For Ti-doped hematite photoanodes, high temperature annealing drastically increases the water oxidation plateau photocurrent, but also induces an anodic shift of onset potential by about 100 m V, thus hindering the pe...For Ti-doped hematite photoanodes, high temperature annealing drastically increases the water oxidation plateau photocurrent, but also induces an anodic shift of onset potential by about 100 m V, thus hindering the performance under low applied bias. To the best of our knowledge, the effects of high temperature annealing on the onset potential have been rarely studied. Herein, both X-ray photoelectron spectroscopy(XPS) measurements and theoretical calculations indicated that the increase of surface Ti/Fe atomic ratio after high temperature annealing decreased the adsorption capacity of hydroxide ions on the hematite surface. Subsequently, the flatband potential(i.e., the theoretical onset potential) of Ti doped hematite photoanodes positively shifted, which was supported by the Mott-Schottky measurements.展开更多
With the unique properties,layered transition metal dichalcogenide(TMD)and its heterostructures exhibit great potential for applications in electronics.The electrical performance,e.g.,contact barrier and resistance to...With the unique properties,layered transition metal dichalcogenide(TMD)and its heterostructures exhibit great potential for applications in electronics.The electrical performance,e.g.,contact barrier and resistance to electrodes,of TMD heterostructure devices can be significantly tailored by employing the functional layers,called interlayer engineering.At the interface between different TMD layers,the dangling-bond states normally exist and act as traps against charge carrier flow.In this study,we propose a technique to suppress such carrier trap that uses enhanced interlayer hybridization to saturate dangling-bond states,as demonstrated in a strongly interlayer-coupled monolayer-bilayer PtSe2 heterostructure.The hybridization between the unsaturated states and the interlayer electronic states of PtSe2 significantly reduces the depth of carrier traps at the interface,as corroborated by our scanning tunnelling spectroscopic measurements and density functional theory calculations.The suppressed interfacial trap demonstrates that interlayer saturation may offer an efficient way to relay the charge flow at the interface of TMD heterostructures.Thus,this technique provides an effective way for optimizing the interface contact,the crucial issue exists in two-dimensional electronic community.展开更多
Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely ...Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely puckered pentagonal VTe_(2)(PP-VTe_(2)),intriguing atomic and electronic structures of which were firmly validated from first-principles calculations.The PP-VTe_(2) exhibits strong intrinsic ferromagnetism and semiconducting property distinct from the half-metallic bulk pyrite VTe_(2)(BP-VTe_(2))phase.An unusual magnetic anisotropy with large magnetic exchange energies is found.More interestingly,the multiferroic coupling between its 2D ferroelasticity and in-plane magnetization is further identified in PP-VTe_(2),lending it unprecedented controllability with external strains and electric fields.Serving as an emergent 2D ferromagnetic semiconductor with a novel crystal structure,monolayer PP-VTe_(2) provides an ideal platform for exploring exotic crystalline and spin configurations in low-dimensional systems.展开更多
Two-dimensional(2D)materials with defects are desired for catalysis after the adsorption of monodispersed noble metal atoms.High-performance catalysts with the absolute value of Gibbs free energy(|△GH|)close to zero,...Two-dimensional(2D)materials with defects are desired for catalysis after the adsorption of monodispersed noble metal atoms.High-performance catalysts with the absolute value of Gibbs free energy(|△GH|)close to zero,is one of the ultimate goals in the catalytic field.Here,we report the formation of monolayer titanium selenide(TiSe2)with line defects.The low-temperature scanning tunneling microscopy/spectroscopy(STM/S)measurements revealed the structure and electronic states of the line defect.Density functional theory(DFT)calculation results confirmed that the line defects were induced by selenium vacancies and the STM simulation was in good agreement with the experimental results.Further,DFT calculations show that monolayer TiSe_(2) with line defects have good catalytic activity for hydrogen evolution reaction(HER).If the defects are decorated with single Pt atom,the HER catalytic activity will be enhanced dramatically(|△GH|=0.006 eV),which is much better than Pt metal(|△GH|=0.09 eV).Line defects in monolayer TiSe_(2)/Au(111)provide a wonderful platform for the design of high-performance catalysts.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 21473090, U1663228)
文摘For Ti-doped hematite photoanodes, high temperature annealing drastically increases the water oxidation plateau photocurrent, but also induces an anodic shift of onset potential by about 100 m V, thus hindering the performance under low applied bias. To the best of our knowledge, the effects of high temperature annealing on the onset potential have been rarely studied. Herein, both X-ray photoelectron spectroscopy(XPS) measurements and theoretical calculations indicated that the increase of surface Ti/Fe atomic ratio after high temperature annealing decreased the adsorption capacity of hydroxide ions on the hematite surface. Subsequently, the flatband potential(i.e., the theoretical onset potential) of Ti doped hematite photoanodes positively shifted, which was supported by the Mott-Schottky measurements.
基金We acknowledged the financial support from the Beijing Natural Science Foundation(Nos.Z190006 and 4192054)the National Natural Science Foundation of China(Nos.61725107,11622437,61674171,11974422,61761166009,and 61888102)+3 种基金the National Key Research&Development Projects of China(Nos.2016YFA0202301,2019YFA0308000,and 2018YFE0202700)the Fundamental Research Funds for the Central Universities,China and the Research Funds of Renmin University of China(Nos.16XNLQ01 and 19XNQ025)the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB30000000 and XDB28000000)Calculations were performed at the Physics Lab of High-Performance Computing of Renmin University of China and Shanghai Supercomputer Center.
文摘With the unique properties,layered transition metal dichalcogenide(TMD)and its heterostructures exhibit great potential for applications in electronics.The electrical performance,e.g.,contact barrier and resistance to electrodes,of TMD heterostructure devices can be significantly tailored by employing the functional layers,called interlayer engineering.At the interface between different TMD layers,the dangling-bond states normally exist and act as traps against charge carrier flow.In this study,we propose a technique to suppress such carrier trap that uses enhanced interlayer hybridization to saturate dangling-bond states,as demonstrated in a strongly interlayer-coupled monolayer-bilayer PtSe2 heterostructure.The hybridization between the unsaturated states and the interlayer electronic states of PtSe2 significantly reduces the depth of carrier traps at the interface,as corroborated by our scanning tunnelling spectroscopic measurements and density functional theory calculations.The suppressed interfacial trap demonstrates that interlayer saturation may offer an efficient way to relay the charge flow at the interface of TMD heterostructures.Thus,this technique provides an effective way for optimizing the interface contact,the crucial issue exists in two-dimensional electronic community.
基金supported by the National Key Research and Development Program of China(Nos.2020YFA0308800,2016YFA0202300,and 2016YFA0300902)the National Natural Science Foundation of China(Nos.91850120 and 11974045)the Strategic Priority Research Program(B)of CAS(No.XDB30000000)。
文摘Two-dimensional(2D)magnetic crystals have been extensively explored thanks to their potential applications in spintronics,valleytronics,and topological superconductivity.Here we report a novel monolayer magnet,namely puckered pentagonal VTe_(2)(PP-VTe_(2)),intriguing atomic and electronic structures of which were firmly validated from first-principles calculations.The PP-VTe_(2) exhibits strong intrinsic ferromagnetism and semiconducting property distinct from the half-metallic bulk pyrite VTe_(2)(BP-VTe_(2))phase.An unusual magnetic anisotropy with large magnetic exchange energies is found.More interestingly,the multiferroic coupling between its 2D ferroelasticity and in-plane magnetization is further identified in PP-VTe_(2),lending it unprecedented controllability with external strains and electric fields.Serving as an emergent 2D ferromagnetic semiconductor with a novel crystal structure,monolayer PP-VTe_(2) provides an ideal platform for exploring exotic crystalline and spin configurations in low-dimensional systems.
基金We thank Guangchao Chen for his help.This work was supported by the National Key R&D Program of China(Nos.2019YFA0308500 and 2018YFA0305800)the National Natural Science Foundation of China(Nos.61925111 and 61888102)+1 种基金Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB28000000 and XDB30000000)the Fundamental Research Funds for the Central Universities,and CAS Key Laboratory of Vacuum Physics.
文摘Two-dimensional(2D)materials with defects are desired for catalysis after the adsorption of monodispersed noble metal atoms.High-performance catalysts with the absolute value of Gibbs free energy(|△GH|)close to zero,is one of the ultimate goals in the catalytic field.Here,we report the formation of monolayer titanium selenide(TiSe2)with line defects.The low-temperature scanning tunneling microscopy/spectroscopy(STM/S)measurements revealed the structure and electronic states of the line defect.Density functional theory(DFT)calculation results confirmed that the line defects were induced by selenium vacancies and the STM simulation was in good agreement with the experimental results.Further,DFT calculations show that monolayer TiSe_(2) with line defects have good catalytic activity for hydrogen evolution reaction(HER).If the defects are decorated with single Pt atom,the HER catalytic activity will be enhanced dramatically(|△GH|=0.006 eV),which is much better than Pt metal(|△GH|=0.09 eV).Line defects in monolayer TiSe_(2)/Au(111)provide a wonderful platform for the design of high-performance catalysts.