Since the D-band center theory was proposed,it has been widely used in the fields of surface chemistry by almost all researchers,due to its easy understanding,convenient operation and relative accuracy.However,with th...Since the D-band center theory was proposed,it has been widely used in the fields of surface chemistry by almost all researchers,due to its easy understanding,convenient operation and relative accuracy.However,with the continuous development of material systems and modification strategies,researchers have gradually found that D-band center theory is usually effective for large metal particle systems,but for small metal particle systems or semiconductors,such as single atom systems,the opposite conclusion to the D-band center theory is often obtained.To solve the issue above,here we propose a bonding and anti-bonding orbitals stable electron intensity difference(BASED)theory for surface chemistry.The newly-proposed BASED theory can not only successfully explain the abnormal phenomena of D-band center theory,but also exhibits a higher accuracy for prediction of adsorption energy and bond length of intermediates on active sites.Importantly,a new phenomenon of the spin transition state in the adsorption process is observed based on the BASED theory,where the active center atom usually yields an unstable high spin transition state to enhance its adsorption capability in the adsorption process of intermediates when their distance is about 2.5Å.In short,the BASED theory can be considered as a general principle to understand catalytic mechanism of intermediates on surfaces.展开更多
Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation ...Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation and alkanes activation, etc., however, thedetailed spectroscopic characterizations remain challenging. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has become a powerful tool in surface studies, asit provides access to local structural characterizations at atomic level from multipleviews, with comprehensive information on chemical bonding and spatial structures. Inthis review, we summarized and discussed the latest research developments on thesuccessful application of ssNMR to characterize surface MeH species on solid catalystsincluding supported single-site heterogeneous catalysts, bulk metal oxides and metalmodified zeolites. We also discussed the opportunities and challenges in this field, aswell as the potential application/development of state-of-the-art ssNMR technologies toenable further exploration of metal hydrides in heterogeneous catalysis.展开更多
The adsorption and reaction of formic acid （HCOOH） on clean and atomic oxygen‐covered Au（997） surfaces were studied by temperature‐programmed desorption/reaction spectroscopy （TPRS） and X‐ray photoelectron sp...The adsorption and reaction of formic acid （HCOOH） on clean and atomic oxygen‐covered Au（997） surfaces were studied by temperature‐programmed desorption/reaction spectroscopy （TPRS） and X‐ray photoelectron spectroscopy （XPS）. At 105 K, HCOOH molecularly adsorbs on clean Au（997） and interacts more strongly with low‐coordinated Au atoms at （111） step sites than with those at （111） terrace sites. On an atomic oxygen‐covered Au（997） surface, HCOOH reacts with oxygen at‐oms to form HCOO and OH at 105 K. Upon subsequent heating, surface reactions occur among ad‐sorbed HCOO, OH, and atomic oxygen and produce CO2, H2O, and HCOOH between 250 and 400 K. The Au（111） steps bind surface adsorbates more strongly than the Au（111） terraces and exhibit larger barriers for HCOO（a） oxidation reactions. The surface reactions also depend on the relative coverages of co‐existing surface species. Our results elucidate the elementary surface reactions between formic acid and oxygen adatoms on Au surfaces and highlight the effects of the coordina‐tion number of the Au atoms on the Au catalysis.展开更多
Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si（001） imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompa...Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si（001） imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maximum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.展开更多
Different TiOx thin films prepared by graded or sufficient oxidization of Ti are applied with Pt or Ag electrode in metal？insulator-metal （MIM） structures for studying the properties and mechanisms of resistive swi...Different TiOx thin films prepared by graded or sufficient oxidization of Ti are applied with Pt or Ag electrode in metal？insulator-metal （MIM） structures for studying the properties and mechanisms of resistive switching. The differences on the mobile oxygen vacancies in TiOx films and different work functions of the electrode films result in different insulator-metal interface states, which are displayed as ohmic-like or non-ohmic contact. Based on the interface states, the electrical models for MIM devices are analyzed and extracted. The electrode-limited effect and the bulk-limited effect can be unified to explain the mechanisms for resistive switching behavior as the dominant effect respectively in various conditions. All the current-voltage curves of the four kinds of specimens measured in the experiments can be explained and proved in accordance with the theory.展开更多
Sum frequency generation(SFG) vibrational spectroscopy has been proven an excellent tool to measure the molecular structures, symmetries and orientations at surfaces/interfaces because of its strong polarization depen...Sum frequency generation(SFG) vibrational spectroscopy has been proven an excellent tool to measure the molecular structures, symmetries and orientations at surfaces/interfaces because of its strong polarization dependence. However, a precise quantitative analysis of SFG spectral intensity and molecular orientation at interfaces must be carefully performed. In this work, we summarized the parameters and factors that are often ignored and illustrated them by evaluating studies of CO adsorption on the(111) facet of platinum(Pt) and palladium(Pd) single crystals at the gas(ultra-high vacuum, UHV)/solid interfaces and methanol(water) adsorption at the air/liquid(solid/liquid) interfaces in the presence of sodium iodide(chloride) salts. To intuitively estimate the influence of incidence angles and refractive indices on the SFG intensity, solely a defined factor of|Fyyz| was discussed, which can be individually separated from the macroscopic second-order non-linear susceptibility χ yyz^(2) term and represents the SSP intensity. Moreover, effects of refractive indices and the molecular hyperpolarizability ratio(R) were discussed in the orientational analysis of interfacial CO and methanol molecules. When IPPP/ISSP was identical, molecules with a larger R had smaller tilting angles(q) on Pt(assuming q < 51°), and CO molecules on Pd would tilt much closer to the surface than they did on Pt. A total internal reflection(TIR) geometry enhanced the SFG intensity, but it also amplified the influence of refractive index on SFG intensity at the solid(silica)/liquid interface. The refractive index and R-value had similar influence on the methanol orientation in the presence of sodium iodide salts at air/liquid and solid/liquid interfaces. This work should provide a guideline for analyzing the orientation of molecules with different R, which are adsorbed on catalysts or located at liquid interfaces involving changes of refractive indices.展开更多
The electrochemical reduction of carbon dioxide(CO_(2))into value‐added fuels and chemicals presents a sustainable route to alleviate CO_(2) emissions,promote carbon‐neutral cycles and reduce the dependence on fossi...The electrochemical reduction of carbon dioxide(CO_(2))into value‐added fuels and chemicals presents a sustainable route to alleviate CO_(2) emissions,promote carbon‐neutral cycles and reduce the dependence on fossil fuels.Considering the thermodynamic stability of the CO_(2) molecule and sluggish reaction kinetics,it is still a challenge to design highly efficient electrocatalysts for the CO_(2) reduction reaction(CO_(2)RR).It has been found that the surface and interface chemistry of electrocatalysts can modulate the electronic structure and increase the active sites,which is favorable for CO_(2) adsorption,electron transfer,mass transport,and optimizing adsorption strength of reaction intermediates.However,the effect of surface and interface chemistry on metal‐free electrocatalysts(MFEs)for CO_(2)RR has not been comprehensively reviewed.Herein,we discuss the importance of the surface and interface chemistry on MFEs for improving the electrochemical CO_(2)RR performance based on thermodynamic and kinetic views.The fundamentals and challenges of CO_(2)RR are firstly presented.Then,the recent advances of the surface and interface chemistry in improving reaction rate and overcoming reaction constraints are reviewed from regulating electronic structure,active sites,electron transfer,mass transport,and intermediate binding energy.Finally,the research challenges and prospects are proposed to suggest the future designs of advanced MFEs in CO_(2)RR.展开更多
文摘Since the D-band center theory was proposed,it has been widely used in the fields of surface chemistry by almost all researchers,due to its easy understanding,convenient operation and relative accuracy.However,with the continuous development of material systems and modification strategies,researchers have gradually found that D-band center theory is usually effective for large metal particle systems,but for small metal particle systems or semiconductors,such as single atom systems,the opposite conclusion to the D-band center theory is often obtained.To solve the issue above,here we propose a bonding and anti-bonding orbitals stable electron intensity difference(BASED)theory for surface chemistry.The newly-proposed BASED theory can not only successfully explain the abnormal phenomena of D-band center theory,but also exhibits a higher accuracy for prediction of adsorption energy and bond length of intermediates on active sites.Importantly,a new phenomenon of the spin transition state in the adsorption process is observed based on the BASED theory,where the active center atom usually yields an unstable high spin transition state to enhance its adsorption capability in the adsorption process of intermediates when their distance is about 2.5Å.In short,the BASED theory can be considered as a general principle to understand catalytic mechanism of intermediates on surfaces.
基金the National Natural Science Foundation of China(Grant Nos.21902158,21773230,91945302)the National Key R&D Program of China(No.2021YFA1502803)LiaoNing Revitalization Talents Program(XLYC1807207),DICP I202104.
文摘Metal hydrides (MeH) on solid surfaces, i.e., surface MeH, are ubiquitous but criticalspecies in heterogeneous catalysis, and their intermediate roles have been proposed innumerous reactions such as (de)hydrogenation and alkanes activation, etc., however, thedetailed spectroscopic characterizations remain challenging. Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has become a powerful tool in surface studies, asit provides access to local structural characterizations at atomic level from multipleviews, with comprehensive information on chemical bonding and spatial structures. Inthis review, we summarized and discussed the latest research developments on thesuccessful application of ssNMR to characterize surface MeH species on solid catalystsincluding supported single-site heterogeneous catalysts, bulk metal oxides and metalmodified zeolites. We also discussed the opportunities and challenges in this field, aswell as the potential application/development of state-of-the-art ssNMR technologies toenable further exploration of metal hydrides in heterogeneous catalysis.
基金supported by the National Basic Research Program of China (973 Program, 2013CB933104)the National Natural Science Foundation of China (21525313, 20973161, 21373192)+1 种基金the Fundamental Research Funds for the Central Universities (WK2060030017)Collaborative In-novation Center of Suzhou Nano Science and Technology~~
文摘The adsorption and reaction of formic acid （HCOOH） on clean and atomic oxygen‐covered Au（997） surfaces were studied by temperature‐programmed desorption/reaction spectroscopy （TPRS） and X‐ray photoelectron spectroscopy （XPS）. At 105 K, HCOOH molecularly adsorbs on clean Au（997） and interacts more strongly with low‐coordinated Au atoms at （111） step sites than with those at （111） terrace sites. On an atomic oxygen‐covered Au（997） surface, HCOOH reacts with oxygen at‐oms to form HCOO and OH at 105 K. Upon subsequent heating, surface reactions occur among ad‐sorbed HCOO, OH, and atomic oxygen and produce CO2, H2O, and HCOOH between 250 and 400 K. The Au（111） steps bind surface adsorbates more strongly than the Au（111） terraces and exhibit larger barriers for HCOO（a） oxidation reactions. The surface reactions also depend on the relative coverages of co‐existing surface species. Our results elucidate the elementary surface reactions between formic acid and oxygen adatoms on Au surfaces and highlight the effects of the coordina‐tion number of the Au atoms on the Au catalysis.
基金supported by the Special Project of Shanghai Nano Technology (0852nm02400 and 0752nm012)Shaoxing Science and Technology Commission (2007A21015)+3 种基金Shanghai Rising-Star Program (07QA14026)the National Natural Science Foundation of China (10804072)the Key Fundamental Project of Shanghai (08JC1410400)Shanghai Education Commission (07zz143)
文摘Synchrotron radiation photoemission spectroscopy was used to study the formation process of Er2O3/Si（001） imerface and film during epitaxial growth on Si. A shift in the O core-level binding energy was found accompanied by a shift in the Er2O3 valence band maximum. This shift depended on the oxide layer thickness and interfacial structure. An interfacial layer was observed at the initial growth of Er2O3 film on Si, which was supposed to be attributed to the effect of Er atom catalytic oxidation effect.
文摘Different TiOx thin films prepared by graded or sufficient oxidization of Ti are applied with Pt or Ag electrode in metal？insulator-metal （MIM） structures for studying the properties and mechanisms of resistive switching. The differences on the mobile oxygen vacancies in TiOx films and different work functions of the electrode films result in different insulator-metal interface states, which are displayed as ohmic-like or non-ohmic contact. Based on the interface states, the electrical models for MIM devices are analyzed and extracted. The electrode-limited effect and the bulk-limited effect can be unified to explain the mechanisms for resistive switching behavior as the dominant effect respectively in various conditions. All the current-voltage curves of the four kinds of specimens measured in the experiments can be explained and proved in accordance with the theory.
基金in part supported by the Austrian Science Fund FWF through projects Com Cat(I 1041-N28)and DK+Solids4Fun(W1243)by TU Wien via the Innovative Project “SFG Spectroscopy”
文摘Sum frequency generation(SFG) vibrational spectroscopy has been proven an excellent tool to measure the molecular structures, symmetries and orientations at surfaces/interfaces because of its strong polarization dependence. However, a precise quantitative analysis of SFG spectral intensity and molecular orientation at interfaces must be carefully performed. In this work, we summarized the parameters and factors that are often ignored and illustrated them by evaluating studies of CO adsorption on the(111) facet of platinum(Pt) and palladium(Pd) single crystals at the gas(ultra-high vacuum, UHV)/solid interfaces and methanol(water) adsorption at the air/liquid(solid/liquid) interfaces in the presence of sodium iodide(chloride) salts. To intuitively estimate the influence of incidence angles and refractive indices on the SFG intensity, solely a defined factor of|Fyyz| was discussed, which can be individually separated from the macroscopic second-order non-linear susceptibility χ yyz^(2) term and represents the SSP intensity. Moreover, effects of refractive indices and the molecular hyperpolarizability ratio(R) were discussed in the orientational analysis of interfacial CO and methanol molecules. When IPPP/ISSP was identical, molecules with a larger R had smaller tilting angles(q) on Pt(assuming q < 51°), and CO molecules on Pd would tilt much closer to the surface than they did on Pt. A total internal reflection(TIR) geometry enhanced the SFG intensity, but it also amplified the influence of refractive index on SFG intensity at the solid(silica)/liquid interface. The refractive index and R-value had similar influence on the methanol orientation in the presence of sodium iodide salts at air/liquid and solid/liquid interfaces. This work should provide a guideline for analyzing the orientation of molecules with different R, which are adsorbed on catalysts or located at liquid interfaces involving changes of refractive indices.
基金CSIRO Energy Centre and Kick‐Start ProjectAustralian Research Council(ARC)Future Fellowships,Grant/Award Numbers:FT210100298,FT210100806+9 种基金Key Project of Scientific Research of the Education Department of Liaoning Province,Grant/Award Number:LZD201902National Natural Science Foundation of China,Grant/Award Numbers:51873085,52071171Liaoning Revitalization Talents Program‐Pan Deng Scholars,Grant/Award Numbers:XLYC1802005,XLYC2007056Industrial Transformation Training Centre,Grant/Award Number:IC180100005Shenyang Science and Technology Project,Grant/Award Number:21‐108‐9‐04veski-Study Melbourne Research Partnerships(SMRP)projectLiaoning BaiQianWan Talents Program,Grant/Award Number:LNBQW2018B0048Natural Science Fund of Liaoning Province for Excellent Young Scholars,Grant/Award Number:2019‐YQ‐04Discovery Project,Grant/Award Number:DP220100603Linkage project,Grant/Award Number:LP210100467。
文摘The electrochemical reduction of carbon dioxide(CO_(2))into value‐added fuels and chemicals presents a sustainable route to alleviate CO_(2) emissions,promote carbon‐neutral cycles and reduce the dependence on fossil fuels.Considering the thermodynamic stability of the CO_(2) molecule and sluggish reaction kinetics,it is still a challenge to design highly efficient electrocatalysts for the CO_(2) reduction reaction(CO_(2)RR).It has been found that the surface and interface chemistry of electrocatalysts can modulate the electronic structure and increase the active sites,which is favorable for CO_(2) adsorption,electron transfer,mass transport,and optimizing adsorption strength of reaction intermediates.However,the effect of surface and interface chemistry on metal‐free electrocatalysts(MFEs)for CO_(2)RR has not been comprehensively reviewed.Herein,we discuss the importance of the surface and interface chemistry on MFEs for improving the electrochemical CO_(2)RR performance based on thermodynamic and kinetic views.The fundamentals and challenges of CO_(2)RR are firstly presented.Then,the recent advances of the surface and interface chemistry in improving reaction rate and overcoming reaction constraints are reviewed from regulating electronic structure,active sites,electron transfer,mass transport,and intermediate binding energy.Finally,the research challenges and prospects are proposed to suggest the future designs of advanced MFEs in CO_(2)RR.
