Vanadium is a strategic metal in many countries,and it is mainly extracted from vanadium slag produced in titanomagnetite metallurgy.The traditional sodium roasting process for vanadium extraction poses environmental ...Vanadium is a strategic metal in many countries,and it is mainly extracted from vanadium slag produced in titanomagnetite metallurgy.The traditional sodium roasting process for vanadium extraction poses environmental threats,and a green calcification pro-cess has been proposed.However,the vanadium extraction rate in the calcification process is much lower than in the sodium roasting pro-cess,which is related to vanadium solid solubility in Fe_(2)TiO_(5).Previous studies about vanadium behavior in Fe_(2)TiO_(5) were conducted in air,with a vanadium oxidation state of V5+.Vanadium with lower oxidation states has been detected in the tailings in the calcification process.The present paper studied the effects of vanadium oxidation states on the solid solubility in Fe_(2)TiO_(5) through solid-state reaction,X-ray diffraction characterization,transmission electron microscopy characterization,X-ray photoelectron spectroscopy analysis,and solid solu-tion modeling.The relative interaction values between vanadium oxides and Fe_(2)TiO_(5) are obtained as|L_(V_(2)O_(3))|>|L_(V_(2)O_(4))|>|L_(V_(2)O_(5)),indicating that vanadium with lower valence is preferable to be solid dissolved in Fe_(2)TiO_(5).The results imply that insufficiently oxidized vanadium increases the vanadium content in the Fe_(2)TiO_(5) phase during vanadium slag’s calcification roasting.Besides,experimental conditions op-timization shows that higher experimental temperature,vanadium introduction as V2O3,and a high-purity argon atmosphere would lead to higher vanadium solubility in Fe_(2)TiO_(5),and high temperature is beneficial for the release of vanadium from vanadium-containing Fe_(2)TiO_(5) when dissociated in air.展开更多
Negatively charged open-framework metal sulfides(NOSs),taking advantages of the characteristics of excellent visible light absorption,easily exchanged cations,and abundant active sites,hold significant promise as high...Negatively charged open-framework metal sulfides(NOSs),taking advantages of the characteristics of excellent visible light absorption,easily exchanged cations,and abundant active sites,hold significant promise as highly efficient photocatalysts for hydrogen evolution.However,their applications in photocatalytic hydrogen evolution(PHE)are infrequently documented and the corresponding photocatalytic mechanism has not yet been explored.Herein,we excavated a novel NOS photocatalyst of(Me_(2)NH_(2))_(6)In_(10)S_(18)(MIS)with a three-dimensional(3D)structure,and successfully incorporated divalent Co(Ⅱ)and metal Co(0)into its cavities via the convenient cation exchange-assisted approach to regulate the critical steps of photocatalytic reactions.As the introduced Co(0)allows for more efficient light utilization and adroitly surficial hydrogen desorption,and meanwhile acts as the‘electron pump’for rapid charge transfer,Co(0)-modified MIS delivers a surprising PHE activity in the initial stage of photocatalysis.With the prolonging of illumination,metal Co(0)gradually escapes from MIS framework,resulting in the decline of PHE performance.By stark contrast,the incorporated Co(Ⅱ)can establish a strong interaction with MIS framework,and simultaneously capture photogenerated electrons from MIS to produce Co(0),which constructs a stable photocatalytic system as well as provides additional channels for spatially separating photogenerated carriers.Thus,Co(Ⅱ)-modified MIS exhibits a robust and highly stable PHE activity of~4944μmol/g/h during the long-term photocatalytic reactions,surpassing most of the previously reported In–S framework photocatalysts.This work represents a breakthrough in the study of PHE performance and mechanism of NOS-based photocatalysts,and sheds light on the design of vip confined NOS-based photocatalysts towards high-efficiency solar-to-chemical energy conversion.展开更多
The dominant oxidation state for lanthanide ions is+3 due to the loss of 5d and 6s electrons from their shared configuration of[Xe]4f^(0-14)5d^(0-16)s(2).There are however several exceptions because of the completely ...The dominant oxidation state for lanthanide ions is+3 due to the loss of 5d and 6s electrons from their shared configuration of[Xe]4f^(0-14)5d^(0-16)s(2).There are however several exceptions because of the completely empty(Ce(Ⅳ)),half-filled(Eu(Ⅱ)),or fully filled(Yb(Ⅱ))4f subshell.As such,stable complexes are formed primarily with Ln(Ⅲ)ions[1].展开更多
Si,as the most promising anode with high theoretical capacity for next-generation lithium-ion batteries(LIBs),is hampered in commercial application by its poor electrical conductivity and significant volume expansion....Si,as the most promising anode with high theoretical capacity for next-generation lithium-ion batteries(LIBs),is hampered in commercial application by its poor electrical conductivity and significant volume expansion.Herein,the core-shell Si@SiO_(x)/C@C-Ar(SSC-A)or Si@SiO_(x)/C@C-H_(2)/Ar(SSC-H)composites are purposefully designed by in situ introduction of inorganic SiO_(x)in pure Ar or H_(2)/Ar atmosphere to realize a Si-based anode for LIBs.By introducing different atmospheres,the valence states of SiO_(x)are regulated.The inorganic transition layer formed by the combination of SiO_(x)with higher average valence and asphalt-derived carbon demonstrates better performance in both stabilizing the core-shell structure and inhibiting the agglomeration of Si particles.Given these advantages,the SSC-A electrode exhibits excellent electrochemical performance(1163 mAh g^(-1)after 400 cycles at 1 A g^(-1)),and the commercial blended graphite-SSC-A electrode reaches a specific capacity of 442 mAh g^(-1)with 74.8%capacity retention under the same conditions.Even the SSC-A electrode without Super P maintains an ultrahigh discharge specific capacity of 803 mAh g^(-1)with 60.6%after cycling.Importantly,the full batteries based on SSC-A without Super P achieve a discharge specific capacity of 126 mAh g^(-1)with 28.2%capacity decay after 200 cycles,demonstrating the superior commercial application potential.展开更多
Single-atom catalysts(SACs)have attracted considerable interest in the fields of energy and environmental science due to their adjustable catalytic activity.In this study,we investigated the matching of valence electr...Single-atom catalysts(SACs)have attracted considerable interest in the fields of energy and environmental science due to their adjustable catalytic activity.In this study,we investigated the matching of valence electron numbers between single atoms and adsorbed intermediates(O,N,C,and H)in MXene-anchored SACs(M-Ti_(2)C/M-Ti_(2)CO_(2)).The density functional theory results demonstrated that the sum of the valence electron number(VM)of the interface-doped metal and the valence electron number(VA)of the adsorbed intermediates in M-Ti_(2)C followed the 10-valence electron matching law.Furthermore,based on the 10-valence electron matching law,we deduced that the sum of the valence electron number(k)and VMfor the molecular adsorption intermediate interactions in M-Ti_(2)CO_(2)adhered to the 11-valence electron matching law.Electrostatic repulsion between the interface electrons in M-Ti_(2)CO_(2)and H_(2)O weakened the adsorption of intermediates,Furthermore,we applied the 11-valence electron matching law to guide the design of catalysts for nitrogen reduction reaction,specifically for N_(2)→NNH conversion,in the MTi_(2)CO_(2)structure.The sure independence screening and sparsifying operator algorithm was used to fit a simple three-dimensional descriptor of the adsorbate(R_(2)up to 0.970)for catalyst design.Our study introduced a valence electron matching principle between doped metals(single atoms)and adsorbed intermediates(atomic and molecular)for MXene-based catalysts,providing new insights into the design of high-performance SACs.展开更多
We take the contribution of all valence electrons into consideration and propose a new valence electrons equilibration method to calculate the equalized electronegativity including molecular electronegativity, group e...We take the contribution of all valence electrons into consideration and propose a new valence electrons equilibration method to calculate the equalized electronegativity including molecular electronegativity, group electronegativity, and atomic charge. The ionization potential of alkanes and mono-substituted alkanes, the chemical shift of 1H NMR, and the gas phase proton affinity of aliphatic amines, alcohols, and ethers were estimated. All the expressions have good correlations. Moreover, the Sanderson method and Bratsch method were modified on the basis of the valence electrons equilibration theory. The modified Sanderson method and modified Bratsch method are more effective than their original methods to estimate these properties.展开更多
The catalytic effects of the organic compounds of iron,tin and manganese on the degradation of low density polyethylene (LDPE) at compost temperature are discussed.A series of samples were aged in a simulating compost...The catalytic effects of the organic compounds of iron,tin and manganese on the degradation of low density polyethylene (LDPE) at compost temperature are discussed.A series of samples were aged in a simulating compost environment.The mechanical properties,viscosity average molecular weight (M η) of PE and hydroperoxide (POOH) concentration in the samples were measured.FT IR and DSC were also applied to characterize some samples.It was shown that the above mentioned metallic organic compounds can catalyze the degradation of LDPE efficiently.After 2 months aging,all samples with catalysts became fragile and the M η of the material decreased dramatically.Furthermore,the concentration of carbonyl and the degree of crystallinity of the material increased with the aging time.展开更多
High-purity titanium powder was prepared by molten salt electrorefining from sponge titanium in NaCl-KCl-TiClx salts. The titanium valence, purity and electrocrystallization during electrolysis process were studied. T...High-purity titanium powder was prepared by molten salt electrorefining from sponge titanium in NaCl-KCl-TiClx salts. The titanium valence, purity and electrocrystallization during electrolysis process were studied. The XPS analysis showed that the titanium valences are mainly ＋4, ＋3 and ＋2 at the earlier, medium and later stages of electrolysis, respectively. During the electrolysis process, the contents of impurities Si, Cr, Mn, Al vary little, and the contents of impurities Fe, Cu, Ni decrease markedly, while the contents of impurities O, N, H increase obviously. The residual impurities are usually distributed in small tunnel of dendritic crystals. Enhancing the electrolysis temperature and prolonging the electrolysis time can increase the titanium particle size. The TEM analysis showed that the electrodeposited titanium is not a single crystal, but contains many nanostructured grains and subgrains, with grain size of 100-500 nm. The electrolysis mechanisms were also discussed.展开更多
Electrocatalysis for the oxygen evolution reactions(OER)has attracted much attention due to its important role in water splitting and rechargeable metal-air batteries.Therefore,designing highly efficient and low-cost ...Electrocatalysis for the oxygen evolution reactions(OER)has attracted much attention due to its important role in water splitting and rechargeable metal-air batteries.Therefore,designing highly efficient and low-cost catalysts for OER process is essential as the conventional catalysts still rely on precious metals.Transition metal-based compounds have been widely investigated as active OER catalysts,and renewed interest in the high valence metals engineered compounds has been achieved for superior catalytic activity and stability.However,an in-depth understanding of the construction strategies and induced effects for the high valence metals engineered catalysts is still lacking and desired.In this review,we have summarized the construction strategies of high valence metals as dopants or formed heterostructures with the iron/cobalt/nickel(Fe/Co/Ni)-based catalysts.Then the induced effects on Fe/Co/Ni-based catalysts by incorporating high valence metals,e.g.,accelerating the surface reconstruction,forming amorphous structure,generating vacancies/defects,and acting as stabilizers,are highlighted.The impacts of high valence metals on OER performance are elucidated based on different elements,including molybdenum(Mo),tungsten(W),cerium(Ce),vanadium(V),chromium(Cr),manganese(Mn),niobium(Nb),zirconium(Zr).The correlations of construction strategies,induced effects,catalytic activity and OER reaction pathways are elaborated.Finally,the remaining challenges for further enhancements of OER performance induced by high valence metals are presented.展开更多
AV4+-V2O5 cathode with mixed vanadium valences was prepared via a novel synthetic method using VOOH as the precursor,and its zinc-ion storage performance was evaluated.The products are hollow spheres consisting of nan...AV4+-V2O5 cathode with mixed vanadium valences was prepared via a novel synthetic method using VOOH as the precursor,and its zinc-ion storage performance was evaluated.The products are hollow spheres consisting of nanoflakes.The V4+-V2O5 cathode exhibits a prominent cycling performance,with a specific capacity of 140 mAhg-1 after 1000 cycles at 10 A g.1,and an excellent rate capability.The good electrochemical performance is attributed to the presence of V4+,which leads to higher electrochemical activity,lower polarization,faster ion diffusion,and higher electrical conductivity than V2O5 without V4+.This engineering strategy of valence state manipulation may pave the way for designing high-performance cathodes for elucidating advanced battery chemistry.展开更多
The valenceofelementyttrium of Y2 O3 Mocathode materialhasbeenstudied by usingther mal weight analysis, X ray diffraction analysis, Scanning electron microscopy and X rayphotoelectronspectrum . It hasbeen proved...The valenceofelementyttrium of Y2 O3 Mocathode materialhasbeenstudied by usingther mal weight analysis, X ray diffraction analysis, Scanning electron microscopy and X rayphotoelectronspectrum . It hasbeen provedthatyttrium oxidecan bereduced by molybdenum carbide. Thereaction between powdered Y2 O3 and Mo2 Ccan happen at 1173 , and Y2 O3may bereduced to metallicyttrium . Afterthepowder mixtureof Y2 O3 and Mo2 Cwasheat treated at1873 K, Yttrium existsin two kinds of chemicalstate- yttrium of zero valence and yttrium ofthreevalences.展开更多
Chloroplasts were isolated from spinach treated with taCl3, CeCl3, and NdCl3. Because of owning 4f electron characteristics and alternation valence, Ce treatment presented the highest enhancement in light absorption, ...Chloroplasts were isolated from spinach treated with taCl3, CeCl3, and NdCl3. Because of owning 4f electron characteristics and alternation valence, Ce treatment presented the highest enhancement in light absorption, energy transfer from LHC Ⅱ to PS Ⅱ, excitation energy distribution from PS Ⅰ to PS Ⅱ, and fluorescence quantum yield around 680 nm. Compared with Ce treatment, Nd treatment resulted in relatively lower enhancement in these physiological indices, as Nd did not have alternation valence. La treatment presented the lowest enhancement, as La did not have either 4f electron or alternation valence. The increase in activities of whole chain electron transport, PS ⅡDCPIP photoreduction, and oxygen evolution of chloroplasts was of the following order： Ce〉Nd 〉La〉 control. However, the photoreduction activities of spinach PS I almost did not change with La, Ce, or Nd treatments. The results suggested that 4f electron characteristics and alternation valence of rare earths had a close relationship with photosynthesis improvement.展开更多
In this study,complete tetracycline(TTC)and above 50%of total organic carbon(TOC)were removed by Fe S/PS after 30 min under optimized conditions.Although free radicals and high-valent iron ions were identified to gene...In this study,complete tetracycline(TTC)and above 50%of total organic carbon(TOC)were removed by Fe S/PS after 30 min under optimized conditions.Although free radicals and high-valent iron ions were identified to generate in the process,the apparent similarity between intermediate products of Fe S/PS,Fe/PS,and UV/PS systems demonstrated that the degradation of TTC was due to sulfate radicals(SO_(4)·^(-))and hydroxyl radicals(·OH).Based on the reaction between free radicals and organic matter,we speculated that TTC in the Fe S/PS system was decomposed and mineralized by dehydration,dehydrogenation,hydroxyl addition,demethylation,substitution,E-transfer,and ring-opening.Furthermore,a new understanding of Fe S-mediated PS activation based on stoichiometry and kinetic analysis showed that there were both homogeneous and heterogeneous reactions that occurred in the entire progress.However,due to the effect of p H on the dissolution of iron ions,the homogeneous reaction became the principal process with iron ions concentration exceeding 1.35 mg/L.This work provides a theoretical basis for the study of the degradation of TTC-containing wastewater by the iron-based advanced oxidation process.展开更多
Developing the highly active, cost-effective, environmental-friendly, and ultra-stable nonprecious electrocatalysts for hydrogen evolution reaction(HER) is distinctly indispensable for the large-scale practical applic...Developing the highly active, cost-effective, environmental-friendly, and ultra-stable nonprecious electrocatalysts for hydrogen evolution reaction(HER) is distinctly indispensable for the large-scale practical applications of hydrolytic hydrogen production. Herein, we report the synthesis of well-integrated electrode, NiV layered double hydroxide nanosheet array grown in-situ on porous nickel foam(abbreviated as in-NiV-LDH/NF) via the facile one-step hydrothermal route. Interestingly, the valence configuration of vanadium(V) sites in such NiV-LDH are well dominated by the innovative use of NF as the reducing regulator, achieving the reassembled in-NiV-LDH/NF with a high proportion of trivalent V ions(V3+), and then an enhanced intrinsic electrocatalytic HER activity. The HER testing results show that the in-NiVLDH/NF drives the current densities of 10 and 100 mA cm-2 at extremely low overpotentials of 114 and 245 mV without iR-compensation respectively, even outperforms commercial 20 wt% Pt/C at the large current density of over 80 mA cm-2 in alkaline media, as well as gives robust catalytic durability of at least 100 h in both alkaline and neutral media. More importantly, this work provides a fresh perspective for designing bimetal(oxy) hydroxides electrocatalysts with efficient hydrogen generation.展开更多
The crystal structure and physical properties of Nb_(25)Mo_(5+x)Re_(35)Ru_(25-x)Rh_(10)(0≤x≤10)and Nb_(5)Mo_(35-y)Re_(15+y)Ru_(35)Rh_(10)(0≤y≤15)high-entropy alloys(HEAs)have been studied by X-ray diffraction,elec...The crystal structure and physical properties of Nb_(25)Mo_(5+x)Re_(35)Ru_(25-x)Rh_(10)(0≤x≤10)and Nb_(5)Mo_(35-y)Re_(15+y)Ru_(35)Rh_(10)(0≤y≤15)high-entropy alloys(HEAs)have been studied by X-ray diffraction,electrical resistivity,magnetic susceptibility,and specific heat measurements.The results show that the former HEAs with valence electron concentration(VEC)values of 6.7-6.9 crystallize in a noncentrosymmetric cubicα-Mn structure,while the latter ones with VEC values of 7.1-7.25 adopt a centrosymmetric hexagonal close-packed(hcp)structure.Despite different structures,both series of HEAs are found to be bulk superconductors with a full energy gap,and the superconducting transition temperature Tc tends to decrease with the increase of VEC.Nevertheless,the Tc values of the hcp-type HEAs are higher than those of theα-Mn-type ones,likely due to a stronger electron phonon coupling.Furthermore,we show that VEC and electronegativity difference are two key parameters to control the stability ofα-Mn and hcp-type HEAs.These results not only are helpful for the design of such HEAs,but also represent the first realization of structurally different HEA superconductors without changing the constituent elements.展开更多
Relieving the stress or strain associated with volume change is highly desirable for high-performance SiOx anodes in terms of stable solid electrolyte interphase(SEI)-film growth.Herein,a Si-valence gradient is optimi...Relieving the stress or strain associated with volume change is highly desirable for high-performance SiOx anodes in terms of stable solid electrolyte interphase(SEI)-film growth.Herein,a Si-valence gradient is optimized in SiOx composites to circumvent the large volume strain accompanied by lithium insertion/extraction.SiO_(x)@C annealed at 850℃ has a gentle Si-valence gradient along the radial direction and excellent electrochemical performances,delivering a high capacity of 506.9 mAh g^(−1) at 1.0 A g^(−1) with a high Coulombic efficiency of~99.8%over 400 cycles.Combined with the theoretical prediction,the obtained results indicate that the gentle Si-valence gradient in SiO_(x)@C is useful for suppressing plastic deformation and maintaining the inner connection integrity within the SiO_(x)@C particle.Moreover,a gentle Si-valence gradient is expected to form a stress gradient and affect the distribution of dangling bonds,resulting in local stress relief during the lithiation/delithiation process and enhanced Li-ion kinetic diffusion.Furthermore,the lowest interfacial stress variation ensures a stable SEI film at the interface and consequently increases cycling stability.Therefore,rational design of a Si-valence gradient in SiOx can provide further insights into achieving high-performance SiOx anodes with large-scale production.展开更多
High valence state species are significant in the energy-relevant electrochemical oxidation reactions.Herein,the high active state of Ni^(3+)formation induced by Mo^(6+)and their efficient synergism in NiS_(2)-MoS_(2)...High valence state species are significant in the energy-relevant electrochemical oxidation reactions.Herein,the high active state of Ni^(3+)formation induced by Mo^(6+)and their efficient synergism in NiS_(2)-MoS_(2)hetero-nanorods powder catalyst with the rough layered structure are demonstrated,as proof of concept,for the urea-assisted water electrolysis.This catalyst can be derived from the sulfidation of NiMoO_(4) nanorods that can realize individual metal sulfides sufficiently mixing at a domain size in the nanoscale which creates lots of active sites and nanointerfaces.The high valence state of Mo^(6+)and Ni^(3+)formation and increased conductive phase of 1 T MoS_(2)in the hetero-nanorods compared to the counterpart pure phases are revealed by spectral study and microscopic analysis;high electrochemical surface area and active site exposure are found due to the nano-interface formation and layered rough nanosheets over the surface of nanorods.They show much higher catalytic performance than their pure phases for urea oxidation,including high catalytic activity,stability,charge transfer ability and catalytic kinetics resulting from more active Ni^(3+)species formation and electronic synergism of high valence metals.Transformation of 1 T MoS_(2)to Mo^(6+)and increased amount of Mo^(6+)and Ni^(3+)after stability test indicate their involvement and synergism for the catalysis reaction.The current work offers a novel understanding of the synergistic effect based on the high valence state synergism for heterogeneous catalysts in electrocatalysis.展开更多
The low valence electron concentration(VEC)Al_(x)CoCrFeNiSi(x=0.5,1.0,1.5 and 2.0)high-entropy alloys(HEAs)were designed by the fundamental properties of the constituent elements and prepared by vacuum arc melting met...The low valence electron concentration(VEC)Al_(x)CoCrFeNiSi(x=0.5,1.0,1.5 and 2.0)high-entropy alloys(HEAs)were designed by the fundamental properties of the constituent elements and prepared by vacuum arc melting method.The effects of Al addition on the crystal structure and microstructure were investigated.The microhardness and wear property were also researched.The results showed that the microstructure transformed from dendritic crystal to equiaxed crystal.It was found that FCC phase gradually decreased with the increasing Al content and disappeared until in a composition of 1.0 in Al_(x)CoCrFeNiSi HEAs.Little FCC phase was found with continuously adding Al,while the phase fraction of BCC increased from 85.0% to 91.8%,and VEC decreased from 7.00 to 6.14.The microhardness was increased gradually from 598 up to 909 HV with addition of Al from 0.5 to 2.0.It was the same of the compressive strength results,which improved from 1200 to 1920 MPa.The wear coefficient and mass loss were in line with mechanical properties evolution,which was attributed to the microstructure transformation into equiaxed crystal and the increase in BCC phase.展开更多
By measuring the hardness of carburized layer of a new type supersaturated carburizing steel （35Cr3SiMnMoV） at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and t...By measuring the hardness of carburized layer of a new type supersaturated carburizing steel （35Cr3SiMnMoV） at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and the temper temperature is established. The result indicates that the hardness goes down firstly, then up and down, just like a wave consistent with the temperature increase. A secondary hardening peak appears at 570 ℃ or so. Based on Empirical Election Theory （EET） of Solids and Molecules, the valence electron structures （VESs） containing α-Fe-C, α-Fe-C-Me segregation structure units and carbide are calculated. The laws of temper process and hardness change with the temper temperature are explained, and the fact that reconstruction of θ-Fe3C is prior to that of special carbide at high tempering is analyzed with the phase structure formation factor, S, being taken into consideration. Therefore, the laws of temper process and hardness change of supersaturated carburized layer at different temper temperature can be traced back to valence electron structure （VES） level of alloy phase.展开更多
The possibilities of hexagonal boron nitride(hBN) and lithium boron nitride(Li_3BN_2) transition into cubic boron nitride(cBN) under synthetic pressure 5.0 GPa and synthetic temperature 1700 K are analyzed with the us...The possibilities of hexagonal boron nitride(hBN) and lithium boron nitride(Li_3BN_2) transition into cubic boron nitride(cBN) under synthetic pressure 5.0 GPa and synthetic temperature 1700 K are analyzed with the use of the empirical electron theory of solids and molecules. The relative differences in electron density are calculated for dozens of bi-phase interfaces hBN/cBN, Li_3BN_2/cBN. These relative differences of hBN/cBN are in good agreement with the first order of approximation(<10%), while those of Li_3BN_2/cBN are much greater than 10%.This analysis suggests that Li_3BN_2 is impossible to be intermediate phase but is a catalyst and cBN should be directly transformed by hBN.展开更多
基金supported by the National Key Research and Development Program of China(No.2023YFC2908304).
文摘Vanadium is a strategic metal in many countries,and it is mainly extracted from vanadium slag produced in titanomagnetite metallurgy.The traditional sodium roasting process for vanadium extraction poses environmental threats,and a green calcification pro-cess has been proposed.However,the vanadium extraction rate in the calcification process is much lower than in the sodium roasting pro-cess,which is related to vanadium solid solubility in Fe_(2)TiO_(5).Previous studies about vanadium behavior in Fe_(2)TiO_(5) were conducted in air,with a vanadium oxidation state of V5+.Vanadium with lower oxidation states has been detected in the tailings in the calcification process.The present paper studied the effects of vanadium oxidation states on the solid solubility in Fe_(2)TiO_(5) through solid-state reaction,X-ray diffraction characterization,transmission electron microscopy characterization,X-ray photoelectron spectroscopy analysis,and solid solu-tion modeling.The relative interaction values between vanadium oxides and Fe_(2)TiO_(5) are obtained as|L_(V_(2)O_(3))|>|L_(V_(2)O_(4))|>|L_(V_(2)O_(5)),indicating that vanadium with lower valence is preferable to be solid dissolved in Fe_(2)TiO_(5).The results imply that insufficiently oxidized vanadium increases the vanadium content in the Fe_(2)TiO_(5) phase during vanadium slag’s calcification roasting.Besides,experimental conditions op-timization shows that higher experimental temperature,vanadium introduction as V2O3,and a high-purity argon atmosphere would lead to higher vanadium solubility in Fe_(2)TiO_(5),and high temperature is beneficial for the release of vanadium from vanadium-containing Fe_(2)TiO_(5) when dissociated in air.
基金financial supports provided by the Natural Science Foundation of Fujian Province(No.2024J01195)the National Nature Science Foundation of China(No.21905279)+1 种基金Sanming University(Nos.22YG11 and PYT2201)the Education Scientific Research Project of Youth Teachers in the Education Department of Fujian Province(No.JAT220351).
文摘Negatively charged open-framework metal sulfides(NOSs),taking advantages of the characteristics of excellent visible light absorption,easily exchanged cations,and abundant active sites,hold significant promise as highly efficient photocatalysts for hydrogen evolution.However,their applications in photocatalytic hydrogen evolution(PHE)are infrequently documented and the corresponding photocatalytic mechanism has not yet been explored.Herein,we excavated a novel NOS photocatalyst of(Me_(2)NH_(2))_(6)In_(10)S_(18)(MIS)with a three-dimensional(3D)structure,and successfully incorporated divalent Co(Ⅱ)and metal Co(0)into its cavities via the convenient cation exchange-assisted approach to regulate the critical steps of photocatalytic reactions.As the introduced Co(0)allows for more efficient light utilization and adroitly surficial hydrogen desorption,and meanwhile acts as the‘electron pump’for rapid charge transfer,Co(0)-modified MIS delivers a surprising PHE activity in the initial stage of photocatalysis.With the prolonging of illumination,metal Co(0)gradually escapes from MIS framework,resulting in the decline of PHE performance.By stark contrast,the incorporated Co(Ⅱ)can establish a strong interaction with MIS framework,and simultaneously capture photogenerated electrons from MIS to produce Co(0),which constructs a stable photocatalytic system as well as provides additional channels for spatially separating photogenerated carriers.Thus,Co(Ⅱ)-modified MIS exhibits a robust and highly stable PHE activity of~4944μmol/g/h during the long-term photocatalytic reactions,surpassing most of the previously reported In–S framework photocatalysts.This work represents a breakthrough in the study of PHE performance and mechanism of NOS-based photocatalysts,and sheds light on the design of vip confined NOS-based photocatalysts towards high-efficiency solar-to-chemical energy conversion.
基金supported by the National Natural Science Foundation of China(22101116,92261203,21971106)Shenzhen Fundamental Research Program(JCYJ20220530115001002 and JCYJ20220818100417037).
文摘The dominant oxidation state for lanthanide ions is+3 due to the loss of 5d and 6s electrons from their shared configuration of[Xe]4f^(0-14)5d^(0-16)s(2).There are however several exceptions because of the completely empty(Ce(Ⅳ)),half-filled(Eu(Ⅱ)),or fully filled(Yb(Ⅱ))4f subshell.As such,stable complexes are formed primarily with Ln(Ⅲ)ions[1].
基金financially supported by the National Natural Science Foundation of China(Nos.U22A20145,52072151,52171211,and 52271218)Jinan Independent Innovative Team(No.2020GXRC015)+3 种基金the Major Program of Shandong Province Natural Science Foundation(No.ZR2023ZD43)Natural Science Foumdation of Jiangsu Province(No.BK20241973)High-level Training Talents of'333'Project in Jiangsu Provincethe Science and Technology Program of University of Jinan(No.XKY2119)
文摘Si,as the most promising anode with high theoretical capacity for next-generation lithium-ion batteries(LIBs),is hampered in commercial application by its poor electrical conductivity and significant volume expansion.Herein,the core-shell Si@SiO_(x)/C@C-Ar(SSC-A)or Si@SiO_(x)/C@C-H_(2)/Ar(SSC-H)composites are purposefully designed by in situ introduction of inorganic SiO_(x)in pure Ar or H_(2)/Ar atmosphere to realize a Si-based anode for LIBs.By introducing different atmospheres,the valence states of SiO_(x)are regulated.The inorganic transition layer formed by the combination of SiO_(x)with higher average valence and asphalt-derived carbon demonstrates better performance in both stabilizing the core-shell structure and inhibiting the agglomeration of Si particles.Given these advantages,the SSC-A electrode exhibits excellent electrochemical performance(1163 mAh g^(-1)after 400 cycles at 1 A g^(-1)),and the commercial blended graphite-SSC-A electrode reaches a specific capacity of 442 mAh g^(-1)with 74.8%capacity retention under the same conditions.Even the SSC-A electrode without Super P maintains an ultrahigh discharge specific capacity of 803 mAh g^(-1)with 60.6%after cycling.Importantly,the full batteries based on SSC-A without Super P achieve a discharge specific capacity of 126 mAh g^(-1)with 28.2%capacity decay after 200 cycles,demonstrating the superior commercial application potential.
基金funded by the National Natural Science Foundation of China(61701288,51706128)the Natural Science Basic Research Program of Shaanxi Province(2021JM-485)+2 种基金the Key Scientific Research Project of Shaanxi Provincial Education Department(20JS019)the High-level Achievement Cultivation Project of Collaborative Innovation Center for Comprehensive Development of Qinba Biological Resources(QBXT-17-8)the Postgraduate Innovation Project of Shaanxi University of Technology(SLGYCX2410).
文摘Single-atom catalysts(SACs)have attracted considerable interest in the fields of energy and environmental science due to their adjustable catalytic activity.In this study,we investigated the matching of valence electron numbers between single atoms and adsorbed intermediates(O,N,C,and H)in MXene-anchored SACs(M-Ti_(2)C/M-Ti_(2)CO_(2)).The density functional theory results demonstrated that the sum of the valence electron number(VM)of the interface-doped metal and the valence electron number(VA)of the adsorbed intermediates in M-Ti_(2)C followed the 10-valence electron matching law.Furthermore,based on the 10-valence electron matching law,we deduced that the sum of the valence electron number(k)and VMfor the molecular adsorption intermediate interactions in M-Ti_(2)CO_(2)adhered to the 11-valence electron matching law.Electrostatic repulsion between the interface electrons in M-Ti_(2)CO_(2)and H_(2)O weakened the adsorption of intermediates,Furthermore,we applied the 11-valence electron matching law to guide the design of catalysts for nitrogen reduction reaction,specifically for N_(2)→NNH conversion,in the MTi_(2)CO_(2)structure.The sure independence screening and sparsifying operator algorithm was used to fit a simple three-dimensional descriptor of the adsorbate(R_(2)up to 0.970)for catalyst design.Our study introduced a valence electron matching principle between doped metals(single atoms)and adsorbed intermediates(atomic and molecular)for MXene-based catalysts,providing new insights into the design of high-performance SACs.
文摘We take the contribution of all valence electrons into consideration and propose a new valence electrons equilibration method to calculate the equalized electronegativity including molecular electronegativity, group electronegativity, and atomic charge. The ionization potential of alkanes and mono-substituted alkanes, the chemical shift of 1H NMR, and the gas phase proton affinity of aliphatic amines, alcohols, and ethers were estimated. All the expressions have good correlations. Moreover, the Sanderson method and Bratsch method were modified on the basis of the valence electrons equilibration theory. The modified Sanderson method and modified Bratsch method are more effective than their original methods to estimate these properties.
文摘The catalytic effects of the organic compounds of iron,tin and manganese on the degradation of low density polyethylene (LDPE) at compost temperature are discussed.A series of samples were aged in a simulating compost environment.The mechanical properties,viscosity average molecular weight (M η) of PE and hydroperoxide (POOH) concentration in the samples were measured.FT IR and DSC were also applied to characterize some samples.It was shown that the above mentioned metallic organic compounds can catalyze the degradation of LDPE efficiently.After 2 months aging,all samples with catalysts became fragile and the M η of the material decreased dramatically.Furthermore,the concentration of carbonyl and the degree of crystallinity of the material increased with the aging time.
基金Project(20110942K)supported by Open Fund of State Key Laboratory of Powder Metallurgy,ChinaProject(51021063)supported by the National Natural Science Foundation of China
文摘High-purity titanium powder was prepared by molten salt electrorefining from sponge titanium in NaCl-KCl-TiClx salts. The titanium valence, purity and electrocrystallization during electrolysis process were studied. The XPS analysis showed that the titanium valences are mainly ＋4, ＋3 and ＋2 at the earlier, medium and later stages of electrolysis, respectively. During the electrolysis process, the contents of impurities Si, Cr, Mn, Al vary little, and the contents of impurities Fe, Cu, Ni decrease markedly, while the contents of impurities O, N, H increase obviously. The residual impurities are usually distributed in small tunnel of dendritic crystals. Enhancing the electrolysis temperature and prolonging the electrolysis time can increase the titanium particle size. The TEM analysis showed that the electrodeposited titanium is not a single crystal, but contains many nanostructured grains and subgrains, with grain size of 100-500 nm. The electrolysis mechanisms were also discussed.
基金supported by the Australian Research Council(ARC)through the Discovery Project(DP180102297)the Future Fellow Project(FT180100705)+2 种基金the support from the Open Project of State Key Laboratory of Advanced Special Steelthe Shanghai Key Laboratory of Advanced Ferrometallurgy,Shanghai University(SKLASS 2021-**)the Science and Technology Commission of Shanghai Municipality(No.19DZ2270200,20511107700)。
文摘Electrocatalysis for the oxygen evolution reactions(OER)has attracted much attention due to its important role in water splitting and rechargeable metal-air batteries.Therefore,designing highly efficient and low-cost catalysts for OER process is essential as the conventional catalysts still rely on precious metals.Transition metal-based compounds have been widely investigated as active OER catalysts,and renewed interest in the high valence metals engineered compounds has been achieved for superior catalytic activity and stability.However,an in-depth understanding of the construction strategies and induced effects for the high valence metals engineered catalysts is still lacking and desired.In this review,we have summarized the construction strategies of high valence metals as dopants or formed heterostructures with the iron/cobalt/nickel(Fe/Co/Ni)-based catalysts.Then the induced effects on Fe/Co/Ni-based catalysts by incorporating high valence metals,e.g.,accelerating the surface reconstruction,forming amorphous structure,generating vacancies/defects,and acting as stabilizers,are highlighted.The impacts of high valence metals on OER performance are elucidated based on different elements,including molybdenum(Mo),tungsten(W),cerium(Ce),vanadium(V),chromium(Cr),manganese(Mn),niobium(Nb),zirconium(Zr).The correlations of construction strategies,induced effects,catalytic activity and OER reaction pathways are elaborated.Finally,the remaining challenges for further enhancements of OER performance induced by high valence metals are presented.
基金supported by National Natural Science Foundation of China(Nos.51802356,51872334,and 51572299)Innovation-Driven Project of Central South University(No.2018CX004)
文摘AV4+-V2O5 cathode with mixed vanadium valences was prepared via a novel synthetic method using VOOH as the precursor,and its zinc-ion storage performance was evaluated.The products are hollow spheres consisting of nanoflakes.The V4+-V2O5 cathode exhibits a prominent cycling performance,with a specific capacity of 140 mAhg-1 after 1000 cycles at 10 A g.1,and an excellent rate capability.The good electrochemical performance is attributed to the presence of V4+,which leads to higher electrochemical activity,lower polarization,faster ion diffusion,and higher electrical conductivity than V2O5 without V4+.This engineering strategy of valence state manipulation may pave the way for designing high-performance cathodes for elucidating advanced battery chemistry.
文摘The valenceofelementyttrium of Y2 O3 Mocathode materialhasbeenstudied by usingther mal weight analysis, X ray diffraction analysis, Scanning electron microscopy and X rayphotoelectronspectrum . It hasbeen provedthatyttrium oxidecan bereduced by molybdenum carbide. Thereaction between powdered Y2 O3 and Mo2 Ccan happen at 1173 , and Y2 O3may bereduced to metallicyttrium . Afterthepowder mixtureof Y2 O3 and Mo2 Cwasheat treated at1873 K, Yttrium existsin two kinds of chemicalstate- yttrium of zero valence and yttrium ofthreevalences.
基金Project supported by the National Natural Science Foundation of China (20671067, 30470150)
文摘Chloroplasts were isolated from spinach treated with taCl3, CeCl3, and NdCl3. Because of owning 4f electron characteristics and alternation valence, Ce treatment presented the highest enhancement in light absorption, energy transfer from LHC Ⅱ to PS Ⅱ, excitation energy distribution from PS Ⅰ to PS Ⅱ, and fluorescence quantum yield around 680 nm. Compared with Ce treatment, Nd treatment resulted in relatively lower enhancement in these physiological indices, as Nd did not have alternation valence. La treatment presented the lowest enhancement, as La did not have either 4f electron or alternation valence. The increase in activities of whole chain electron transport, PS ⅡDCPIP photoreduction, and oxygen evolution of chloroplasts was of the following order： Ce〉Nd 〉La〉 control. However, the photoreduction activities of spinach PS I almost did not change with La, Ce, or Nd treatments. The results suggested that 4f electron characteristics and alternation valence of rare earths had a close relationship with photosynthesis improvement.
基金supported by the National Natural Science Foundation of China(No.21876130)Natural Science Foundation of Shanghai(No.18ZR1440800)。
文摘In this study,complete tetracycline(TTC)and above 50%of total organic carbon(TOC)were removed by Fe S/PS after 30 min under optimized conditions.Although free radicals and high-valent iron ions were identified to generate in the process,the apparent similarity between intermediate products of Fe S/PS,Fe/PS,and UV/PS systems demonstrated that the degradation of TTC was due to sulfate radicals(SO_(4)·^(-))and hydroxyl radicals(·OH).Based on the reaction between free radicals and organic matter,we speculated that TTC in the Fe S/PS system was decomposed and mineralized by dehydration,dehydrogenation,hydroxyl addition,demethylation,substitution,E-transfer,and ring-opening.Furthermore,a new understanding of Fe S-mediated PS activation based on stoichiometry and kinetic analysis showed that there were both homogeneous and heterogeneous reactions that occurred in the entire progress.However,due to the effect of p H on the dissolution of iron ions,the homogeneous reaction became the principal process with iron ions concentration exceeding 1.35 mg/L.This work provides a theoretical basis for the study of the degradation of TTC-containing wastewater by the iron-based advanced oxidation process.
基金supported by the National Natural Science Foundation of China (Nos.21701107, 51672165)Natural Science Foundation of Shaanxi Province (2019JQ-018)+3 种基金Doctoral Scientific Research Startup Foundation of Shaanxi University of Science and Technology (2016QNBT-07)Platform construction Fund for Imported talent of Shaanxi University of Science and Technology (134080038)National Key R&D Program of China (2017YFB0308300)Xi’an Key Laboratory of Green Manufacture of Ceramic materials Foundation (2019220214SYS017CG039)。
文摘Developing the highly active, cost-effective, environmental-friendly, and ultra-stable nonprecious electrocatalysts for hydrogen evolution reaction(HER) is distinctly indispensable for the large-scale practical applications of hydrolytic hydrogen production. Herein, we report the synthesis of well-integrated electrode, NiV layered double hydroxide nanosheet array grown in-situ on porous nickel foam(abbreviated as in-NiV-LDH/NF) via the facile one-step hydrothermal route. Interestingly, the valence configuration of vanadium(V) sites in such NiV-LDH are well dominated by the innovative use of NF as the reducing regulator, achieving the reassembled in-NiV-LDH/NF with a high proportion of trivalent V ions(V3+), and then an enhanced intrinsic electrocatalytic HER activity. The HER testing results show that the in-NiVLDH/NF drives the current densities of 10 and 100 mA cm-2 at extremely low overpotentials of 114 and 245 mV without iR-compensation respectively, even outperforms commercial 20 wt% Pt/C at the large current density of over 80 mA cm-2 in alkaline media, as well as gives robust catalytic durability of at least 100 h in both alkaline and neutral media. More importantly, this work provides a fresh perspective for designing bimetal(oxy) hydroxides electrocatalysts with efficient hydrogen generation.
基金financial support by the foundation of Westlake Universitysupported by the National Key Research Development Program of China(No.2017YFA0303002)。
文摘The crystal structure and physical properties of Nb_(25)Mo_(5+x)Re_(35)Ru_(25-x)Rh_(10)(0≤x≤10)and Nb_(5)Mo_(35-y)Re_(15+y)Ru_(35)Rh_(10)(0≤y≤15)high-entropy alloys(HEAs)have been studied by X-ray diffraction,electrical resistivity,magnetic susceptibility,and specific heat measurements.The results show that the former HEAs with valence electron concentration(VEC)values of 6.7-6.9 crystallize in a noncentrosymmetric cubicα-Mn structure,while the latter ones with VEC values of 7.1-7.25 adopt a centrosymmetric hexagonal close-packed(hcp)structure.Despite different structures,both series of HEAs are found to be bulk superconductors with a full energy gap,and the superconducting transition temperature Tc tends to decrease with the increase of VEC.Nevertheless,the Tc values of the hcp-type HEAs are higher than those of theα-Mn-type ones,likely due to a stronger electron phonon coupling.Furthermore,we show that VEC and electronegativity difference are two key parameters to control the stability ofα-Mn and hcp-type HEAs.These results not only are helpful for the design of such HEAs,but also represent the first realization of structurally different HEA superconductors without changing the constituent elements.
基金This study was supported by a grant from the National Natural Science Foundation of China(No.61804030)the Solar Energy Conversion&Energy Storage Engineering Technology Innovation Platform(No.2018L3006)the Fujian Natural Science Foundation for Distinguished Young Scholars(Grant No.2020J06042).
文摘Relieving the stress or strain associated with volume change is highly desirable for high-performance SiOx anodes in terms of stable solid electrolyte interphase(SEI)-film growth.Herein,a Si-valence gradient is optimized in SiOx composites to circumvent the large volume strain accompanied by lithium insertion/extraction.SiO_(x)@C annealed at 850℃ has a gentle Si-valence gradient along the radial direction and excellent electrochemical performances,delivering a high capacity of 506.9 mAh g^(−1) at 1.0 A g^(−1) with a high Coulombic efficiency of~99.8%over 400 cycles.Combined with the theoretical prediction,the obtained results indicate that the gentle Si-valence gradient in SiO_(x)@C is useful for suppressing plastic deformation and maintaining the inner connection integrity within the SiO_(x)@C particle.Moreover,a gentle Si-valence gradient is expected to form a stress gradient and affect the distribution of dangling bonds,resulting in local stress relief during the lithiation/delithiation process and enhanced Li-ion kinetic diffusion.Furthermore,the lowest interfacial stress variation ensures a stable SEI film at the interface and consequently increases cycling stability.Therefore,rational design of a Si-valence gradient in SiOx can provide further insights into achieving high-performance SiOx anodes with large-scale production.
基金supported by the National Natural Science Foundation of China(21972124,21603041)the Priority Academic Program Development of Jiangsu Higher Education Institutionthe support of the Six Talent Peaks Project of Jiangsu Province(XCL-070-2018)。
文摘High valence state species are significant in the energy-relevant electrochemical oxidation reactions.Herein,the high active state of Ni^(3+)formation induced by Mo^(6+)and their efficient synergism in NiS_(2)-MoS_(2)hetero-nanorods powder catalyst with the rough layered structure are demonstrated,as proof of concept,for the urea-assisted water electrolysis.This catalyst can be derived from the sulfidation of NiMoO_(4) nanorods that can realize individual metal sulfides sufficiently mixing at a domain size in the nanoscale which creates lots of active sites and nanointerfaces.The high valence state of Mo^(6+)and Ni^(3+)formation and increased conductive phase of 1 T MoS_(2)in the hetero-nanorods compared to the counterpart pure phases are revealed by spectral study and microscopic analysis;high electrochemical surface area and active site exposure are found due to the nano-interface formation and layered rough nanosheets over the surface of nanorods.They show much higher catalytic performance than their pure phases for urea oxidation,including high catalytic activity,stability,charge transfer ability and catalytic kinetics resulting from more active Ni^(3+)species formation and electronic synergism of high valence metals.Transformation of 1 T MoS_(2)to Mo^(6+)and increased amount of Mo^(6+)and Ni^(3+)after stability test indicate their involvement and synergism for the catalysis reaction.The current work offers a novel understanding of the synergistic effect based on the high valence state synergism for heterogeneous catalysts in electrocatalysis.
基金financially supported by the Natural Science Foundation of Liaoning Province(No.2019-MS-247)the Liaoning Revitalization Talents Program(XLYC1807178).
文摘The low valence electron concentration(VEC)Al_(x)CoCrFeNiSi(x=0.5,1.0,1.5 and 2.0)high-entropy alloys(HEAs)were designed by the fundamental properties of the constituent elements and prepared by vacuum arc melting method.The effects of Al addition on the crystal structure and microstructure were investigated.The microhardness and wear property were also researched.The results showed that the microstructure transformed from dendritic crystal to equiaxed crystal.It was found that FCC phase gradually decreased with the increasing Al content and disappeared until in a composition of 1.0 in Al_(x)CoCrFeNiSi HEAs.Little FCC phase was found with continuously adding Al,while the phase fraction of BCC increased from 85.0% to 91.8%,and VEC decreased from 7.00 to 6.14.The microhardness was increased gradually from 598 up to 909 HV with addition of Al from 0.5 to 2.0.It was the same of the compressive strength results,which improved from 1200 to 1920 MPa.The wear coefficient and mass loss were in line with mechanical properties evolution,which was attributed to the microstructure transformation into equiaxed crystal and the increase in BCC phase.
基金Funded by the Science and Technology Foundation of Retuned Students Studying Abroad of Shanxi Province of China(No. 1995-26)
文摘By measuring the hardness of carburized layer of a new type supersaturated carburizing steel （35Cr3SiMnMoV） at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and the temper temperature is established. The result indicates that the hardness goes down firstly, then up and down, just like a wave consistent with the temperature increase. A secondary hardening peak appears at 570 ℃ or so. Based on Empirical Election Theory （EET） of Solids and Molecules, the valence electron structures （VESs） containing α-Fe-C, α-Fe-C-Me segregation structure units and carbide are calculated. The laws of temper process and hardness change with the temper temperature are explained, and the fact that reconstruction of θ-Fe3C is prior to that of special carbide at high tempering is analyzed with the phase structure formation factor, S, being taken into consideration. Therefore, the laws of temper process and hardness change of supersaturated carburized layer at different temper temperature can be traced back to valence electron structure （VES） level of alloy phase.
基金Supported by the National Natural Science Foundation of China under Grant No 51272139
文摘The possibilities of hexagonal boron nitride(hBN) and lithium boron nitride(Li_3BN_2) transition into cubic boron nitride(cBN) under synthetic pressure 5.0 GPa and synthetic temperature 1700 K are analyzed with the use of the empirical electron theory of solids and molecules. The relative differences in electron density are calculated for dozens of bi-phase interfaces hBN/cBN, Li_3BN_2/cBN. These relative differences of hBN/cBN are in good agreement with the first order of approximation(<10%), while those of Li_3BN_2/cBN are much greater than 10%.This analysis suggests that Li_3BN_2 is impossible to be intermediate phase but is a catalyst and cBN should be directly transformed by hBN.
