An integrated strategy towards the facile synthesis of core-shell SiC-derived carbon@N-doped carbon for high-performance supercapacitors

Porous active core-shell carbon material with excellent synergistic effect has been regarded as a prospective material for supercapacitors.Herein,we report an integrated method for the facile synthesis of carbide-derived carbon(CDC)encapsulated with porous N-doped carbon(CDC@NC)towards highperformance supercapacitors.Polydopamine(PDA)as nitrogen and carbon sources was simply coated on SiC nanospheres to form SiC@PDA,which was then directly transformed into CDC@NC via a onestep molten salt electro-etching/in-situ doping process.The synthesized CDC@NC with hierarchically porous structure has a high specific surface area of 1191 m^(2) g^(-1).The CDC core and NC shell are typical amorphous carbon and more ordered N-doped carbon,respectively.Benefitting from its unique dual porous structures,the CDC@NC demonstrates high specific capacitances of 255 and 193 F g^(-1) at 0.5 and20 A g^(-1),respectively.The reaction mechanism of the electro-etching/in-situ doping process has also been investigated through experimental characterizations and theoretical density functional theory calculations.It is suggested that the molten salt electro-etching/in-situ doping strategy is promising for the synthesis of active core-shell porous carbon materials with synergistic properties for supercapacitors without the need for additional doping/activation processes.

半金属氢氧化物材料用于电化学水氧化

寻找具有高本征活性的水氧化催化剂材料对许多清洁能源技术的发展至关重要.氢氧化物半导体对析氧反应具有一定的电催化活性.然而,该材料导电性较差,限制着其电催化本征活性的提升.本文提出一种兼具高导电性和高催化活性的半金属氢氧化物析氧电催化材料.通过阳离子掺杂和阴离子空位协同作用,镍铁水滑石半导体可转化为半金属材料,其电阻率降低了两个数量级.相应半金属氢氧化物阵列电极的电催化活性显著提升,在10 mA cm^(-2)电流密度下其析氧过电势仅为195 mV,Tafel斜率仅为40.9 mV dec^(-1),显著优于商用RuO_(2)催化剂(316 mV,99.6 mV dec^(-1)).原位拉曼光谱和理论计算结果表明,半金属氢氧化物可在较低过电位下转化为羟基氧化物中间体,有助于高价态金属活性位点的形成与稳定,从而提升材料的析氧本征活性.本研究表明,兼具优异导电性和催化活性的半金属氢氧化物可作为先进的电极材料.

Low-temperature selective synthesis of metastableα-MoC with electrochemical properties:Electrochemical co-reduction of CO_(2)and MoO_(3)in molten salts

Metastable molybdenum carbide(α-MoC),as a catalyst and an excellent support for metal catalysts,has been widely used in thermo/electro-catalytic reactions.However,the selective synthesis ofα-MoC remains a great challenge.Herein,a simple one-pot synthetic strategy for the selective preparation of metastableα-MoC is proposed by electrochemical co-reduction of CO_(2)and MoO_(3)in a low-temperature eutectic molten carbonate.The synthesizedα-MoC shows a reed flower-like morphology.By controlling the electrolysis time and monitoring the phase and morphology of the obtained products,the growth process ofα-MoC is revealed,where the carbon matrix is deposited first followed by the growth ofα-MoC from the carbon matrix.Moreover,by analyzing the composition of the electrolytic products,the formation mechanism forα-MoC is proposed.In addition,through this one-pot synthetic strategy,S-dopedα-MoC is successfully synthesized.Density functional theory(DFT)calculations reveal that S doping enhanced the HER performance ofα-MoC by facilitating water absorption and dissociation and weakening the bond energy of Mo-H to accelerate H desorption.The present work not only highlights the valuable utilization of CO_(2) but also offers a new perspective on the design and controllable synthesis of metal carbides and their derivatives.

Recent Advances in Electrochemical-Based Silicon Production Technologies with Reduced Carbon Emission

Sustainable and low-carbon-emission silicon production is currently one of the main focuses for the metallurgical and materials science communities.Electrochemistry,considered a promising strategy,has been explored to produce silicon due to prominent advantages:(a)high electricity utilization efficiency;(b)low-cost silica as a raw material;and(c)tunable morphologies and structures,including films,nanowires,and nanotubes.This review begins with a summary of early research on the extraction of silicon by electrochemistry.Emphasis has been placed on the electro-deoxidation and dissolution–electrodeposition of silica in chloride molten salts since the 21st century,including the basic reaction mechanisms,the fabrication of photoactive Si films for solar cells,the design and production of nanoSi and various silicon components for energy conversion,as well as storage applications.Besides,the feasibility of silicon electrodeposition in room-temperature ionic liquids and its unique opportunities are evaluated.On this basis,the challenges and future research directions for silicon electrochemical production strategies are proposed and discussed,which are essential to achieve large-scale sustainable production of silicon by electrochemistry.

Gap engineering of sandwich plasmonic gap nanostructures for boosting plasmon-enhanced electrocatalysis

Plasmonic catalysis is emerging as a dynamic field in heterogeneous catalysis and holds great promise for the efficient utilization of solar energy.Central to the development of plasmonic catalysis is the design of efficient plasmonic nanocatalysts.In this report,plasmonic gap nanostructures(PGNs)on the basis of Au@poly(o-phenylenediamine)(POPD)@Pd sandwich nanostructures are synthesized as plasmonic nanocatalysts by an in-situ reduction synthetic strategy,which allows for the precise engineering of the POPD gap size between plasmonic Au and catalytic Pd components.The introduction of conducting POPD nanogap in PGNs not only effectively enhances their light harvesting capability,but also provides an effective charge transfer channel for harnessing the photogenerated hot charge carriers.In this respect,distinct gap-dependent performances in plasmon-enhanced electrocatalysis of ethanol oxidation reactions(EOR)are demonstrated with the PGN nanocatalysts and over 2.5 folds of enhancement can be achieved.A volcano plot is derived to describe the relationship between the catalytic activities and gap size of the PGN nanocatalysts,which is well explained by the interplay of their light harvesting and charge transport capabilities.These results highlight the importance of gap engineering in PGNs for plasmonic catalysis and offer the promise of developing efficient plasmonic nanocatalysts for other heterogeneous catalytic reactions.

Engineering Colloidal Metal-Semiconductor Nanorods Hybrid Nanostructures for Photocatalysis

Emerging engineering strategies of colloidal metal-semiconductor nanorod hybrid nanostructures spanning from type,size,dimension,and location of both metal nanoparticles and semiconductors,co-catalyst,band gap structure,surface ligand to hole scavenger are elaborated symmetrically to rationalize the design of this type of intriguing materials for efficient photocatalytic applications.

Enhanced visible-light-driven heterogeneous photocatalytic CO_(2) methanation using a Cu_(2)O@Cu-MOF-74 thin film

Cuprous oxide is a potential photocatalyst for the reduction of CO_(2).However,its high rate of charge recombina-tion and low ability to adsorb CO_(2) limit its activity,particularly when gaseous CO_(2) was used.Herein,a Cu-based metal-organic framework(Cu-MOF-74)with high CO_(2) adsorption is coated onto Cu_(2) O nanowires by a topotactic transformation method.The optimized Cu_(2) O@Cu-MOF-74 composite thin film showed a CH 4 evolution rate 4.5 times higher than that of bare Cu_(2) O under visible light illumination(>420 nm),with water vapor as the electron donor.Analysis results of electrochemical impedance spectroscopy,transient photocurrent measurements,and fluorescence spectroscopy collectively suggest that the decoration of Cu_(2) O with Cu-MOF-74 facilitates electron extraction from excited Cu_(2) O,thereby inducing long-lived photocharges for the reduction of CO_(2).This study provides insights into the modification of transition metal oxides for application in photocatalysis by coating the surface with metal-organic frameworks.