Ru has recently been regarded as a promising catalyst for hydrogen oxidation reaction(HOR)and hydrogen evolution reaction(HER)due to its similar binding energy towards*H but lower price compared to Pt.Nevertheless,the...Ru has recently been regarded as a promising catalyst for hydrogen oxidation reaction(HOR)and hydrogen evolution reaction(HER)due to its similar binding energy towards*H but lower price compared to Pt.Nevertheless,the quest of high-efficiency Ru-based catalysts for HOR and HER is driven by the current disadvantages including low activity and unsatisfactory stability.Herein,we have fabricated and engineered two-dimensional(2D)Ru-based snow-like nanosheets with Ru/Ru O2interface(Ru/Ru O2SNSs)via a post-annealing treatment.Detailed characterizations and theoretical calculations indicate that the interfacial synergy,which is dependent on the temperature for annealing,can alter the hydrogen binding energy(HBE)and hydroxide binding energy(OHBE),as a result of the enhanced HOR and HER performance.Impressively,the optimal Ru/RuO_(2)SNSs display a mass activity of 9.13 A mgRu^(–1)at an overpotential of 50 m V in 0.1 mol L^(–1)KOH for HOR,which is 65,304,and 21 times higher than those of Ru SNSs(0.14 A mg_(Ru)^(–1)),RuO_(2)SNSs(0.03 A mg_(Ru)^(–1)),and commercial Pt/C(0.43 A mg_(Ru)^(–1)),respectively.Moreover,Ru/RuO_(2)SNSs display improved HER activity with a low overpotential of 20.2 m V for achieving10 m A cm^(-2)in 1 mol L^(–1)KOH.This work not only provides an efficient catalyst for HOR and HER,but also promotes fundamental research on the fabrication and modification of catalysts in heterogeneous catalysis.展开更多
在过去的十多年中,X射线自由电子激光器（X-ray Free Electron Laser,XFEL）的成功研制和快速发展,极大地推动了超快X射线光谱学实验技术的发展,并且在物理、化学和生物科学等不同研究领域获得了广泛的应用。通过飞秒激光脉冲对样品的激...在过去的十多年中,X射线自由电子激光器（X-ray Free Electron Laser,XFEL）的成功研制和快速发展,极大地推动了超快X射线光谱学实验技术的发展,并且在物理、化学和生物科学等不同研究领域获得了广泛的应用。通过飞秒激光脉冲对样品的激发,X射线可以在不同时间尺度下,跟踪固态、液态和气态等各种情况下样品的微观结构动力学过程。X射线吸收和发射光谱,衍射和散射是探测激光诱导结构变化的典型工具。文章将介绍近年来飞秒X射线技术的发展,及其在化学与能源材料领域的应用。相信随着上海X射线自由电子激光器的建成,将使得飞秒X射线技术在更多的科学领域发挥作用。展开更多
In-plane heteroatom substitution of graphene is a promising strategy to modify its properties. The ability to dope graphene with electron-donor nitrogen heteroatoms is highly important for modulating electrical proper...In-plane heteroatom substitution of graphene is a promising strategy to modify its properties. The ability to dope graphene with electron-donor nitrogen heteroatoms is highly important for modulating electrical properties of graphene. Here we demonstrate a transfer-free method to directly grow large area quasi free-standing N-doped graphene bilayers on an insulating substrate （Si3N4）. Electron-bombardment heating under nitrogen flux results in simultaneous growth of N-doped graphene and a Si3N4 layer on the SiC surface. The decoupling of N-doped graphene from the substrate and the presence of Si3N4 are identified by X-ray photoemission spectroscopy and low-energy electron diffraction. The substitution of nitrogen atoms in the graphene planes was confirmed using high resolution X-ray photoemission spectroscopy which reveals several atomic configurations for the nitrogen atoms： Graphitic-like, pyridine-like, and pyrrolic- like. Furthermore, we demonstrated for the first time that N-doped graphene could be used to efficiently probe oxygen molecules via nitrogen atom defects.展开更多
The remarkable properties of graphene have shown promise for new perspectives in future electronics, notably for nanometer scale devices. Here we grow graphene epitaxially on an off-axis 4H-SiC（0001） substrate and d...The remarkable properties of graphene have shown promise for new perspectives in future electronics, notably for nanometer scale devices. Here we grow graphene epitaxially on an off-axis 4H-SiC（0001） substrate and demonstrate the formation of periodic arrangement of monolayer graphene on planar （0001） terraces and Bernal bilayer graphene on （1120） nanofacets of SiC. We investigate these lateral superlattices using Raman spectroscopy, atomic force microscopy/ electrostatic force microscopy （AFM/EFM） and X-ray and angle resolved photoemission spectroscopy （XPS/ARPES）. The correlation of EFM and ARPES reveals the appearance of permanent electronic band gaps in AB-stacked bilayer graphene on （1120） SiC nanofacets of 150 meV. This feature is confirmed by density functional theory （DFT） calculations. The charge transfer between the substrate and graphene bilayer results in an asymmetric charge distribution between the top and the bottom graphene layers opening an energy gap. This surface organization can be thus defined as self-organized metal-semiconductor graphene.展开更多
With the ever-increasing demands of grid-scale energy storage,aqueous zinc-ion batteries(ZIBs)have garnered increasing attention around the world.However,limited Zn^(2+)host materials have hindered the commercializati...With the ever-increasing demands of grid-scale energy storage,aqueous zinc-ion batteries(ZIBs)have garnered increasing attention around the world.However,limited Zn^(2+)host materials have hindered the commercialization of ZIBs.Hence,Mo-V oxides with different phase structures(orth-,tri-,and tetra-MoVO)were precisely constructed to develop phase-dependent Mo-V oxide cathodes for Zn^(2+)storage in ZIBs.The open frameworks and varied tunnel structures formed a favorable alternative for achieving suitable Zn^(2+)diffusion kinetics.With optimized phase engineering,the high specific capacity of approximately 400 mA h g^(−1) and excellent cyclic stability of 1000 cycles were achieved with orth-MoVO as the cathode.The large amount of six-and seven-member rings in the orth-MoVO phase,which allow for alternative Zn^(2+)insertion,play a vital role in hosting Zn^(2+)ions reversibly.The proposed phase engineering strategy provides a new approach toward cathode design in ZIBs.展开更多
基金supported by the National Key R&D Program of China(2020YFB1505802)the Ministry of Science and Technology of China(2017YFA0208200,2016YFA0204100)+4 种基金the National Natural Science Foundation of China(22025108,U21A20327,and22121001)China Postdoctoral Science Foundation(2020M682083)Guangdong Provincial Natural Science Fund for Distinguished Young Scholars(2021B1515020081)Start-up Support from Xiamen University and the Guangzhou Key Laboratory of Low Dimensional Materials and Energy Storage Devices(20195010002)。
文摘Ru has recently been regarded as a promising catalyst for hydrogen oxidation reaction(HOR)and hydrogen evolution reaction(HER)due to its similar binding energy towards*H but lower price compared to Pt.Nevertheless,the quest of high-efficiency Ru-based catalysts for HOR and HER is driven by the current disadvantages including low activity and unsatisfactory stability.Herein,we have fabricated and engineered two-dimensional(2D)Ru-based snow-like nanosheets with Ru/Ru O2interface(Ru/Ru O2SNSs)via a post-annealing treatment.Detailed characterizations and theoretical calculations indicate that the interfacial synergy,which is dependent on the temperature for annealing,can alter the hydrogen binding energy(HBE)and hydroxide binding energy(OHBE),as a result of the enhanced HOR and HER performance.Impressively,the optimal Ru/RuO_(2)SNSs display a mass activity of 9.13 A mgRu^(–1)at an overpotential of 50 m V in 0.1 mol L^(–1)KOH for HOR,which is 65,304,and 21 times higher than those of Ru SNSs(0.14 A mg_(Ru)^(–1)),RuO_(2)SNSs(0.03 A mg_(Ru)^(–1)),and commercial Pt/C(0.43 A mg_(Ru)^(–1)),respectively.Moreover,Ru/RuO_(2)SNSs display improved HER activity with a low overpotential of 20.2 m V for achieving10 m A cm^(-2)in 1 mol L^(–1)KOH.This work not only provides an efficient catalyst for HOR and HER,but also promotes fundamental research on the fabrication and modification of catalysts in heterogeneous catalysis.
文摘在过去的十多年中,X射线自由电子激光器（X-ray Free Electron Laser,XFEL）的成功研制和快速发展,极大地推动了超快X射线光谱学实验技术的发展,并且在物理、化学和生物科学等不同研究领域获得了广泛的应用。通过飞秒激光脉冲对样品的激发,X射线可以在不同时间尺度下,跟踪固态、液态和气态等各种情况下样品的微观结构动力学过程。X射线吸收和发射光谱,衍射和散射是探测激光诱导结构变化的典型工具。文章将介绍近年来飞秒X射线技术的发展,及其在化学与能源材料领域的应用。相信随着上海X射线自由电子激光器的建成,将使得飞秒X射线技术在更多的科学领域发挥作用。
文摘In-plane heteroatom substitution of graphene is a promising strategy to modify its properties. The ability to dope graphene with electron-donor nitrogen heteroatoms is highly important for modulating electrical properties of graphene. Here we demonstrate a transfer-free method to directly grow large area quasi free-standing N-doped graphene bilayers on an insulating substrate （Si3N4）. Electron-bombardment heating under nitrogen flux results in simultaneous growth of N-doped graphene and a Si3N4 layer on the SiC surface. The decoupling of N-doped graphene from the substrate and the presence of Si3N4 are identified by X-ray photoemission spectroscopy and low-energy electron diffraction. The substitution of nitrogen atoms in the graphene planes was confirmed using high resolution X-ray photoemission spectroscopy which reveals several atomic configurations for the nitrogen atoms： Graphitic-like, pyridine-like, and pyrrolic- like. Furthermore, we demonstrated for the first time that N-doped graphene could be used to efficiently probe oxygen molecules via nitrogen atom defects.
文摘The remarkable properties of graphene have shown promise for new perspectives in future electronics, notably for nanometer scale devices. Here we grow graphene epitaxially on an off-axis 4H-SiC（0001） substrate and demonstrate the formation of periodic arrangement of monolayer graphene on planar （0001） terraces and Bernal bilayer graphene on （1120） nanofacets of SiC. We investigate these lateral superlattices using Raman spectroscopy, atomic force microscopy/ electrostatic force microscopy （AFM/EFM） and X-ray and angle resolved photoemission spectroscopy （XPS/ARPES）. The correlation of EFM and ARPES reveals the appearance of permanent electronic band gaps in AB-stacked bilayer graphene on （1120） SiC nanofacets of 150 meV. This feature is confirmed by density functional theory （DFT） calculations. The charge transfer between the substrate and graphene bilayer results in an asymmetric charge distribution between the top and the bottom graphene layers opening an energy gap. This surface organization can be thus defined as self-organized metal-semiconductor graphene.
基金supported by Guangdong Natural Science Foundation(2019A1515010675)the Science and Technology Project of Shenzhen(JCYJ20180305125106329,KQJSCX20180328094001794)。
文摘With the ever-increasing demands of grid-scale energy storage,aqueous zinc-ion batteries(ZIBs)have garnered increasing attention around the world.However,limited Zn^(2+)host materials have hindered the commercialization of ZIBs.Hence,Mo-V oxides with different phase structures(orth-,tri-,and tetra-MoVO)were precisely constructed to develop phase-dependent Mo-V oxide cathodes for Zn^(2+)storage in ZIBs.The open frameworks and varied tunnel structures formed a favorable alternative for achieving suitable Zn^(2+)diffusion kinetics.With optimized phase engineering,the high specific capacity of approximately 400 mA h g^(−1) and excellent cyclic stability of 1000 cycles were achieved with orth-MoVO as the cathode.The large amount of six-and seven-member rings in the orth-MoVO phase,which allow for alternative Zn^(2+)insertion,play a vital role in hosting Zn^(2+)ions reversibly.The proposed phase engineering strategy provides a new approach toward cathode design in ZIBs.
