Investigation of Electron-Phonon Coupling in Epitaxial Silicene by In-situ Raman Spectroscopy

In this letter, we report that the special coupling between Dirac fermion and lattice vibrations, in other words, electron-phonon coupling (EPC), in silicene layers on Ag(111) surface was probed by an in-situ Raman spectroscopy. We find the EPC is significantly modulated due to tensile strain, which results from the lattice mismatch between silicene and the substrate, and the charge doping from the substrate. The special phonon modes corresponding to two-dimensional electron gas scattering at edge sites in the silicene were identified. Detecting relationship between EPC and Dirac fermion through the Raman scattering will provide a direct route to investigate the exotic property in buckled two-dimensional honeycomb materials.Comment: 15 pages, 4 figure

Promoted Photocharge Separation in 2D Lateral Epitaxial Heterostructure for Visible‐Light‐Driven CO2 Photoreduction

Photocarrier recombination remains a big barrier for the improvement of solar energy conversion efficiency. For 2D materials, construction of heterostructures represents an efficient strategy to promote photoexcited carrier separation via an internal electric field at the heterointerface. However, due to the difficulty in seeking two components with suitable crystal lattice mismatch, most of the current 2D heterostructures are vertical heterostructures and the exploration of 2D lateral heterostructures is scarce and limited. Here, lateral epitaxial heterostructures of BiOCl @ Bi2O3 at the atomic level are fabricated via sonicating‐assisted etching of Cl in BiOCl. This unique lateral heterostructure expedites photoexcited charge separation and transportation through the internal electric field induced by chemical bonding at the lateral interface. As a result, the lateral BiOCl @ Bi2O3 heterostructure demonstrates superior CO2 photoreduction properties with a CO yield rate of about 30 µmol g−1 h−1 under visible light illumination. The strategy to fabricate lateral epitaxial heterostructures in this work is expected to provide inspiration for preparing other 2D lateral heterostructures used in optoelectronic devices, energy conversion, and storage fields

Promoted Photocharge Separation in 2D Lateral Epitaxial Heterostructure for Visible-Light-Driven CO2 Photoreduction

Photocarrier recombination remains a big barrier for the improvement of solar energy conversion efficiency. For 2D materials, construction of heterostructures represents an efficient strategy to promote photoexcited carrier separation via an internal electric field at the heterointerface. However, due to the difficulty in seeking two components with suitable crystal lattice mismatch, most of the current 2D heterostructures are vertical heterostructures and the exploration of 2D lateral heterostructures is scarce and limited. Here, lateral epitaxial heterostructures of BiOCl @ Bi2O3 at the atomic level are fabricated via sonicating-assisted etching of Cl in BiOCl. This unique lateral heterostructure expedites photoexcited charge separation and transportation through the internal electric field induced by chemical bonding at the lateral interface. As a result, the lateral BiOCl @ Bi2O3 heterostructure demonstrates superior CO2 photoreduction properties with a CO yield rate of about 30 µmol g−1 h−1 under visible light illumination. The strategy to fabricate lateral epitaxial heterostructures in this work is expected to provide inspiration for preparing other 2D lateral heterostructures used in optoelectronic devices, energy conversion, and storage fields

Silicene: A Promising Anode for Lithium-Ion Batteries

Silicene, a single-layer-thick silicon nanosheet with a honeycomb structure, is successfully fabricated by the molecular-beam-epitaxy (MBE) deposition method on metallic substrates and by the solid-state reaction method. Here, recent progress on the features of silicene that make it a prospective anode for lithium-ion batteries (LIBs) are discussed, including its charge-carrier mobility, chemical stability, and metal-silicene interactions. The electrochemical performance of silicene is reviewed in terms of both theoretical predictions and experimental measurements, and finally, its challenges and outlook are considered

Electronic Band Engineering in Elemental 2D Materials

Research on 2D materials is one of the leading topics in the fields of condensed matter physics and materials science, due to their novel properties which are absent in their bulk allotropes. The 2D limitation provides great flexibility to engineer the electronic properties, which is crucial for innovative device applications. In this review, the recent research on the electronic properties of elemental 2D materials, which do not exist in nature, is focused. These 2D materials are stabilized by their underlying substrates, leading to the abundant buckled structures. The buckling can break symmetries, making it possible to explore new emerging physics, such as topological superconductivity, valley-polarized metals, and the quantum spin Hall effect in these 2D materials. The relationship between the degree of buckling and the electronic structures in these 2D materials is reviewed from both the experimental side and simulation results, and finally, the challenges and outlook for this field are discussed

Dirac Signature in Germanene on Semiconducting Substrate

2D Dirac materials supported by nonmetallic substrates are of particular interest due to their significance for the realization of the quantum spin Hall effect and their application in field-effect transistors. Here, monolayer germanene is successfully fabricated on semiconducting germanium film with the support of a Ag(111) substrate. Its linear-like energy-momentum dispersion and large Fermi velocity are derived from the pronounced quasiparticle interference patterns in a √3 x √3 superstructure. In addition to Dirac fermion characteristics, the theoretical simulations reveal that the energy gap opens at the Brillouin zone center of the √3 x √3 restructured germanene, which is evoked by the symmetry-breaking perturbation potential. These results demonstrate that the germanium nanosheets with √3 x √3 germanene can be an ideal platform for fundamental research and for the realization of high-speed and low-energy-consumption field-effect transistors

In-situ grafting of N-doped carbon nanotubes with Ni encapsulation onto MOF-derived hierarchical hybrids for efficient electrocatalytic hydrogen evolution

© 2020 Elsevier Ltd Developing highly efficient and cost-effective catalysts for the hydrogen evolution reaction (HER) is of paramount importance to solve the problems arising from the depletion of non-renewable fossil fuels and increasing air pollution issues. Herein, an in-situ heterogeneous catalytic synthesis approach is developed for constructing hierarchical Ni/carbon hybrids via grafting nitrogen-doped-carbon (NC) nanotubes with Ni encapsulation onto the metal-organic framework (MOF)-derived carbon matrix. Following the “nanotube tip-growth model” involved in the in-situ catalytic synthesis process, the morphology and size of the nanotubes and encapsulated particles of the as-prepared hierarchical Ni-based carbon hybrids can be controlled by regulating the conditions during the thermal decomposition of the Ni-MOF in the presence of melamine. The grafting and decoration of the Ni-encapsulated carbon nanotubes on the MOF-derived architecture rapidly enhance the HER electrocatalytic performance of the bare thermally decomposed Ni/N-doped carbon composite. Due to the synergistic effects of the stable metallic Ni active sites and the N-doped carbon support, the optimized Ni@NC6-600 sample exhibits stable and high catalytic activity, only requiring an overpotential of 181 mV to drive 10 mA/cm2 towards the HER in alkaline media