The development of highly active and stable reversible oxygen electrocatalysts is crucial for improving the efficiency of metal‐air battery devices.Herein,an efficient liquid exfoliation strategy was designed for pro...The development of highly active and stable reversible oxygen electrocatalysts is crucial for improving the efficiency of metal‐air battery devices.Herein,an efficient liquid exfoliation strategy was designed for producing silk‐like FeS2/NiS2 hybrid nanocrystals with enhanced reversible oxygen catalytic performance that displayed excellent properties for Zn‐air batteries.Because of the unique silk‐like morphology and interface nanocrystal structure,they can catalyze the oxygen evolution reaction(OER)efficiently with a low overpotential of 233 mV at j=10 mA cm?2.This is an improvement from the recently reported catalysts in 1.0 M KOH.Meanwhile,the oxygen reduction reaction(ORR)activity of the silk‐like FeS2/NiS2 hybrid nanocrystals showed an onset potential of 911 mV and a half‐wave potential of 640 mV.In addition,the reversible oxygen electrode activity of the silk‐like FeS2/NiS2 hybrid nanocrystals was calculated to be 0.823 V,based on the potential of the OER and ORR.Further,the homemade rechargeable Zn‐air batteries using FeS2/NiS2 hybrid nanocrystals as the air‐cathode displayed a high open‐circuit voltage of 1.25 V for more than 17 h and an excellent rechargeable performance for 25 h.The solid Zn‐air batteries exhibited an excellent rechargeable performance for 15 h.This study provided a new method for designing interface nanocrystals with a unique morphology for efficient multifunctional electrocatalysts in electrochemical reactions and renewable energy devices.展开更多
MoS_(2) is a promising anode material in sodium-ion battery technologies for possessing high theoretical capacity.However,the sluggish Na^(+) diffusion kinetics and low electronic conductivity hinder the promises.Here...MoS_(2) is a promising anode material in sodium-ion battery technologies for possessing high theoretical capacity.However,the sluggish Na^(+) diffusion kinetics and low electronic conductivity hinder the promises.Herein,a unique MoS_(2)/FeS_(2)/C heterojunction with abundant defects and hollow structure(MFCHHS)was constructed.The synergy of defect engineering in MoS_(2),FeS_(2),and the carbon layer of MFCHHS with a larger specific surface area provides multiple storage sites of Na^(+)corresponding to the surface-controlled process.The MoS_(2)/FeS_(2)/C heterostructure and rich defects in MoS_(2) and carbon layer lower the Na^(+) diffusion energy barrier.Additionally,the construction of MoS_(2)/FeS_(2) heterojunction promotes electron transfer at the interface,accompanying with excellent conductivity of the carbon layer to facilitate reversible electrochemical reactions.The abundant defects and mismatches at the interface of MoS_(2)/FeS_(2) and MoS_(2)/C heterojunctions could relieve lattice stress and volume change sequentially.As a result,the MFCHHS anode exhibits the high capacity of 613.1 mA h g^(-1)at 0.5 A g^(-1) and 306.1 mA h g^(-1) at 20 A g^(-1).The capacity retention of 85.0%after 1400 cycles at 5.0 A g^(-1) is achieved.The density functional theory(DFT)calculation and in situ transmission electron microscope(TEM),Raman,ex-situ X-ray photon spectroscopy(XPS)studies confirm the low volume change during intercalation/deintercalation process and the efficient Na^(+)storage in the layered structure of MoS_(2) and carbon layer,as well as the defects and heterostructures in MFCHHS.We believe this work could provide an inspiration for constructing heterojunction with abundant defects to foster fast electron and Na^(+) diffusion kinetics,resulting in excellent rate capability and cycling stability.展开更多
NiS2 is a promising cocatalyst to improve the photocatalytic performance of g-C3N4 for the production of H2.However,the synthesis of the NiS2 cocatalyst usually requires harsh conditions,which risks destroying the mic...NiS2 is a promising cocatalyst to improve the photocatalytic performance of g-C3N4 for the production of H2.However,the synthesis of the NiS2 cocatalyst usually requires harsh conditions,which risks destroying the microstructures of the g-C3N4 photocatalysts.In this study,a facile and low-temperature（80 ℃） impregnation method was developed to prepare NiS2/g-C3N4 photocatalysts.First,the g-C3N4 powders were processed by the hydrothermal method in order to introduce oxygen-containing functional groups（such as-OH and-C0NH-） to the surface of g-C3N4.Then,the Ni^2＋ ions could be adsorbed near the g-C3N4 via strong electrostatic interaction between g-C3N4 and Ni^2＋ ions upon the addition of Ni（NO3）2 solution.Finally,NiS2 nanoparticles were formed on the surface of g-C3N4 upon the addition of TAA.It was found that the NiS2 nanoparticles were solidly and homogeneously grafted on the surface of g-C3N4,resulting in greatly improved photocatalytic H2production.When the amount of NiS2 was 3 wt%,the resultant NiS2/g-C3N4 photocatalyst showed the highest H2 evolution rate（116.343 μmol h^-1 g^-1）,which is significantly higher than that of the pure g-C3N4（3 μmol h^-1 g^-1）.Moreover,the results of a recycling test for the NiS2/g-C3N4（3 wt%）sample showed that this sample could maintain a stable and effective photocatalytic H2-evolution performance under visible-light irradiation.Based on the above results,a possible mechanism of the improved photocatalytic performance was proposed for the presented NiS2/g-C3N4 photocatalysts,in which the photogenerated electrons of g-C3N4 can be rapidly transferred to the NiS2 nanoparticles via the close and continuous contact between them;then,the photogenerated electrons rapidly react with H2O adsorbed on the surface of NiS2,which has a surficial metallic character and high catalytic activity,to produce H2.Considering the mild and facile synthesis method,the presented low-cost and highly efficient NiS2-modified g-C3N4 photocatalysts would have great potential for practical use in photocatalytic H2 production.展开更多
基于试验数据,利用扩展有限元方法(extended finite element method,XFEM)和内聚力模型(cohesive zone model,CZM),对20Cr2Ni3钢顶头表面氧化膜的断裂行为进行了数值分析,研究了氧化膜受力方向和孔洞对裂纹生长行为的影响。结果表明:氧...基于试验数据,利用扩展有限元方法(extended finite element method,XFEM)和内聚力模型(cohesive zone model,CZM),对20Cr2Ni3钢顶头表面氧化膜的断裂行为进行了数值分析,研究了氧化膜受力方向和孔洞对裂纹生长行为的影响。结果表明:氧化膜受力方向影响裂纹扩展路径,外层氧化膜裂纹尖端的J积分和应力强度因子K_I随着θ角(受力方向与氧化膜的夹角)的增大而减小,当θ角增大到90°时裂纹停止生长;外层氧化膜上孔洞使得裂纹尖端的J积分和应力强度因子K_I减小。同时,孔洞的存在使得外力传递到内层氧化膜时产生应力集中和偏移,导致内层裂纹受力不均,减小了受力方向对内层裂纹生长的影响。展开更多
基金supported by the National Basic Research Program of China(21571089,21503102,51571125)the Fundamental Research Funds for the Central Universities(lzujbky-2016-k02,lzujbky-2018-k08,lzujbky-2017-it42)~~
文摘The development of highly active and stable reversible oxygen electrocatalysts is crucial for improving the efficiency of metal‐air battery devices.Herein,an efficient liquid exfoliation strategy was designed for producing silk‐like FeS2/NiS2 hybrid nanocrystals with enhanced reversible oxygen catalytic performance that displayed excellent properties for Zn‐air batteries.Because of the unique silk‐like morphology and interface nanocrystal structure,they can catalyze the oxygen evolution reaction(OER)efficiently with a low overpotential of 233 mV at j=10 mA cm?2.This is an improvement from the recently reported catalysts in 1.0 M KOH.Meanwhile,the oxygen reduction reaction(ORR)activity of the silk‐like FeS2/NiS2 hybrid nanocrystals showed an onset potential of 911 mV and a half‐wave potential of 640 mV.In addition,the reversible oxygen electrode activity of the silk‐like FeS2/NiS2 hybrid nanocrystals was calculated to be 0.823 V,based on the potential of the OER and ORR.Further,the homemade rechargeable Zn‐air batteries using FeS2/NiS2 hybrid nanocrystals as the air‐cathode displayed a high open‐circuit voltage of 1.25 V for more than 17 h and an excellent rechargeable performance for 25 h.The solid Zn‐air batteries exhibited an excellent rechargeable performance for 15 h.This study provided a new method for designing interface nanocrystals with a unique morphology for efficient multifunctional electrocatalysts in electrochemical reactions and renewable energy devices.
基金the National Natural Science Foundation of China(NSFC)(22105059,22279112)the Talent Introduction Program of Hebei Agricultural University(YJ201810)+5 种基金the Youth Topnotch Talent Foundation of Hebei Provincial Universities(BJK2022023)the Natural Science Foundation of Hebei Province(B2022203018)the Fok Ying-Tong Education Foundation of China(171064)the Natural Science Foundation of Shandong Province,China(ZR2021QE192)the China Postdoctoral Science Foundation(2018M630747)the 333 Talent Program of Hebei Province(C20221018)for their support。
文摘MoS_(2) is a promising anode material in sodium-ion battery technologies for possessing high theoretical capacity.However,the sluggish Na^(+) diffusion kinetics and low electronic conductivity hinder the promises.Herein,a unique MoS_(2)/FeS_(2)/C heterojunction with abundant defects and hollow structure(MFCHHS)was constructed.The synergy of defect engineering in MoS_(2),FeS_(2),and the carbon layer of MFCHHS with a larger specific surface area provides multiple storage sites of Na^(+)corresponding to the surface-controlled process.The MoS_(2)/FeS_(2)/C heterostructure and rich defects in MoS_(2) and carbon layer lower the Na^(+) diffusion energy barrier.Additionally,the construction of MoS_(2)/FeS_(2) heterojunction promotes electron transfer at the interface,accompanying with excellent conductivity of the carbon layer to facilitate reversible electrochemical reactions.The abundant defects and mismatches at the interface of MoS_(2)/FeS_(2) and MoS_(2)/C heterojunctions could relieve lattice stress and volume change sequentially.As a result,the MFCHHS anode exhibits the high capacity of 613.1 mA h g^(-1)at 0.5 A g^(-1) and 306.1 mA h g^(-1) at 20 A g^(-1).The capacity retention of 85.0%after 1400 cycles at 5.0 A g^(-1) is achieved.The density functional theory(DFT)calculation and in situ transmission electron microscope(TEM),Raman,ex-situ X-ray photon spectroscopy(XPS)studies confirm the low volume change during intercalation/deintercalation process and the efficient Na^(+)storage in the layered structure of MoS_(2) and carbon layer,as well as the defects and heterostructures in MFCHHS.We believe this work could provide an inspiration for constructing heterojunction with abundant defects to foster fast electron and Na^(+) diffusion kinetics,resulting in excellent rate capability and cycling stability.
基金supported by the National Natural Science Foundation of China (21277107, 21477094, 51672203, 51472192)the Program for New Century Excellent Talents in University (NCET-13-0944)the Fundamental Research Funds for the Central Universities (WUT 2015IB002)~~
文摘NiS2 is a promising cocatalyst to improve the photocatalytic performance of g-C3N4 for the production of H2.However,the synthesis of the NiS2 cocatalyst usually requires harsh conditions,which risks destroying the microstructures of the g-C3N4 photocatalysts.In this study,a facile and low-temperature（80 ℃） impregnation method was developed to prepare NiS2/g-C3N4 photocatalysts.First,the g-C3N4 powders were processed by the hydrothermal method in order to introduce oxygen-containing functional groups（such as-OH and-C0NH-） to the surface of g-C3N4.Then,the Ni^2＋ ions could be adsorbed near the g-C3N4 via strong electrostatic interaction between g-C3N4 and Ni^2＋ ions upon the addition of Ni（NO3）2 solution.Finally,NiS2 nanoparticles were formed on the surface of g-C3N4 upon the addition of TAA.It was found that the NiS2 nanoparticles were solidly and homogeneously grafted on the surface of g-C3N4,resulting in greatly improved photocatalytic H2production.When the amount of NiS2 was 3 wt%,the resultant NiS2/g-C3N4 photocatalyst showed the highest H2 evolution rate（116.343 μmol h^-1 g^-1）,which is significantly higher than that of the pure g-C3N4（3 μmol h^-1 g^-1）.Moreover,the results of a recycling test for the NiS2/g-C3N4（3 wt%）sample showed that this sample could maintain a stable and effective photocatalytic H2-evolution performance under visible-light irradiation.Based on the above results,a possible mechanism of the improved photocatalytic performance was proposed for the presented NiS2/g-C3N4 photocatalysts,in which the photogenerated electrons of g-C3N4 can be rapidly transferred to the NiS2 nanoparticles via the close and continuous contact between them;then,the photogenerated electrons rapidly react with H2O adsorbed on the surface of NiS2,which has a surficial metallic character and high catalytic activity,to produce H2.Considering the mild and facile synthesis method,the presented low-cost and highly efficient NiS2-modified g-C3N4 photocatalysts would have great potential for practical use in photocatalytic H2 production.
文摘基于试验数据,利用扩展有限元方法(extended finite element method,XFEM)和内聚力模型(cohesive zone model,CZM),对20Cr2Ni3钢顶头表面氧化膜的断裂行为进行了数值分析,研究了氧化膜受力方向和孔洞对裂纹生长行为的影响。结果表明:氧化膜受力方向影响裂纹扩展路径,外层氧化膜裂纹尖端的J积分和应力强度因子K_I随着θ角(受力方向与氧化膜的夹角)的增大而减小,当θ角增大到90°时裂纹停止生长;外层氧化膜上孔洞使得裂纹尖端的J积分和应力强度因子K_I减小。同时,孔洞的存在使得外力传递到内层氧化膜时产生应力集中和偏移,导致内层裂纹受力不均,减小了受力方向对内层裂纹生长的影响。
