NiS2 has become a research hotspot of anode materials for Na-ion batteries due to its high theoretical specific capacity.However,the volume effect,the dissolution of polysulfide intermediates and the low conductivity ...NiS2 has become a research hotspot of anode materials for Na-ion batteries due to its high theoretical specific capacity.However,the volume effect,the dissolution of polysulfide intermediates and the low conductivity during the charge/discharge process lead to the low specific capacity and poor cycling stability.NiS2/rGO nanocomposite was prepared by a facile two-step process:GO was prepared by modified Hummers method,and then NiS2/rGO nanocomposite was synthesized by L-cys assisted hydrothermal method.NiS2/rGO nanocomposite shows excellent cycle performance and rate performance,which could be attributed to the mesoporous structure on the graphene skeleton with high conductivity.Besides,the chemical constraint of a unique S—O bond on NiS2 could inhibit the dissolution of intermediates and the loss of irreversible capacity.展开更多
The insulator-metal transition triggered by pressure in charge transfer insulator NiS2 is investigated by combining high-pressure electrical transport,synchrotron x-ray diffraction and Raman spectroscopy measurements ...The insulator-metal transition triggered by pressure in charge transfer insulator NiS2 is investigated by combining high-pressure electrical transport,synchrotron x-ray diffraction and Raman spectroscopy measurements up to40-50 GPa.Upon compression,we show that the metallization firstly appears in the low temperature region at^3.2 GPa and then extends to room temperature at^8.0 GPa.During the insulator-metal transition,the bond length of S-S dimer extracted from the synchrotron x-ray diffraction increases with pressure,which is supported by the observation of abnormal red-shift of the Raman modes between 3.2 and 7.1 GPa.Considering the decreasing bonding-antibonding splitting due to the expansion of S-S dimer,the charge gap between the S-ppπ* band and the upper Hubbard band of Ni-3 d eg state is remarkabl.y decreased.These results consistently indicate that the elongated S-S dimer plays a predominant role in the insulator-metal transition under high pressure,even though the p-d hybridization is enhanced simultaneously,in accordance with a scenario of charge-gap-controlled type.展开更多
Electrocatalytic synthesis of value-added chemicals is attracting significant research attention owing to its mild reaction conditions, environmental benignity, and potentially scalable application to organic syntheti...Electrocatalytic synthesis of value-added chemicals is attracting significant research attention owing to its mild reaction conditions, environmental benignity, and potentially scalable application to organic synthetic chemistry. Herein, we report the preparation of a single-crystalline NiS2 nanostructure film of N 50 nm thickness grown directly on a carbon fiber doth （NiSJCFC） by a facile vapor-phase hydrothermal （VPH） method. NiSJCFC as an electrocatalyst exhibits activity for both the oxygen evolution reaction （OER） and the hydrogen evolution reaction （HER） in alkaline media. Furthermore, a series of alcohols （2-propanol, 2-butanol, 2-pentanol, and cyclohexanol） were electrocatalytically converted to the corresponding ketones with high selectivity, efficienc and durability using the NiSJCFC electrode in alkaline media. In the presence of 0.45 M alcohol, a remarkably decreased overpotential （- 150 mV, vs. RHE） at the NiS2/CFC anode compared with that for water oxidation to generate O2, i.e., the OER, in alkaline media leads to significantly improved H2 generation. For instance, the H2 generation rate in the presence of 0.45 M 2-propanol is almost 1.2-times of that obtained for pure water splitting, but in a system that employs an applied voltage at least 280 mV lower than that required for water splitting to achieve the same current density （20 mA-crn-2）. Thus, our results demonstrate the applicability of our bifunctional non-precious-metal electrocatalyst for organic synthesis and simultaneous H2 production.展开更多
Nickle sulfides are attractive anode materials for sodium-ion batteries(SIBs) due to their rich structures and natural abundance. However, their applications are greatly hindered by the large volume expansion and poor...Nickle sulfides are attractive anode materials for sodium-ion batteries(SIBs) due to their rich structures and natural abundance. However, their applications are greatly hindered by the large volume expansion and poor cycling properties. The introduction of hollow structures and heteroatom-doped carbon layers are effective ways to solve these issues. Here, nitrogen, sulfur co-doped carbon coated Ni3S2(abbreviated as, Ni3S2@NSC) nanotubes were prepared by a novel templating route. During the annealing process, NiS2 acts as both a precursor to Ni3S2 and an S-doped sulfur source.No additional sulfur source was used during the S-doping procedure, suggesting an atomically economic synthesis process. As anodes for sodium-ion half-cells, Ni3S2@NSCs exhibited high discharge capacity of 481 mA h g^-1 at 0.1 A g^-1 after 100 cycles with exceptional capacity retention of 98.6%.Furthermore, they maintained excellent rate capability of 318 mA h g^-1 even at elevated current density of 5 A g^-1. Sodium-ion full-cells assembled from the Ni3S2@NSC anodes and Na3V2(PO4)3(NVP@C) cathodes also presented superior capacities and cyclabilities. These features can be attributed to the N, S co-doped carbon coated hollow structure that provided sufficient contact between the electrode and electrolyte,enhanced surface ion storage performance(capacitive effect),and improved structural stability of electrode materials.展开更多
奥氏体耐热钢由于良好的高温性能因而在火电、核电、航空航天等领域有着重要的应用.细小的晶粒尺寸及基体中弥散分布的碳化物是奥氏体钢具有优异高温性能的关键.奥氏体钢在服役过程中受热循环的影响,其显微组织发生衰退.为探究热循环过...奥氏体耐热钢由于良好的高温性能因而在火电、核电、航空航天等领域有着重要的应用.细小的晶粒尺寸及基体中弥散分布的碳化物是奥氏体钢具有优异高温性能的关键.奥氏体钢在服役过程中受热循环的影响,其显微组织发生衰退.为探究热循环过程中组织演变对力学性能的影响,针对一种供货态的奥氏体耐热钢0Cr25Ni13Si2MoN开展了三组热循环实验.借助光镜(optical microscope,OM)、扫描电镜(scanning electron microscope,SEM)、透射电镜(transmission electron microscope,TEM)和冲击试验机等试验设备,对不同热循环次数后的试样分别进行了显微组织及力学性能分析.结果表明:热循环过程中的组织演变表现出一定的时间依赖性,一次热循环过程完成了回复与再结晶,晶界处析出网状分布的M 23 C 6,降低了材料的韧性.后两次的热循环过程退火孪晶密度增大,但晶界处碳化物数量增加并发生粗化,材料的韧性逐渐恶化.展开更多
基金support from the National Natural Science Foundation of China(NSFC,No.51171033)The Fundamental Research Funds for the Central Universities(No.DUT19LAB29)。
文摘NiS2 has become a research hotspot of anode materials for Na-ion batteries due to its high theoretical specific capacity.However,the volume effect,the dissolution of polysulfide intermediates and the low conductivity during the charge/discharge process lead to the low specific capacity and poor cycling stability.NiS2/rGO nanocomposite was prepared by a facile two-step process:GO was prepared by modified Hummers method,and then NiS2/rGO nanocomposite was synthesized by L-cys assisted hydrothermal method.NiS2/rGO nanocomposite shows excellent cycle performance and rate performance,which could be attributed to the mesoporous structure on the graphene skeleton with high conductivity.Besides,the chemical constraint of a unique S—O bond on NiS2 could inhibit the dissolution of intermediates and the loss of irreversible capacity.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2018YFA0305700 and2016YFA0401804the National Natural Science Foundation of China under Grant Nos 11574323,11704387,11874362,11804344,11804341,61774136,11605276 and U1632275+3 种基金the Major Program of Development Foundation of Hefei Center for Physical Science and Technology under Grant No 2018ZYFX002the Users with Excellence Project of Hefei Science Center of Chinese Academy of Sciences under Grant No 2018HSC-UE012the Natural Science Foundation of Anhui Province under Grant Nos 1808085MA06,1908085QA18 and 1708085QA19the Director’s Fund of Hefei Institutes of Physical Science of Chinese Academy of Sciences under Grant No YZJJ201621
文摘The insulator-metal transition triggered by pressure in charge transfer insulator NiS2 is investigated by combining high-pressure electrical transport,synchrotron x-ray diffraction and Raman spectroscopy measurements up to40-50 GPa.Upon compression,we show that the metallization firstly appears in the low temperature region at^3.2 GPa and then extends to room temperature at^8.0 GPa.During the insulator-metal transition,the bond length of S-S dimer extracted from the synchrotron x-ray diffraction increases with pressure,which is supported by the observation of abnormal red-shift of the Raman modes between 3.2 and 7.1 GPa.Considering the decreasing bonding-antibonding splitting due to the expansion of S-S dimer,the charge gap between the S-ppπ* band and the upper Hubbard band of Ni-3 d eg state is remarkabl.y decreased.These results consistently indicate that the elongated S-S dimer plays a predominant role in the insulator-metal transition under high pressure,even though the p-d hybridization is enhanced simultaneously,in accordance with a scenario of charge-gap-controlled type.
文摘Electrocatalytic synthesis of value-added chemicals is attracting significant research attention owing to its mild reaction conditions, environmental benignity, and potentially scalable application to organic synthetic chemistry. Herein, we report the preparation of a single-crystalline NiS2 nanostructure film of N 50 nm thickness grown directly on a carbon fiber doth （NiSJCFC） by a facile vapor-phase hydrothermal （VPH） method. NiSJCFC as an electrocatalyst exhibits activity for both the oxygen evolution reaction （OER） and the hydrogen evolution reaction （HER） in alkaline media. Furthermore, a series of alcohols （2-propanol, 2-butanol, 2-pentanol, and cyclohexanol） were electrocatalytically converted to the corresponding ketones with high selectivity, efficienc and durability using the NiSJCFC electrode in alkaline media. In the presence of 0.45 M alcohol, a remarkably decreased overpotential （- 150 mV, vs. RHE） at the NiS2/CFC anode compared with that for water oxidation to generate O2, i.e., the OER, in alkaline media leads to significantly improved H2 generation. For instance, the H2 generation rate in the presence of 0.45 M 2-propanol is almost 1.2-times of that obtained for pure water splitting, but in a system that employs an applied voltage at least 280 mV lower than that required for water splitting to achieve the same current density （20 mA-crn-2）. Thus, our results demonstrate the applicability of our bifunctional non-precious-metal electrocatalyst for organic synthesis and simultaneous H2 production.
基金supported by the National Natural Science Foundation of China (51772082, 51804106 and 51574117)the Natural Science Foundation of Hunan Province (2019JJ30002 and 2019JJ50061)the China Postdoctoral Science Foundation (2018T110822 and 2017M610495)
文摘Nickle sulfides are attractive anode materials for sodium-ion batteries(SIBs) due to their rich structures and natural abundance. However, their applications are greatly hindered by the large volume expansion and poor cycling properties. The introduction of hollow structures and heteroatom-doped carbon layers are effective ways to solve these issues. Here, nitrogen, sulfur co-doped carbon coated Ni3S2(abbreviated as, Ni3S2@NSC) nanotubes were prepared by a novel templating route. During the annealing process, NiS2 acts as both a precursor to Ni3S2 and an S-doped sulfur source.No additional sulfur source was used during the S-doping procedure, suggesting an atomically economic synthesis process. As anodes for sodium-ion half-cells, Ni3S2@NSCs exhibited high discharge capacity of 481 mA h g^-1 at 0.1 A g^-1 after 100 cycles with exceptional capacity retention of 98.6%.Furthermore, they maintained excellent rate capability of 318 mA h g^-1 even at elevated current density of 5 A g^-1. Sodium-ion full-cells assembled from the Ni3S2@NSC anodes and Na3V2(PO4)3(NVP@C) cathodes also presented superior capacities and cyclabilities. These features can be attributed to the N, S co-doped carbon coated hollow structure that provided sufficient contact between the electrode and electrolyte,enhanced surface ion storage performance(capacitive effect),and improved structural stability of electrode materials.
文摘奥氏体耐热钢由于良好的高温性能因而在火电、核电、航空航天等领域有着重要的应用.细小的晶粒尺寸及基体中弥散分布的碳化物是奥氏体钢具有优异高温性能的关键.奥氏体钢在服役过程中受热循环的影响,其显微组织发生衰退.为探究热循环过程中组织演变对力学性能的影响,针对一种供货态的奥氏体耐热钢0Cr25Ni13Si2MoN开展了三组热循环实验.借助光镜(optical microscope,OM)、扫描电镜(scanning electron microscope,SEM)、透射电镜(transmission electron microscope,TEM)和冲击试验机等试验设备,对不同热循环次数后的试样分别进行了显微组织及力学性能分析.结果表明:热循环过程中的组织演变表现出一定的时间依赖性,一次热循环过程完成了回复与再结晶,晶界处析出网状分布的M 23 C 6,降低了材料的韧性.后两次的热循环过程退火孪晶密度增大,但晶界处碳化物数量增加并发生粗化,材料的韧性逐渐恶化.
