The adsorption behavior of methyl nitrite （MN） on the closed-packed Pd（111） sur- face has been investigated in detail by using density functional theory （DFT）. MN binds to the surface in two alternative forms, u...The adsorption behavior of methyl nitrite （MN） on the closed-packed Pd（111） sur- face has been investigated in detail by using density functional theory （DFT）. MN binds to the surface in two alternative forms, using the nitrogen atom attached to the surface. An overall net charge transfer from the substrate to the cis-MN molecule is also confirmed. In addition, the reaction mechanism for the dissociation of MN on the Pd（111） surface has been identified and compared with the methanol decomposition via O-H scission. The results demonstrate that MN is a more active reactant than methanol for the oxidative addition to the Pd catalyst. The possible reason has been analyzed from the adsorption behaviors and reaction barriers, that is, MN is chemically absorbed on the Pd（111） surface; the CHaO-NO bond scission, leading to the formation of adsorbed methoxy species, is much more favorable than that of the O-H bond scission and has a large exothermic behavior.展开更多
The adsorption and decomposition of trimethylgallium （Ga（CH3）3, TMG） on Pd（111） and the effect of pre-covered H and O were studied by temperature programmed desorption spectroscopy and X-ray photoelectron spectr...The adsorption and decomposition of trimethylgallium （Ga（CH3）3, TMG） on Pd（111） and the effect of pre-covered H and O were studied by temperature programmed desorption spectroscopy and X-ray photoelectron spectroscopy. TMG adsorbs dissociatively at 140 K and the surface is covered by a mixture of Ga（CH3）x （x=1, 2 or 3） and CHx（a） （x=1, 2 or 3） species. During the heating process, the decomposition of Ga（CH3）3 on clean Pd（111） follows a progressive Ga-C bond cleavage process with CH4 and H2 as the desorption products. The desorption of Ga-containing molecules （probably GaCH3） is also identi ed in the temperature range of 275-325 K. At higher annealing temperature, carbon deposits and metallic Ga are left on the surface and start to di use into the bulk of the substrate. The presence of precovered H（a） and O（a） has a signi cant effect on the adsorption and decomposition behavior of TMG. When the surface is pre-covered by saturated H2, CH4, and H2 desorptions are mainly observed at 315 K, which is ascribed to the dissociation of GaCH3 intermediate. In the case of O-precovered surface, the dissociation mostly occurs at 258 K, of which a Pd-O-Ga（CH3）2 structure is assumed to be the precusor. The presented results may provide some insights into the mechanism of surface reaction during the lm deposition by using trimethylgallium as precursor.展开更多
Thiophene adsorption on the（111） surfaces of Pd and Pt have been investigated by density functional theory.The results indicate that the adsorption at the hollow sites is the most stable.To our interest,the molecula...Thiophene adsorption on the（111） surfaces of Pd and Pt have been investigated by density functional theory.The results indicate that the adsorption at the hollow sites is the most stable.To our interest,the molecular plane of thiophene ring is distorted with C=C bond being elongated to 1.450 and C–C bond being shortened to 1.347 ,and the C–H bonds tilt 13.91～44.05o away from this plane.Furthermore,analysis on population and density of states verified the calculated adsorption geometries.Finally,charge analysis suggests that thiophene molecule is an electron acceptor,reflecting the interaction between the lone pair of sulfur and the d-orbitals of metal.展开更多
Phosphoric acid/phosphate solu-tions are commonly used as buffer solutions in the fundamental stud-ies in electrochemistry.Informa-tion on the nature of adsorbed(bi)phosphate as well as the do-main structures is of gr...Phosphoric acid/phosphate solu-tions are commonly used as buffer solutions in the fundamental stud-ies in electrochemistry.Informa-tion on the nature of adsorbed(bi)phosphate as well as the do-main structures is of great impor-tance in unveiling the impact on electrochemical processes occur-ring at electrode electrolyte interface.In this work,the pH effect on the adsorption of phosphate related species on Pd(111)electrode has been investigated by cyclic voltammetry over a broad pH range from 1 to 14.Af-ter carefully analyzing the related onset desorption potential of(bi)phosphate adsorbate to the thermodynamic equilibrium potential of the corresponding electrode reactions,three dif-ferent phosphate related adsorbates have been identified,which are highly pH-dependent.Our analysis reveals that the dominant phosphate anions in bulk solution undergo deprotona-tion upon adsorption.At pH<1.5,the main adsorbate on Pd(111)is;H_(2)PO_(4)^(λ_(1)^(-))in solutions with 1.5<pH<7,the main adsorbate changes into.HPO_(4)^(λ_2^(-))At higher pHs,PO_(4)^(λ_(3)^(-))on electrode surface dominates.The exact charging value ofλ_(i),which represents the true va-lence of the(bi)phosphate adsorbate,could be determined using theoretical calculations.In addition,our results can not rule out the possibility of co-adsorbed H_(3)PO_(4)molecules on Pd(111)at pH<1.5,which needs to be proved by infrared spectroscopy in the future.展开更多
Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activiti...Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activities of the heterogeneous catalysts.Here in this work,we have investigated the growth behavior of Pd particles on the polar surfaces of ZnO with scanning tunneling microscopy(STM).By systematically varying the coverages as well as the annealing temperatures,we found that at room temperature Pd tends to form three-dimensional(3D)round particles on the ZnO(000)surface but grow into monolayer two-dimensional(2D)hexagonal islands on the ZnO(0001)surface.During annealing processes,the Pd particles on ZnO(000)aggregate gently while maintaining the 3D morphology in the mild temperature range but then quickly transform in-to tall hexagonal islands at elevated temperatures.In contrast,the segregation of Pd islands on ZnO(0001)occurs gradually along with the temperature rising without changing the 2D morphology.These results directly reflect the different interaction strengths of Pd on the dis-tinct ZnO polar surfaces.They also provide important input for understanding the facet-de-pendent catalytic mechanisms of the Pd/ZnO catalytic systems.展开更多
By performing with density functional theory(DFT) method, the detailed adsorption process and the catalytic decarbonylation mechanisms of furfural over Pd(111) and M/Pd(111)(M = Ni, Cu, Ru) surfaces toward furan were ...By performing with density functional theory(DFT) method, the detailed adsorption process and the catalytic decarbonylation mechanisms of furfural over Pd(111) and M/Pd(111)(M = Ni, Cu, Ru) surfaces toward furan were clarified. The results of atomic size factor, formation energy and d-band center showed that Ru/Pd(111) surface was the most stable and active. The adsorption energies of furfural on the different surfaces followed the order Ru/Pd(111) > Cu/Pd(111) > Pd(111) > Ni/Pd(111). After analyzing Mulliken atomic charge population and the deformation density, we can find that on Ru/Pd(111) surface, the number of charge transfer was the most and the interaction was the strongest. Therefore, its adsorption energy was the highest. Furthermore, the furfural decarbonylation pathway is more kinetically feasible on bimetallic surface, and the reaction is the most likely to occur on Ru/Pd(111).展开更多
Cu electrocatalysts have been demonstrated to have unique ability to reduce CO_(2)to various high value-added C_(2) products like ethylene and alcohols.However,realizing high selectivity of C_(2) products are still a ...Cu electrocatalysts have been demonstrated to have unique ability to reduce CO_(2)to various high value-added C_(2) products like ethylene and alcohols.However,realizing high selectivity of C_(2) products are still a main challenge due to complex CO_(2)electroreduction pathways and small opportunity of C-C coupling reactions.Here,we found the origin of enhanced CO_(2)electroreduction reaction activity and product selectivity towards C_(2) products and C-C coupling mechanism at halogen atoms-adsorbed Cu/H_(2)O interfaces,the corresponding CO_(2)electroreduction evolution mechanisms at the halogen atoms-modified Cu/H_(2)O interfaces are systematically studied via theoretical modeling and calculations.The calculated results indicate that halide anions modifications are beneficial to CO dimerization into OCCO dimer,especially Cl^(-)-adsorbed Cu(111)/H_(2)O interface has the optimum activity and selectivity towards OCCO dimer,subsequent Cl-adsorbed Cu(111)/H_(2)O interface can selectively reduce CO_(2)into C_(2)H_(4) product.The function relationship between adsorption free energy of Cl atom and electrode potential explain why the adsorption of Cl^(-)can enhance selectivity of C_(2)H_(4) product.The determinations of onset potentials indicate that electroreduction pathways of CO_(2)towards C_(2)H_(4) product are facile to take place and further explain the origin of the significantly enhanced CO production activity and C_(2)H_(4) product selectivity.This work on selective realization of CO_(2)electroreduction towards C_(2)H_(4) product via Cl^(-)-modified Cu(111)/H_(2)O interface provide a theoretical guideline for how to selectively realize other high value-added C_(2) products.展开更多
基金supported by the National Natural Science Foundation of China (21171039)
文摘The adsorption behavior of methyl nitrite （MN） on the closed-packed Pd（111） sur- face has been investigated in detail by using density functional theory （DFT）. MN binds to the surface in two alternative forms, using the nitrogen atom attached to the surface. An overall net charge transfer from the substrate to the cis-MN molecule is also confirmed. In addition, the reaction mechanism for the dissociation of MN on the Pd（111） surface has been identified and compared with the methanol decomposition via O-H scission. The results demonstrate that MN is a more active reactant than methanol for the oxidative addition to the Pd catalyst. The possible reason has been analyzed from the adsorption behaviors and reaction barriers, that is, MN is chemically absorbed on the Pd（111） surface; the CHaO-NO bond scission, leading to the formation of adsorbed methoxy species, is much more favorable than that of the O-H bond scission and has a large exothermic behavior.
文摘The adsorption and decomposition of trimethylgallium （Ga（CH3）3, TMG） on Pd（111） and the effect of pre-covered H and O were studied by temperature programmed desorption spectroscopy and X-ray photoelectron spectroscopy. TMG adsorbs dissociatively at 140 K and the surface is covered by a mixture of Ga（CH3）x （x=1, 2 or 3） and CHx（a） （x=1, 2 or 3） species. During the heating process, the decomposition of Ga（CH3）3 on clean Pd（111） follows a progressive Ga-C bond cleavage process with CH4 and H2 as the desorption products. The desorption of Ga-containing molecules （probably GaCH3） is also identi ed in the temperature range of 275-325 K. At higher annealing temperature, carbon deposits and metallic Ga are left on the surface and start to di use into the bulk of the substrate. The presence of precovered H（a） and O（a） has a signi cant effect on the adsorption and decomposition behavior of TMG. When the surface is pre-covered by saturated H2, CH4, and H2 desorptions are mainly observed at 315 K, which is ascribed to the dissociation of GaCH3 intermediate. In the case of O-precovered surface, the dissociation mostly occurs at 258 K, of which a Pd-O-Ga（CH3）2 structure is assumed to be the precusor. The presented results may provide some insights into the mechanism of surface reaction during the lm deposition by using trimethylgallium as precursor.
基金Supported by the National Natural Science Foundation of China (No 20273013)the Important Special Foundation of Fujian Province (No 2005HZ01-2-6)the Natural Education Department Foundation of PhD Unit (No 20050386003)
文摘Thiophene adsorption on the（111） surfaces of Pd and Pt have been investigated by density functional theory.The results indicate that the adsorption at the hollow sites is the most stable.To our interest,the molecular plane of thiophene ring is distorted with C=C bond being elongated to 1.450 and C–C bond being shortened to 1.347 ,and the C–H bonds tilt 13.91～44.05o away from this plane.Furthermore,analysis on population and density of states verified the calculated adsorption geometries.Finally,charge analysis suggests that thiophene molecule is an electron acceptor,reflecting the interaction between the lone pair of sulfur and the d-orbitals of metal.
基金supported by the National Natural Science Foundation of China(No.22172151)。
文摘Phosphoric acid/phosphate solu-tions are commonly used as buffer solutions in the fundamental stud-ies in electrochemistry.Informa-tion on the nature of adsorbed(bi)phosphate as well as the do-main structures is of great impor-tance in unveiling the impact on electrochemical processes occur-ring at electrode electrolyte interface.In this work,the pH effect on the adsorption of phosphate related species on Pd(111)electrode has been investigated by cyclic voltammetry over a broad pH range from 1 to 14.Af-ter carefully analyzing the related onset desorption potential of(bi)phosphate adsorbate to the thermodynamic equilibrium potential of the corresponding electrode reactions,three dif-ferent phosphate related adsorbates have been identified,which are highly pH-dependent.Our analysis reveals that the dominant phosphate anions in bulk solution undergo deprotona-tion upon adsorption.At pH<1.5,the main adsorbate on Pd(111)is;H_(2)PO_(4)^(λ_(1)^(-))in solutions with 1.5<pH<7,the main adsorbate changes into.HPO_(4)^(λ_2^(-))At higher pHs,PO_(4)^(λ_(3)^(-))on electrode surface dominates.The exact charging value ofλ_(i),which represents the true va-lence of the(bi)phosphate adsorbate,could be determined using theoretical calculations.In addition,our results can not rule out the possibility of co-adsorbed H_(3)PO_(4)molecules on Pd(111)at pH<1.5,which needs to be proved by infrared spectroscopy in the future.
基金supported by the National Natural Science Foundation of China(No.22172152,No.21872130)the National Key R&D Program of China(No.2021YFA1502801).
文摘Researching the dispersion as well as the stability of metals on the oxide surfaces is essentially important for understanding the interaction mecha-nisms at the metal/oxide interfaces and thus optimizing the activities of the heterogeneous catalysts.Here in this work,we have investigated the growth behavior of Pd particles on the polar surfaces of ZnO with scanning tunneling microscopy(STM).By systematically varying the coverages as well as the annealing temperatures,we found that at room temperature Pd tends to form three-dimensional(3D)round particles on the ZnO(000)surface but grow into monolayer two-dimensional(2D)hexagonal islands on the ZnO(0001)surface.During annealing processes,the Pd particles on ZnO(000)aggregate gently while maintaining the 3D morphology in the mild temperature range but then quickly transform in-to tall hexagonal islands at elevated temperatures.In contrast,the segregation of Pd islands on ZnO(0001)occurs gradually along with the temperature rising without changing the 2D morphology.These results directly reflect the different interaction strengths of Pd on the dis-tinct ZnO polar surfaces.They also provide important input for understanding the facet-de-pendent catalytic mechanisms of the Pd/ZnO catalytic systems.
基金supported by the National Natural Science Foundation of China(No.21503188)
文摘By performing with density functional theory(DFT) method, the detailed adsorption process and the catalytic decarbonylation mechanisms of furfural over Pd(111) and M/Pd(111)(M = Ni, Cu, Ru) surfaces toward furan were clarified. The results of atomic size factor, formation energy and d-band center showed that Ru/Pd(111) surface was the most stable and active. The adsorption energies of furfural on the different surfaces followed the order Ru/Pd(111) > Cu/Pd(111) > Pd(111) > Ni/Pd(111). After analyzing Mulliken atomic charge population and the deformation density, we can find that on Ru/Pd(111) surface, the number of charge transfer was the most and the interaction was the strongest. Therefore, its adsorption energy was the highest. Furthermore, the furfural decarbonylation pathway is more kinetically feasible on bimetallic surface, and the reaction is the most likely to occur on Ru/Pd(111).
基金supported by the Natural Science Foundation of Hunan Province(No.2025JJ50059)Key Program of Hunan University of Arts and Science(No.23ZZ03)Aid Program for Science and Technology Innovative Research Team in Higher Educational Institutions of Hunan Province and National Natural Science Foundation of China(No.21303048).
文摘Cu electrocatalysts have been demonstrated to have unique ability to reduce CO_(2)to various high value-added C_(2) products like ethylene and alcohols.However,realizing high selectivity of C_(2) products are still a main challenge due to complex CO_(2)electroreduction pathways and small opportunity of C-C coupling reactions.Here,we found the origin of enhanced CO_(2)electroreduction reaction activity and product selectivity towards C_(2) products and C-C coupling mechanism at halogen atoms-adsorbed Cu/H_(2)O interfaces,the corresponding CO_(2)electroreduction evolution mechanisms at the halogen atoms-modified Cu/H_(2)O interfaces are systematically studied via theoretical modeling and calculations.The calculated results indicate that halide anions modifications are beneficial to CO dimerization into OCCO dimer,especially Cl^(-)-adsorbed Cu(111)/H_(2)O interface has the optimum activity and selectivity towards OCCO dimer,subsequent Cl-adsorbed Cu(111)/H_(2)O interface can selectively reduce CO_(2)into C_(2)H_(4) product.The function relationship between adsorption free energy of Cl atom and electrode potential explain why the adsorption of Cl^(-)can enhance selectivity of C_(2)H_(4) product.The determinations of onset potentials indicate that electroreduction pathways of CO_(2)towards C_(2)H_(4) product are facile to take place and further explain the origin of the significantly enhanced CO production activity and C_(2)H_(4) product selectivity.This work on selective realization of CO_(2)electroreduction towards C_(2)H_(4) product via Cl^(-)-modified Cu(111)/H_(2)O interface provide a theoretical guideline for how to selectively realize other high value-added C_(2) products.
