Lithium–sulfur(Li–S)batteries have attracted much attention due to their ultrahigh theoretical specific capacity.However,serious capacity attenuation caused by shuttle effect still inhibits the performance improveme...Lithium–sulfur(Li–S)batteries have attracted much attention due to their ultrahigh theoretical specific capacity.However,serious capacity attenuation caused by shuttle effect still inhibits the performance improvement.Herein,a modified separator consists of the few-layer graphene as a highly conductive network and stable scaffold to support P-doped boron nitride(denoted as BN-P@GO)as the functional interlayer of Li–S batteries.The cell with the interlayer provides an initial discharge capacity as high as1045.3 mAh g^-1,and retains a high reversible capacity of 728.7 mAh g^-1 at 1 C after 500 cycles with a capacity decay of 0.061%per cycle.Moreover,the rate capability is also superior to cells with BN@GO or BN-P interlayers,i.e.reversible capcity of 457.9 mAh g^-1 even at 3 C.The excellent electrochemical performance is ascribed to the synergistic effect of physical barrier and chemical adsorption for dissolved polysulfides provided by the modified layer.Furhtermore,it also mitigates the polarization and promotes kinetic reactions of the cells.This work provides a concise and effective method for commercialization of lithium–sulfur batteries.展开更多
The construction of electrode materials for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)has gradually been an appealing and attractive technology in energy storage research field.In the present work,a fac...The construction of electrode materials for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)has gradually been an appealing and attractive technology in energy storage research field.In the present work,a facile strategy of synthesizing ultrathin amorphous/nanocrystal dual-phase P-doped Bi_(2)MoO_(6)(denoted as P-BiMO)nanosheets via a one-step wet-chemical synthesis approach is explored.Quite distinct from conventional two-dimensional(2D)nanosheets,our newly developed ultrathin P-BiMO nanosheets exhibit a unique tunable amorphous/nanocrystalline dual-phase structure with several compelling advantages including fast ion exchange ability and superb volume change buffer capability.The experimental results reveal that our prepared P-BiMO-6 electrode delivers an excellent reversible capacity of 509.6 mA·g^(−1) after continuous 1,500 cycles at the current densities of 1,500 mA·g^(−1) and improved rate performance for LIBs.In the meanwhile,the P-BiMO-6 electrode also shows a reversible capacity of 300.6 mA·g^(−1) after 100 cycles at 50 mA·g^(−1) when being used as the SIBs electrodes.This present work uncovers an effective dual-phase nanosheet structure to improve the performance of batteries,providing an attractive paradigm to develop superior electrode materials.展开更多
Single-atom catalysts (SACs) especially supported on two-dimensional nitrogen-doped carbon substrate have been widely reported to be able to effectively promote electrocatalytic N_(2) reduction reaction (eNRR). The pr...Single-atom catalysts (SACs) especially supported on two-dimensional nitrogen-doped carbon substrate have been widely reported to be able to effectively promote electrocatalytic N_(2) reduction reaction (eNRR). The precise design of single-metal-atom active site (SMAS) calls for fundamental understanding of its working mechanism for enhanced eNRR performance. Herein, by means of density functional theory calculations, we theoretically investigate the eNRR performance of nine prototypical SMAS, namely, MN_(2)B_(2) (M: transition metals of IIIB, IVB and VB groups) which comprises of asymmetric ligands of N_(2)B_(2) embedded in defective BN nanosheet. Our results reveal the significant role of spin state of SMAS in tuning the potential-determining steps of eNRR, in which MN_(2)B_(2) site with higher spin magnetic moment (μ) is beneficial to reducing limiting potentials (U_(L)) of eNRR. Specially, CrN_(2)B_(2) (μ = 4μB), VN_(2)B_(2) (μ = 3μB) and MoN_(2)B_(2) (μ = 2μB) demonstrate high activity and selectivity to eNRR. The asymmetric ligands of N_(2)B_(2) are deemed to be superior over mono-symmetric ligands. More importantly, our results demonstrate that breaking (or deviating) of the scaling relations between key N-containing intermediates (*N_(2)H/*N_(2) and *NH2/*N_(2)) on MN_(2)B_(2) can be realized by enhancing spin state of SMAS which renders the active site a balanced N-affinity critical for efficient eNRR. This observation is validated by the calculated Sabatier volcano-shape relation between eNRR limiting potentials and N_(2) adsorption energy. Our study develops the guidance for catalyst design to boost eNRR performance by tuning the spin state of an active site.展开更多
A higher value of the dielectric constant of h-BN makes it quite favourable material in energy storing device. The variation in dielectric constant was observed as a function of thickness. In this research work multil...A higher value of the dielectric constant of h-BN makes it quite favourable material in energy storing device. The variation in dielectric constant was observed as a function of thickness. In this research work multilayers of Hexagonal Boron Nitride (h-BN) was fabricated by using the Chemical exfoliation method. Two solvents Dimethylformamide (DMF) and Isopropyl Alcohol (IPA) were used for the exfoliation of h-BN. Successful sonication of hexagonal boron nitride led to the formation of Boron Nitride nanosheets (BNNs). The stable dispersibility of h-BN in Dimethylformamide and Isopropyl Alcohol was confirmed by UV Visible Spectroscopy, X-ray diffraction (XRD) and Scanning electron microscopy (SEM) confirm the mono crystallite structure (002) and nanoflakes like morphology of h-BN respectively. This appropriate strategy offered a feasible route to produce multilayer of hexagonal boron nitride. After the successful fabrication of h-BN multilayers its dielectric properties were calculated by using LCR meter. Profilometer revealed the variation in thickness and value of Dielectric constant was calculated by using its formula.展开更多
基金the financial supports provided by the National Natural Science Foundation of China(21871164)Young Scholars Program of Shandong University(No.2017WLJH15)+2 种基金the China Postdoctoral Science Foundation(Nos.2017M610419 and 2018T110680)the Special Fund for Postdoctoral Innovation Program of Shandong Province(No.201701003)the Taishan Scholar Project of Shandong Province(No.ts201511004)
文摘Lithium–sulfur(Li–S)batteries have attracted much attention due to their ultrahigh theoretical specific capacity.However,serious capacity attenuation caused by shuttle effect still inhibits the performance improvement.Herein,a modified separator consists of the few-layer graphene as a highly conductive network and stable scaffold to support P-doped boron nitride(denoted as BN-P@GO)as the functional interlayer of Li–S batteries.The cell with the interlayer provides an initial discharge capacity as high as1045.3 mAh g^-1,and retains a high reversible capacity of 728.7 mAh g^-1 at 1 C after 500 cycles with a capacity decay of 0.061%per cycle.Moreover,the rate capability is also superior to cells with BN@GO or BN-P interlayers,i.e.reversible capcity of 457.9 mAh g^-1 even at 3 C.The excellent electrochemical performance is ascribed to the synergistic effect of physical barrier and chemical adsorption for dissolved polysulfides provided by the modified layer.Furhtermore,it also mitigates the polarization and promotes kinetic reactions of the cells.This work provides a concise and effective method for commercialization of lithium–sulfur batteries.
基金supported by Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project:HZQB-KCZYB-2020030the National Key R&D Program of China(Project No.2017YFA0204403)Hong Kong Innovation and Technology Commission via the Hong Kong Branch of National Precious Metals Material Engineering Research Center.
文摘The construction of electrode materials for lithium-ion batteries(LIBs)and sodium-ion batteries(SIBs)has gradually been an appealing and attractive technology in energy storage research field.In the present work,a facile strategy of synthesizing ultrathin amorphous/nanocrystal dual-phase P-doped Bi_(2)MoO_(6)(denoted as P-BiMO)nanosheets via a one-step wet-chemical synthesis approach is explored.Quite distinct from conventional two-dimensional(2D)nanosheets,our newly developed ultrathin P-BiMO nanosheets exhibit a unique tunable amorphous/nanocrystalline dual-phase structure with several compelling advantages including fast ion exchange ability and superb volume change buffer capability.The experimental results reveal that our prepared P-BiMO-6 electrode delivers an excellent reversible capacity of 509.6 mA·g^(−1) after continuous 1,500 cycles at the current densities of 1,500 mA·g^(−1) and improved rate performance for LIBs.In the meanwhile,the P-BiMO-6 electrode also shows a reversible capacity of 300.6 mA·g^(−1) after 100 cycles at 50 mA·g^(−1) when being used as the SIBs electrodes.This present work uncovers an effective dual-phase nanosheet structure to improve the performance of batteries,providing an attractive paradigm to develop superior electrode materials.
基金This work was supported by the National Natural Science Foundation of China(No.21673137)the Science and Technology Commission of Shanghai Municipality(No.16ZR1413900)W.A.gratefully acknowledges the support from the Program for Top Talents in Songjiang District of Shanghai.The DFT calculations were performed using resources of the Center for Functional Nanomaterials,which is a U.S.DOE Office of Science Facility,and the Scientific Data and Computing Center,a component of the Computational Science Initiative,at Brookhaven National Laboratory under Contract No.DE-SC0012704.
文摘Single-atom catalysts (SACs) especially supported on two-dimensional nitrogen-doped carbon substrate have been widely reported to be able to effectively promote electrocatalytic N_(2) reduction reaction (eNRR). The precise design of single-metal-atom active site (SMAS) calls for fundamental understanding of its working mechanism for enhanced eNRR performance. Herein, by means of density functional theory calculations, we theoretically investigate the eNRR performance of nine prototypical SMAS, namely, MN_(2)B_(2) (M: transition metals of IIIB, IVB and VB groups) which comprises of asymmetric ligands of N_(2)B_(2) embedded in defective BN nanosheet. Our results reveal the significant role of spin state of SMAS in tuning the potential-determining steps of eNRR, in which MN_(2)B_(2) site with higher spin magnetic moment (μ) is beneficial to reducing limiting potentials (U_(L)) of eNRR. Specially, CrN_(2)B_(2) (μ = 4μB), VN_(2)B_(2) (μ = 3μB) and MoN_(2)B_(2) (μ = 2μB) demonstrate high activity and selectivity to eNRR. The asymmetric ligands of N_(2)B_(2) are deemed to be superior over mono-symmetric ligands. More importantly, our results demonstrate that breaking (or deviating) of the scaling relations between key N-containing intermediates (*N_(2)H/*N_(2) and *NH2/*N_(2)) on MN_(2)B_(2) can be realized by enhancing spin state of SMAS which renders the active site a balanced N-affinity critical for efficient eNRR. This observation is validated by the calculated Sabatier volcano-shape relation between eNRR limiting potentials and N_(2) adsorption energy. Our study develops the guidance for catalyst design to boost eNRR performance by tuning the spin state of an active site.
文摘A higher value of the dielectric constant of h-BN makes it quite favourable material in energy storing device. The variation in dielectric constant was observed as a function of thickness. In this research work multilayers of Hexagonal Boron Nitride (h-BN) was fabricated by using the Chemical exfoliation method. Two solvents Dimethylformamide (DMF) and Isopropyl Alcohol (IPA) were used for the exfoliation of h-BN. Successful sonication of hexagonal boron nitride led to the formation of Boron Nitride nanosheets (BNNs). The stable dispersibility of h-BN in Dimethylformamide and Isopropyl Alcohol was confirmed by UV Visible Spectroscopy, X-ray diffraction (XRD) and Scanning electron microscopy (SEM) confirm the mono crystallite structure (002) and nanoflakes like morphology of h-BN respectively. This appropriate strategy offered a feasible route to produce multilayer of hexagonal boron nitride. After the successful fabrication of h-BN multilayers its dielectric properties were calculated by using LCR meter. Profilometer revealed the variation in thickness and value of Dielectric constant was calculated by using its formula.
