu-Loaded LaH_2+xElectride