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
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 valences of Cu in Y_(1-x)Ca_(x)Ba_(2)Cu_(3)O_(6+y) have been investigated by using complex chemical bond theory.The results for the valences of Cu(1)and Cu(2)in the calculation suggest that the holes introduced by...The valences of Cu in Y_(1-x)Ca_(x)Ba_(2)Cu_(3)O_(6+y) have been investigated by using complex chemical bond theory.The results for the valences of Cu(1)and Cu(2)in the calculation suggest that the holes introduced by calcium substitution only reside in CuO_(2) planes,and there is a competition mechanism for the hole density in CuO_(2) planes between Ca doping and oxygen depletion.These conclusions are satisfactorily in agreement with experiments.展开更多
The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron co...The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron concentration−relative electronegativity(VEC−REN)composite descriptor was developed to effectively predict the mechanical properties of HEBs.The results demonstrate that with a fixed VEC,the rise of the REN makes HEBs harder but more brittle when the electronegativity of doped TM atoms is lower than that of boron atoms.However,HEBs become softer and more ductile as REN increases if the doped TM atoms have higher electronegativity than boron atoms.The VEC−REN composite descriptor can accurately classify and predict the mechanical properties of HEBs with different components,which provides important theoretical guidance for the rapid design and development of novel high-entropy ceramic materials.展开更多
O3-types layered cathode materials in sodium-ion batteries(SIBs)suffer from the obvious lattice distortion induced by the complex phase transitions during Na^(+)intercalation/deintercalation process,leading to severe ...O3-types layered cathode materials in sodium-ion batteries(SIBs)suffer from the obvious lattice distortion induced by the complex phase transitions during Na^(+)intercalation/deintercalation process,leading to severe structural collapse and performance degradation.Herein,a series of high valence tantalum(Ta^(5+))doped Na(Ni_(0.4)Fe_(0.2)Mn_(0.4))_(1−x)Ta_(x)O_(2)(x=0/0.0025/0.005/0.01)secondary spherical particles are firstly developed,where Ta^(5+)doping enables the refined primary grain with a tightly stacked rod-like morphology.Comprehensive structural analysis via Neutron powder diffraction(NPD)and Synchrotron radiation X-ray diffraction(SXRD)reveals an expanded NaO_(2)slab and a reduction in Na site vacancy.The potential charge compensation mechanism is further illustrated by X-ray absorption spectroscopy(XAS)and X-ray photoelectron spectroscopy(XPS),unveiling a partial reduction from Ni^(3+)to Ni^(2+)with Ta^(5+)doping.In situ X-ray diffraction(in situ XRD)suggests that the decorated sample undergoes a volume change as low as 0.8%,in contrast with the pristine one(1.5%).Thus,the optimized sample with x=0.005 retains an enhanced capacity retention up to 70.4%at 1 C after 300 cycles in half-cell and delivers a high energy density of 251 Wh kg^(-1)(0.1 C)and with a good capacity retention of 81.0%at 1 C after 200 cycles in full-cell.Our findings provide new insights into the mechanism of high valence Ta^(5+)doping in stabilizing layered oxides cathode materials for SIBs.展开更多
Herein,a series of manganese oxide catalysts with different valences(Mn_(3)O_(4),Mn_(2)O_(3),and MnO_(2))were designed and synthesized for the synthesis of ethylene urea(EU)from ethylenediamine(EDA)and carbon dioxide(...Herein,a series of manganese oxide catalysts with different valences(Mn_(3)O_(4),Mn_(2)O_(3),and MnO_(2))were designed and synthesized for the synthesis of ethylene urea(EU)from ethylenediamine(EDA)and carbon dioxide(CO_(2)).With a maximal EDA conversion of 82%and EU selectivity of 99%at 160℃ for 2 h,Mn_(2)O_(3) catalysts had the best catalytic activity among them,which was superior to the reported catalysts.In the following order:Mn_(2)O_(3)>MnO_(2)>Mn_(3)O_(4),the catalytic activity for the synthesis of EU from CO_(2) and EDA decreased.Further characterization showed the Mn_(2)O_(3) catalyst possessed a greater Mn^(3+)/Mn4+ratio and more surface oxygen vacancies than the MnO_(2) and Mn_(3)O_(4),which improved its capacity to adsorb and activate CO_(2) and EDA.After four recycling runs,the EDA conversion slightly declined from 82%to 56%on Mn_(2)O_(3) catalyst,while no obvious change in EU selectivity was observed.The loss of surface Ov contents and Mn^(3+)proportion were concluded as main reasons for the decrease in catalytic activity over Mn_(2)O_(3) catalyst.This work demonstrated a metal oxide catalyst that was efficient in producing EU from CO_(2) and EDA.展开更多
Layered rare earth magnets make a prolific source of unconventional quantum phases and functional properties.Recently,a class of Zintl materials EuA2X2has emerged as holding promise for ideal Weyl and axion physics.Th...Layered rare earth magnets make a prolific source of unconventional quantum phases and functional properties.Recently,a class of Zintl materials EuA2X2has emerged as holding promise for ideal Weyl and axion physics.The question is whether the magnetic structure,strongly coupled to the topology,can be controlled in such mate rials via a minimal yet selective modification of their chemical composition.Here,we report qualitative changes in the magnetic structure due to charge imbalance.Such imbalance is probed by replacement of Eu with Gd.The two elements form isoelectronic 4f7cations but contribute to different numbers of electrons.A synthetic route to epitaxial films of GdAl_(2)Ge_(2)on Ge,employing a selfsacrificial template,is proposed.The ato mic and magnetic structures of the films,as well as their electron transport properties were studied by a combination of techniques.It is established that the change in the magnetic structure caused by the cationic replacement influences the magnetotransport properties of the films.The results suggest that the charge imbalance in Zintl compounds may provide an instrument to open new routes to functional layered materials with potential applications in spintronics.展开更多
Sounds,like screams,which contain acoustic nonlinearities can elicit fearful,emotional responses in animals.In humans,screams activate the amygdala and are perceived as less positive than spoken words.We conducted a p...Sounds,like screams,which contain acoustic nonlinearities can elicit fearful,emotional responses in animals.In humans,screams activate the amygdala and are perceived as less positive than spoken words.We conducted a playback experiment to see if two skink species(one of which is known to negatively respond to nonlinearities)responded differently to human spoken words and screams.We broadcast short phrases of humans screaming,humans speaking,or a control,a novel bird song.We studied the immediate response by quantifying the change in rates of vigilance and locomotion.We also studied a slightly delayed response in risk assessments by measuring skink flight initiation distance after the playback.Furthermore,we conducted experiments in nonresidential and residential areas to understand how human exposure may influence human discrimination and potentially valence perception(i.e.,how sound is emotionally perceived).Blue-tailed skinks(Emoia impar)altered both immediate behavior and their delayed risk assessment when human screaming was broadcast,but only in residential areas.By contrast,white-bellied copper-striped skinks(Emoia cyanura)only altered their delayed risk assessment when human stimuli were broadcast in residential areas.These results indicate that skinks respond differently to human vocalizations depending on their exposure to humans and based on species-specific behaviors.Our results suggest the importance of considering many variables when studying cognition in nature.The amount of human exposure and the acoustic cues contained in auditory stimuli may affect an individual's risk assessment and behavioral responses.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
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
The recently established theory has built clear connections between hardness and toughness and electron structure involving both valence electron concentration(VEC)and core electron count(CEC)in transition metal nitri...The recently established theory has built clear connections between hardness and toughness and electron structure involving both valence electron concentration(VEC)and core electron count(CEC)in transition metal nitride(TMN)ceramics.However,the underlying deformation mechanisms remain unclear.Herein,we conduct in-depth analysis on microstructure evolution during deformation of the high VEC-CEC solution TiMoN coatings having desired combination of high hardness and toughness.The effects of solid solution,preferred orientation linked with symbiotic compressive stress,grain size and dislocations are systematically discussed.We discover that numerous dislocations have been implanted into the nanocrystals of the TiMoN coating during the high-ionization arc deposition.Using two-beam bright-field imaging,we count the dislocation density and confirm occurrence of dislocation multiplication to form effective plastic deformation,which contributes to significant strain hardening,comparable to solid solution hardening,fine-grain hardening and compressive stress hardening.The improved dislocation activities also play a crucial role in enhancing the toughness by providing extra energy dissipation paths.This work gains new insights into the origins of mechanical properties of ceramic coatings and possibility to tune them via defects.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
Graphene-metal based materials have been utilized in lithium-sulfur(Li–S)batteries owing to their integrated functionalities thus far.However,their synthesis has predominantly relied on wet-chemistry routes,which lim...Graphene-metal based materials have been utilized in lithium-sulfur(Li–S)batteries owing to their integrated functionalities thus far.However,their synthesis has predominantly relied on wet-chemistry routes,which limited their practical activity in Li–S reaction systems.In this study,we introduce a chemical vapor deposition(CVD)-triggered dry-chemistry approach for the preparation of graphene-cobalt(Co)based catalysts.The versatile CVD technique provides a dry and controllable reaction environment,effectively pledging the compact and clean catalytic interfaces between graphene and Co-based components.Additionally,programmed reactions introduce defects such as vacancies and nitrogen heteroatoms into the catalysts.Notably,the graphene layer number and Co valence state can be delicately manipulated by altering the CVD reaction temperature.Specifically,few-layer graphene wrapped Co/Co_(3)O_(4)(FGr-Co/Co_(3)O_(4))prepared at 450 ℃ shows higher catalytic activity than the multi-layer graphene wrapped Co/CoO(MGr-Co/CoO)synthesized at 550 ℃,attributed to its comprehensive control of clean interface,valence distribution range and defects.Leveraging these advantages,the battery with FGr-Co/Co_(3)O_(4)shows favorable working stability with a degradation rate of only 0.08%over 500 cycles at 1.0 C.Furthermore,under an elevated sulfur loading of 6.1 mg cm^(–2),the battery harvests a remarkable areal capacity of 5.9 mA h cm^(–2)along with stable cyclic operation.展开更多
In this work,we proposed a method to enhance the magnetic properties of(Nd,Ce)-Fe-B magnets with Ce/TRE ratios below 25 wt%by introducing a moderate amount of La elements.The segregation behavior of La elements toward...In this work,we proposed a method to enhance the magnetic properties of(Nd,Ce)-Fe-B magnets with Ce/TRE ratios below 25 wt%by introducing a moderate amount of La elements.The segregation behavior of La elements towards grain boundaries(GBs)was utilized to optimize the GB phase structure.Incorporation of La atoms into the main phase induces lattice expansion,leading to an increased formation of Ce^(3+)ions with enhanced magnetic moments.Comparative analysis with the original magnet(La/Ce=0 wt%)demonstrates that the magnet with a La/Ce ratio of 10 wt%exhibits improvements of 0.3%in remanence,12.6%in coercivity,and 0.6%in maximum energy produ ct.These results underscore that the moderate addition of La elements enhances the fluidity of the rare earth-rich phase and optimizes the distribution of lamellar GB,consequently reinforcing the magnetic isolation effect.Furthermore,the promotion of the transformation from Ce^(4+)to Ce^(3+)ons contributes to the comprehensive enhancement of the magnetic properties.This research offers a novel strategy for fabricating high-performance and resource-e fficient sintered magnets based on LaCe alloys.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
The capacity to predict X-ray transition and K-edge energies in dense finite-temperatur plasmas with high precision is of primary importance for atomic physics of matter under extreme conditions.The dual characteristi...The capacity to predict X-ray transition and K-edge energies in dense finite-temperatur plasmas with high precision is of primary importance for atomic physics of matter under extreme conditions.The dual characteristics of bound and continuum states in dense matter are modeled by a valence-band-like structure in a generalized ion-sphere approach with states that are either bound,free,or mixed.The self-consistent combination of this model with the Dirac wave equations of multielectron bound states allows one to fully respect the Pauli principle and to take into account the exact nonlocal exchange terms.The generalized method allows very high precision without implication of calibration shifts and scaling parameters and therefore has predictive power.This leads to new insights in the analysis of various data.The simple ionization model representing the K-edge is generalized to excitation–ionization phenomena resulting in an advanced interpretation of ionization depression data in near-solid-density plasmas.The model predicts scaling relations along the isoelectronic sequences and the existence of bound M-states that are in excellent agreement with experimental data,whereas other methods have failed.The application to unexplained data from compound materials also gives good agreement without the need to invoke any additional assumptions in the generalized model,whereas other methods have lacked consistency.展开更多
Cu metal and its oxides have attracted much attention for photocatalytic CO_(2)reduction reaction(CO_(2)RR),but the stability and effects of Cu oxidation states on CO_(2)RR are not fully understood.Cu^(x+)/Cu^(0)-load...Cu metal and its oxides have attracted much attention for photocatalytic CO_(2)reduction reaction(CO_(2)RR),but the stability and effects of Cu oxidation states on CO_(2)RR are not fully understood.Cu^(x+)/Cu^(0)-loaded graphitic carbon nitride(g-C_(3)N_(4))heterojunctions(Cu-CuO_(x)/g-C_(3)N_(4))are fabricated via a stepwise calcination method for efficient photocatalytic CO_(2)RR.Cu_(2)O is the main component of Cu-CuO_(x)and the mixed valence Cu includes Cu^(0),Cu^(+),and Cu^(2+),which play the role of charge trapping sites and redox catalytic centers during the photocatalytic CO_(2)RR process.The main products were CO and CH_(4)for the CO_(2)RR with production rates of 14.45 and 0.66μmol g^(-1)h^(-1)for CO and CH_(4),which were higher than those for g-C_(3)N_(4)and Cu-CuO_(x),respectively.This photocatalytic CO_(2)RR performance is attributed to the ultrafast switching of“Cu^(x+)−Cu^(0)”and e_(CB^(−))/h_(VB^(+))trapping transformation in Cu-CuO_(x)benefited from the built-in IEF between Cu-CuO_(x)and g-C_(3)N_(4),increasing the efficient photogenerated e_(CB^(−)),and enabling the stability of Cu-CuO_(x)/g-C_(3)N_(4).Cu^(x+)adsorbed by H_(2)O works as the electron trapping site to change to Cu^(0)and switch to the hole trapping site;Cu^(0)works as the hole trapping site to change to Cu^(x+)and switch to the electron trapping site,causing the CO_(2)RR of the adsorbed CO_(2).Moreover,the coordinated Cu^(0)and Cu^(+)species facilitate the activation of the adsorbed CO_(2)and^(∗)CO generation,these adsorbed^(∗)CO on Cu^(0)and Cu^(+)detected by in-situ DRIFTS quickly transformed to^(∗)CHO with a lower energy barrier benefited from the mixed Cu^(0)/Cu^(+)active sites during CORR to produce CH_(4).This finding provides a new insight into the influence of mixed valence Cu during photocatalytic CO_(2)RR.展开更多
The mechanical,thermodynamic properties and electrical conductivities of L1_(2)-Al_(3)X(X=Zr,Sc,Er,Yb,Hf)structural phases in aluminum conductors were investigated through a first-principles study.The results demonstr...The mechanical,thermodynamic properties and electrical conductivities of L1_(2)-Al_(3)X(X=Zr,Sc,Er,Yb,Hf)structural phases in aluminum conductors were investigated through a first-principles study.The results demonstrate that all structural phases have good alloy-forming ability and structural stability,where Al_(3)Zr is the most superior.Al_(3)Zr,Al_(3)Hf and Al_(3)Sc have enhanced shear and deformation resistance in comparison to other phases.Within the temperature range of 200−600 K,Al_(3)Er and Al_(3)Yb possess the greatest thermodynamic stability,followed by Al_(3)Hf,Al_(3)Zr and Al_(3)Sc.Al_(3)Er and Al_(3)Yb have higher thermodynamic stability than Al_(3)Hf,Al_(3)Zr and Al_(3)Sc.All structural phases exhibit substantial metallic properties,indicating their good electrical conductivity.The electrical conductivities of Al_(3)Hf and Al_(3)Zr are higher than those of Al_(3)Er,Al_(3)Yb and Al_(3)Sc.The covalent bond properties in Al_(3)Sc,Al_(3)Er and Al_(3)Yb enhance the hardness,brittleness and thermodynamic stability of the structural phase.The thermodynamic stability of Al_(3)Sc is significantly reduced by ionic bonds.展开更多
Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ ...Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ hydrolysis method.The NaBH_(4) regulated the ZnVO/V-Zn(O,S)-3 with rich Vo and suitable n(V^(4+))/n(V^(5+))ratio achieved an excellent photocatalytic nitrogen fixation activity of 301.7μmol/(g×h)and apparent quantum efficiency of 1.148%at 420 nm without any sacrificial agent,which is 11 times than that of V-Zn(O,S).The Vo acts as the active site to trap and activate N_(2) molecules and to trap and activate H_(2)O to produce the H for N_(2) molecules photocatalytic reduction.The rich Vo defects can also reduce the competitive adsorption of H_(2)O and N_(2) molecules on the surface active site of the catalyst.The heterovalent vanadium states act as the photogenerated electrons,quickly hopping between V^(4+)and V^(5+)to transfer for the photocatalytic N_(2) reduction reaction.Additionally,the Z-scheme heterojunction effectively minimizes photogenerated carrier recombination.These synergistic effects collectively boost the photocatalytic nitrogen fixation activity.This study provides a practical method for designing Z-scheme heterojunctions for efficient photocatalytic N_(2) fixation under mild conditions.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 valences of Cu in Y_(1-x)Ca_(x)Ba_(2)Cu_(3)O_(6+y) have been investigated by using complex chemical bond theory.The results for the valences of Cu(1)and Cu(2)in the calculation suggest that the holes introduced by calcium substitution only reside in CuO_(2) planes,and there is a competition mechanism for the hole density in CuO_(2) planes between Ca doping and oxygen depletion.These conclusions are satisfactorily in agreement with experiments.
基金the National Natural Science Foundation of China (Nos. 52071179, 52271033)the Key Program of National Natural Science Foundation of China (No. 51931003)+2 种基金the Natural Science Foundation of Jiangsu Province, China (No. BK20221493)the Jiangsu Province Leading Edge Technology Basic Research Major Project, China (No. BK20222014)the Foundation of “Qinglan Project” for Colleges and Universities in Jiangsu Province, China。
文摘The composition−property relationship of 18 quaternary high entropy diborides(HEBs)consisting of boron and IVB,VB and VIB transition metals(TM)was investigated using first-principles calculations.A valence electron concentration−relative electronegativity(VEC−REN)composite descriptor was developed to effectively predict the mechanical properties of HEBs.The results demonstrate that with a fixed VEC,the rise of the REN makes HEBs harder but more brittle when the electronegativity of doped TM atoms is lower than that of boron atoms.However,HEBs become softer and more ductile as REN increases if the doped TM atoms have higher electronegativity than boron atoms.The VEC−REN composite descriptor can accurately classify and predict the mechanical properties of HEBs with different components,which provides important theoretical guidance for the rapid design and development of novel high-entropy ceramic materials.
基金supported by the National Natural Science Foundation of China (52402298, 52172224, 52202228, 22479112)the Science and Technology Correspondent Project of Tianjin(24YDTPJC00240)+3 种基金Science Research Project of Hebei Education Department (BJK2022011)Central Funds Guiding the Local Science and Technology Development of Hebei Province (236Z4404G)the Beijing Tianjin Hebei Basic Research Cooperation Special Project(E2024202273)Tianjin Sci.&Tech. Program (22YFYSHZ00220)
文摘O3-types layered cathode materials in sodium-ion batteries(SIBs)suffer from the obvious lattice distortion induced by the complex phase transitions during Na^(+)intercalation/deintercalation process,leading to severe structural collapse and performance degradation.Herein,a series of high valence tantalum(Ta^(5+))doped Na(Ni_(0.4)Fe_(0.2)Mn_(0.4))_(1−x)Ta_(x)O_(2)(x=0/0.0025/0.005/0.01)secondary spherical particles are firstly developed,where Ta^(5+)doping enables the refined primary grain with a tightly stacked rod-like morphology.Comprehensive structural analysis via Neutron powder diffraction(NPD)and Synchrotron radiation X-ray diffraction(SXRD)reveals an expanded NaO_(2)slab and a reduction in Na site vacancy.The potential charge compensation mechanism is further illustrated by X-ray absorption spectroscopy(XAS)and X-ray photoelectron spectroscopy(XPS),unveiling a partial reduction from Ni^(3+)to Ni^(2+)with Ta^(5+)doping.In situ X-ray diffraction(in situ XRD)suggests that the decorated sample undergoes a volume change as low as 0.8%,in contrast with the pristine one(1.5%).Thus,the optimized sample with x=0.005 retains an enhanced capacity retention up to 70.4%at 1 C after 300 cycles in half-cell and delivers a high energy density of 251 Wh kg^(-1)(0.1 C)and with a good capacity retention of 81.0%at 1 C after 200 cycles in full-cell.Our findings provide new insights into the mechanism of high valence Ta^(5+)doping in stabilizing layered oxides cathode materials for SIBs.
基金supported by the National Natural Science Foundation of China(No.22278041)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering(No.2022-K78)+1 种基金Jiangsu Province Key Laboratory of Fine Petrochemical Engineering(No.KF2107)the Advanced Catalysis and Green Manufacturing Collab-orative Innovation Center(No.ACGM2022-10-07)。
文摘Herein,a series of manganese oxide catalysts with different valences(Mn_(3)O_(4),Mn_(2)O_(3),and MnO_(2))were designed and synthesized for the synthesis of ethylene urea(EU)from ethylenediamine(EDA)and carbon dioxide(CO_(2)).With a maximal EDA conversion of 82%and EU selectivity of 99%at 160℃ for 2 h,Mn_(2)O_(3) catalysts had the best catalytic activity among them,which was superior to the reported catalysts.In the following order:Mn_(2)O_(3)>MnO_(2)>Mn_(3)O_(4),the catalytic activity for the synthesis of EU from CO_(2) and EDA decreased.Further characterization showed the Mn_(2)O_(3) catalyst possessed a greater Mn^(3+)/Mn4+ratio and more surface oxygen vacancies than the MnO_(2) and Mn_(3)O_(4),which improved its capacity to adsorb and activate CO_(2) and EDA.After four recycling runs,the EDA conversion slightly declined from 82%to 56%on Mn_(2)O_(3) catalyst,while no obvious change in EU selectivity was observed.The loss of surface Ov contents and Mn^(3+)proportion were concluded as main reasons for the decrease in catalytic activity over Mn_(2)O_(3) catalyst.This work demonstrated a metal oxide catalyst that was efficient in producing EU from CO_(2) and EDA.
基金Project supported by NRC "Kurchatov Institute"the Russian Science Foundation (22-13-00004 (synthesis)),24-19-00038 (magnetism studies)and 20-79-10028 (electron transport studies)the President's scholarship for D.V.A.(SP 3111.2022.5)。
文摘Layered rare earth magnets make a prolific source of unconventional quantum phases and functional properties.Recently,a class of Zintl materials EuA2X2has emerged as holding promise for ideal Weyl and axion physics.The question is whether the magnetic structure,strongly coupled to the topology,can be controlled in such mate rials via a minimal yet selective modification of their chemical composition.Here,we report qualitative changes in the magnetic structure due to charge imbalance.Such imbalance is probed by replacement of Eu with Gd.The two elements form isoelectronic 4f7cations but contribute to different numbers of electrons.A synthetic route to epitaxial films of GdAl_(2)Ge_(2)on Ge,employing a selfsacrificial template,is proposed.The ato mic and magnetic structures of the films,as well as their electron transport properties were studied by a combination of techniques.It is established that the change in the magnetic structure caused by the cationic replacement influences the magnetotransport properties of the films.The results suggest that the charge imbalance in Zintl compounds may provide an instrument to open new routes to functional layered materials with potential applications in spintronics.
文摘Sounds,like screams,which contain acoustic nonlinearities can elicit fearful,emotional responses in animals.In humans,screams activate the amygdala and are perceived as less positive than spoken words.We conducted a playback experiment to see if two skink species(one of which is known to negatively respond to nonlinearities)responded differently to human spoken words and screams.We broadcast short phrases of humans screaming,humans speaking,or a control,a novel bird song.We studied the immediate response by quantifying the change in rates of vigilance and locomotion.We also studied a slightly delayed response in risk assessments by measuring skink flight initiation distance after the playback.Furthermore,we conducted experiments in nonresidential and residential areas to understand how human exposure may influence human discrimination and potentially valence perception(i.e.,how sound is emotionally perceived).Blue-tailed skinks(Emoia impar)altered both immediate behavior and their delayed risk assessment when human screaming was broadcast,but only in residential areas.By contrast,white-bellied copper-striped skinks(Emoia cyanura)only altered their delayed risk assessment when human stimuli were broadcast in residential areas.These results indicate that skinks respond differently to human vocalizations depending on their exposure to humans and based on species-specific behaviors.Our results suggest the importance of considering many variables when studying cognition in nature.The amount of human exposure and the acoustic cues contained in auditory stimuli may affect an individual's risk assessment and behavioral responses.
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supported by the Distinguished Young Scholars of China(No.52025014)Natural Science Foundation of Zhejiang Province(No.LQ23E010002)Innovation 2025 Major Project of Ningbo(Nos.2022Z011 and 2023Z022).
文摘The recently established theory has built clear connections between hardness and toughness and electron structure involving both valence electron concentration(VEC)and core electron count(CEC)in transition metal nitride(TMN)ceramics.However,the underlying deformation mechanisms remain unclear.Herein,we conduct in-depth analysis on microstructure evolution during deformation of the high VEC-CEC solution TiMoN coatings having desired combination of high hardness and toughness.The effects of solid solution,preferred orientation linked with symbiotic compressive stress,grain size and dislocations are systematically discussed.We discover that numerous dislocations have been implanted into the nanocrystals of the TiMoN coating during the high-ionization arc deposition.Using two-beam bright-field imaging,we count the dislocation density and confirm occurrence of dislocation multiplication to form effective plastic deformation,which contributes to significant strain hardening,comparable to solid solution hardening,fine-grain hardening and compressive stress hardening.The improved dislocation activities also play a crucial role in enhancing the toughness by providing extra energy dissipation paths.This work gains new insights into the origins of mechanical properties of ceramic coatings and possibility to tune them via defects.
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support of the National Natural Science Foundation of China(Grant No.52172239,52202038,and 52402247)the Innovative Funds Plan of Henan University of Technology(Grant No.2020ZKCJ07)the Natural Science Foundation of Shandong Province(Grant No.ZR2022QE081)。
文摘Graphene-metal based materials have been utilized in lithium-sulfur(Li–S)batteries owing to their integrated functionalities thus far.However,their synthesis has predominantly relied on wet-chemistry routes,which limited their practical activity in Li–S reaction systems.In this study,we introduce a chemical vapor deposition(CVD)-triggered dry-chemistry approach for the preparation of graphene-cobalt(Co)based catalysts.The versatile CVD technique provides a dry and controllable reaction environment,effectively pledging the compact and clean catalytic interfaces between graphene and Co-based components.Additionally,programmed reactions introduce defects such as vacancies and nitrogen heteroatoms into the catalysts.Notably,the graphene layer number and Co valence state can be delicately manipulated by altering the CVD reaction temperature.Specifically,few-layer graphene wrapped Co/Co_(3)O_(4)(FGr-Co/Co_(3)O_(4))prepared at 450 ℃ shows higher catalytic activity than the multi-layer graphene wrapped Co/CoO(MGr-Co/CoO)synthesized at 550 ℃,attributed to its comprehensive control of clean interface,valence distribution range and defects.Leveraging these advantages,the battery with FGr-Co/Co_(3)O_(4)shows favorable working stability with a degradation rate of only 0.08%over 500 cycles at 1.0 C.Furthermore,under an elevated sulfur loading of 6.1 mg cm^(–2),the battery harvests a remarkable areal capacity of 5.9 mA h cm^(–2)along with stable cyclic operation.
基金Project supported by the National Natural Science Foundation of China(52071004,52301228,51971005,52171168)the Program of Top Disciplines Construction in Beijing(PXM2019_014204_500031)the International Research Cooperation Seed Fund of Beijing University of Technology(2021B23)。
文摘In this work,we proposed a method to enhance the magnetic properties of(Nd,Ce)-Fe-B magnets with Ce/TRE ratios below 25 wt%by introducing a moderate amount of La elements.The segregation behavior of La elements towards grain boundaries(GBs)was utilized to optimize the GB phase structure.Incorporation of La atoms into the main phase induces lattice expansion,leading to an increased formation of Ce^(3+)ions with enhanced magnetic moments.Comparative analysis with the original magnet(La/Ce=0 wt%)demonstrates that the magnet with a La/Ce ratio of 10 wt%exhibits improvements of 0.3%in remanence,12.6%in coercivity,and 0.6%in maximum energy produ ct.These results underscore that the moderate addition of La elements enhances the fluidity of the rare earth-rich phase and optimizes the distribution of lamellar GB,consequently reinforcing the magnetic isolation effect.Furthermore,the promotion of the transformation from Ce^(4+)to Ce^(3+)ons contributes to the comprehensive enhancement of the magnetic properties.This research offers a novel strategy for fabricating high-performance and resource-e fficient sintered magnets based on LaCe alloys.
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.
基金supported by the NSFC under Grant Nos.11374315 and 12074395the Invited Scientist Program of CNRS at Ecole Polytechnique,Palaiseau,France。
文摘The capacity to predict X-ray transition and K-edge energies in dense finite-temperatur plasmas with high precision is of primary importance for atomic physics of matter under extreme conditions.The dual characteristics of bound and continuum states in dense matter are modeled by a valence-band-like structure in a generalized ion-sphere approach with states that are either bound,free,or mixed.The self-consistent combination of this model with the Dirac wave equations of multielectron bound states allows one to fully respect the Pauli principle and to take into account the exact nonlocal exchange terms.The generalized method allows very high precision without implication of calibration shifts and scaling parameters and therefore has predictive power.This leads to new insights in the analysis of various data.The simple ionization model representing the K-edge is generalized to excitation–ionization phenomena resulting in an advanced interpretation of ionization depression data in near-solid-density plasmas.The model predicts scaling relations along the isoelectronic sequences and the existence of bound M-states that are in excellent agreement with experimental data,whereas other methods have failed.The application to unexplained data from compound materials also gives good agreement without the need to invoke any additional assumptions in the generalized model,whereas other methods have lacked consistency.
基金support of the National Natu-ral Science Foundation of China(No.62004143,22476058,and 22076052)the Key R&D Program of Hubei Province(No.2022BAA084).
文摘Cu metal and its oxides have attracted much attention for photocatalytic CO_(2)reduction reaction(CO_(2)RR),but the stability and effects of Cu oxidation states on CO_(2)RR are not fully understood.Cu^(x+)/Cu^(0)-loaded graphitic carbon nitride(g-C_(3)N_(4))heterojunctions(Cu-CuO_(x)/g-C_(3)N_(4))are fabricated via a stepwise calcination method for efficient photocatalytic CO_(2)RR.Cu_(2)O is the main component of Cu-CuO_(x)and the mixed valence Cu includes Cu^(0),Cu^(+),and Cu^(2+),which play the role of charge trapping sites and redox catalytic centers during the photocatalytic CO_(2)RR process.The main products were CO and CH_(4)for the CO_(2)RR with production rates of 14.45 and 0.66μmol g^(-1)h^(-1)for CO and CH_(4),which were higher than those for g-C_(3)N_(4)and Cu-CuO_(x),respectively.This photocatalytic CO_(2)RR performance is attributed to the ultrafast switching of“Cu^(x+)−Cu^(0)”and e_(CB^(−))/h_(VB^(+))trapping transformation in Cu-CuO_(x)benefited from the built-in IEF between Cu-CuO_(x)and g-C_(3)N_(4),increasing the efficient photogenerated e_(CB^(−)),and enabling the stability of Cu-CuO_(x)/g-C_(3)N_(4).Cu^(x+)adsorbed by H_(2)O works as the electron trapping site to change to Cu^(0)and switch to the hole trapping site;Cu^(0)works as the hole trapping site to change to Cu^(x+)and switch to the electron trapping site,causing the CO_(2)RR of the adsorbed CO_(2).Moreover,the coordinated Cu^(0)and Cu^(+)species facilitate the activation of the adsorbed CO_(2)and^(∗)CO generation,these adsorbed^(∗)CO on Cu^(0)and Cu^(+)detected by in-situ DRIFTS quickly transformed to^(∗)CHO with a lower energy barrier benefited from the mixed Cu^(0)/Cu^(+)active sites during CORR to produce CH_(4).This finding provides a new insight into the influence of mixed valence Cu during photocatalytic CO_(2)RR.
基金National Natural Science Foundation of China (No. 52274403)。
文摘The mechanical,thermodynamic properties and electrical conductivities of L1_(2)-Al_(3)X(X=Zr,Sc,Er,Yb,Hf)structural phases in aluminum conductors were investigated through a first-principles study.The results demonstrate that all structural phases have good alloy-forming ability and structural stability,where Al_(3)Zr is the most superior.Al_(3)Zr,Al_(3)Hf and Al_(3)Sc have enhanced shear and deformation resistance in comparison to other phases.Within the temperature range of 200−600 K,Al_(3)Er and Al_(3)Yb possess the greatest thermodynamic stability,followed by Al_(3)Hf,Al_(3)Zr and Al_(3)Sc.Al_(3)Er and Al_(3)Yb have higher thermodynamic stability than Al_(3)Hf,Al_(3)Zr and Al_(3)Sc.All structural phases exhibit substantial metallic properties,indicating their good electrical conductivity.The electrical conductivities of Al_(3)Hf and Al_(3)Zr are higher than those of Al_(3)Er,Al_(3)Yb and Al_(3)Sc.The covalent bond properties in Al_(3)Sc,Al_(3)Er and Al_(3)Yb enhance the hardness,brittleness and thermodynamic stability of the structural phase.The thermodynamic stability of Al_(3)Sc is significantly reduced by ionic bonds.
文摘Herein,we established a Zn_(3)(OH)_(2)(V_(2)O_(7))(H_(2)O)_(2)/V-Zn(O,S)Z-scheme heterojunction labeled ZnVO/V-Zn(O,S)with a heterovalent V^(4+)/V^(5+)states and oxygen vacancies in both phases via a one-step in-situ hydrolysis method.The NaBH_(4) regulated the ZnVO/V-Zn(O,S)-3 with rich Vo and suitable n(V^(4+))/n(V^(5+))ratio achieved an excellent photocatalytic nitrogen fixation activity of 301.7μmol/(g×h)and apparent quantum efficiency of 1.148%at 420 nm without any sacrificial agent,which is 11 times than that of V-Zn(O,S).The Vo acts as the active site to trap and activate N_(2) molecules and to trap and activate H_(2)O to produce the H for N_(2) molecules photocatalytic reduction.The rich Vo defects can also reduce the competitive adsorption of H_(2)O and N_(2) molecules on the surface active site of the catalyst.The heterovalent vanadium states act as the photogenerated electrons,quickly hopping between V^(4+)and V^(5+)to transfer for the photocatalytic N_(2) reduction reaction.Additionally,the Z-scheme heterojunction effectively minimizes photogenerated carrier recombination.These synergistic effects collectively boost the photocatalytic nitrogen fixation activity.This study provides a practical method for designing Z-scheme heterojunctions for efficient photocatalytic N_(2) fixation under mild conditions.
