The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerat...The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerated CO dissociation. The H2 was adsorbed first, and activated to form H＊ over metal sites, then reacted with carbonaceous species. The oxygen species for CO2 formation in the presence of hydrogen was mostly OH^＊, which reacted with adsorbed CO subsequently via CO^＊＋OH^＊ → CO2^＊＋H^＊; however, the direct CO dissociation was not excluded in CO hydrogenation. The dissociation of C-O bond in the presence of H2 proceeded by a concerted mechanism, which assisted the Boudourd reaction of adsorbed CO on the surface via CO^＊＋2H^＊ → CH^＊＋OH^＊. The formation of the surface species （CH） from adsorbed CO proceeded as indicated with the participation of surface hydrogen, was favored in the initial step of the Fischer-Tropsch synthesis.展开更多
A DFT study of H2 dissociation on a series of Mo x S y clusters was performed, including homolytic and heterolytic dissociation. The preference for the two pathways on these models show much difference, as the Mo coor...A DFT study of H2 dissociation on a series of Mo x S y clusters was performed, including homolytic and heterolytic dissociation. The preference for the two pathways on these models show much difference, as the Mo coordination number increases, the homolytic dissociation becomes easier, whereas the heterolytic dissociation becomes more difficult. Furthermore, frontier orbital theory was used to analyze the dissociation mechanisms of these two pathways. It was found that the symmetry and energy gap of Mo x S y's HOMO and H2's LUMO are the decisive factors in H2 activation.展开更多
Graphene-based materials are promising for hydrogen production and storage. In this work, using density functional theory calculations, we explored how a hydroxyl group influences H2 dissociation on graphene. Presence...Graphene-based materials are promising for hydrogen production and storage. In this work, using density functional theory calculations, we explored how a hydroxyl group influences H2 dissociation on graphene. Presence of the hydroxyl group makes the binding of H atom with graphene stronger, as the binding energy of H atom with the hydroxyl-modified graphene is higher than that with the pristine graphene. The para-site is the most favorable site for H2 dissociation on both the pristine and hydroxyl-modified graphene. The energy barrier of H2 dissociation at para-site on the pristine graphene is 3.10 eV whereas that on the hydroxyl-modified graphene is 2.46 eV, indicating a more facile H2 dissociation on the hydroxyl-modified graphene.展开更多
The dissociation of H2 molecule is the first step for chemical storage of hydrogen, and the energy barrier of the dissociation is the key factor to determine the kinetics of the regeneration of the storage material. I...The dissociation of H2 molecule is the first step for chemical storage of hydrogen, and the energy barrier of the dissociation is the key factor to determine the kinetics of the regeneration of the storage material. In this paper, we investigate the hydrogen adsorption and dissociation on Mg-coated B12C6N6. The B12C6N6 is an electron deficient fullerene, and Mg atoms can be strongly bound to this cage by donating their valance electrons to the virtual 2p orbitals of carbon in the cluster. The preferred binding sites for Mg atoms are the B2C2 tetragonal rings. The positive charge quantity on the Mg atom is 1.50 when a single Mg atom is coated on a B2C2 ring. The stable dissociation products are determined and the dissociation processes are traced. Strong orbital interaction between the hydrogen and the cluster occurs in the process of dissociation, and H2 molecule can be easily dissociated. We present four dissociation paths, and the lowest energy barrier is only 0.11 eV, which means that the dissociation can take place at ambient temperature.展开更多
We examined the water adsorption and dissociation on ceria surfaces as well as ceria‐supported Au single‐atom catalysts using density functional theory calculations.Molecular and dissociative water were observed to ...We examined the water adsorption and dissociation on ceria surfaces as well as ceria‐supported Au single‐atom catalysts using density functional theory calculations.Molecular and dissociative water were observed to coexist on clean CeO2and reduced Au1/CeO2?x surfaces because of the small difference in adsorption energies,whereas the presence of dissociative water was highly favorable on reduced CeO2?x and clean Au1/CeO2surfaces.Positively charged Au single atoms on the ceria surface not only provided activation sites for water adsorption but also facilitated water dissociation by weakening the intramolecular O-H bonds.In contrast,negatively charged Au single atoms were not reactive for water adsorption because of the saturation of Au5d and6s electron shells.This work provides a fundamental understanding of the interaction between water and single‐atom Au catalysts.展开更多
Spin-polarized periodic density functional theory was performed to characterize H2S adsorp- tion and dissociation on graphene oxides （GO） surface. The comprehensive reaction network of H2S oxidation with epoxy and h...Spin-polarized periodic density functional theory was performed to characterize H2S adsorp- tion and dissociation on graphene oxides （GO） surface. The comprehensive reaction network of H2S oxidation with epoxy and hydroxyl groups of GO was discussed. It is shown that the reduction reaction is mainly governed by epoxide ring opening and hydroxyl hydrogenation which is initiated by H transfer from H2S or its derivatives, hlrthermore, the presence of another OH group at the opposite side relative to the adsorbed H2S activates the oxygen group to facilitate epoxide ring opening and hydroxyl hydrogenation. For H2S interaction with -O and -OH groups adsorption on each side of graphene, the pathway is a favorable reaction path by the introduction of intermediate states, the predicted energy barriers are 3.2 and 10.4 kcal/mol, respectively, the second H transfer is tile rate-determining step in the whole reaction process. In addition, our calculations suggest that both epoxy and hydroxyl groups can enhance tile binding of S to the C-C bonds and the effect of hydroxyl group is more local than that of the epoxy.展开更多
Dissociation of molecular hydrogen （H2） is extensively studied to understand the mechanism of hydrogenation reactions. In this study, H2 dissociation by Aul-doped closed-shell titanium oxide cluster anions AuTi3O7 a...Dissociation of molecular hydrogen （H2） is extensively studied to understand the mechanism of hydrogenation reactions. In this study, H2 dissociation by Aul-doped closed-shell titanium oxide cluster anions AuTi3O7 and AuTi3O8 has been identified by mass spectrometry and quantum chemistry calculations. The clusters were generated by laser ablation and mass- selected to react with H2 in art ion trap reactor. In the reaction of AuTi3O8 with H2, the ion pair Au＋-O22 rather than Au＋-O2 is the active site to promote H2 dissociation. This finding is in contrast with the previous result that the lattice oxygen is usually the reactive oxygen species in H2 dissociation. The higher reactivity of the peroxide species is further supported by frontier molecular orbital analysis. This study provides new insights into gold catalysis involving H2 activation and dissociation.展开更多
CaS formed during the retorting process of oil shale has a hazardous influence on surface water quality. Interaction of retorted oil shale with water generates highly alkaline leachate with a high content of sulfur du...CaS formed during the retorting process of oil shale has a hazardous influence on surface water quality. Interaction of retorted oil shale with water generates highly alkaline leachate with a high content of sulfur due to the CaS component. A theoretical model describing the behavior of solid calcium sulfide in contact with water was developed. The model was consistent with the measurements showing change in dissolution behavior when solid CaS remained in the solution. Experimental measurements of pH and concentrations of ions were carried out in oxy- gen-free water at 25 ~C using CaS concentrations from 24.2-131.5 mgoL-1 （0.335--1.823 mmol/L）. Analysis of pH and concentrations of ions in the solution and calculations by the developed model showed that the solubility of CaS was estimated as 125.0 mg·L 1 （1.733 mmol/L）, and therefore the solubility product of CaS is 3.41×10^-10 （mo·L^-1）^2 at a temperature of 25℃.展开更多
Carbon nitride (CN) in CN encapsulated Ni/ Al2O3 (denoted as CN/Ni/Al2O3) catalyst was evidenced previously as a material in electron-rich state and possessed H-2-dissociative adsorption activity due to the electron d...Carbon nitride (CN) in CN encapsulated Ni/ Al2O3 (denoted as CN/Ni/Al2O3) catalyst was evidenced previously as a material in electron-rich state and possessed H-2-dissociative adsorption activity due to the electron doping effect from underlying nickel. In this report, iron oxide loaded on the CN/Ni/Al2O3 was synthesized and investigated by Fischer-Tropsch (F-T) synthesis to test the special effect of electron-rich support on the catalytic activity of iron oxide. The Fe/CN/Al2O3 and CN/Ni/Al2O3 samples were accordingly synthesized for comparison. In Fe/CN/Ni/Al2O3, the iron oxide was reduced to magnetite by syngas as evidenced by the in-situ XPS measurements and XRD pattern of used catalyst. Compared with Fe/CN/Al2O3, more light hydrocarbons over Fe/CN/Ni/Al2O3 were observed. It should be understood by the interaction between iron oxide and support mainly due to the effect of electron-rich state and thus enhanced H-2 adsorption ability. In addition, such a novel support facilitated the CO conversion and retarded the water-gas shift reaction and CO2 formation. The new type of adjustment on electronic state should be useful for novel catalyst design. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.展开更多
基金The National Key Project for Basic Research of China(973 Project)(No.2005CB221402)China National Petroleum Corporation
文摘The activation of adsorbed CO is an important step in CO hydrogenation. The results from TPSR of pre-adsorbed CO with H2 and syngas suggested that the presence of H2 increased the amount of CO adsorption and accelerated CO dissociation. The H2 was adsorbed first, and activated to form H＊ over metal sites, then reacted with carbonaceous species. The oxygen species for CO2 formation in the presence of hydrogen was mostly OH^＊, which reacted with adsorbed CO subsequently via CO^＊＋OH^＊ → CO2^＊＋H^＊; however, the direct CO dissociation was not excluded in CO hydrogenation. The dissociation of C-O bond in the presence of H2 proceeded by a concerted mechanism, which assisted the Boudourd reaction of adsorbed CO on the surface via CO^＊＋2H^＊ → CH^＊＋OH^＊. The formation of the surface species （CH） from adsorbed CO proceeded as indicated with the participation of surface hydrogen, was favored in the initial step of the Fischer-Tropsch synthesis.
基金the funding by the State Key Project (Grant Nos. 2012CB224802 and 2012BAE05B03)by the Technology Development Project of SINOPEC (S112101)
文摘A DFT study of H2 dissociation on a series of Mo x S y clusters was performed, including homolytic and heterolytic dissociation. The preference for the two pathways on these models show much difference, as the Mo coordination number increases, the homolytic dissociation becomes easier, whereas the heterolytic dissociation becomes more difficult. Furthermore, frontier orbital theory was used to analyze the dissociation mechanisms of these two pathways. It was found that the symmetry and energy gap of Mo x S y's HOMO and H2's LUMO are the decisive factors in H2 activation.
基金supported by the National High Technology Research and Development Program of China 863(2012AA022606)
文摘Graphene-based materials are promising for hydrogen production and storage. In this work, using density functional theory calculations, we explored how a hydroxyl group influences H2 dissociation on graphene. Presence of the hydroxyl group makes the binding of H atom with graphene stronger, as the binding energy of H atom with the hydroxyl-modified graphene is higher than that with the pristine graphene. The para-site is the most favorable site for H2 dissociation on both the pristine and hydroxyl-modified graphene. The energy barrier of H2 dissociation at para-site on the pristine graphene is 3.10 eV whereas that on the hydroxyl-modified graphene is 2.46 eV, indicating a more facile H2 dissociation on the hydroxyl-modified graphene.
基金supported by the National Natural Science Foundation of China(Grant Nos.11164024 and 11164034)
文摘The dissociation of H2 molecule is the first step for chemical storage of hydrogen, and the energy barrier of the dissociation is the key factor to determine the kinetics of the regeneration of the storage material. In this paper, we investigate the hydrogen adsorption and dissociation on Mg-coated B12C6N6. The B12C6N6 is an electron deficient fullerene, and Mg atoms can be strongly bound to this cage by donating their valance electrons to the virtual 2p orbitals of carbon in the cluster. The preferred binding sites for Mg atoms are the B2C2 tetragonal rings. The positive charge quantity on the Mg atom is 1.50 when a single Mg atom is coated on a B2C2 ring. The stable dissociation products are determined and the dissociation processes are traced. Strong orbital interaction between the hydrogen and the cluster occurs in the process of dissociation, and H2 molecule can be easily dissociated. We present four dissociation paths, and the lowest energy barrier is only 0.11 eV, which means that the dissociation can take place at ambient temperature.
基金supported by the National Natural Science Foundation of China(21590792,91645203 and 21521091)~~
文摘We examined the water adsorption and dissociation on ceria surfaces as well as ceria‐supported Au single‐atom catalysts using density functional theory calculations.Molecular and dissociative water were observed to coexist on clean CeO2and reduced Au1/CeO2?x surfaces because of the small difference in adsorption energies,whereas the presence of dissociative water was highly favorable on reduced CeO2?x and clean Au1/CeO2surfaces.Positively charged Au single atoms on the ceria surface not only provided activation sites for water adsorption but also facilitated water dissociation by weakening the intramolecular O-H bonds.In contrast,negatively charged Au single atoms were not reactive for water adsorption because of the saturation of Au5d and6s electron shells.This work provides a fundamental understanding of the interaction between water and single‐atom Au catalysts.
基金This work was supported by the National Natu- ral Science Foundation of China （No.21004009） and the Foundation of Jiangxi Educational Committee （No.G J J13447 and No.G J J14485）. We are grateful to High Performance Computer Center of State Key Lab- oratory of Physical Chemistry of Solid Surface （Xiamen University）.
文摘Spin-polarized periodic density functional theory was performed to characterize H2S adsorp- tion and dissociation on graphene oxides （GO） surface. The comprehensive reaction network of H2S oxidation with epoxy and hydroxyl groups of GO was discussed. It is shown that the reduction reaction is mainly governed by epoxide ring opening and hydroxyl hydrogenation which is initiated by H transfer from H2S or its derivatives, hlrthermore, the presence of another OH group at the opposite side relative to the adsorbed H2S activates the oxygen group to facilitate epoxide ring opening and hydroxyl hydrogenation. For H2S interaction with -O and -OH groups adsorption on each side of graphene, the pathway is a favorable reaction path by the introduction of intermediate states, the predicted energy barriers are 3.2 and 10.4 kcal/mol, respectively, the second H transfer is tile rate-determining step in the whole reaction process. In addition, our calculations suggest that both epoxy and hydroxyl groups can enhance tile binding of S to the C-C bonds and the effect of hydroxyl group is more local than that of the epoxy.
基金supported by the National Natural Science Foundation of China(No.21573246,No.21773253,and No.21773254)the Beijing Natural Science Foundation(2172059)the Youth Innovation Promotion Association,Chinese Academy of Sciences(2016030)
文摘Dissociation of molecular hydrogen （H2） is extensively studied to understand the mechanism of hydrogenation reactions. In this study, H2 dissociation by Aul-doped closed-shell titanium oxide cluster anions AuTi3O7 and AuTi3O8 has been identified by mass spectrometry and quantum chemistry calculations. The clusters were generated by laser ablation and mass- selected to react with H2 in art ion trap reactor. In the reaction of AuTi3O8 with H2, the ion pair Au＋-O22 rather than Au＋-O2 is the active site to promote H2 dissociation. This finding is in contrast with the previous result that the lattice oxygen is usually the reactive oxygen species in H2 dissociation. The higher reactivity of the peroxide species is further supported by frontier molecular orbital analysis. This study provides new insights into gold catalysis involving H2 activation and dissociation.
文摘CaS formed during the retorting process of oil shale has a hazardous influence on surface water quality. Interaction of retorted oil shale with water generates highly alkaline leachate with a high content of sulfur due to the CaS component. A theoretical model describing the behavior of solid calcium sulfide in contact with water was developed. The model was consistent with the measurements showing change in dissolution behavior when solid CaS remained in the solution. Experimental measurements of pH and concentrations of ions were carried out in oxy- gen-free water at 25 ~C using CaS concentrations from 24.2-131.5 mgoL-1 （0.335--1.823 mmol/L）. Analysis of pH and concentrations of ions in the solution and calculations by the developed model showed that the solubility of CaS was estimated as 125.0 mg·L 1 （1.733 mmol/L）, and therefore the solubility product of CaS is 3.41×10^-10 （mo·L^-1）^2 at a temperature of 25℃.
基金supported by the Ministry of Science and Technology of China (2009CB623504)the National Science Foundation of China (20673054,21273107)Sinopec Shanghai Research Institute of Petrochemical Technology
文摘Carbon nitride (CN) in CN encapsulated Ni/ Al2O3 (denoted as CN/Ni/Al2O3) catalyst was evidenced previously as a material in electron-rich state and possessed H-2-dissociative adsorption activity due to the electron doping effect from underlying nickel. In this report, iron oxide loaded on the CN/Ni/Al2O3 was synthesized and investigated by Fischer-Tropsch (F-T) synthesis to test the special effect of electron-rich support on the catalytic activity of iron oxide. The Fe/CN/Al2O3 and CN/Ni/Al2O3 samples were accordingly synthesized for comparison. In Fe/CN/Ni/Al2O3, the iron oxide was reduced to magnetite by syngas as evidenced by the in-situ XPS measurements and XRD pattern of used catalyst. Compared with Fe/CN/Al2O3, more light hydrocarbons over Fe/CN/Ni/Al2O3 were observed. It should be understood by the interaction between iron oxide and support mainly due to the effect of electron-rich state and thus enhanced H-2 adsorption ability. In addition, such a novel support facilitated the CO conversion and retarded the water-gas shift reaction and CO2 formation. The new type of adjustment on electronic state should be useful for novel catalyst design. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.
