MXene is an emerging class of two-dimensional(2D)layered transition metal carbides or nitrides.Due to the highly tunable components and surface functional groups,it holds great potential in electrocatalytic hydrogen e...MXene is an emerging class of two-dimensional(2D)layered transition metal carbides or nitrides.Due to the highly tunable components and surface functional groups,it holds great potential in electrocatalytic hydrogen evolution reaction(HER).However,MXene nanosheet suffers from a strong tendency to restack and a lack of active edge sites.In this work,the porous Ti_(3)C_(2)T_(x)was synthesized by an oxidation and etching two-step strategy and then characterized by a series of spectroscopic techniques.The obtained porous Ti_(3)C_(2)T_(x)possesses a large number of in-plane pores.This not only creates abundant active edge sites but also enhances the mass transfer and increases the accessibility of the active sites.Compared with Ti_(3)C_(2)T_(x),in a 0.5 mol/L H_(2)SO_(4)electrolyte,the porous Ti_(3)C_(2)T_(x)shows a 65.6%higher electrochemical surface area(ECSA)(440 mF/cm^(2)),a 95.2%lower charge transfer resistance(12.8Ω),and a 69.8%lower Tafel slope(144 mV/dec),and thus exhibits lower overpotential with good stability at a current density of 10 mA/cm^(2).At the same time,the HER performance of the porous Ti_(3)C_(2)T_(x)can be further enhanced by near-infrared laser irradiation based on the localized surface plasmon resonance effect.展开更多
MoS_2 samples with controllable morphologies and structures were synthesized using surfactantassisted hydrothermal processes.The effects of surfactants（PEG,PVP,P123,SDS,AOT,and CTAB）on the morphologies and structure...MoS_2 samples with controllable morphologies and structures were synthesized using surfactantassisted hydrothermal processes.The effects of surfactants（PEG,PVP,P123,SDS,AOT,and CTAB）on the morphologies and structures of MoS_2 samples were investigated.The results revealed that spherical,bulk-like,and flower-like MoS_2 particles assembled by NH4~＋-intercalated MoS_2 nano-sheets were synthesized.The morphologies of the MoS_2 samples and their structures（including the slab length and the number of stacked layers） of MoS_2 nano-sheets in these samples could be controlled by adjusting the surfactants.Mono-dispersed spherical MoS_2 particles could be synthesized with PEG via the creation of MoS_2 nano-sheets with slab lengths shorter than 15 nm and fewer than six stacked layers.Possible formation mechanisms of these MoS_2 samples created via surfactant-assisted hydrothermal processes are proposed.Further,the catalytic activities of MoS_2 samples for anthracene hydrogenation were evaluated in a slurry-bed reactor.The catalyst synthesized with the surfactant PEG exhibited the highest catalytic hydrogenation activity.Compared with the other catalysts,it had a smaller particle size,mono-dispersed spherical morphology,shorter slab length,and fewer stacked layers;these were all beneficial to exposing its active edges.This work provides an efficient approach to synthesize transition metal sulfides with controllable morphologies and structures.展开更多
Designing an efficient electrocatalyst for hydrogen evolution reaction(HER)is rather essential for the field of electrocatalytic hydrogen production.We here report a three-dimensional(3D)graphene nanowire grown on our...Designing an efficient electrocatalyst for hydrogen evolution reaction(HER)is rather essential for the field of electrocatalytic hydrogen production.We here report a three-dimensional(3D)graphene nanowire grown on our self-made porous nickel tube prepared by a microwave plasma enhanced chemical vapor deposition(MPCVD)method.Then,the MoS_(2) nanosheets are in situ grown on graphene in a vertically stacked manner through a simple hydrothermal synthesis method.It is found that these vertical graphene nanosheets can be used as an effective support to anchor MoS_(2) nanosheets stably and evenly on its surface.As a result,the prepared catalyst exhibits excellent HER electrocatalytic activity,which is attributed to plentiful edge active sites provided by the vertical MoS_(2) nanosheets and the efficient electron transport pathway provided by graphene on a matrix with good conductivity.In addition,the outwardly extending nanowire-like structure of the catalyst increases its surface area,as well as reduces the steric hindrance between active sites and the electrolyte.展开更多
Mapping shoreline changes along coastal regions is critically important in monitoring continuously rising sea surface heights due to climate change and frequent severe storms. Thus, it is especially important if the r...Mapping shoreline changes along coastal regions is critically important in monitoring continuously rising sea surface heights due to climate change and frequent severe storms. Thus, it is especially important if the region has very high tidal ranges over very gentle tidal flats, which is a very vulnerable region. Although the various remote sensing platforms can be used to map shoreline changes, the spatial and temporal resolutions are not enough to obtain it for a short time. Accordingly, in this study we introduce the newly developed low altitude Helikite remote sensing platform to achieve much better resolutions of shorelines and a bathymetry. The Helikite stands for Helium balloon and Kite, which is a kind of aerial platform that uses the advantages of both a Helium balloon and a kite. Field experiments were conducted in the Jaebu Island, off the coast of the west Korean Peninsula in January 29, 2011. In order to extract shorelines from the consecutive images taken by the low altitude Helikite remote sensing platform, active contours without edges （ACWE） is used. Edges or boundaries exist primarily on places between one type of objective and the other. Since the hydrodynamic pressure has an effect everywhere, the locations of the waterlines can be the isobath lines. We could map several waterlines, which would enable us to complete a local bathymetry map ranges from 35 to 60 cm depth. The error resulting from applying ACWE algorithm to the imagery to determine the waterline is approximately less than 1 m. Therefore, it is very unique way to obtain such high resolutions of bathymetry with high accuracy for the regions of extremely high tidal ranges for a short time.展开更多
As a promising alternative hydrogen evolution catalyst,MoS_(2)is well known for its active edge sites and the inert basal plane.Now,1T′-MoS_(2)crystals are prepared and processed into different electrochemical microc...As a promising alternative hydrogen evolution catalyst,MoS_(2)is well known for its active edge sites and the inert basal plane.Now,1T′-MoS_(2)crystals are prepared and processed into different electrochemical microcells based on individual MoS_(2)nanosheets to reveal that the basal plane of 1T′-MoS_(2)is highly catalytically active.展开更多
The mechanics of structural ceramics,especially the toughness,are crucial to their service reliability and need to be continuously optimized.Inspired by the“brick-mortar”structure and further adjusting the microstru...The mechanics of structural ceramics,especially the toughness,are crucial to their service reliability and need to be continuously optimized.Inspired by the“brick-mortar”structure and further adjusting the microstructure of“mortar”on the interface,ceramic with strength and toughness up to 444.16 MPa and 13.79 MPa⋅m^(1/2) is constructed by hot pressed sintering with alumina(Al_(2)O_(3))as brick and vertical graphene(VG)with active atomic edges as mortar.Relying on the covalent interface between VG grown in-situ and Al_(2)O_(3),the sliding of Al_(2)O_(3)links the shear-deformation process of the crosslinked and interlocked nanointerface formed by VG,making the VG-enhanced Al_(2)O_(3)ceramics(AVG)obtain super toughness.Moreover,the structure of interlocked VG-nanointerface exhibits an excellent high-temperature resistance,which makes AVG still show the excellent strength of 437.66 MPa and toughness of 11.16 MPa⋅m^(1/2)after heat treatment at 1500℃for 100 h and they are respective 2.51 times and 3.18 times higher than Al_(2)O_(3)in the same condition.This work provides a new thought for the preparation of high-strength,ultra-tough and high-temperature mechanical stable ceramics.展开更多
Though the transition-metal dichalcogenides （TMDs） were proven to have a better performance on the hydrogen evolution reaction （HER）, the bulk production of active TMD materials remains a challenging work. This re...Though the transition-metal dichalcogenides （TMDs） were proven to have a better performance on the hydrogen evolution reaction （HER）, the bulk production of active TMD materials remains a challenging work. This report overcomes those barriers by showing a simple procedure to synthesize TaS2 nanosheets through modifying the arc discharge process. The usage of chloride as the transporting agent reduces the growth period of the formed TaS2 with active edge sites. TaS2 is found to have a uniform thickness （4 nm） with high crystallinity and adopt a 2H polytype （double-layered hexagonal） structure. The as-synthesized TaS2 has superior activity for HER with the potential of 280 mV.展开更多
文摘MXene is an emerging class of two-dimensional(2D)layered transition metal carbides or nitrides.Due to the highly tunable components and surface functional groups,it holds great potential in electrocatalytic hydrogen evolution reaction(HER).However,MXene nanosheet suffers from a strong tendency to restack and a lack of active edge sites.In this work,the porous Ti_(3)C_(2)T_(x)was synthesized by an oxidation and etching two-step strategy and then characterized by a series of spectroscopic techniques.The obtained porous Ti_(3)C_(2)T_(x)possesses a large number of in-plane pores.This not only creates abundant active edge sites but also enhances the mass transfer and increases the accessibility of the active sites.Compared with Ti_(3)C_(2)T_(x),in a 0.5 mol/L H_(2)SO_(4)electrolyte,the porous Ti_(3)C_(2)T_(x)shows a 65.6%higher electrochemical surface area(ECSA)(440 mF/cm^(2)),a 95.2%lower charge transfer resistance(12.8Ω),and a 69.8%lower Tafel slope(144 mV/dec),and thus exhibits lower overpotential with good stability at a current density of 10 mA/cm^(2).At the same time,the HER performance of the porous Ti_(3)C_(2)T_(x)can be further enhanced by near-infrared laser irradiation based on the localized surface plasmon resonance effect.
基金supported by the National Natural Science Foundation of China(21303186)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA07020300)~~
文摘MoS_2 samples with controllable morphologies and structures were synthesized using surfactantassisted hydrothermal processes.The effects of surfactants（PEG,PVP,P123,SDS,AOT,and CTAB）on the morphologies and structures of MoS_2 samples were investigated.The results revealed that spherical,bulk-like,and flower-like MoS_2 particles assembled by NH4~＋-intercalated MoS_2 nano-sheets were synthesized.The morphologies of the MoS_2 samples and their structures（including the slab length and the number of stacked layers） of MoS_2 nano-sheets in these samples could be controlled by adjusting the surfactants.Mono-dispersed spherical MoS_2 particles could be synthesized with PEG via the creation of MoS_2 nano-sheets with slab lengths shorter than 15 nm and fewer than six stacked layers.Possible formation mechanisms of these MoS_2 samples created via surfactant-assisted hydrothermal processes are proposed.Further,the catalytic activities of MoS_2 samples for anthracene hydrogenation were evaluated in a slurry-bed reactor.The catalyst synthesized with the surfactant PEG exhibited the highest catalytic hydrogenation activity.Compared with the other catalysts,it had a smaller particle size,mono-dispersed spherical morphology,shorter slab length,and fewer stacked layers;these were all beneficial to exposing its active edges.This work provides an efficient approach to synthesize transition metal sulfides with controllable morphologies and structures.
基金sponsored by the National Natural Science Foundation of China(No.22522818 and 22308381)Science Foundation of China University of Petroleum-Beijing(No.2462023QNXZ002).
文摘Designing an efficient electrocatalyst for hydrogen evolution reaction(HER)is rather essential for the field of electrocatalytic hydrogen production.We here report a three-dimensional(3D)graphene nanowire grown on our self-made porous nickel tube prepared by a microwave plasma enhanced chemical vapor deposition(MPCVD)method.Then,the MoS_(2) nanosheets are in situ grown on graphene in a vertically stacked manner through a simple hydrothermal synthesis method.It is found that these vertical graphene nanosheets can be used as an effective support to anchor MoS_(2) nanosheets stably and evenly on its surface.As a result,the prepared catalyst exhibits excellent HER electrocatalytic activity,which is attributed to plentiful edge active sites provided by the vertical MoS_(2) nanosheets and the efficient electron transport pathway provided by graphene on a matrix with good conductivity.In addition,the outwardly extending nanowire-like structure of the catalyst increases its surface area,as well as reduces the steric hindrance between active sites and the electrolyte.
基金A 2-Year Research Grant of Pusan National University
文摘Mapping shoreline changes along coastal regions is critically important in monitoring continuously rising sea surface heights due to climate change and frequent severe storms. Thus, it is especially important if the region has very high tidal ranges over very gentle tidal flats, which is a very vulnerable region. Although the various remote sensing platforms can be used to map shoreline changes, the spatial and temporal resolutions are not enough to obtain it for a short time. Accordingly, in this study we introduce the newly developed low altitude Helikite remote sensing platform to achieve much better resolutions of shorelines and a bathymetry. The Helikite stands for Helium balloon and Kite, which is a kind of aerial platform that uses the advantages of both a Helium balloon and a kite. Field experiments were conducted in the Jaebu Island, off the coast of the west Korean Peninsula in January 29, 2011. In order to extract shorelines from the consecutive images taken by the low altitude Helikite remote sensing platform, active contours without edges （ACWE） is used. Edges or boundaries exist primarily on places between one type of objective and the other. Since the hydrodynamic pressure has an effect everywhere, the locations of the waterlines can be the isobath lines. We could map several waterlines, which would enable us to complete a local bathymetry map ranges from 35 to 60 cm depth. The error resulting from applying ACWE algorithm to the imagery to determine the waterline is approximately less than 1 m. Therefore, it is very unique way to obtain such high resolutions of bathymetry with high accuracy for the regions of extremely high tidal ranges for a short time.
文摘As a promising alternative hydrogen evolution catalyst,MoS_(2)is well known for its active edge sites and the inert basal plane.Now,1T′-MoS_(2)crystals are prepared and processed into different electrochemical microcells based on individual MoS_(2)nanosheets to reveal that the basal plane of 1T′-MoS_(2)is highly catalytically active.
基金supported by the National Natural Science Foundation of China under Grant Nos.52222204,52172103,52293371,52072304,and Natural Science Basic Research Program in Shaanxi(2022JC-25).
文摘The mechanics of structural ceramics,especially the toughness,are crucial to their service reliability and need to be continuously optimized.Inspired by the“brick-mortar”structure and further adjusting the microstructure of“mortar”on the interface,ceramic with strength and toughness up to 444.16 MPa and 13.79 MPa⋅m^(1/2) is constructed by hot pressed sintering with alumina(Al_(2)O_(3))as brick and vertical graphene(VG)with active atomic edges as mortar.Relying on the covalent interface between VG grown in-situ and Al_(2)O_(3),the sliding of Al_(2)O_(3)links the shear-deformation process of the crosslinked and interlocked nanointerface formed by VG,making the VG-enhanced Al_(2)O_(3)ceramics(AVG)obtain super toughness.Moreover,the structure of interlocked VG-nanointerface exhibits an excellent high-temperature resistance,which makes AVG still show the excellent strength of 437.66 MPa and toughness of 11.16 MPa⋅m^(1/2)after heat treatment at 1500℃for 100 h and they are respective 2.51 times and 3.18 times higher than Al_(2)O_(3)in the same condition.This work provides a new thought for the preparation of high-strength,ultra-tough and high-temperature mechanical stable ceramics.
基金This work was supported by the National Natural Science Foundation of China （Grant Nos. 21576289 and 21322609）, the Science Foundation Research Funds Provided to New Recruitments of China University of Petroleum, Beijing （2462014QZDX01） and the Thousand Talents Program.
文摘Though the transition-metal dichalcogenides （TMDs） were proven to have a better performance on the hydrogen evolution reaction （HER）, the bulk production of active TMD materials remains a challenging work. This report overcomes those barriers by showing a simple procedure to synthesize TaS2 nanosheets through modifying the arc discharge process. The usage of chloride as the transporting agent reduces the growth period of the formed TaS2 with active edge sites. TaS2 is found to have a uniform thickness （4 nm） with high crystallinity and adopt a 2H polytype （double-layered hexagonal） structure. The as-synthesized TaS2 has superior activity for HER with the potential of 280 mV.
