Pub Date : 2025-11-26DOI: 10.1016/j.susc.2025.122896
Yuhan Wang, Xingzhou Zhang, Zhiyuheng Li, Yan Li, Nanyu Cheng, Yijing Huang, Yongxin Wang
The dehydrogenation on group IV elements Si, Ge, or Sn doped MgH2(110) surface was investigated by first-principles calculations. In addition, the dopant site preference was determined by comparing the total energies of different doping site systems. The results showed that Si and Ge prefer to occupy interstitial sites, while Sn prefers to replace one Mg atom. The electronic structure and density of states show that the doping of Si, Ge, or Sn significantly weakens the Mg-H bond on the surface of MgH2(110), and the band gap of the system is reduced, leading to structural instability. Finally, the calculated results of dehydrogenation energy and activation energy barrier indicated that Ge best improves the thermodynamics and hydrogen desorption kinetics of the MgH2(110) surface, followed by Si and Sn.
{"title":"First-principles study of dehydrogenation on group IV elements Si, Ge, or Sn doped MgH2(110) surface","authors":"Yuhan Wang, Xingzhou Zhang, Zhiyuheng Li, Yan Li, Nanyu Cheng, Yijing Huang, Yongxin Wang","doi":"10.1016/j.susc.2025.122896","DOIUrl":"10.1016/j.susc.2025.122896","url":null,"abstract":"<div><div>The dehydrogenation on group IV elements Si, Ge, or Sn doped MgH<sub>2</sub>(110) surface was investigated by first-principles calculations. In addition, the dopant site preference was determined by comparing the total energies of different doping site systems. The results showed that Si and Ge prefer to occupy interstitial sites, while Sn prefers to replace one Mg atom. The electronic structure and density of states show that the doping of Si, Ge, or Sn significantly weakens the Mg-H bond on the surface of MgH<sub>2</sub>(110), and the band gap of the system is reduced, leading to structural instability. Finally, the calculated results of dehydrogenation energy and activation energy barrier indicated that Ge best improves the thermodynamics and hydrogen desorption kinetics of the MgH<sub>2</sub>(110) surface, followed by Si and Sn.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"766 ","pages":"Article 122896"},"PeriodicalIF":1.8,"publicationDate":"2025-11-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145683019","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-25DOI: 10.1016/j.susc.2025.122895
Tong Liu , Enqiang Hao , Xujie Wang , Congcong Zhu , Kaiyue Wang
The low-concentration adsorption of nitrogen oxide (NOx) gases on traditional gas-sensitive materials poses significant challenges for the development of gas sensor devices. Two-dimensional materials, represented by transition metal sulfides, are regarded as one of the most promising candidates for next-generation gas-sensitive materials. In this study, we constructed a two-dimensional MoS2 monolayer structure with strong hybridization capability via d-orbital transition metal Ti substitution doping (Ti–MoS2). By modulating the electronic structure and bonding coordination between Ti and the MoS2 matrix, we aimed to achieve highly efficient adsorption of NOx. Based on density functional theory (DFT) calculations, we systematically compared and analyzed the energy band structures, charge density distributions, adsorption properties, and sensitivity of four gas molecules (NO2, NO, CO, and CO2) within the MoS2 adsorption system before and after Ti doping. The results demonstrate that strong interactions and favorable charge transfer occur between the gas molecules and the substrate upon Ti doping, leading to significantly enhanced adsorption performance for all four gas molecules on the Ti–MoS2 monolayer. In particular, the adsorption energies for NO2 and NO increased by 2 to 4 times. Furthermore, using orbital hybridization theory and bonding theory, we deeply analyzed the influence of Ti doping on the energy bands and orbital hybridization, elucidating the interaction mechanism between Ti–MoS2 and nitrogen oxides. This work provides a feasible strategy for enhancing the NOx capture performance of two-dimensional molybdenum-based material systems.
{"title":"First-principles calculations of Ti doping-induced charge transfer between NOx and MoS2 to enhance gas-sensitive sensing performance","authors":"Tong Liu , Enqiang Hao , Xujie Wang , Congcong Zhu , Kaiyue Wang","doi":"10.1016/j.susc.2025.122895","DOIUrl":"10.1016/j.susc.2025.122895","url":null,"abstract":"<div><div>The low-concentration adsorption of nitrogen oxide (NO<sub>x</sub>) gases on traditional gas-sensitive materials poses significant challenges for the development of gas sensor devices. Two-dimensional materials, represented by transition metal sulfides, are regarded as one of the most promising candidates for next-generation gas-sensitive materials. In this study, we constructed a two-dimensional MoS<sub>2</sub> monolayer structure with strong hybridization capability via d-orbital transition metal Ti substitution doping (Ti–MoS<sub>2</sub>). By modulating the electronic structure and bonding coordination between Ti and the MoS<sub>2</sub> matrix, we aimed to achieve highly efficient adsorption of NO<sub>x</sub>. Based on density functional theory (DFT) calculations, we systematically compared and analyzed the energy band structures, charge density distributions, adsorption properties, and sensitivity of four gas molecules (NO<sub>2</sub>, NO, CO, and CO<sub>2</sub>) within the MoS<sub>2</sub> adsorption system before and after Ti doping. The results demonstrate that strong interactions and favorable charge transfer occur between the gas molecules and the substrate upon Ti doping, leading to significantly enhanced adsorption performance for all four gas molecules on the Ti–MoS<sub>2</sub> monolayer. In particular, the adsorption energies for NO<sub>2</sub> and NO increased by 2 to 4 times. Furthermore, using orbital hybridization theory and bonding theory, we deeply analyzed the influence of Ti doping on the energy bands and orbital hybridization, elucidating the interaction mechanism between Ti–MoS<sub>2</sub> and nitrogen oxides. This work provides a feasible strategy for enhancing the NO<sub>x</sub> capture performance of two-dimensional molybdenum-based material systems.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"766 ","pages":"Article 122895"},"PeriodicalIF":1.8,"publicationDate":"2025-11-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617280","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-24DOI: 10.1016/j.susc.2025.122892
Ulrike Küst , Calley Eads , Julia Prumbs , Weijia Wang , Robert Temperton , Alexander Klyushin , Andrey Shavorskiy , Jan Knudsen
Catalytic active phases are often separated from inactive ones by their appearance/removal in heating/cooling experiments. Such experiments can reveal ignition, extinction, and often an associated hysteresis. The corresponding behavior and hysteresis under rapid gas composition changes in the milliseconds regime remain largely unexplored. However, such experiments can potentially be highly rewarding as catalytic properties of surfaces that have not yet equilibrated to the gas phase can be studied. Here, we use time-resolved Ambient Pressure X-ray Photoelectron Spectroscopy (tr-APXPS) to study ethylene oxidation on polycrystalline Pd during modulation of the C2H4:O2 ratio. By combining 10 Hz gas pulsing with 25 kHz spectral acquisition, we track both gas phase and surface chemistry under non-equilibrium conditions and reveal and discuss a pronounced hysteresis.
{"title":"Operando hysteresis of a palladium surface during high-frequency gas-pulsing of ethylene into oxygen","authors":"Ulrike Küst , Calley Eads , Julia Prumbs , Weijia Wang , Robert Temperton , Alexander Klyushin , Andrey Shavorskiy , Jan Knudsen","doi":"10.1016/j.susc.2025.122892","DOIUrl":"10.1016/j.susc.2025.122892","url":null,"abstract":"<div><div>Catalytic active phases are often separated from inactive ones by their appearance/removal in heating/cooling experiments. Such experiments can reveal ignition, extinction, and often an associated hysteresis. The corresponding behavior and hysteresis under rapid gas composition changes in the milliseconds regime remain largely unexplored. However, such experiments can potentially be highly rewarding as catalytic properties of surfaces that have not yet equilibrated to the gas phase can be studied. Here, we use time-resolved Ambient Pressure X-ray Photoelectron Spectroscopy (tr-APXPS) to study ethylene oxidation on polycrystalline Pd during modulation of the C<sub>2</sub>H<sub>4</sub>:O<sub>2</sub> ratio. By combining 10<!--> <!-->Hz gas pulsing with 25<!--> <!-->kHz spectral acquisition, we track both gas phase and surface chemistry under non-equilibrium conditions and reveal and discuss a pronounced hysteresis.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"766 ","pages":"Article 122892"},"PeriodicalIF":1.8,"publicationDate":"2025-11-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145617279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-14DOI: 10.1016/j.susc.2025.122891
Qing An , Junhua Wang , Ying He , Jianing Zhou , Xiaolan Yang
In the works, the effect of noble metal atoms (Ag, Au, Pd, Pt) as dopants on the behaviour of WSe2 monolayer for adsorption of four key dissolved gases (C2H2, CH4, CO, H2) in transformer oil has been studied in depth using density-functional theory (DFT). It is shown that WSe₂ exhibits weak adsorption energies for C₂H₂, CH₄, CO, and H₂ molecules (below -0.02 eV). Calculations revealed that Ag, Au, Pd, and Pt doping significantly enhanced the interactions between gas molecules and the WSe₂ surface. Notably, the adsorption energy for C₂H₂ increased to -1.0 eV, with other molecules also showing marked increases, the adsorption capacity of Ag, Au, Pd, Pt- WSe₂ nanosheets for dissolved gases in transformer oils is in the order of C2H2 > CH4 > H2> CO, Ag, Au, Pd, and Pt atoms enhance the chemical adsorption capacity of WSe₂ by acting as electron donors and undergoing charge transfer with gas molecules. By calculating recovery times, it is predicted that Ag, Au, Pd, and Pt doped WSe₂ monolayers can detect C₂H₂ gas at 398 K after brief heating (8.17 s, 1.64 s, 6.28 s, and 2.47 s, respectively). This study provides a theoretical reference of significant value for WSe2 sensors in monitoring dissolved gases generated by internal faults in transformer oil.
{"title":"The sensing mechanism of metal (Ag, Au, Pd, Pt)-doped WSe2 monolayer for dissolved gases in transformer oil: A first-principle study","authors":"Qing An , Junhua Wang , Ying He , Jianing Zhou , Xiaolan Yang","doi":"10.1016/j.susc.2025.122891","DOIUrl":"10.1016/j.susc.2025.122891","url":null,"abstract":"<div><div>In the works, the effect of noble metal atoms (Ag, Au, Pd, Pt) as dopants on the behaviour of WSe<sub>2</sub> monolayer for adsorption of four key dissolved gases (C<sub>2</sub>H<sub>2</sub>, CH<sub>4</sub>, CO, H<sub>2</sub>) in transformer oil has been studied in depth using density-functional theory (DFT). It is shown that WSe₂ exhibits weak adsorption energies for C₂H₂, CH₄, CO, and H₂ molecules (below -0.02 eV). Calculations revealed that Ag, Au, Pd, and Pt doping significantly enhanced the interactions between gas molecules and the WSe₂ surface. Notably, the adsorption energy for C₂H₂ increased to -1.0 eV, with other molecules also showing marked increases, the adsorption capacity of Ag, Au, Pd, Pt- WSe₂ nanosheets for dissolved gases in transformer oils is in the order of C<sub>2</sub>H<sub>2</sub> > CH<sub>4</sub> > H<sub>2</sub>> CO, Ag, Au, Pd, and Pt atoms enhance the chemical adsorption capacity of WSe₂ by acting as electron donors and undergoing charge transfer with gas molecules. By calculating recovery times, it is predicted that Ag, Au, Pd, and Pt doped WSe₂ monolayers can detect C₂H₂ gas at 398 K after brief heating (8.17 s, 1.64 s, 6.28 s, and 2.47 s, respectively). This study provides a theoretical reference of significant value for WSe<sub>2</sub> sensors in monitoring dissolved gases generated by internal faults in transformer oil.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"765 ","pages":"Article 122891"},"PeriodicalIF":1.8,"publicationDate":"2025-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145569910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-12DOI: 10.1016/j.susc.2025.122890
Oloruntoba S. Agbelusi , Subash Pandey , Sonam , Neetu Goel , R.M. D. Naveen Tharaka , Journey A. Lopez , Kathryn A. Perrine
Monochloramine (NH2Cl) is a secondary disinfectant used for water purification and interacts with iron materials in various environments. Iron surfaces undergo reduction-oxidation and corrosion, where zero-valent iron sites are produced at complex interfaces. The initial stages of the reaction of monochloramine (NH2Cl) have been studied on Fe(111), as a model for iron pipelines and mineral surfaces, at the gas/solid interface in ultra-high vacuum conditions. Using in situ infrared reflection absorption spectroscopy, NH2Cl was found to adsorb molecularly at -160 °C, by observation of amine vibrational signatures. Auger electron spectroscopy was used to detect the presence of chloride to amine in a 3:1 ratio. Upon annealing, the NH2Cl multilayer was found to desorb from Fe(111) at -120 °C, and the monolayer also undergoes molecular dissociation. At 34 °C, NH2Cl primarily binds through the chloride species, thus blocking sites for NH2 adsorption. Density functional theory computations and X-ray photoelectron spectroscopy confirmed two favorable chemisorbed orientations, both through binding of chloride. Further annealing allowed for chloride desorption before 400 °C, suggesting decomposition. The NH2Cl is found to undergo a dechlorination mechanism, similar to chlorohydrocarbon reactions on iron surfaces. These findings reveal the mechanism of the chloramine disinfectant on metallic iron interfaces and its role in pipelines and water systems.
{"title":"Surface chemistry of monochloramine catalyzed by Fe(111)","authors":"Oloruntoba S. Agbelusi , Subash Pandey , Sonam , Neetu Goel , R.M. D. Naveen Tharaka , Journey A. Lopez , Kathryn A. Perrine","doi":"10.1016/j.susc.2025.122890","DOIUrl":"10.1016/j.susc.2025.122890","url":null,"abstract":"<div><div>Monochloramine (NH<sub>2</sub>Cl) is a secondary disinfectant used for water purification and interacts with iron materials in various environments. Iron surfaces undergo reduction-oxidation and corrosion, where zero-valent iron sites are produced at complex interfaces. The initial stages of the reaction of monochloramine (NH<sub>2</sub>Cl) have been studied on Fe(111), as a model for iron pipelines and mineral surfaces, at the gas/solid interface in ultra-high vacuum conditions. Using <em>in situ</em> infrared reflection absorption spectroscopy, NH<sub>2</sub>Cl was found to adsorb molecularly at -160 °C, by observation of amine vibrational signatures. Auger electron spectroscopy was used to detect the presence of chloride to amine in a 3:1 ratio. Upon annealing, the NH<sub>2</sub>Cl multilayer was found to desorb from Fe(111) at -120 °C, and the monolayer also undergoes molecular dissociation. At 34 °C, NH<sub>2</sub>Cl primarily binds through the chloride species, thus blocking sites for NH<sub>2</sub> adsorption. Density functional theory computations and X-ray photoelectron spectroscopy confirmed two favorable chemisorbed orientations, both through binding of chloride. Further annealing allowed for chloride desorption before 400 °C, suggesting decomposition. The NH<sub>2</sub>Cl is found to undergo a dechlorination mechanism, similar to chlorohydrocarbon reactions on iron surfaces. These findings reveal the mechanism of the chloramine disinfectant on metallic iron interfaces and its role in pipelines and water systems.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"766 ","pages":"Article 122890"},"PeriodicalIF":1.8,"publicationDate":"2025-11-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145737854","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Mott collapse is of significant interest, as it can lead to exotic behaviors such as high-temperature superconductivity, making its underlying mechanisms crucial to understand. The Mott state is realized in 1T-TaS₂, a member of transition metal dichalcogenides, due to in-plane interactions among Ta d-electrons. In this study, we investigated how the Mott state collapsed near an atomic defect in 1T-TaS₂ scanning tunneling microscopy (STM)/scanning tunneling spectroscopy (STS) measurements at 4.2 K. As the STM tip approached the atomic defect, we observed an overall shift of the dI/dV spectra towards positive bias, accompanied by the emergence of spatially localized in-gap states above the Fermi energy. In closer proximity to the defect, the gap structure at the Fermi energy transformed into a single-peak feature. This sequence of spatial evolution in the electronic structure can be interpreted as the Mott collapse in response to the amount of hole doping.
{"title":"Spatial evolution of the electronic states near a defect in 1T-TaS₂","authors":"Yuto Nakashima , Sora Kobayashi , Atsushi Nomura , Hideaki Sakata","doi":"10.1016/j.susc.2025.122888","DOIUrl":"10.1016/j.susc.2025.122888","url":null,"abstract":"<div><div>The Mott collapse is of significant interest, as it can lead to exotic behaviors such as high-temperature superconductivity, making its underlying mechanisms crucial to understand. The Mott state is realized in 1<em>T</em>-TaS₂, a member of transition metal dichalcogenides, due to in-plane interactions among Ta d-electrons. In this study, we investigated how the Mott state collapsed near an atomic defect in 1<em>T</em>-TaS₂ scanning tunneling microscopy (STM)/scanning tunneling spectroscopy (STS) measurements at 4.2 K. As the STM tip approached the atomic defect, we observed an overall shift of the dI/dV spectra towards positive bias, accompanied by the emergence of spatially localized in-gap states above the Fermi energy. In closer proximity to the defect, the gap structure at the Fermi energy transformed into a single-peak feature. This sequence of spatial evolution in the electronic structure can be interpreted as the Mott collapse in response to the amount of hole doping.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"765 ","pages":"Article 122888"},"PeriodicalIF":1.8,"publicationDate":"2025-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145569908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-10DOI: 10.1016/j.susc.2025.122889
Víctor A. Ranea
Hydrogen storage is one of the growing topics in recent years. In the present manuscript, hydrogen adsorption on the pristine and titanium-functionalized Mg(0001) surface is studied applying density functional theory. Ti adsorption between the external layers is more stable than on the surface. Increasing slightly the Titanium coverage, increases the binding energy per Ti atom. Molecular hydrogen interaction with the clean Mg surface is weak (adsorption energy of -0.03 eV/H) whereas dissociative adsorption is not stable. However, hydrogen dissociative adsorption between the external layers near adsorbed Titanium atoms, is stable. This indicates the adsorbed Ti atoms enhance the hydrogen storage of the Mg surface. Hydrogen adsorption is less stable as its coverage increases (in the hydrogen low coverage regime). Charge density analysis and activation energy calculations are performed. Titanium-functionalized Mg(0001) surface seems to be a promising material in the topic hydrogen storage.
{"title":"Hydrogen interlayer adsorption on Ti-functionalized Mg(0001). A density functional theory research","authors":"Víctor A. Ranea","doi":"10.1016/j.susc.2025.122889","DOIUrl":"10.1016/j.susc.2025.122889","url":null,"abstract":"<div><div>Hydrogen storage is one of the growing topics in recent years. In the present manuscript, hydrogen adsorption on the pristine and titanium-functionalized Mg(0001) surface is studied applying density functional theory. Ti adsorption between the external layers is more stable than on the surface. Increasing slightly the Titanium coverage, increases the binding energy per Ti atom. Molecular hydrogen interaction with the clean Mg surface is weak (adsorption energy of <span><math><mo>≈</mo></math></span>-0.03 eV/H<span><math><msub><mrow></mrow><mrow><mn>2</mn></mrow></msub></math></span>) whereas dissociative adsorption is not stable. However, hydrogen dissociative adsorption between the external layers near adsorbed Titanium atoms, is stable. This indicates the adsorbed Ti atoms enhance the hydrogen storage of the Mg surface. Hydrogen adsorption is less stable as its coverage increases (in the hydrogen low coverage regime). Charge density analysis and activation energy calculations are performed. Titanium-functionalized Mg(0001) surface seems to be a promising material in the topic hydrogen storage.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"765 ","pages":"Article 122889"},"PeriodicalIF":1.8,"publicationDate":"2025-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-08DOI: 10.1016/j.susc.2025.122877
Yenner Bentarcurt , Mónica Calatayud , Javier Fernández-Sanz , Jaime Klapp , Fernando Ruette
The theoretical investigation of the H2 interaction with the stable (001) oxidized maghemite surface revealed the feasibility of physisorption on different O-top and Fe-O bridge sites. Water and O vacancy formations at O-center sites occurred in a single step with energy barriers ranging from 1.65 to 2.20 eV. Two reaction steps were identified for the formation of O vacancies (Ov) on heterolytic two-center sites. In the first step, the H2 dissociation occurs through an intermediate with OH and Fe-H bonds on the surface, the energy barriers being the range of 0.45–0.87 eV. In the second step, Fe-bonded hydrogen migrates to the nearby O atom, with energy barriers of 0.25–0.65 eV. The formation of an Ov results in a reduction of the surface accompanied by an increase in the d-electron states close to the Fermi level, as indicated by the rise of Fe electronic density. A second H2 molecule heterolytically dissociated on the reduced surface exhibited similar dissociation energies but higher stability than that on the oxidized surface. The PDOS of the 1s orbitals of H atoms adsorbed on the reduced surface showed that those bonded to Fe atoms were close to the Fermi level, indicating high reactivity toward hydrogenation.
{"title":"Theoretical study of hydrogen activation and reduction of an oxidized maghemite surface, γ-Fe₂O₃, (001) by monovacancy formation: An analysis using density functional theory (DFT)","authors":"Yenner Bentarcurt , Mónica Calatayud , Javier Fernández-Sanz , Jaime Klapp , Fernando Ruette","doi":"10.1016/j.susc.2025.122877","DOIUrl":"10.1016/j.susc.2025.122877","url":null,"abstract":"<div><div>The theoretical investigation of the H<sub>2</sub> interaction with the stable (001) oxidized maghemite surface revealed the feasibility of physisorption on different O-top and Fe-O bridge sites. Water and O vacancy formations at O-center sites occurred in a single step with energy barriers ranging from 1.65 to 2.20 eV. Two reaction steps were identified for the formation of O vacancies (Ov) on heterolytic two-center sites. In the first step, the H<sub>2</sub> dissociation occurs through an intermediate with O<img>H and Fe-H bonds on the surface, the energy barriers being the range of 0.45–0.87 eV. In the second step, Fe-bonded hydrogen migrates to the nearby O atom, with energy barriers of 0.25–0.65 eV. The formation of an Ov results in a reduction of the surface accompanied by an increase in the d-electron states close to the Fermi level, as indicated by the rise of Fe electronic density. A second H<sub>2</sub> molecule heterolytically dissociated on the reduced surface exhibited similar dissociation energies but higher stability than that on the oxidized surface. The PDOS of the 1<em>s</em> orbitals of H atoms adsorbed on the reduced surface showed that those bonded to Fe atoms were close to the Fermi level, indicating high reactivity toward hydrogenation.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"765 ","pages":"Article 122877"},"PeriodicalIF":1.8,"publicationDate":"2025-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145569909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-07DOI: 10.1016/j.susc.2025.122878
Sun Myung Kim , Imants Dirba , Oliver Gutfleisch , Wolfgang Donner , Jan P. Hofmann
Iron single crystals Fe(100), Fe(111) and Fe(110) were reduced with a high-pressure autoclave H2-treatment to obtain clean surfaces. By increasing the pressure, the reduction was finished after 3 hours with temperature T = 600°C and pressure P = 50 bar. Typical contaminations present in Fe single crystals are C, O and S. Especially S contamination is hard to remove and usually requires week-long atmospheric pressure hydrogen treatments at high temperatures. In this work, we show a fast method that achieves a deep removal of non-metal trace impurities of the Fe surface and bulk in under a day. The cleanliness of the single crystals was studied by low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). The cleaning procedure consisted of a high-pressure H2-treatment and subsequent sputtering and annealing in vacuum at ∼650°C to obtain clean LEED images. Clean (1 × 1) patterns were recorded for Fe(100), Fe(111) and Fe(110). Before undergoing high-pressure H2-treatment, impurities in Fe(100) and Fe(111) present faceted surfaces, whereas Fe(110) shows complex overstructures. Further confirmation for successful reduction is given by XPS results. Fe2p3/2 of cleaned samples is shown to be at 706.7 eV. Moreover, ultraviolet photoelectron spectroscopy (UPS) was employed for valence band and work function measurements.
{"title":"High pressure H2 treatment for deep cleaning of Fe single crystals","authors":"Sun Myung Kim , Imants Dirba , Oliver Gutfleisch , Wolfgang Donner , Jan P. Hofmann","doi":"10.1016/j.susc.2025.122878","DOIUrl":"10.1016/j.susc.2025.122878","url":null,"abstract":"<div><div>Iron single crystals Fe(100), Fe(111) and Fe(110) were reduced with a high-pressure autoclave H<sub>2</sub>-treatment to obtain clean surfaces. By increasing the pressure, the reduction was finished after 3 hours with temperature <em>T</em> = 600°C and pressure <em>P</em> = 50 bar. Typical contaminations present in Fe single crystals are C, O and S. Especially S contamination is hard to remove and usually requires week-long atmospheric pressure hydrogen treatments at high temperatures. In this work, we show a fast method that achieves a deep removal of non-metal trace impurities of the Fe surface and bulk in under a day. The cleanliness of the single crystals was studied by low-energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS). The cleaning procedure consisted of a high-pressure H<sub>2</sub>-treatment and subsequent sputtering and annealing in vacuum at ∼650°C to obtain clean LEED images. Clean (1 × 1) patterns were recorded for Fe(100), Fe(111) and Fe(110). Before undergoing high-pressure H<sub>2</sub>-treatment, impurities in Fe(100) and Fe(111) present faceted surfaces, whereas Fe(110) shows complex overstructures. Further confirmation for successful reduction is given by XPS results. Fe2p<sub>3/2</sub> of cleaned samples is shown to be at 706.7 eV. Moreover, ultraviolet photoelectron spectroscopy (UPS) was employed for valence band and work function measurements.</div></div>","PeriodicalId":22100,"journal":{"name":"Surface Science","volume":"765 ","pages":"Article 122878"},"PeriodicalIF":1.8,"publicationDate":"2025-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145518122","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-11-04DOI: 10.1016/j.susc.2025.122876
Peyman Koohsari , Muhammad Shadman , Jamal Davoodi , Zohreh Ahadi , Chérif F. Matta
While carbon-based nanomaterials have been extensively studied for water confinement, far less is known about the influence of molybdenum disulfide (MoS2) nanotubes on the phase behavior of ice. Using molecular dynamics (MD) simulations, this study unveils how MoS2 nanotubes, owing to their unique semi-polar hydrophilic surfaces, significantly affect the stability and melting of hexagonal ice under nanoconfinement. We investigate two distinct confinement modes: (1) within the nanotubes and (2) in the interstitial space between them for both hydrogen-ordered and defect-introduced ice structures. A striking ∼30 K upward shift in melting temperature is observed for hydrogen-disordered (defect-introduced) ice confined between nanotubes. This effect is absent in comparable carbon nanostructures, highlighting the critical role of defect-introduced ice and surface interactions. Furthermore, we systematically assess the influence of nanotube diameter and heating rate, revealing that melting behavior is dominated more by molecular-level interactions than by geometrical confinement alone. These results demonstrate the novel potential of MoS2 as a tunable platform for phase-change control, with broad implications for cryopreservation, energy storage, pharmaceuticals, and the design of nanostructured thermal materials.
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