Ultrathin small MoS2nanosheets exhibit a higher electrocatalytic activity for the hydrogen evolution reaction.However,strong interactions between MoS2layers may result in aggregation;together with the low conductivity...Ultrathin small MoS2nanosheets exhibit a higher electrocatalytic activity for the hydrogen evolution reaction.However,strong interactions between MoS2layers may result in aggregation;together with the low conductivity of MoS2,this may lower its electrocatalytic activity.In this paper we present a method that we developed to directly produce solid S,N co‐doped carbon(SNC)with a graphite structure and multiple surface groups through a hydrothermal route.When Na2MoO4was added to the reaction,polymolybdate could be anchored into the carbon materials via a chemical interaction that helps polymolybdate disperse uniformly into the SNC.After a high temperature treatment,polymolybdate transformed into MoS2at800°C for6h in a N2atmosphere at a heating rate of5°C/min,owing to S2?being released from the SNC during the treatment(denoted as MoS2/SNC‐800‐6h).The SNC effectively prevents MoS2from aggregating into large particles,and we successfully prepared highly dispersed MoS2in the SNC matrix.Electrochemical characterizations indicate that MoS2/SNC‐900‐12h exhibits a low onset potential of115mV and a low overpotential of237mV at a current density of10mA/cm2.Furthermore,MoS2/SNC‐900‐12h also had an excellent stability with only^2.6%decay at a current density of10mA/cm2after5000test cycles.展开更多
Phosphorus doped silicon-carbon composite particles were synthesized through a DC arc plasma torch.Silane(SiH4) and methane(CH4) were introduced into the reaction chamber as the precursor of silicon and carbon,respect...Phosphorus doped silicon-carbon composite particles were synthesized through a DC arc plasma torch.Silane(SiH4) and methane(CH4) were introduced into the reaction chamber as the precursor of silicon and carbon,respectively.Phosphine(PH3) was used as a phosphorus dopant gas.Characterization of synthesized particles were carried out by scanning electron microscopy(SEM),X-ray diffractometry(XRD),X-ray photoelectron spectroscopy(XPS) and bulk resistivity measurement.Electrochemical properties were investigated by cyclic test and electrochemical voltage spectroscopy(EVS).In the experimental range,phosphorus doped silicon-carbon composite electrode exhibits enhanced cycle performance than intrinsic silicon and phosphorus doped silicon.It can be explained that incorporation of carbon into silicon acts as a buffer matrix and phosphorus doping plays an important role to enhance the conductivity of the electrode,which leads to the improvement of the cycle performance of the cell.展开更多
Graphite as a promising anode candidate of K-ion batteries(KIBs)has been increasingly studied currently,but corresponding rate performance and cycling stability are usually inferior to amorphous carbon materials.To pr...Graphite as a promising anode candidate of K-ion batteries(KIBs)has been increasingly studied currently,but corresponding rate performance and cycling stability are usually inferior to amorphous carbon materials.To protect the layer structure and further boost performance,tempura-like carbon/carbon nanocomposite of graphite@pitch-derived S-doped carbon(G@PSC)is designed and prepared by a facile and low-temperature modified molten salt method.This robust encapsulation structure makes their respective advantages complementary to each other,showing mutual promotion of electrochemical performances caused by synergy effect.As a result,the G@PSC electrode is applied in KIBs,delivering impressive rate capabilities(465,408,370,332,290,and 227 m A h g^(-1)at 0.05,0.2,0.5,1,2,and 5 A g^(-1))and ultralong cyclic stability(163 m A g^(-1)remaining even after 8000 cycles at 2 A g^(-1)).On basis of ex-situ studies,the sectionalized K-storage mechanism with adsorption(pseudocapacitance caused by S doping)-intercalation(pitch-derived carbon and graphite)pattern is revealed.Moreover,the exact insights into remarkable rate performances are taken by electrochemical kinetics tests and density functional theory calculation.In a word,this study adopts a facile method to synthesize high-performance carbon/carbon nanocomposite and is of practical significance for development of carbonaceous anode in KIBs.展开更多
Even though transition metal carbonates(TMCs, TM = Fe, Mn, Co, Ni etc.), show high theoretical capacities, rich reserves and environmental friendliness as anodes for lithium-ion batteries(LIBs), they suffer from slugg...Even though transition metal carbonates(TMCs, TM = Fe, Mn, Co, Ni etc.), show high theoretical capacities, rich reserves and environmental friendliness as anodes for lithium-ion batteries(LIBs), they suffer from sluggish electronic/ionic conductivities and huge volume variation, which severely deteriorate the rate capacities and cycling performances. Understanding the intrinsic reaction mechanism and further developing ideal TMC-based anode with high specific capacity, excellent rate capabilities, and longterm cycling stability are critical for the practical application of TMCs. In this review, we firstly focus on the fundamental electrochemical energy-storage mechanisms of TMCs, in terms of conversionreaction process, pseudocapacitance-type charge storage, valence change for charge storage and catalytic conversion mechanisms. Based on the reaction mechanisms, various modification strategies to improve the electrochemical performance of TMCs are summarized, covering:(i) micro-nano structural engineering, in which the influence factors on the morphology are discussed, and multiple architectures are listed;(ii) elemental doping, in which the intrinsic mechanisms of metal/nonmetal elements doping on the electrochemical performance are deeply explored;(iii) multifunctional compositing strategies, in which the specific affections on structure, electronic conductivity and chemo-mechanical stability are summarized.Finally, the key challenges and opportunities to develop high-performance TMCs are discussed and some solutions are also proposed. This timely review sheds light on the path towards achieving cost-effective and safe LIBs with high energy density and long cycling life using TMCs-based anode materials.展开更多
Tailored design and synthesis of high-quality electrocatalysts is vital for the advancement of oxygen evolution reaction(OER).Herein,we report a powerful puffing method to fabricate hierarchical porous N-doped carbon ...Tailored design and synthesis of high-quality electrocatalysts is vital for the advancement of oxygen evolution reaction(OER).Herein,we report a powerful puffing method to fabricate hierarchical porous N-doped carbon with numerous embedded Ni nanoparticles.Interestingly,during the puffing and annealing process,rice precursor with N and Ni sources can be in-situ converted into Ni-embedded N-doped porous carbon(N-PC/Ni) composite.The obtained N-PC/Ni composite possesses a cross-linked porous architecture containing conductive carbon backbone and active Ni nanoparticles electrocatalysts for OER.The pore formation in N-PC/Ni composite is also proposed because of carbothermic reduction.The N-PC/Ni composite is fully studied as electrocatalysts for OER.Due to increased active surface area,enhanced electronic conductivity and reactivity,the designed N-PC/Ni composite exhibits superior OER performance with a low Tafel slope(~88 mV/dec) and a low overpotential as well as excellent long-term stability in alkaline solution.Our proposed rational design strategy may provide a new way to construct other advanced metal/heteroatom-doped composites for widespread application in electrocatalysis.展开更多
基金supported by the National Natural Science Foundation of China(21671011)Beijing High-Level Talent program~~
文摘Ultrathin small MoS2nanosheets exhibit a higher electrocatalytic activity for the hydrogen evolution reaction.However,strong interactions between MoS2layers may result in aggregation;together with the low conductivity of MoS2,this may lower its electrocatalytic activity.In this paper we present a method that we developed to directly produce solid S,N co‐doped carbon(SNC)with a graphite structure and multiple surface groups through a hydrothermal route.When Na2MoO4was added to the reaction,polymolybdate could be anchored into the carbon materials via a chemical interaction that helps polymolybdate disperse uniformly into the SNC.After a high temperature treatment,polymolybdate transformed into MoS2at800°C for6h in a N2atmosphere at a heating rate of5°C/min,owing to S2?being released from the SNC during the treatment(denoted as MoS2/SNC‐800‐6h).The SNC effectively prevents MoS2from aggregating into large particles,and we successfully prepared highly dispersed MoS2in the SNC matrix.Electrochemical characterizations indicate that MoS2/SNC‐900‐12h exhibits a low onset potential of115mV and a low overpotential of237mV at a current density of10mA/cm2.Furthermore,MoS2/SNC‐900‐12h also had an excellent stability with only^2.6%decay at a current density of10mA/cm2after5000test cycles.
基金supported by a grant(code #05K1501-01920) from ‘Center for Nanostructured Materials Technology’ under ‘21st Century Frontier R&D Programs’ of the Ministry of Science and Technology,Korea
文摘Phosphorus doped silicon-carbon composite particles were synthesized through a DC arc plasma torch.Silane(SiH4) and methane(CH4) were introduced into the reaction chamber as the precursor of silicon and carbon,respectively.Phosphine(PH3) was used as a phosphorus dopant gas.Characterization of synthesized particles were carried out by scanning electron microscopy(SEM),X-ray diffractometry(XRD),X-ray photoelectron spectroscopy(XPS) and bulk resistivity measurement.Electrochemical properties were investigated by cyclic test and electrochemical voltage spectroscopy(EVS).In the experimental range,phosphorus doped silicon-carbon composite electrode exhibits enhanced cycle performance than intrinsic silicon and phosphorus doped silicon.It can be explained that incorporation of carbon into silicon acts as a buffer matrix and phosphorus doping plays an important role to enhance the conductivity of the electrode,which leads to the improvement of the cycle performance of the cell.
基金the financial support from the National Natural Science Foundation of China(No.91963118)the 111 Project(No.B13013)supported by the Open Project Program of Key Laboratory of Preparation and Application of Environmental Friendly Materials(Jilin Normal University),Ministry of Education,China(No.2020004)。
文摘Graphite as a promising anode candidate of K-ion batteries(KIBs)has been increasingly studied currently,but corresponding rate performance and cycling stability are usually inferior to amorphous carbon materials.To protect the layer structure and further boost performance,tempura-like carbon/carbon nanocomposite of graphite@pitch-derived S-doped carbon(G@PSC)is designed and prepared by a facile and low-temperature modified molten salt method.This robust encapsulation structure makes their respective advantages complementary to each other,showing mutual promotion of electrochemical performances caused by synergy effect.As a result,the G@PSC electrode is applied in KIBs,delivering impressive rate capabilities(465,408,370,332,290,and 227 m A h g^(-1)at 0.05,0.2,0.5,1,2,and 5 A g^(-1))and ultralong cyclic stability(163 m A g^(-1)remaining even after 8000 cycles at 2 A g^(-1)).On basis of ex-situ studies,the sectionalized K-storage mechanism with adsorption(pseudocapacitance caused by S doping)-intercalation(pitch-derived carbon and graphite)pattern is revealed.Moreover,the exact insights into remarkable rate performances are taken by electrochemical kinetics tests and density functional theory calculation.In a word,this study adopts a facile method to synthesize high-performance carbon/carbon nanocomposite and is of practical significance for development of carbonaceous anode in KIBs.
基金financially supported by the National Natural Science Foundation of China(51802091,51902102,22075074,U21A2081)the Outstanding Young Scientists Research Funds from Hunan Province(2020JJ2004)+3 种基金the Major Science and Technology Program of Hunan Province(2020WK2013)the China Postdoctoral Science Foundation(2020 M672478)the Natural Science Foundation of Hunan Province(2020JJ5035,2021JJ40047,2020JJ5042)the Major Science and Technology Program of Changsha(kq1804010)。
文摘Even though transition metal carbonates(TMCs, TM = Fe, Mn, Co, Ni etc.), show high theoretical capacities, rich reserves and environmental friendliness as anodes for lithium-ion batteries(LIBs), they suffer from sluggish electronic/ionic conductivities and huge volume variation, which severely deteriorate the rate capacities and cycling performances. Understanding the intrinsic reaction mechanism and further developing ideal TMC-based anode with high specific capacity, excellent rate capabilities, and longterm cycling stability are critical for the practical application of TMCs. In this review, we firstly focus on the fundamental electrochemical energy-storage mechanisms of TMCs, in terms of conversionreaction process, pseudocapacitance-type charge storage, valence change for charge storage and catalytic conversion mechanisms. Based on the reaction mechanisms, various modification strategies to improve the electrochemical performance of TMCs are summarized, covering:(i) micro-nano structural engineering, in which the influence factors on the morphology are discussed, and multiple architectures are listed;(ii) elemental doping, in which the intrinsic mechanisms of metal/nonmetal elements doping on the electrochemical performance are deeply explored;(iii) multifunctional compositing strategies, in which the specific affections on structure, electronic conductivity and chemo-mechanical stability are summarized.Finally, the key challenges and opportunities to develop high-performance TMCs are discussed and some solutions are also proposed. This timely review sheds light on the path towards achieving cost-effective and safe LIBs with high energy density and long cycling life using TMCs-based anode materials.
基金supported by Zhejiang Provincial Natural Science Foundation of China(No.LY17E040001)。
文摘Tailored design and synthesis of high-quality electrocatalysts is vital for the advancement of oxygen evolution reaction(OER).Herein,we report a powerful puffing method to fabricate hierarchical porous N-doped carbon with numerous embedded Ni nanoparticles.Interestingly,during the puffing and annealing process,rice precursor with N and Ni sources can be in-situ converted into Ni-embedded N-doped porous carbon(N-PC/Ni) composite.The obtained N-PC/Ni composite possesses a cross-linked porous architecture containing conductive carbon backbone and active Ni nanoparticles electrocatalysts for OER.The pore formation in N-PC/Ni composite is also proposed because of carbothermic reduction.The N-PC/Ni composite is fully studied as electrocatalysts for OER.Due to increased active surface area,enhanced electronic conductivity and reactivity,the designed N-PC/Ni composite exhibits superior OER performance with a low Tafel slope(~88 mV/dec) and a low overpotential as well as excellent long-term stability in alkaline solution.Our proposed rational design strategy may provide a new way to construct other advanced metal/heteroatom-doped composites for widespread application in electrocatalysis.
