Sandwiching Sulfur into the Dents Between N,O Co-Doped Graphene Layered Blocks with Strong Physicochemical Confinements for Stable and High-Rate Li-S Batteries

The development of lithium-sulfur batteries(LSBs)is restricted by their poor cycle stability and rate performance due to the low conductivity of sulfur and severe shuttle effect.Herein,an N,O co-doped graphene layered block(NOGB)with many dents on the graphene sheets is designed as effective sulfur host for high-performance LSB s.The sulfur platelets are physically confined into the dents and closely contacted with the graphene scaffold,ensuring structural stability and high conductivity.The highly doped N and O atoms can prevent the shuttle effect of sulfur species by strong chemical adsorption.Moreover,the micropores on the graphene sheets enable fast Li^+transport through the blocks.As a result,the obtained NOGB/S composite with 76 wt%sulfur content shows a high capacity of 1413 mAh g^-1 at 0.1 C,good rate performance of 433 mAh g^-1 at 10 C,and remarkable stability with 526 mAh g^-1 at after 1000 cycles at 1 C(average decay rate:0.038%per cycle).Our design provides a comprehensive route for simultaneously improving the conductivity,ion transport kinetics,and preventing the shuttle effect in LSBs.

3D Carbon Frameworks for Ultrafast Charge/Discharge Rate Supercapacitors with High Energy‑Power Density

Carbon-based electric double layer capacitors(EDLCs)hold tremendous potentials due to their high-power performance and excellent cycle stability.However,the practical use of EDLCs is limited by the low energy density in aqueous electrolyte and sluggish diffusion kinetics in organic or/and ionic liquids electrolyte.Herein,3D carbon frameworks(3DCFs)constructed by interconnected nanocages(10-20 nm)with an ultrathin wall of ca.2 nm have been fabricated,which possess high specific surface area,hierarchical porosity and good conductive network.After deoxidization,the deoxidized 3DCF(3DCFDO)exhibits a record low IR drop of 0.064 V at 100 A g^−1 and ultrafast charge/discharge rate up to 10 V s^−1.The related device can be charged up to 77.4%of its maximum capacitance in 0.65 s at 100 A g^−1 in 6 M KOH.It has been found that the 3DCF-DO has a great affinity to EMIMBF4,resulting in a high specific capacitance of 174 F g^−1 at 1 A g^−1,and a high energy density of 34 Wh kg^−1 at an ultrahigh power density of 150 kW kg^−1 at 4 V after a fast charge in 1.11 s.This work provides a facile fabrication of novel 3D carbon frameworks for supercapacitors with ultrafast charge/discharge rate and high energy-power density.

Recent Developments of Transition Metal Compounds-Carbon Hybrid Electrodes for High Energy/Power Supercapacitors

Due to their rapid power delivery,fast charging,and long cycle life,supercapacitors have become an important energy storage technology recently.However,to meet the continuously increasing demands in the fields of portable electronics,transportation,and future robotic technologies,supercapacitors with higher energy densities without sacrificing high power densities and cycle stabilities are still challenged.Transition metal compounds(TMCs)possessing high theoretical capacitance are always used as electrode materials to improve the energy densities of supercapacitors.However,the power densities and cycle lives of such TMCs-based electrodes are still inferior due to their low intrinsic conductivity and large volume expansion during the charge/discharge process,which greatly impede their large-scale applications.Most recently,the ideal integrating of TMCs and conductive carbon skeletons is considered as an effective solution to solve the above challenges.Herein,we summarize the recent developments of TMCs/carbon hybrid electrodes which exhibit both high energy/power densities from the aspects of structural design strategies,including conductive carbon skeleton,interface engineering,and electronic structure.Furthermore,the remaining challenges and future perspectives are also highlighted so as to provide strategies for the high energy/power TMCs/carbon-based supercapacitors.

Advanced carbon materials with different spatial dimensions for supercapacitors

Supercapacitors(SCs)have attracted extensive attention due to their ultrahigh power density,fast charging/discharging rate,excellent electrochemical stability and environmental friendliness.Currently,the main commercial electrode materials for SCs are carbon materials in term of low cost,excellent conductivity,large specific surface area and good electrochemical stability.Recently,various dimensional carbon materials including zero dimensional(0D)carbon materials(nanosphere,dot etc.),1D carbon materials(nanotube,nanofiber etc.),2D carbon materials(nanosheet)as well as 3D carbon materials have been developed for SCs.Carbon materials with different spatial dimensions have their unique properties when used as the electrode materials for SCs.In this review,recent advances in the fabrication of different dimensional carbons for SCs are summarized.Several key issues for enhancing the electrochemical properties of carbon-based SCs and some mutual relationships among various influence parameters are reviewed,and challenges and perspectives in this field are also discussed.

Nickel Sulfide/Graphene/Carbon Nanotube Composites as Electrode Material for the Supercapacitor Application in the Sea Flashing Signal System

这个工作介绍 NiS/graphene/carbon nanotube (NiS/GNS/CNT ) 是的 composites 为在海闪光的 supercapacitor 应用程序的电极材料信号系统。NiS nanosheets 仔细在传导性的 GNS-CNT 网络上被抛锚。作为结果， NiS/GNS/CNT 电极显示出 2 377 F 的一个高特定的电容 ? 獵湩 ? 剘? 湡 ? 桴 ? 楰瑴湩 ? 湯愠畬業楮浵愠 ?? 敲?瑬漠 ? 慧癬湡捩挠牯潲楳湯眠獡栠杩汨杩?摥椠 ? 整浲 ? 景瀠瑩搠灥桴 ? 楳敺愠摮搠湥楳祴漠 ? 楰? 甠楳杮愠栠杩 ?敲潳畬楴湯洠捩潲 '

Effect of ultramicropores and inner space of carbon materials on the capacitive sodium storage performance

1.Introduction Carbon materials have been widely investigated as the anode materials for Na+storage due to their moderate capacity,good stability,and low cost.The Na+storage mechanisms of carbon are generally classified into diffusion-controlled interlayer insertion/desertion and capacitive-controlled surface adsorption/desorption[1].

A facial synthesis of nitrogen-doped reduced graphene oxide quantum dot and its application in aqueous organics degradation

N-doped reduced graphene oxide quantum dots(N-rGQDs) have attracted more and more attention in efficient catalytic degradation of aqueous organic pollutants.However,the synthesis of N-rGQDs is generally a complex and high energy required process for the reduction and N-doping steps.In this study,a facile and green fabrication approach of N-rGQDs is established,based on a metal-free Fenton reaction without additional energy-input.The N structures of N-rGQDs play a significant role in the promotion of their catalytic performance.The N-rGQDs with relatively high percentage of aromatic nitrogen(NAr-rGQDs) perform excellent catalytic activities,with which the degradation efficiency of pollutant is enhanced by 25 times.Density functional theory(DFT) calculation also indicates aromatic nitrogen structures with electron-rich sites are prone to transfer electron,presenting a key role in the catalytic reaction.This metal-free Fenton process provides a green and costeffective strategy for one-step fabrication of N-rGQDs with controllable features and potential environmental catalytic applications.

Toward the Design of High-performance Supercapacitors by Prussian Blue, its Analogues and their Derivatives

Supercapacitors(SCs)with high power output have attracted increasing attention as efficient and environmentally friendly energy storage devices.Prussian blue and its analogues(PB/PBAs)are simple coordination polymers with tunable chemical compositions and open framework.Prussian blue can act as electrode materials in its pristine form and has also been utilized to derive various metallic nanostructures for electrochemical applications due to their simple fabrication process,non-toxic characteristics,and low price.Here,we firstly describe the charge storage mechanisms of SCs briefly followed by an introduction of the fabrication methods of PB/PBAs and their derivatives.Then,a comprehensive review on recent studies of the use of PB/PBAs and their derivatives as the electrode materials for SCs are given with a focus on strategies to improve their electrochemical performances.Finally,we discuss critical challenges in this research area and propose some general ideas for future research.

Interfacial engineering of atomic platinum-doped molybdenum carbide quantum dots for high-rate and stable hydrogen evolution reaction in proton exchange membrane water electrolysis

Platinum(Pt)-based electrocatalysts remain the only practical cathode catalysts for proton exchange membrane water electrolysis(PEMWE),due to their excellent catalytic activity for acidic hydrogen evolution reaction(HER),but are greatly limited by their low reserves and high cost.Here,we report an interfacial engineering strategy to obtain a promising low-Pt loading catalyst with atomically Pt-doped molybdenum carbide quantum dots decorated on conductive porous carbon(Pt-MoCx@C)for high-rate and stable HER in PEMWE.Benefiting from the strong interfacial interaction between Pt atoms and the ultra-small MoCx quantum dots substrate,the Pt-MoCx catalyst exhibits a high mass activity of 8.00 A·mgPt−1,5.6 times higher than that of commercial 20 wt.%Pt/C catalyst.Moreover,the strong interfacial coupling of Pt and MoCx substrate greatly improves the HER stability of the Pt-MoCx catalyst.Density functional theory studies further confirm the strong metal-support interaction on Pt-MoCx,the critical role of MoCx substrate in the stabilization of surface Pt atoms,as well as activation of MoCx substrate by Pt atoms for improving HER durability and activity.The optimized Pt-MoCx@C catalyst demonstrates>2000 h stability under a water-splitting current of 1000 mA·cm^(−2)when applied to the cathode of a PEM water electrolyzer,suggesting the potential for practical applications.

One-step synthesis of biomass derived O, N-codoped hierarchical porous carbon with high surface area for supercapacitors

We report a convenient method to synthesize O,N-codoped hierarchical porous carbon by one-step carbonization of the mixture of KHCO3,urea and alginic acid.Benefiting from KHCO3 and urea syne rgistic effect,the obtained O,N-codoped hierarchical porous carbon(NPC-700) material has a well-developed interconnected porous framework with ultrahigh specific surface area(2846 m2/g) and massive heteroatoms functional groups.Consequence,such porous carbon displays high specific capacitance(324 F/g at 1 A/g),excellent rate performance(212 F/g at 30 A/g) and good electrochemical stabilization in 6 mol/L KOH solution.More importantly,the assembled NPC-700//NPC-700 symmetrical supercapacitor can achieve a high energy density of 18.8 Wh/kg and good electrochemical stabilization in 1 mol/L Na2SO4 solution.This process opens up a new way to design heteroatoms-doped hierarchical porous carbon derived from biomass materials for supercapacitors.

Porphyrin-based heterogeneous photocatalysts for solar energy conversion

In recent years,porphyrins with a similar structure to chlorophyll are often used as photosensitizers or reaction centers to improve the light absorption capacity or catalytic selectivity of existing photocatalytic systems.However,photocatalytic reactions include photoelectric conversion,photocarrier transport,and surface reaction,which requires the overall design of porphyrin-based photocatalysts.In this paper,the research work of porphyrin molecular design in heterogeneous photocatalysis in recent years is reviewed.Besides,the application of interface control and spatial confinement effect in porphyrin-based hybrid photocatalyst is introduced.Finally,the future development direction of porphyrin-based photocatalysts is prospected and the main challenges in the research of porphyrin-based photocatalysts are given.

Design of layered-stacking graphene assemblies as advanced electrodes for supercapacitors

Graphene is a competitive electrode material for supercapacitors due to its unique two-dimensional structure,large surface area,high conductivity,and good physicochemical stability.However,random agglomeration and restacking of graphene sheets result in a reduced surface area and a loose structure with low density,which severely restricts the application for high gravimetric/volumetric energy density devices.Rational design of the layered-stacking structure of graphene assemblies can effectively prevent the restacking of graphene sheets,construct efficient ion transport channels,and improve spatial utilization,demonstrating the huge potential for developing advanced electrode materials.Herein,from the aspect of improving the electrochemical kinetics through designing efficient electron and ion transport paths,we first highlight the advantages of layered-stacking graphene assemblies,describe some common routes for preparing graphene building units,and then summarize the novel methods to design layered-stacking structures.A comprehensive review of the typical structure including nanocarbon pillared graphene,porous graphene blocks,and graphene ribbon films is provided with a focus on the mechanisms behind the performance improvements.Finally,critical challenges and some general ideas for future development are proposed,which may open up new opportunities for material chemistry and device innovation.

Holey graphene oxide-templated construction of nano nickel-based metal–organic framework for highly efficient asymmetric supercapacitor

Metal–organic frameworks(MOFs)with redox-active metal sites and controllable crystalline structures make it possible to access the merits of highly-efficient electrode materials in electrochemical energy storage systems.However,most MOFs suffer from low capacitance and poor cycling stability that largely thwart their application.Herein,we present the holey graphene oxide(HGO)template strategy to prepare nano two-dimensional Ni(BDC)with HGO as both template and capping agent(denoted as Ni(BDC)-HGOx,x=10,20,30,and 40 according to the added HGO amount).Structural analyses reveal that HGO can significantly inhibit the Ni(BDC)agglomeration,thus offering a high ion-accessible surface area.Ni(BDC)-HGO30 with well-exposed active sites exhibits a high capacitance of 1,115.6 F·g^(−1) at 1 A·g^(−1) in 6 M KOH aqueous,1.8 times that of bulk Ni(BDC).An asymmetric supercapacitor with Ni(BDC)-HGO30 as a positive electrode and activated carbon as the opposing electrode delivers an energy density of 52.5 W·h·kg^(−1) and a power density up to 18.0 kW·kg−1,with 92.5%capacitance retention after 10,000 cycles.Galvanostatic intermittent titration technique and in situ electrochemical–Raman measurements were exploited to elucidate the electrochemical behavior of Ni(BDC)-HGO30.These results pave the way for the development of rationally tuned MOF materials for enhancing supercapacitor performances.

In situ rapid versatile method for the preparation of zirconium metal-organic framework filters

The development of the rapid preparation of highly stable metal-organic framework(MOF)-based devices provides the possibility of meeting the increasing demands of MOF in industrial applications.However,MOFs experience poor processability and stable high-valence-metal(Ⅳ)-based MOFs favor forming either thermodynamically stable metal hydroxides or oxides during their growth and nucleation,which hinders their practical applications.Herein,we present a versatile deep eutectic solvent(DES)-assisted hot pressing method to in situ rapidly prepare six distinct zirconium-based MOF nanocrystals on fibers(denoted as Zr-MOFilters)within 20 min.A small amount of DES promotes MOF precursor contact and accelerates Zr-MOF growth.Temperature and pressure facilitate the formation of Zr-MOFs onto desired substrates.In situ1H nuclear magnetic resonance spectra and time-dependent Fourier-transform infrared spectra were conducted to elucidate the growth of Zr-MOF nanocrystals.As a proof-of-concept,the abilities of Zr-MOFilters for Cr_(2)O_(7)^(2−) and micro(nano)plastics removal have been demonstrated.This strategy paves the way for the rapid fabrication of highly stable MOF-based devices and brings MOFs a step closer to practical application.