The titanium-based ion sieve H2TiO_(3)(HTO)is recognized for its high lithium adsorption capacity and exceptional structural stability,making it a leading candidate for lithium extraction from aqueous resources.In thi...The titanium-based ion sieve H2TiO_(3)(HTO)is recognized for its high lithium adsorption capacity and exceptional structural stability,making it a leading candidate for lithium extraction from aqueous resources.In this study,chromium-doped H2TiO_(3)(HCTO)was synthesized via a high-temperature solid-state method to enhance lithium adsorption performance.A series of characterization techniques were employed to analyze HCTO's structure,morphology,specific surface area,and valence state evolution.Static adsorption experiments were performed to evaluate HCTO's adsorption performance and elucidate its mechanism.Experimental results and density functional theory(DFT)calculations demonstrate that Cr^(3+)doping induces oxygen vacancies(Ovs)formation in the HTO lattice,reduces Li^(+)diffusion barriers in the solid phase,enhances electron transport efficiency,and strengthens electrostatic Li^(+)-adsorbent interactions,collectively improving Li^(+)adsorption performance.Cr^(3+)incorporation effectively mitigates particle agglomeration,resulting in HCTO's specific surface area reaching 46.04 m2g^(-1).Additionally,the crystal defects induced by Cr^(3+)doping create a"pinning effect",thereby enhancing the structural stability of the adsorbent material.Experimental data demonstrate that HCTO-1%achieves a Li^(+)adsorption capacity of 48.07 mg g^(-1)in lithium-containing solutions,representing a 61.58%enhancement compared to unmodified HTO.After five adsorptionDdesorption cycles,the Ti^(4+)dissolution rate in HCTO-1%remained below 0.20%,demonstrating excellent cycling stability.In salt lake brine,HCTO-1%exhibits high Li^(+)selectivity over competing cations.Mechanistic studies reveal that the adsorption process of Li^(+)on HCTO-1%follows an ion exchange mechanism,involving the breaking of ODH bonds and the formation of ODLi bonds.展开更多
Nonprecious-metal-group single-metal-atom catalysts with bifunctional catalytic capabilities toward the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)are highly sought after in energy-conversion and ...Nonprecious-metal-group single-metal-atom catalysts with bifunctional catalytic capabilities toward the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)are highly sought after in energy-conversion and storage technology.However,producing renewable and sustainable energy sources remains challenging.Currently,single-transition metal atoms anchored onπ-πconjugated two-dimensional(2D)graphitic carbon nitride substrates formπ-d conjugated conductive channels that enhance the overall electrocatalytic activity.Herein,firstprinciples calculations were carried out to design and demonstrate a novel macropore graphitic carbon nitride(gC_(10)N_(3))as a promising 2D electrocatalyst substrate to support single-transition metal(TM,from Sc to Au).The"donation-acceptance"charge interaction in the TM-N_(2)moiety effectively balances the adsorption strength of oxygenated intermediates in Ni@g-C_(10)N_(3)and Rh@gC_(10)N_3,making them effective bifunctional OER/ORR electrocatalysts with IrO_(2)/Pt-beyond overpotentials being as low as 0.39/0.38 V and 0.54/0.44 V,respectively.Additionally,they possess high stability and conductivity and are less susceptible to oxidation and corrosion under working conditions.This guarantees high activity under ambient conditions.Then,the origin of the OER/ORR activity of TM@g-C_(10)N_(3) is explained using multilevel descriptors:intrinsic(p,Bader charge,integral crystal orbital Hamilton population(ICOHP),bond length,and d-band center(εd).In particular,for optimal Ni@g-C_(10)N_(3),the clear hybridization between the Ni-d orbital and surface O-p orbital causes the paired electrons to occupy the bonding orbitals.This enables OH~*to be adsorbed on the Ni@g-C_(10)N_(3),thereby achieving the highest catalytic performance.展开更多
Recent advances in monochromatic aberration corrected electron microscopy make it possible to detect the lattice vibrations with both high-energy resolution and high spatial resolution. Here, we use sub-10 meV electro...Recent advances in monochromatic aberration corrected electron microscopy make it possible to detect the lattice vibrations with both high-energy resolution and high spatial resolution. Here, we use sub-10 meV electron energy loss spectroscopy to investigate the local vibrational properties of the SiO_2/Si surface and interface. The energy of the surface mode is thickness dependent, showing a blue shift as z-thickness(parallel to the fast electron beam)of SiO_2 film increases, while the energy of the bulk mode and the interface mode keeps constant. The intensity of the surface mode is well-described by a Bessel function of the second kind. The mechanism of the observed spatially dependent vibrational behavior is discussed and compared with dielectric response theory analysis. Our nanometer scale measurements provide useful information on the bonding conditions at the surface and interface.展开更多
Electromagnetic V-shape bending of small size sheet blank is investigated numerically and experimentally. Three-dimensional electromagnetic field models are established to calculate the magnetic force distribution on ...Electromagnetic V-shape bending of small size sheet blank is investigated numerically and experimentally. Three-dimensional electromagnetic field models are established to calculate the magnetic force distribution on the sheet by software ANSYS / EMAG. Series of electromagnetic V-shape bending forming experiments are presented,in which small size uniform pressure coil and big size round flat spiral coil are used. The results show that small size uniform pressure coil is not suitable for electromagnetic forming of small size flat sheet,and the coil is susceptible to failure such as bulging,ablation and cracking. When the plane dimension of round flat spiral coil is bigger than sheet blank sizes,the induced current crowding effect will be resulted which seriously influence the magnetic force distribution on the sheet. In this case,magnetic force distribution can be adjusted through the change of the relative position between coil and sheet,the desired deformation can be obtained finally. Therefore,big size round flat spiral coil can be well applied to electromagnetic V-shape bending forming of small size flat sheet.展开更多
基金financially supported by Qinghai Provincial Key Research and Development(R&D)and Transformation Program(No.2025-QY-240)Tianjin UniversityQinghai Minzu University Joint Innovation Fund(Nos.24TQ003,2022TQ05,and 2023TQ002)
文摘The titanium-based ion sieve H2TiO_(3)(HTO)is recognized for its high lithium adsorption capacity and exceptional structural stability,making it a leading candidate for lithium extraction from aqueous resources.In this study,chromium-doped H2TiO_(3)(HCTO)was synthesized via a high-temperature solid-state method to enhance lithium adsorption performance.A series of characterization techniques were employed to analyze HCTO's structure,morphology,specific surface area,and valence state evolution.Static adsorption experiments were performed to evaluate HCTO's adsorption performance and elucidate its mechanism.Experimental results and density functional theory(DFT)calculations demonstrate that Cr^(3+)doping induces oxygen vacancies(Ovs)formation in the HTO lattice,reduces Li^(+)diffusion barriers in the solid phase,enhances electron transport efficiency,and strengthens electrostatic Li^(+)-adsorbent interactions,collectively improving Li^(+)adsorption performance.Cr^(3+)incorporation effectively mitigates particle agglomeration,resulting in HCTO's specific surface area reaching 46.04 m2g^(-1).Additionally,the crystal defects induced by Cr^(3+)doping create a"pinning effect",thereby enhancing the structural stability of the adsorbent material.Experimental data demonstrate that HCTO-1%achieves a Li^(+)adsorption capacity of 48.07 mg g^(-1)in lithium-containing solutions,representing a 61.58%enhancement compared to unmodified HTO.After five adsorptionDdesorption cycles,the Ti^(4+)dissolution rate in HCTO-1%remained below 0.20%,demonstrating excellent cycling stability.In salt lake brine,HCTO-1%exhibits high Li^(+)selectivity over competing cations.Mechanistic studies reveal that the adsorption process of Li^(+)on HCTO-1%follows an ion exchange mechanism,involving the breaking of ODH bonds and the formation of ODLi bonds.
基金financially supported by the National Natural Science Foundation of China(No.21905175)。
文摘Nonprecious-metal-group single-metal-atom catalysts with bifunctional catalytic capabilities toward the oxygen evolution reaction(OER)and oxygen reduction reaction(ORR)are highly sought after in energy-conversion and storage technology.However,producing renewable and sustainable energy sources remains challenging.Currently,single-transition metal atoms anchored onπ-πconjugated two-dimensional(2D)graphitic carbon nitride substrates formπ-d conjugated conductive channels that enhance the overall electrocatalytic activity.Herein,firstprinciples calculations were carried out to design and demonstrate a novel macropore graphitic carbon nitride(gC_(10)N_(3))as a promising 2D electrocatalyst substrate to support single-transition metal(TM,from Sc to Au).The"donation-acceptance"charge interaction in the TM-N_(2)moiety effectively balances the adsorption strength of oxygenated intermediates in Ni@g-C_(10)N_(3)and Rh@gC_(10)N_3,making them effective bifunctional OER/ORR electrocatalysts with IrO_(2)/Pt-beyond overpotentials being as low as 0.39/0.38 V and 0.54/0.44 V,respectively.Additionally,they possess high stability and conductivity and are less susceptible to oxidation and corrosion under working conditions.This guarantees high activity under ambient conditions.Then,the origin of the OER/ORR activity of TM@g-C_(10)N_(3) is explained using multilevel descriptors:intrinsic(p,Bader charge,integral crystal orbital Hamilton population(ICOHP),bond length,and d-band center(εd).In particular,for optimal Ni@g-C_(10)N_(3),the clear hybridization between the Ni-d orbital and surface O-p orbital causes the paired electrons to occupy the bonding orbitals.This enables OH~*to be adsorbed on the Ni@g-C_(10)N_(3),thereby achieving the highest catalytic performance.
基金Supported by the National Key R&D Program of China under Grant No 2016YFA0300804the National Natural Science Foundation of China under Grant Nos 51502007 and 51672007+2 种基金the National Equipment Program of China under Grant No ZDYZ2015-1the National Program for Thousand Young Talents of Chinathe ‘2011 Program’ Peking-Tsinghua-IOP Collaborative Innovation Center of Quantum Matter
文摘Recent advances in monochromatic aberration corrected electron microscopy make it possible to detect the lattice vibrations with both high-energy resolution and high spatial resolution. Here, we use sub-10 meV electron energy loss spectroscopy to investigate the local vibrational properties of the SiO_2/Si surface and interface. The energy of the surface mode is thickness dependent, showing a blue shift as z-thickness(parallel to the fast electron beam)of SiO_2 film increases, while the energy of the bulk mode and the interface mode keeps constant. The intensity of the surface mode is well-described by a Bessel function of the second kind. The mechanism of the observed spatially dependent vibrational behavior is discussed and compared with dielectric response theory analysis. Our nanometer scale measurements provide useful information on the bonding conditions at the surface and interface.
基金Sponsored by the National Basic Research Program of China(Grant No.2011CB012800 and 2011CB012804)
文摘Electromagnetic V-shape bending of small size sheet blank is investigated numerically and experimentally. Three-dimensional electromagnetic field models are established to calculate the magnetic force distribution on the sheet by software ANSYS / EMAG. Series of electromagnetic V-shape bending forming experiments are presented,in which small size uniform pressure coil and big size round flat spiral coil are used. The results show that small size uniform pressure coil is not suitable for electromagnetic forming of small size flat sheet,and the coil is susceptible to failure such as bulging,ablation and cracking. When the plane dimension of round flat spiral coil is bigger than sheet blank sizes,the induced current crowding effect will be resulted which seriously influence the magnetic force distribution on the sheet. In this case,magnetic force distribution can be adjusted through the change of the relative position between coil and sheet,the desired deformation can be obtained finally. Therefore,big size round flat spiral coil can be well applied to electromagnetic V-shape bending forming of small size flat sheet.
