Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication ...Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.展开更多
Fe–N_(x)nanoparticles-embedded porous carbons with a desirable superstructure have attracted immense attention as promising catalysts for electrochemical oxygen reduction reaction.Herein,we employed Fe-coordinated co...Fe–N_(x)nanoparticles-embedded porous carbons with a desirable superstructure have attracted immense attention as promising catalysts for electrochemical oxygen reduction reaction.Herein,we employed Fe-coordinated covalent triazine polymer for the fabrication of Fe–N_(x)nanoparticle-embedded porous carbon nanoflorets(Fe/N@CNFs)employing a hypersaline-confinement-conversion strategy.Presence of tailored N types within the covalent triazine polymer interwork in high proportions contributes to the generation of Fe/N coordination and subsequent Fe–N_(x)nanoparticles.Owing to the utilization of NaCl crystals,the resultant Fe/N@CNF-800 which was generated by pyrolysis at 800℃showed nanoflower structure and large specific surface area,which remarkably suppressed the agglomeration of high catalytic active sites.As expect,the Fe/N@CNF-800 exhibited unexpected oxygen reduction reaction catalytic performance with an ultrahigh half-wave potential(0.89 V vs.reversible hydrogen electrode),a dominant 4e–transfer approach and great cycle stability(>92%after 100000 s).As a demonstration,the Fe/N-PCNF-800-assembled zinc–air battery delivered a high open circuit voltage of 1.51 V,a maximum peak power density of 164 mW·cm^(-2),as well as eminent rate performance,surpassing those of commercial Pt/C.This contribution offers a valuable avenue to exploit efficient metal nanoparticles-based carbon catalysts towards energy-related electrocatalytic reactions and beyond.展开更多
Accurate information for consumer phase connectivity in a low-voltage distribution network(LVDN)is critical for the management of line losses and the quality of customer service.The wide application of smart meters pr...Accurate information for consumer phase connectivity in a low-voltage distribution network(LVDN)is critical for the management of line losses and the quality of customer service.The wide application of smart meters provides the data basis for the phase identification of LVDN.However,the measurement errors,poor communication,and data distortion have significant impacts on the accuracy of phase identification.In order to solve this problem,this paper proposes a phase identification method of LVDN based on stepwise regression(SR)method.First,a multiple linear regression model based on the principle of energy conservation is established for phase identification of LVDN.Second,the SR algorithm is used to identify the consumer phase connectivity.Third,by defining a significance correction factor,the results from the SR algorithm are updated to improve the accuracy of phase identification.Finally,an LVDN test system with 63 consumers is constructed based on the real load.The simulation results prove that the identification accuracy achieved by the proposed method is higher than other phase identification methods under the influence of various errors.展开更多
Four-channel off-axis holography is proposed to simultaneously understand the polarization states and the mode coefficients of linearly polarized (LP) modes in few-mode fiber. Far-field off-axis holograms in the four ...Four-channel off-axis holography is proposed to simultaneously understand the polarization states and the mode coefficients of linearly polarized (LP) modes in few-mode fiber. Far-field off-axis holograms in the four polarization directions ofthe fiber laser were acquired at the same moment through a four-channel holographic device. The weights, the relativephase differences, and the polarization parameters of the vector fiber laser mode can be solved simultaneously. The simulated and experimental mode analysis of the laser output by 1060-XP fiber with 6 LP modes at 632.8 nm is conducted, whichshows that the similarity of the total intensity distribution of the laser before and after mode analysis is above 0.97. Themode polarization states, the mode weights, and the relative phase differences of the few-mode laser can be determinedsimultaneously in a single shot by four-channel off-axis holography.展开更多
Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction(OER)and the impairment of chlorine electroch...Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction(OER)and the impairment of chlorine electrochemistry at anode.Herein,we report a heterostructure of Ni_(3)S_(2)nanoarray with secondary Fe-Ni(OH)_(2)lamellar edges that exposes abundant active sites towards seawater oxidation.The resultant Fe-Ni(OH)_(2)/Ni_(3)S_(2)nanoarray works directly as a free-standing anodic electrode in alkaline artificial seawater.It only requires an overpotential of 269 mV to afford a current density of 10 mA·cm^(-2)and the Tafel slope is as low as 46 m V·dec^(-1).The 27-hour chronopotentiometry operated at high current density of 100 mA·cm^(-2)shows negligible deterioration,suggesting good stability of the Fe-Ni(OH)_(2)/Ni_(3)S_(2)@NF electrode.Faraday efficiency for oxygen evolution is up to〜95%,revealing decent selectivity of the catalyst in saline water.Such desirable catalytic performance could be benefitted from the introduction of Fe activator and the heterostructure that offers massive active and selective sites.The density functional theory(DFT)calculations indicate that the OER has lower theoretical overpotential than Cl_(2) evolution reaction in Fe sites,which is contrary to that of Ni sites.The experimental and theoretical study provides a strong support for the rational design of high-performance Fe-based electrodes for industrial seawater electrolysis.展开更多
混合型纳米电极材料的合理设计及合成对于其不同的应用具有重要意义,尤其是对于可用于下一代电动汽车和电子设备供电的高效纳米结构超级电容器(SCs)储能器件.本文报道了一种简便可控合成核-壳Ni_(3)S_(2)@NiWO_(4)纳米阵列的方法,并将...混合型纳米电极材料的合理设计及合成对于其不同的应用具有重要意义,尤其是对于可用于下一代电动汽车和电子设备供电的高效纳米结构超级电容器(SCs)储能器件.本文报道了一种简便可控合成核-壳Ni_(3)S_(2)@NiWO_(4)纳米阵列的方法,并将其用于混合超级电容器的独立电极.在5 mA cm^(-2)的条件下,所制备的Ni_(3)S_(2)@NiWO_(4)独立电极表现出高达2032μA h cm^(-2)的面积容量;即使电流密度增至50 mA cm^(-2),其容量保留率仍为63.6%.更重要的是,在功率密度为3.128 mW cm^(-2)时,该Ni_(3)S_(2)@NiWO_(4)纳米阵列混合超级电容器仍表现出1.283 mW h cm^(-2)的最大能量密度;而在能量密度为0.753 mW h cm^(-2)时,该超级电容器表现出的最大功率密度为41.105 mW cm^(-2).此外,该混合超级电容器在连续10,000次循环后仍能保持89.6%的原始容量,从而进一步证明其优异的稳定性.本研究为合理设计各种核壳金属纳米结构提供了便捷途径,有助于促进其在高性能储能器件领域的广泛应用.展开更多
Due to the lack of support from the main grid,the intermittency of renewable energy sources(RESs)and the fluctuation of load will derive uncertainties to the operation of islanded microgrids(IMGs).It is crucial to all...Due to the lack of support from the main grid,the intermittency of renewable energy sources(RESs)and the fluctuation of load will derive uncertainties to the operation of islanded microgrids(IMGs).It is crucial to allocate appropriate reserve capacity for the economic and reliable operation of IMGs.With the high penetration of RESs,it faces both economic and environmental challenges if we only use spinning reserve for reserve support.To solve these problems,a multi-type reserve scheme for IMGs is proposed according to different operation characteristics of generation,load,and storage.The operation risk due to reserve shortage is modeled by the conditional value-at-risk(CVaR)method.The correlation of input variables is considered for the forecasting error modeling of RES and load,and Latin hypercube sampling(LHS)is adopted to generate the random scenarios of the forecasting error,so as to avoid the dimension disaster caused by conventional large-scale scenario sampling approaches.Furthermore,an optimal day-ahead scheduling model of joint energy and reserve considering riskbased reserve decision is established to coordinate the security and economy of the operation of IMGs.Finally,the comparison of numerical results of different schemes demonstrate the rationality and effectiveness of the proposed scheme and model.展开更多
基金supported financially by the National Natural Science Foundation of China,China(Grant No.51702180,51572136,91963113,21703116,51372127,51873096)The Scientific and Technical Development Project of Qingdao,China(Grant No.18-2-2-52-jch)+1 种基金The Taishan Scholar Advantage and Characteristic Discipline Team of Eco Chemical Process and TechnologyThe Natural Science Foundation of Hebei Province(B2019204009)。
文摘Efficient bifunctional oxygen electrocatalysts for ORR and OER are fundamental to the development of high performance metal-air batteries.Herein,a facile cost-efficient two-step pyrolysis strategy for the fabrication of a bifunctional oxygen electrocatalyst has been proposed.The efficient non-preciousmetal-based electrocatalyst,Fe/Fe_(3)C@Fe-N_(x)-C consists of highly curved onion-like carbon shells that encapsulate Fe/Fe_(3)C nanoparticles,distributed on an extensively porous graphitic carbon aerogel.The obtained Fe/Fe_(3)C@Fe-N_(x)-C aerogel exhibited superb electrochemical activity,excellent durability,and high methanol tolerance.The experimental results indicated that the assembly of onion-like carbon shells with encapsulated Fe/Fe_(3)C yielded highly curved carbon surfaces with abundant Fe-Nxactive sites,a porous structure,and enhanced electrocatalytic activity towards ORR and OER,hence displaying promising potential for application as an air cathode in rechargeable Zn-air batteries.The constructed Zn-air battery possessed an exceptional peak power density of~147 mW cm^(-2),outstanding cycling stability(200 cycles,1 h per cycle),and a small voltage gap of 0.87 V.This study offers valuable insights regarding the construction of low-cost and highly active bifunctional oxygen electrocatalysts for efficient air batteries.
基金grateful for the financial support from the National Natural Science Foundation of China(Grant Nos.51872147,22006131).
文摘Fe–N_(x)nanoparticles-embedded porous carbons with a desirable superstructure have attracted immense attention as promising catalysts for electrochemical oxygen reduction reaction.Herein,we employed Fe-coordinated covalent triazine polymer for the fabrication of Fe–N_(x)nanoparticle-embedded porous carbon nanoflorets(Fe/N@CNFs)employing a hypersaline-confinement-conversion strategy.Presence of tailored N types within the covalent triazine polymer interwork in high proportions contributes to the generation of Fe/N coordination and subsequent Fe–N_(x)nanoparticles.Owing to the utilization of NaCl crystals,the resultant Fe/N@CNF-800 which was generated by pyrolysis at 800℃showed nanoflower structure and large specific surface area,which remarkably suppressed the agglomeration of high catalytic active sites.As expect,the Fe/N@CNF-800 exhibited unexpected oxygen reduction reaction catalytic performance with an ultrahigh half-wave potential(0.89 V vs.reversible hydrogen electrode),a dominant 4e–transfer approach and great cycle stability(>92%after 100000 s).As a demonstration,the Fe/N-PCNF-800-assembled zinc–air battery delivered a high open circuit voltage of 1.51 V,a maximum peak power density of 164 mW·cm^(-2),as well as eminent rate performance,surpassing those of commercial Pt/C.This contribution offers a valuable avenue to exploit efficient metal nanoparticles-based carbon catalysts towards energy-related electrocatalytic reactions and beyond.
基金supported in part by the National Natural Science Foundation of China(No.52177085)Science and Technology Planning Project of Guangzhou(No.202102021208)。
文摘Accurate information for consumer phase connectivity in a low-voltage distribution network(LVDN)is critical for the management of line losses and the quality of customer service.The wide application of smart meters provides the data basis for the phase identification of LVDN.However,the measurement errors,poor communication,and data distortion have significant impacts on the accuracy of phase identification.In order to solve this problem,this paper proposes a phase identification method of LVDN based on stepwise regression(SR)method.First,a multiple linear regression model based on the principle of energy conservation is established for phase identification of LVDN.Second,the SR algorithm is used to identify the consumer phase connectivity.Third,by defining a significance correction factor,the results from the SR algorithm are updated to improve the accuracy of phase identification.Finally,an LVDN test system with 63 consumers is constructed based on the real load.The simulation results prove that the identification accuracy achieved by the proposed method is higher than other phase identification methods under the influence of various errors.
基金supported by the National Natural Science Foundation of China(No.61875087)。
文摘Four-channel off-axis holography is proposed to simultaneously understand the polarization states and the mode coefficients of linearly polarized (LP) modes in few-mode fiber. Far-field off-axis holograms in the four polarization directions ofthe fiber laser were acquired at the same moment through a four-channel holographic device. The weights, the relativephase differences, and the polarization parameters of the vector fiber laser mode can be solved simultaneously. The simulated and experimental mode analysis of the laser output by 1060-XP fiber with 6 LP modes at 632.8 nm is conducted, whichshows that the similarity of the total intensity distribution of the laser before and after mode analysis is above 0.97. Themode polarization states, the mode weights, and the relative phase differences of the few-mode laser can be determinedsimultaneously in a single shot by four-channel off-axis holography.
基金the National Natural Science Foundation of China(No.91963113).
文摘Development of efficient non-precious catalysts for seawater electrolysis is of great significance but challenging due to the sluggish kinetics of oxygen evolution reaction(OER)and the impairment of chlorine electrochemistry at anode.Herein,we report a heterostructure of Ni_(3)S_(2)nanoarray with secondary Fe-Ni(OH)_(2)lamellar edges that exposes abundant active sites towards seawater oxidation.The resultant Fe-Ni(OH)_(2)/Ni_(3)S_(2)nanoarray works directly as a free-standing anodic electrode in alkaline artificial seawater.It only requires an overpotential of 269 mV to afford a current density of 10 mA·cm^(-2)and the Tafel slope is as low as 46 m V·dec^(-1).The 27-hour chronopotentiometry operated at high current density of 100 mA·cm^(-2)shows negligible deterioration,suggesting good stability of the Fe-Ni(OH)_(2)/Ni_(3)S_(2)@NF electrode.Faraday efficiency for oxygen evolution is up to〜95%,revealing decent selectivity of the catalyst in saline water.Such desirable catalytic performance could be benefitted from the introduction of Fe activator and the heterostructure that offers massive active and selective sites.The density functional theory(DFT)calculations indicate that the OER has lower theoretical overpotential than Cl_(2) evolution reaction in Fe sites,which is contrary to that of Ni sites.The experimental and theoretical study provides a strong support for the rational design of high-performance Fe-based electrodes for industrial seawater electrolysis.
基金the National Natural Science Foundation of China(91963113)。
文摘混合型纳米电极材料的合理设计及合成对于其不同的应用具有重要意义,尤其是对于可用于下一代电动汽车和电子设备供电的高效纳米结构超级电容器(SCs)储能器件.本文报道了一种简便可控合成核-壳Ni_(3)S_(2)@NiWO_(4)纳米阵列的方法,并将其用于混合超级电容器的独立电极.在5 mA cm^(-2)的条件下,所制备的Ni_(3)S_(2)@NiWO_(4)独立电极表现出高达2032μA h cm^(-2)的面积容量;即使电流密度增至50 mA cm^(-2),其容量保留率仍为63.6%.更重要的是,在功率密度为3.128 mW cm^(-2)时,该Ni_(3)S_(2)@NiWO_(4)纳米阵列混合超级电容器仍表现出1.283 mW h cm^(-2)的最大能量密度;而在能量密度为0.753 mW h cm^(-2)时,该超级电容器表现出的最大功率密度为41.105 mW cm^(-2).此外,该混合超级电容器在连续10,000次循环后仍能保持89.6%的原始容量,从而进一步证明其优异的稳定性.本研究为合理设计各种核壳金属纳米结构提供了便捷途径,有助于促进其在高性能储能器件领域的广泛应用.
基金This work was supported by the National Natural Science Foundation of China(No.51777077)the Natural Science Foundation of Guangdong Province(No.2017A030313304).
文摘Due to the lack of support from the main grid,the intermittency of renewable energy sources(RESs)and the fluctuation of load will derive uncertainties to the operation of islanded microgrids(IMGs).It is crucial to allocate appropriate reserve capacity for the economic and reliable operation of IMGs.With the high penetration of RESs,it faces both economic and environmental challenges if we only use spinning reserve for reserve support.To solve these problems,a multi-type reserve scheme for IMGs is proposed according to different operation characteristics of generation,load,and storage.The operation risk due to reserve shortage is modeled by the conditional value-at-risk(CVaR)method.The correlation of input variables is considered for the forecasting error modeling of RES and load,and Latin hypercube sampling(LHS)is adopted to generate the random scenarios of the forecasting error,so as to avoid the dimension disaster caused by conventional large-scale scenario sampling approaches.Furthermore,an optimal day-ahead scheduling model of joint energy and reserve considering riskbased reserve decision is established to coordinate the security and economy of the operation of IMGs.Finally,the comparison of numerical results of different schemes demonstrate the rationality and effectiveness of the proposed scheme and model.
