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
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
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
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.
