Rational design of vitamin C/defective carbon van der Waals heterostructure for enhanced activity,durability and storage stability toward oxygen reduction reaction

Metal-free defective carbon materials with abundant active sites have been widely studied as low-cost and efficient oxygen reduction reaction(ORR)electrocatalysts in metal-air batteries.However,the active sites in defective carbon are easily subjected to serious oxidation or hydroxylation during ORR or storage,leading to rapid degradation of activity.Herein,we design a van der Waals heterostructure comprised of vitamin C(VC)and defective carbon(DC)to not only boost the activity but also enhance the durability and storage stability of the DC-VC electrocatalyst.The formation of VC van der Waals between DC and VC is demonstrated to be an effective strategy to protect the defect active sites from oxidation and hydroxylation degradation,thus significantly enhancing the electrochemical durability and storage anti-aging performance.Moreover,the DC-VC van der Waals can reduce the reaction energy barrier to facilitate the ORR.These findings are also confirmed by operando Fourier transform infrared spectroscopy and density functional theory calculations.It is necessary to mention that the preparation of this DC-VC electrocatalyst can be scaled up,and the ORR performance of the largely produced electrocatalyst is demonstrated to be very consistent.Furthermore,the DC-VC-based aluminum-air batteries display very competitive power density with good performance maintenance.

Strategies for Scalable Gas-Phase Preparation of Free-Standing Graphene

The preparation of graphene with high quality serves as a prerequisite for its usage.Traditional methods of graphene production,represented by liquid-phase exfoliation and chemical vapor deposition,either sacrifice the quality and purity of graphene or are limited by the substrate and catalyst.Developing simple and scalable preparation methods of high-quality and high-purity graphene remains a big challenge.Herein,we have reviewed the gas-phase methods including carbonization,combustion,arc discharge,and atmospheric plasma for scalable preparation of free-standing graphene,which are catalyst-,substrate-,solvent-free,and without the need for complex post-treatment methods.The obtained graphene exhibits characteristics of high quality and high purity.Moreover,applications of free-standing graphene were also summarized.Finally,perspectives on opportunities and challenges of free-standing graphene have been discussed.

Anisotropic electrical properties of aligned PtSe_(2) nanoribbon arrays grown by a pre-patterned selective selenization process

This study proposes a feasible and scalable production strategy to naturally obtain aligned platinum diselenide(PtSe_(2))nanoribbon arrays with anisotropic conductivity.The anisotropic properties of two-dimensional(2D)materials,especially transition-metal dichalcogenides(TMDs),have attracted great interest in research.The dependence of physical properties on their lattice orientations is of particular interest because of its potential in diverse applications,such as nanoelectronics and optoelectronics.One-dimensional(1D)nanostructures facilitate many feasible production strategies for shaping 2D materials into unidirectional 1D nanostructures,providing methods to investigate the anisotropic properties of 2D materials based on their lattice orientations and dimensionality.The natural alignment of zigzag(ZZ)PtSe_(2) nanoribbons is experimentally demonstrated using angle-resolved polarized Raman spectroscopy(ARPRS),and the selective growth mechanism is further theoretically revealed by comparing edges and edge energies of different orientations using the density functional theory(DFT).Back-gate field-effect transistors(FETs)are also constructed of unidirectional PtSe_(2) nanoribbons to investigate their anisotropic electrical properties,which align with the results of the projected density of states(DOS)calculations.This work provides new insight into the anisotropic properties of 2D materials and a feasible investigation strategy from experimental and theoretical perspectives.

一种超快的碲化法用于非常规相控碲化钯小纳米颗粒的合成

本研究发展了一种超快的碲化方法,可以在碳纳米管上快速制备非常规相控碲化钯小纳米颗粒.这种碲化方法只需要一台家用微波炉,整个过程非常快(60秒),简单,不含表面活性剂,可规模化生产.通过在相同条件下仅调整前驱体Te粉的使用量,可以精确调控合成小尺寸(约5.5 nm)、高产率(约90%)的六方结构PdTe/CNT和菱方结构Pd_(20)Te_7/CNT.其中,六方结构的PdTe/CNT在甘油氧化反应(GOR)和乙二醇氧化反应(EGOR)中表现出卓越的性能.具体来说,六方结构的PdTe/CNT在甘油氧化反应中,最高电流密度可达2.72 A mg_(Pd)^(-1),比菱方结构Pd_(20)Te_7/CNT的最高电流密度高1.9倍,比Pd/CNT最高电流密度高2.8倍,超过了目前文献中报道过的大多数催化剂.同时,六方结构的PdTe/CNT在乙二醇氧化反应中比活性达到3.65 A mg_(pd)^(-1),比菱方结构的Pd_(20)Te_7/CNT和Pd/CNT分别高2.1倍和3.9倍.我们希望这项工作可以为小尺寸非常规相控碲化物催化剂的制备提供新的碲化方法指导,并为相控材料的应用提供启发.