Spontaneous polarization due to symmetry breaking in the transition metal ditellurides(MTe_(2))family exhibits intriguing sliding ferroelectricity.Although theoretical predictions of MTe_(2)ferroelectric metals with n...Spontaneous polarization due to symmetry breaking in the transition metal ditellurides(MTe_(2))family exhibits intriguing sliding ferroelectricity.Although theoretical predictions of MTe_(2)ferroelectric metals with noncentrosymmetric stacking have been reported,the realization of such polarization structure remains a challenge.Here,we demonstrate the synthesis of PtTe_(2)with non-centrosymmetric stacking layers,in contrast to bulk AA stacking,achieved within a scanning transmission electron microscope(STEM)by irradiating amorphous PtxTeythin flms with an electron beam probe.Cross-sectional STEM imaging combined with frst-principles calculations reveals that the diverse stacking confgurations due to an intralayerπ-stacking system break centrosymmetry in PtTe_(2),giving rise to the out-of-plane polarization.Three-dimensional atomic positions identifed by the atomic electron tomography method further demonstrate the local distortions associated with the non-centrosymmetric stacking layers in PtTe_(2).The understanding of the atomic origin of polarization in PtTe_(2)is of signifcant importance for developing devices that integrate ferroelectricity with metallicity.展开更多
Two-dimensional(2D)transition metal dichalcogenides(TMDs)have attracted considerable attention because of their unique properties and great potential in nano-technology applications.Great efforts have been devoted to ...Two-dimensional(2D)transition metal dichalcogenides(TMDs)have attracted considerable attention because of their unique properties and great potential in nano-technology applications.Great efforts have been devoted to fabrication of novel structured TMD monolayers by modifying their pristine structures at the atomic level.Here we propose an intriguing structured 1T-PtTe2 monolayer as hydrogen evolution reaction(HER)catalyst,namely,Pt4Te7,using first-principles calculations.It is found that Pt4Te7 is a stable monolayer material verified by the calculation of formation energy,phonon dispersion,and ab initio molecular dynamics simulations.Remarkably,the novel structured void-containing monolayer exhibits superior catalytic activity toward HER compared with the pristine one,with a Gibbs free energy very close to zero(less than 0.07 eV).These features indicate that Pt4Te7 monolayer is a high-performance HER catalyst with a high platinum utilization.These findings open new perspectives for the functionalization of 2D TMD materials at an atomic level and its application in HER catalysis.展开更多
1T phase of transition metal dichalcogenides(TMDCs)formed by group 10 transition metals(e.g.Pt,Pd)have attracted increasing interests due to their novel properties and potential device applications.Synthesis of large ...1T phase of transition metal dichalcogenides(TMDCs)formed by group 10 transition metals(e.g.Pt,Pd)have attracted increasing interests due to their novel properties and potential device applications.Synthesis of large scale thin films with controlled phase is critical especially considering that these materials have relatively strong interlayer interaction and are difficult to exfoliate.Here we report the growth of centimeter-scale PtTe,1T-PtTe2 and 1T-PtSe2 films via direct deposition of Pt metals followed by tellurization or selenization.We find that by controlling the Te flux,a hitherto-unexplored PtTe phase can also be obtained,which can be further tuned into PtTe2 by high temperature annealing under Te flux.These films with different thickness can be grown on a wide range of substrates,including NaCl which can be further dissolved to obtain free-standing PtTe2 or PtSe2 films.Moreover,a systematic thickness dependent resistivity and Hall conductivity measurements show that distinguished from the semiconducting PtSe2 with hole carriers,PtTe2 and PtTe films are metallic.Our work opens new opportunities for investigating the physical properties and potential applications of group 10 TMDC films and the new monochalcogenide PtTe film.展开更多
PtTe2 and PtSe2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topologica...PtTe2 and PtSe2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topological semimetal to 2D atomic thin films is an important scientific question. While a transition from 3D type-II Dirac semimetal in the bulk to 2D semiconductor in monolayer(ML) film has been reported for PtSe2, so far the evolution of electronic structure of atomically thin PtTe2 films still remains unexplored.Here we report a systematic angle-resolved photoemission spectroscopy(ARPES) study of the electronic structure of high quality PtTe2 films grown by molecular beam epitaxy with thickness from 2 ML to 6 ML.ARPES measurements show that PtTe2 films still remain metallic even down to 2 ML thickness, which is in sharp contrast to the semiconducting property of few layer PtSe2 films. Moreover, a transition from 2D metal to 3D type-II Dirac semimetal occurs at film thickness of 4–6 ML. In addition, Spin-ARPES measurements reveal helical spin textures induced by local Rashba effect in the bulk PtTe2 crystal, suggesting that similar hidden spin is also expected in few monolayer PtTe2 films. Our work reveals the transition from2D metal to 3D topological semimetal and provides new opportunities for investigating metallic 2D films with local Rashba effect.展开更多
Morphology engineering has been developed as one of the most widely used strategies for improving the performance of electrocatalysts.However,the harsh reaction conditions and cumbersome reaction steps during the nano...Morphology engineering has been developed as one of the most widely used strategies for improving the performance of electrocatalysts.However,the harsh reaction conditions and cumbersome reaction steps during the nanomaterials synthesis still limit their industrial applications.Herein,one-dimensional(1D)novel-segmented PtTe porous nanochains(PNCs)were successfully synthesized by the template methods assisted by Pt autocatalytic reduction.The PtTe PNCs consist of consecutive mesoporous architectures that provide a large electrochemical surface area(ECSA)and abundant active sites to enhance methanol oxidation reaction(MOR).Furthermore,1D nanostructure as a robust sustaining frame can maintain a high mass/charge transfer rate in a long-term durability test.After 2,000 cyclic voltammetry(CV)cycles,the ECSA value of PtTe PNCs remained as high as 44.47 m^(2)·gPt^(-1),which was much larger than that of commercial Pt/C(3.95 m^(2)·gPt^(-1)).The high catalytic activity and durability of PtTe PNCs are also supported by CO stripping test and density functional theory calculation.This autocatalytic reduction-assisted synthesis provides new insights for designing efficient low-dimensional nanocatalysts.展开更多
The high-performance anodic electrocatalysts is pivotal for realizing the commercial application of the direct formic acid fuel cells.In this work,a simple polyethyleneimine-assisted galvanic replacement reaction is a...The high-performance anodic electrocatalysts is pivotal for realizing the commercial application of the direct formic acid fuel cells.In this work,a simple polyethyleneimine-assisted galvanic replacement reaction is applied to synthesize the high-quality PtTe alloy nanowires(PtTe NW)by using Te NW as an efficient sacrificial template.The existence of Te atoms separates the continuous Pt atoms,triggering a direct reaction pathway of formic acid electrooxidation reaction(FAEOR)at PtTe NW.The one-dimensional architecture and highly active sites have enabled PtTe NW to reveal outstanding electrocatalytic activity towards FAEOR with the mass/specific activities of 1091.25 mA mg^(-1)/45.34 A m^(-2)at 0.643 V potential,which are 44.72/23.16 and 20.26/11.75 times bigger than those of the commercial Pt and Pd nanoparticles,respectively.Density functional theory calculations reveal that Te atoms optimize the electronic structure of Pt atoms,which decreases the adsorption capacity of CO intermediate and simultaneously improves the durability of PtTe NW towards FAEOR.This work provides the valuable insights into the synthesis and design of efficient Pt-based alloy FAEOR electrocatalysts.展开更多
Engineering the composition and/or morphology of noble metal nanocrystals is a highly effective strategy for enhancing their electrocatalytic performance.Recently,metallenes with specific chemical and physical propert...Engineering the composition and/or morphology of noble metal nanocrystals is a highly effective strategy for enhancing their electrocatalytic performance.Recently,metallenes with specific chemical and physical properties have increasingly attracted attention in the field of electrocatalysis.In this work,two-dimensional ultrathin platinum-tellurium alloy metallene(PtTe A-ML)is synthesized using a conventional liquid-phase chemical reduction method.The high atomic utilization as well as alloy effect endow PtTe A-ML with preeminent electrocatalytic activity for the formic acid oxidation reaction(FAOR).Specifically,the direct oxidation pathway of FAOR can be completely achieved using PtTe A-ML,which suppresses the production of toxic carbon monoxide(CO)intermediates and improves the reaction kinetics of FAOR.Accordingly,the FAOR activity of PtTe AML in acidic media is 43 and 5.6 times higher than that of commercial Pt and Pd nanocrystals,respectively.Meanwhile,PtTe A-ML also exhibits excellent electrocatalytic activity for the CO oxidation reaction because of the introduction of oxygenophilic Te atoms and electron transfer between Pt and Te,which elevates the durability of PtTe A-ML for FAOR.This study provides a simple synthesis strategy for PtTe A-ML and demonstrates that PtTe A-ML has a promising practical prospect for direct formic acid fuel cells.展开更多
基金supported by the National Key R&D Program of China(Grant Nos.2024YFA1208201,2022YFA1403000,and 2021YFA1400204)the National Natural Science Foundation of China(Grant Nos.52322311,12334001,52427802,12174432,12250710675,and 52461160301)the support from Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)。
文摘Spontaneous polarization due to symmetry breaking in the transition metal ditellurides(MTe_(2))family exhibits intriguing sliding ferroelectricity.Although theoretical predictions of MTe_(2)ferroelectric metals with noncentrosymmetric stacking have been reported,the realization of such polarization structure remains a challenge.Here,we demonstrate the synthesis of PtTe_(2)with non-centrosymmetric stacking layers,in contrast to bulk AA stacking,achieved within a scanning transmission electron microscope(STEM)by irradiating amorphous PtxTeythin flms with an electron beam probe.Cross-sectional STEM imaging combined with frst-principles calculations reveals that the diverse stacking confgurations due to an intralayerπ-stacking system break centrosymmetry in PtTe_(2),giving rise to the out-of-plane polarization.Three-dimensional atomic positions identifed by the atomic electron tomography method further demonstrate the local distortions associated with the non-centrosymmetric stacking layers in PtTe_(2).The understanding of the atomic origin of polarization in PtTe_(2)is of signifcant importance for developing devices that integrate ferroelectricity with metallicity.
基金Project supported by the National Key R&D Program of China(Grant Nos.2016YFA0202300,2018YFA0305800,and 2019YFA0308500)the National Natural Science Foundation of China(Grant Nos.61888102,51872284,and 51922011)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB30000000).
文摘Two-dimensional(2D)transition metal dichalcogenides(TMDs)have attracted considerable attention because of their unique properties and great potential in nano-technology applications.Great efforts have been devoted to fabrication of novel structured TMD monolayers by modifying their pristine structures at the atomic level.Here we propose an intriguing structured 1T-PtTe2 monolayer as hydrogen evolution reaction(HER)catalyst,namely,Pt4Te7,using first-principles calculations.It is found that Pt4Te7 is a stable monolayer material verified by the calculation of formation energy,phonon dispersion,and ab initio molecular dynamics simulations.Remarkably,the novel structured void-containing monolayer exhibits superior catalytic activity toward HER compared with the pristine one,with a Gibbs free energy very close to zero(less than 0.07 eV).These features indicate that Pt4Te7 monolayer is a high-performance HER catalyst with a high platinum utilization.These findings open new perspectives for the functionalization of 2D TMD materials at an atomic level and its application in HER catalysis.
基金the National Natural Science Foundation of China(Nos.11725418 and 21975140)the National Key Basic Research Program of China(Nos.2015CB921001,2016YFA0301001 and 2016YFA0301004)+2 种基金Science Challenge Project(No.TZ20164500122)the Basic Science Center Program of NSFC(No.51788104)Beijing Advanced Innovation Center of Future Chip(ICFC)and Tsinghua University Initiative Scientific Research Program.
文摘1T phase of transition metal dichalcogenides(TMDCs)formed by group 10 transition metals(e.g.Pt,Pd)have attracted increasing interests due to their novel properties and potential device applications.Synthesis of large scale thin films with controlled phase is critical especially considering that these materials have relatively strong interlayer interaction and are difficult to exfoliate.Here we report the growth of centimeter-scale PtTe,1T-PtTe2 and 1T-PtSe2 films via direct deposition of Pt metals followed by tellurization or selenization.We find that by controlling the Te flux,a hitherto-unexplored PtTe phase can also be obtained,which can be further tuned into PtTe2 by high temperature annealing under Te flux.These films with different thickness can be grown on a wide range of substrates,including NaCl which can be further dissolved to obtain free-standing PtTe2 or PtSe2 films.Moreover,a systematic thickness dependent resistivity and Hall conductivity measurements show that distinguished from the semiconducting PtSe2 with hole carriers,PtTe2 and PtTe films are metallic.Our work opens new opportunities for investigating the physical properties and potential applications of group 10 TMDC films and the new monochalcogenide PtTe film.
基金supported by the National Natural Science Foundation of China(11725418 and 11334006)the National Basic Research Program of China(2016YFA0301004,2016YFA0301001,and 2015CB921001)+1 种基金Science Challenge Project(TZ2016004)Beijing Advanced Innovation Center for Future Chip(ICFC)
文摘PtTe2 and PtSe2 with trigonal structure have attracted extensive research interests since the discovery of type-II Dirac fermions in the bulk crystals. The evolution of the electronic structure from bulk 3D topological semimetal to 2D atomic thin films is an important scientific question. While a transition from 3D type-II Dirac semimetal in the bulk to 2D semiconductor in monolayer(ML) film has been reported for PtSe2, so far the evolution of electronic structure of atomically thin PtTe2 films still remains unexplored.Here we report a systematic angle-resolved photoemission spectroscopy(ARPES) study of the electronic structure of high quality PtTe2 films grown by molecular beam epitaxy with thickness from 2 ML to 6 ML.ARPES measurements show that PtTe2 films still remain metallic even down to 2 ML thickness, which is in sharp contrast to the semiconducting property of few layer PtSe2 films. Moreover, a transition from 2D metal to 3D type-II Dirac semimetal occurs at film thickness of 4–6 ML. In addition, Spin-ARPES measurements reveal helical spin textures induced by local Rashba effect in the bulk PtTe2 crystal, suggesting that similar hidden spin is also expected in few monolayer PtTe2 films. Our work reveals the transition from2D metal to 3D topological semimetal and provides new opportunities for investigating metallic 2D films with local Rashba effect.
基金This work was supported by the National Natural Science Foundation of China(Nos.52171051,52130103,52271237,52271163,51971026,12034002,and 11904025)the Natural Science Foundation of Henan province(No.222300420086).We thank Dr.Song Hong from the Electron Microscopy Laboratory at Beijing University of Chemical Technology for the help with the aberration-corrected transmission electron microscope.
文摘Morphology engineering has been developed as one of the most widely used strategies for improving the performance of electrocatalysts.However,the harsh reaction conditions and cumbersome reaction steps during the nanomaterials synthesis still limit their industrial applications.Herein,one-dimensional(1D)novel-segmented PtTe porous nanochains(PNCs)were successfully synthesized by the template methods assisted by Pt autocatalytic reduction.The PtTe PNCs consist of consecutive mesoporous architectures that provide a large electrochemical surface area(ECSA)and abundant active sites to enhance methanol oxidation reaction(MOR).Furthermore,1D nanostructure as a robust sustaining frame can maintain a high mass/charge transfer rate in a long-term durability test.After 2,000 cyclic voltammetry(CV)cycles,the ECSA value of PtTe PNCs remained as high as 44.47 m^(2)·gPt^(-1),which was much larger than that of commercial Pt/C(3.95 m^(2)·gPt^(-1)).The high catalytic activity and durability of PtTe PNCs are also supported by CO stripping test and density functional theory calculation.This autocatalytic reduction-assisted synthesis provides new insights for designing efficient low-dimensional nanocatalysts.
基金supported by the National Natural Science Foundation of China(22272103 and 52171145)the Science and Technology Innovation Team of Shaanxi Province(2023-CX-TD27)+1 种基金the Fundamental Research Funds for the Central Universities(GK202202001)the 111 Project(B14041 and D20015)。
文摘The high-performance anodic electrocatalysts is pivotal for realizing the commercial application of the direct formic acid fuel cells.In this work,a simple polyethyleneimine-assisted galvanic replacement reaction is applied to synthesize the high-quality PtTe alloy nanowires(PtTe NW)by using Te NW as an efficient sacrificial template.The existence of Te atoms separates the continuous Pt atoms,triggering a direct reaction pathway of formic acid electrooxidation reaction(FAEOR)at PtTe NW.The one-dimensional architecture and highly active sites have enabled PtTe NW to reveal outstanding electrocatalytic activity towards FAEOR with the mass/specific activities of 1091.25 mA mg^(-1)/45.34 A m^(-2)at 0.643 V potential,which are 44.72/23.16 and 20.26/11.75 times bigger than those of the commercial Pt and Pd nanoparticles,respectively.Density functional theory calculations reveal that Te atoms optimize the electronic structure of Pt atoms,which decreases the adsorption capacity of CO intermediate and simultaneously improves the durability of PtTe NW towards FAEOR.This work provides the valuable insights into the synthesis and design of efficient Pt-based alloy FAEOR electrocatalysts.
基金the National Natural Science Foundation of China(Grant No.22272103)Science and Technology Innovation Team of Shaanxi Province(Grant No.2023-CX-TD-27)+1 种基金the Young Scientist Innovation Project of the School of Materials Science and Engineering at Shaanxi Normal University(Grant No.2022YSIP-MSE-SNNU005)the Fundamental Research Funds for the Central Universities(Grant No.GK202202001).
文摘Engineering the composition and/or morphology of noble metal nanocrystals is a highly effective strategy for enhancing their electrocatalytic performance.Recently,metallenes with specific chemical and physical properties have increasingly attracted attention in the field of electrocatalysis.In this work,two-dimensional ultrathin platinum-tellurium alloy metallene(PtTe A-ML)is synthesized using a conventional liquid-phase chemical reduction method.The high atomic utilization as well as alloy effect endow PtTe A-ML with preeminent electrocatalytic activity for the formic acid oxidation reaction(FAOR).Specifically,the direct oxidation pathway of FAOR can be completely achieved using PtTe A-ML,which suppresses the production of toxic carbon monoxide(CO)intermediates and improves the reaction kinetics of FAOR.Accordingly,the FAOR activity of PtTe AML in acidic media is 43 and 5.6 times higher than that of commercial Pt and Pd nanocrystals,respectively.Meanwhile,PtTe A-ML also exhibits excellent electrocatalytic activity for the CO oxidation reaction because of the introduction of oxygenophilic Te atoms and electron transfer between Pt and Te,which elevates the durability of PtTe A-ML for FAOR.This study provides a simple synthesis strategy for PtTe A-ML and demonstrates that PtTe A-ML has a promising practical prospect for direct formic acid fuel cells.
