It is challenging to create cation vacancies in electrode materials for enhancing the performance of rechargeable lithium ion batteries (LIBs). Herein, we utilized a strong alkaline etching method to successfully crea...It is challenging to create cation vacancies in electrode materials for enhancing the performance of rechargeable lithium ion batteries (LIBs). Herein, we utilized a strong alkaline etching method to successfully create Co vacancies at the interface of atomically thin Co_(3−x)O_(4)/graphene@CNT heterostructure for high-energy/power lithium storage. The creation of Co-vacancies in the sample was confirmed by high-resolution scanning transmission electron microscope (HRSTEM), X-ray photoelectron spectroscopy (XPS) and electron energy loss near-edge structures (ELNES). The obtained Co_(3−x)O_(4)/graphene@CNT delivers an ultra-high capacity of 1688.2 mAh g^(−1) at 0.2 C, excellent rate capability of 83.7% capacity retention at 1 C, and an ultralong life up to 1500 cycles with a reversible capacity of 1066.3 mAh g^(−1). Reaction kinetic study suggests a significant contribution from pseudocapacitive storage induced by the Co-vacancies at the Co_(3−x)O_(4)/graphene@CNT interface. Density functional theory confirms that the Co-vacancies could dramatically enhance the Li adsorption and provide an additional pathway with a lower energy barrier for Li diffusion, which results in an intercalation pseudocapacitive behavior and high-capacity/rate energy storage.展开更多
Although the Mg-air battery with high theoretical energy density is desirable for the energy supply of marine engineering equipment,its applications remain limited due to the low actual discharge voltage and inferior ...Although the Mg-air battery with high theoretical energy density is desirable for the energy supply of marine engineering equipment,its applications remain limited due to the low actual discharge voltage and inferior Mg anode utilization rate.In addition to the microstructure of Mg alloy anodes,the properties of discharge product films are of great importance to the discharge performance.Herein,the discharge behaviors of Mg-Y-Zn alloys are first studied mainly from the perspective of film properties.Through contrastive analysis,it is found that the sufficient Y^(3+) produced during the discharge process can substitute Mg^(2+) in Mg(OH)_(2) to introduce effective cation vacancies.The Mg-Y-Zn anode with profuse cation vacancies in the product film shows a synergy of potential and efficiency,and this can be attributed to an increase in the migration pathway for Mg^(2+),reducing the diffusion over-potential caused by the protective product film.This study is expected to provide a new strategy from the perspective of cation vacancy design of discharge film for developing high-performance Mg-air batteries.展开更多
Cation vacancy engineering is considered to be one of the effective methods to solve the issues of shuttling and sluggish redox kinetics of Li PSs owing to the intrinsic tunability of electronic structure.However,cati...Cation vacancy engineering is considered to be one of the effective methods to solve the issues of shuttling and sluggish redox kinetics of Li PSs owing to the intrinsic tunability of electronic structure.However,cation vacancies are few studied in the Li-S realm due to their complex and rigid preparation methods.In this work,one-step pyrolysis is reported to in situ introduce Fe-vacancies into iron sulfide(Fe_(0.96)S)as a sulfur host.For this host structure,Fe_(0.96)S is first employed as an adsorbent and catalyst in Li-S system.During the carbonization process,a tight contact structure of Fe_(0.96)S crystal and carbon network(Fe_(0.96)S@C)is in situ constructed,and the carbon layer as a conductor provides smooth electrons transfer pathways for redox reactions.Meanwhile,due to the introduction of Fe-vacancies in Fe S crystal,the adsorption capability and catalytic effect for Li PSs have been substantially enhanced.Moreover,the presence of Fe_(0.96)S crystal favors the mobility of electron and diffusion of Li+,which is revealed by the experiments and theoretical calculations.Through synergy respective advantages effect of Fe_(0.96)S and carbon,the Fe_(0.96)S@C-S cathode delivers high-rate capability at 5.0 C and stable long-life performance.Even under a high sulfur loading of 3.5 mg/cm^(2),the durable cyclic stability is still exhibited with the capacity retention of 93%over 400 cycles at 1.0 C,and the coulombic efficiency is≥98%.Noting that this strategy greatly simplifies the synthetic process of currently known cation-vacancy materials and furnishes a universal mentality for designing both divinable and astonishing new cation-vacancy materials.展开更多
Apatite-type lanthanum silicate with special conduction mechanism via interstitial oxygen has attracted considerable interest in recent years. In this work, pure powder of La9.33 2x/3MxSi6O26 （M=Mg, Ca, Sr） is prepa...Apatite-type lanthanum silicate with special conduction mechanism via interstitial oxygen has attracted considerable interest in recent years. In this work, pure powder of La9.33 2x/3MxSi6O26 （M=Mg, Ca, Sr） is prepared by the sol-gel method with sintering at 1000℃. The powder is characterized by X-ray diffraction （XRD） and scanning electron micrograph （SEM）. The apatite can be obtained at relatively low temperature as compared to the conventional solid-state reaction method. The measurements of conductivity of a series of doped samples La9.33-2x/3MxSi6O26 （M=Ca, Mg, Sr） indicate that the type of dopant and the amount have a significant effect on the conductivity. The greatest decrease in conductivity is observed for Mg doping, following the Ca and the Sr doped apatites. The effect is ultimately attributed to the amount of oxygen interstitials, which is affected by the crystal lattice distortion arising from cation vacancies.展开更多
Rechargeable lithium-oxygen batteries(LOBs)have received incremental attention owing to their high energy density and applicability to mobile devices and electric vehicles.However,the lack of robust,low-cost,and envir...Rechargeable lithium-oxygen batteries(LOBs)have received incremental attention owing to their high energy density and applicability to mobile devices and electric vehicles.However,the lack of robust,low-cost,and environmentally benign bifunctional catalysts is a major impediment to the commercial application.The introduction of vacancies is one of the effective strategies to enhance the performance of cathode catalysts for lithium-oxygen batteries,but the preparation is complicated.In this work,needle-like microsphere cathode catalysts of nickel-cobalt oxide containing cationic vacancies are constructed by controlling the annealing temperature.It is demonstrated that the presence of cationic vacancies can modulate the electronic structure of the catalyst,reduce the energy barrier for the oxygen electrode re-action,meanwhile enhance the bifunctional catalytic activity.Impressively,the nickel-cobalt oxide-based LOB with cationic vacancies exhibits large specific capacity(12,205 mAh g^(-1)at 200 mA g^(-1))and good durability.This work provides worthwhile insight into the formation and catalytic enhancement mech-anism of transition metal oxide catalysts with cationic vacancies,and to some extent,the creation of efficient and low-cost oxygen electrocatalysts for LOBs.展开更多
The combination effect of cation vacancies and O2 adsorption on ferromagnetism of Na0.5Bi0.5TiO3（100） surface is studied by using density functional theory. An ideal Na0.5Bi0.5TiO3（100） surface is non-magnetic and...The combination effect of cation vacancies and O2 adsorption on ferromagnetism of Na0.5Bi0.5TiO3（100） surface is studied by using density functional theory. An ideal Na0.5Bi0.5TiO3（100） surface is non-magnetic and the cation vacancy could induce the magnetism. By comparing the formation energies for Na, Bi and Ti vacancy, the Na vacancy is more stable than the others. Therefore, we focus on the configuration and electric structure for the system of O2 molecule adsorption on the Na0.5Bi0.5TiO3（100） surface with a Na vacancy. Among the five physisorption configurations we considered, the most likely adsorption position is Na vacancy. The O2 adsorption enhances the magnetism of the system. The contribution of spin polarization is mainly from the O 2p orbitals. The characteristics of exchange coupling are also calculated, which show that the ferromagnetic coupling is favorable. Compared with the previous calculation results, our calculations could explain the room-temperature ferromagnetism of Na0.5Bi0.5TiO3 nanocrytalline powders more reasonably, because of taking into account adsorbed oxygen and cation vacancies. Moreover, our results also show that adsorption of O2 molecule as well as introduction of cation vacancies may be a promising approach to improve multiferroic materials.展开更多
NiFe-layered double hydroxides(NiFe-LDHs)are among the most promising earth-abundant electrocatalysts for the oxygen evolution reaction(OER)in alkaline media.However,their practical application is hindered by intrinsi...NiFe-layered double hydroxides(NiFe-LDHs)are among the most promising earth-abundant electrocatalysts for the oxygen evolution reaction(OER)in alkaline media.However,their practical application is hindered by intrinsic activity limitations and poor stability,primarily due to the asymmetric adsorption of oxygen intermediates.To overcome this,the binding strength must be synergistically tuned to a moderate level to optimize catalytic performance.Here,we engineered NiFeCoCr LDH through Co doping to enhance electrical conductivity and controlled Cr leaching to introduce cationic vacancies for modulating intermediate binding strength in NiFe LDH.X-ray absorption near-edge structure and extended X-ray absorption fine structure analyses reveal that NiFe-LDH with Co doping and Cr vacancies modulates the Ni oxidation state and local coordination environment,leading to a balanced electronic structure and enhanced structural complexity around the Ni sites.Additionally,these vacancies can trap OH~-/H_2O species,which can serve as a reservoir for OH~-transfer,facilitating the rapid formation of OER intermediates and enhancing catalytic performance at high current densities.As a result,V_(Cr)-NiFeCo LDH achieves 1.6 A cm^(-2)current density at 1.7 V vs.RHE while maintaining stable operation for over 1000 h at 500 mA cm^(-2).Density functional theory(DFT)calculations validate the synergistic effects of Co doping and Cr-induced vacancies on intermediate binding energies and improved OER kinetics.Overall,this work presents a rational design strategy to simultaneously enhance the activity and durability of NiFe-based OER catalysts for their application in high-performance alkaline water electrolysis.展开更多
Cr leaching is anticipated to extensively advance the activity of Cr-containing catalysts towards the oxygen evolution reaction(OER),but the underlying catalytic enhancement mechanism requires further investigation.He...Cr leaching is anticipated to extensively advance the activity of Cr-containing catalysts towards the oxygen evolution reaction(OER),but the underlying catalytic enhancement mechanism requires further investigation.Herein,NiFeCr layered double hydroxide(NiFeCr-LDH)is proposed as a proof-of-concept catalyst to elucidate the evolution of Cr species and its enhancement mechanism in OER.The incorporation of Cr(Ⅲ)ions into the lattice of NiFe-LDH is achieved through a meticulously controlled electrodeposition process,which not only promotes Cr leaching but also deepens surface reconstruction.More importantly,experimental and theoretical results demonstrate that protogenetic CrO_(4)^(2-)anions,derived from the oxidation of leached Cr ions,adsorb onto the surface NiFeCr-LDH under the anodic potential to create a CrO_(4)^(2-)-rich electrical double layer(CrO_(4)^(2-)-rich EDL)and function as co-catalyst to trigger OER.CrO_(4)^(2-)-rich EDL integrated with vacancies balances the Gibbs free energies of the reconstructed NiFeCr-LDH for oxygen-containing intermediates,resulting in an exceptionally low overpotential of 286 mV at 500 mA cm^(−2),which outperforms most state-of-the-art metallic catalysts.Additionally,the anion exchange membrane water electrolysis system assembled with NiFeCr-LDH and Pt/C demonstrates 1000-h stability at a current density of 1.0 A cm^(−2)under a voltage of 1.74 V(at 70°C),highlighting its promising potential for practical,large-scale and sustainable applications.展开更多
The rapid advancement of metal halide perovskites can be attributed to their exceptional optoelectronic properties and facile solution processing technique.Noteworthy strides have been achieved in the realm of perovsk...The rapid advancement of metal halide perovskites can be attributed to their exceptional optoelectronic properties and facile solution processing technique.Noteworthy strides have been achieved in the realm of perovskite solar cells(PSCs),with a certified power conversion efficiency(PCE)escalating to 26.7%over the course of a decade,positioning them as promising contenders for next-generation photovoltaic technologies[1].However,the formation of crystal defects,including anion/cation vacancies,Pb–I antisite defects,and uncoordinated Pb^(2+),along the surface and grain boundaries(GBs)of perovskite layers during the solution processing stage poses a significant challenge,compromising the photoelectric performance and stability of PSCs.展开更多
The synthesis of silicate oxyapatitesLa10-x（SiO4）6O3-1.5x（x=0. 0.17, 0.33, 0.50 and 0.67） via a sol-gel method at 800 ℃ was reported. The apatite phases were characterized by X-ray diffraction （XRD） and conduct...The synthesis of silicate oxyapatitesLa10-x（SiO4）6O3-1.5x（x=0. 0.17, 0.33, 0.50 and 0.67） via a sol-gel method at 800 ℃ was reported. The apatite phases were characterized by X-ray diffraction （XRD） and conducting properties were studied by electrochemical impedance spectroscopy （EIS）. It is found that the conductivities are influenced by the amount of cation vacancies and interstitial oxygen. The conductivity of La9.33 （SiO4）6O2 with more cation vacancies is higher than that of La9.5 （SiO4）6O2.25. The conductivity of La10 （SiO4）6O3 with more interstitial oxygen is 7.98 ×10^-3 S·cm^-1, which is about 5 times higher than that of La9.33（SiO4）6O2 at 700℃. The electrical conductivity is almost independent of the oxygen partial pressure from 105 to 1 Pa, which suggests that the oxyapatites exhibit almost pure O^2- ion conduction over a wide range of oxygen partial pressure.展开更多
Ag-doped manganite powder samples, La0.7Sr0.1AgxMnO3 6 （x = 0.00, 0.025, 0.05, 0.075, and 0.10） were synthesized using the sol-gel method. X-ray diffraction patterns indicated that the samples had two phases with th...Ag-doped manganite powder samples, La0.7Sr0.1AgxMnO3 6 （x = 0.00, 0.025, 0.05, 0.075, and 0.10） were synthesized using the sol-gel method. X-ray diffraction patterns indicated that the samples had two phases with the R-3c perovskite being the dominant phase and Mn3O4 being the second phase. X-ray energy dispersive spectra indicated that the ratio of Ag to La was very close to that of the nominal composition in the samples. The specific saturation magnetizations at 300 K increased from 32.0 A.mZ/kg when x = 0.00 to 46.8 A-mZ/kg when x = 0.10. The Curie temperature, TC, of the samples increased from 310 K when x = 0.00 to 328 K when x = 0.10. Because the atomic concentration ratios of La, Sr, and Mn in the five samples were all the same and only the Ag concentration changed, the variations of the specific saturation magnetizations at 300 K and the Curie temperatures suggested that the Ag cations have been doped into the A sites of the perovskite phase in the samples.展开更多
Vacancies and lattice strain engineering are considered highly promising strategies to tailor electronic structure.However,the simultaneous construction of controllable cation^(vac)ancies and lattice strain remains an...Vacancies and lattice strain engineering are considered highly promising strategies to tailor electronic structure.However,the simultaneous construction of controllable cation^(vac)ancies and lattice strain remains an enormous challenge.Herein,NiFe_(2)O_(4)nanosheets synergetically regulated by divalent/trivalent mixed cation^(vac)ancies and controllable lattice tensile strain(TS-Ni^(vac)Fe_(2)^(vac)O_(4)-X,X:quenching temperature)are formulated through controllable chemical etching along with liquid nitrogen quenching method for the first time.Cation^(vac)ancies within TS-Ni^(vac)Fe_(2)^(vac)O_(4)-X could serve as additional insertion points for alkali cations and endow the surface metal active sites with high electrochemical activity.Lattice tensile strain can efficiently modulate the electronic structure to facilitate the catalytic process.Benefiting from the inherent structural advantage,the obtained TS-Ni^(vac)Fe_(2)^(vac)O_(4)-150 with≈0.56%lattice tensile strain demonstrates outstanding hydrogen evolution reaction(61 mV at 10 mA/cm^(2)),desirable oxygen evolution reaction(342 mV at 10 mA/cm^(2))and agreeable overall water splitting performance(1.6 V at 10 mA/cm^(2))as well as remarkable cycling stability,surpassing most previously reported studies.Notably,the simple route is also feasible for NiCo_(2)O_(4)and CoFe_(2)O_(4),demonstrating the general applicability of the strategy toward the advancement of inexpensive and efficient electrocatalysts.展开更多
Symmetric six oxygen-coordinated Mn structural units(MnO6)in MnO2 with small Mn–O orbital overlap hamper electron transfer rates during energy storage.Herein,we report a novel bond angle modulation strategy to manipu...Symmetric six oxygen-coordinated Mn structural units(MnO6)in MnO2 with small Mn–O orbital overlap hamper electron transfer rates during energy storage.Herein,we report a novel bond angle modulation strategy to manipulate Mn–O orbital overlap in MnO2 through the construction of Mn vacancies(MnO2-VMn),aiming at expediting electron transfer,and thus enhancing energy storage performance.Both experimental and theoretical results disclose that the amplification of Mn–O–Mn bond angles exclusively augments the Mn(dx2-y2)-O(py)orbital overlap and triggers the electron redistribution in MnO2-VMn,inducing an augmented Mn dx2-y2 electron occupation.This heightened presence of active electrons in the Mn dx2-y2 orbital paves the way for accelerating electron transfer and ion transfer in MnO2-VMn.Notably,MnO2-VMn delivers an improved specific capacitance of 425 F g−1 at 1 A g−1 and a superior rate capacity of 265 F g−1 at 20 A g−1.Furthermore,an asymmetric supercapacitor(MnO2-VMn//AC ASC)was fabricated,exhibiting a high energy density of 64.3 Wh kg−1 at a power density of 1000 W kg−1.Furthermore,theoretical insights uncover the profound implications of metal–oxygen–metal bond angle regulation on interatomic orbital overlap modulation.These revelations illuminate pathways for the design of advanced energy storage materials.展开更多
The successful deployment of thermoelectric materials necessitates the concurrent development of highperformance p-type and n-type pairs situated within an identical matrix.Nevertheless,limiting by the low dopant solu...The successful deployment of thermoelectric materials necessitates the concurrent development of highperformance p-type and n-type pairs situated within an identical matrix.Nevertheless,limiting by the low dopant solubility,the conventional doping often cannot transfer the Fermi level to the opposite carrier type.Here,the solubility limit of donor dopants was enhanced to achieve n-type GeSe by inducing additional cationic vacancies through raising crystal symmetry.Converting the intrinsic p-type nature of GeSe to n-type poses significant challenges,primarily due to the exceedingly low dopant solubility within its native orthorhombic structure.To overcome this,the In_(2)Te_(3)alloying was initially employed to transition GeSe from orthorhombic to rhombohedral structure,simultaneously generating a large number of Ge vacancies.Following this,the introduction of Pb acts to mitigate the excessive Ge vacancies,steering the material toward a weak p-type character.Crucially,the elevated Ge vacancy concentration serves to extend the solubility limit of Bi donor dopant,which not only promotes the formation of cubic phase,but also enables the p-n type transition.As a result,a peak zT of 0.18 at 773 K was attained for the n-type cubic Ge_(0.55)Bi_(0.2)Pb_(0.2)5Se(In_(2)Te_(3))_(0.1),marking an 18-fold enhancement in comparison with its n-type orthorhombic counterpart.This work attests to the efficacy of introducing vacancies through enhancing crystal symmetry as an effective means to expand dopant solubility,thereby offering valuable insights into the achievement of compatible p-and n-type chalcogenides within the same matrix.展开更多
In this work,cation vacancies induced the tetrahedral distortion,enhancing the second harmonic generation(SHG)response in the diamond-like(DL)structure compounds.Concretely,the high valence and electronegativity of P^...In this work,cation vacancies induced the tetrahedral distortion,enhancing the second harmonic generation(SHG)response in the diamond-like(DL)structure compounds.Concretely,the high valence and electronegativity of P^(5+)were introduced to substitute the Ge^(4+)in Cd_(4)GeS_(6),which shows a general SHG response of 1.1×AgGaS_(2)(AGS)at 2050 nm.Thus,the isomorphic defective DL Cd_(3.5)PS_(6)was obtained with inherent Cd^(2+)vacancies,leading to an 8.5-fold increase in[CdS_(4)]tetrahedral distortion degree than Cd_(4)GeS_(6).As a result,Cd_(3.5)PS_(6)has a high SHG response of 2×AGS at 2050 nm and a laser-induced damage threshold(LIDT)of 9.4×AGS.Furthermore,equivalent Hg^(2+)substitution concentrates Cd^(2+)vacancies at the Cd(2)site,leading to a 2.66-fold[CdS_(4)]tetrahedral distortion degree than Cd_(3.5)PS_(6).Consequently,Hg_(0.5)Cd_(3)PS_(6)possesses a high SHG response of 2.73×AGS at 2050 nm and LIDT of 5×AGS with a birefringence of 0.076@2050 nm.The results indicate that the cation vacancies and radius scale of mixed atoms provide effective ways to design high-performance nonlinear optical crystals.展开更多
Two-dimensional(2D)transition metal chalcogenides(TMCs)are promising for nanoelectronics and energy applications.Among them,the emerging non-layered TMCs are unique due to their unsaturated dangling bonds on the surfa...Two-dimensional(2D)transition metal chalcogenides(TMCs)are promising for nanoelectronics and energy applications.Among them,the emerging non-layered TMCs are unique due to their unsaturated dangling bonds on the surface and strong intralayer and interlayer bonding.However,the synthesis of non-layered 2D TMCs is challenging and this has made it difficult to study their structures and properties at thin thickness limit.Here,we develop a universal dual-metal precursors method to grow non-layered TMCs in which a mixture of a metal and its chloride serves as the metal source.Taking hexagonal Fe_(1-x)S as an example,the thickness of the Fe_(1-x)S flakes is down to 3 nm with a lateral size of over 100 μm.Importantly,we find ordered cation Fe vacancies in Fe_(1-x)S,which is distinct from layered TMCs like MoS_(2) where anion vacancies are commonly observed.Low-temperature transport measurements and theoretical calculations show that 2D Fe_(1-x)S is a stable semiconductor with a narrow bandgap of60 meV.In addition to Fe_(1-x)S,the method is universal in growing various non-layered 2D TMCs containing ordered cation vacancies,including Fe_(1-x)Se,Co_(1-x)S,Cr_(1-x)S,and V_(1-x)S.This work paves the way to grow and exploit properties of non-layered materials at 2D thickness limit.展开更多
Wurtzite-type ferroelectrics are highly promising for next-generation microelectronic devices due to their ferroelectric properties and integration with exiting semiconductors.However,their high coercive fields,which ...Wurtzite-type ferroelectrics are highly promising for next-generation microelectronic devices due to their ferroelectric properties and integration with exiting semiconductors.However,their high coercive fields,which are close to breakdown electric fields,need to be lowered.To deal with this issue and secure device reliability,much effort has been devoted to exploring novel wurtzite compounds with lower polarization switching barriers and implementing doping strategies.Here,we report first-principles calculations on polarization switching in cation-vacancy ordered wurtziteα-Al2S3,unveiling its uniaxial quadruple-well ferroelectricity and moderate switching barrier,51 meV/cation,which is much lower than that of conventional wurtzite ferroelectrics.There are three important features relevant to the Al vacancies leading to the uncommon quadruple-well ferroelectricity and the moderate switching barrier:mitigation of cation-cation repulsion,structural flexibility that alleviates an in-plane lattice expansion,and formation ofσ-like bonding states consisting of Al 3pz and S 3pz orbitals.Biaxial compressive strain and Ga doping lower the switching barriers by up to 40%.This study encourages experimental investigation of the ferroelectric properties for defective wurtziteα-Al2S3 as a new promising material with unconventional and intriguing ferroelectricity and suggests a potential strategy for reducing switching barriers in wurtzite ferroelectrics:introducing cation vacancies.展开更多
Ni-based electrocatalysts with strong redox abilities are active for the electrochemical oxidation of 5-hydroxymethylfurfural(HMF). Interface engineering is an efficient way to modulate the electronic structure, tune ...Ni-based electrocatalysts with strong redox abilities are active for the electrochemical oxidation of 5-hydroxymethylfurfural(HMF). Interface engineering is an efficient way to modulate the electronic structure, tune the intermediate adsorption, and expose more active sites. Herein, we increased the concentration of interfacial sites with rich defects in a 3D hierarchical nanostructured NiO-Co3O4 electrocatalyst and investigated its catalytic performance for HMF electro-oxidation. The interface effect created abundant cation vacancies, modulated the electronic properties of Co and Ni atoms, and raised the oxidation state of Ni species. The NiO-Co3O4 catalysts show superb HMF oxidation activities with a low onset potential of 1.28 VRHE.Meanwhile, in-situ surface-selective vibrational spectroscopy of sum-frequency generation was performed to study the reaction pathway during the oxidation process on the electrocatalysts. The current study offers an efficient way to create cation vacancies and proves the decisive role of cation vacancies in catalyzing the HMF electro-oxidation.展开更多
With the depletion of fossil fuels and environmental pollution, energy storage and conversion have become the focus of current research. Water splitting and fuel cell technologies have made outstanding contributions t...With the depletion of fossil fuels and environmental pollution, energy storage and conversion have become the focus of current research. Water splitting and fuel cell technologies have made outstanding contributions to energy conversion. However, the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) have slow kinetics, which limit the capacity of fuel cells. It is of great significance to develop catalysts for the OER and ORR and continuously improve their catalytic performance. Many studies have shown that intrinsic defects, especially vacancies (anion and cation vacancies), can effectively improve the efficiency of electrochemical energy storage and conversion. The introduction of intrinsic defects can generally expose more active sites, enhance conductivity, adjust the electronic state, and promote ion diffusion, thereby enhancing the catalytic performance. This review comprehensively summarizes the latest developments regarding the effects of intrinsic defects on the performance of non-noble metal electrocatalysts. According to the type of intrinsic defect, this article reviews in detail the regulation mechanism, preparation methods and advanced characterization techniques of intrinsic defects in different materials (oxides, non-oxides, etc.). Then, the current difficulties and future development of intrinsic defect regulation are analyzed and discussed thoroughly. Finally, the prospect of intrinsic defects in the field of electrochemical energy storage is further explored.展开更多
基金This work was financially supported by the Australian Research Council(ARC)Discovery Projects(DP210103266,DP200100965 and DP200100365)the ARC Discovery Early Career Researcher Award(DE210101102)the Griffith University Postdoctoral Fellowship Scheme(YUDOU 036 Research Internal).
文摘It is challenging to create cation vacancies in electrode materials for enhancing the performance of rechargeable lithium ion batteries (LIBs). Herein, we utilized a strong alkaline etching method to successfully create Co vacancies at the interface of atomically thin Co_(3−x)O_(4)/graphene@CNT heterostructure for high-energy/power lithium storage. The creation of Co-vacancies in the sample was confirmed by high-resolution scanning transmission electron microscope (HRSTEM), X-ray photoelectron spectroscopy (XPS) and electron energy loss near-edge structures (ELNES). The obtained Co_(3−x)O_(4)/graphene@CNT delivers an ultra-high capacity of 1688.2 mAh g^(−1) at 0.2 C, excellent rate capability of 83.7% capacity retention at 1 C, and an ultralong life up to 1500 cycles with a reversible capacity of 1066.3 mAh g^(−1). Reaction kinetic study suggests a significant contribution from pseudocapacitive storage induced by the Co-vacancies at the Co_(3−x)O_(4)/graphene@CNT interface. Density functional theory confirms that the Co-vacancies could dramatically enhance the Li adsorption and provide an additional pathway with a lower energy barrier for Li diffusion, which results in an intercalation pseudocapacitive behavior and high-capacity/rate energy storage.
基金support of the Natural Science Foundation of Heilongjiang Province of China(No.LH2023E059)the National Natural Science Foundation of China(No.52071093)the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology(No.ASMA202205).
文摘Although the Mg-air battery with high theoretical energy density is desirable for the energy supply of marine engineering equipment,its applications remain limited due to the low actual discharge voltage and inferior Mg anode utilization rate.In addition to the microstructure of Mg alloy anodes,the properties of discharge product films are of great importance to the discharge performance.Herein,the discharge behaviors of Mg-Y-Zn alloys are first studied mainly from the perspective of film properties.Through contrastive analysis,it is found that the sufficient Y^(3+) produced during the discharge process can substitute Mg^(2+) in Mg(OH)_(2) to introduce effective cation vacancies.The Mg-Y-Zn anode with profuse cation vacancies in the product film shows a synergy of potential and efficiency,and this can be attributed to an increase in the migration pathway for Mg^(2+),reducing the diffusion over-potential caused by the protective product film.This study is expected to provide a new strategy from the perspective of cation vacancy design of discharge film for developing high-performance Mg-air batteries.
基金supported by the National Natural Science Foundation of China(52173274 and 52172202)the Natural Science Foundation of Guangdong Province 2022A1515010049+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDA16021101)the China Postdoctoral Science Foundation(2021M691228)。
文摘Cation vacancy engineering is considered to be one of the effective methods to solve the issues of shuttling and sluggish redox kinetics of Li PSs owing to the intrinsic tunability of electronic structure.However,cation vacancies are few studied in the Li-S realm due to their complex and rigid preparation methods.In this work,one-step pyrolysis is reported to in situ introduce Fe-vacancies into iron sulfide(Fe_(0.96)S)as a sulfur host.For this host structure,Fe_(0.96)S is first employed as an adsorbent and catalyst in Li-S system.During the carbonization process,a tight contact structure of Fe_(0.96)S crystal and carbon network(Fe_(0.96)S@C)is in situ constructed,and the carbon layer as a conductor provides smooth electrons transfer pathways for redox reactions.Meanwhile,due to the introduction of Fe-vacancies in Fe S crystal,the adsorption capability and catalytic effect for Li PSs have been substantially enhanced.Moreover,the presence of Fe_(0.96)S crystal favors the mobility of electron and diffusion of Li+,which is revealed by the experiments and theoretical calculations.Through synergy respective advantages effect of Fe_(0.96)S and carbon,the Fe_(0.96)S@C-S cathode delivers high-rate capability at 5.0 C and stable long-life performance.Even under a high sulfur loading of 3.5 mg/cm^(2),the durable cyclic stability is still exhibited with the capacity retention of 93%over 400 cycles at 1.0 C,and the coulombic efficiency is≥98%.Noting that this strategy greatly simplifies the synthetic process of currently known cation-vacancy materials and furnishes a universal mentality for designing both divinable and astonishing new cation-vacancy materials.
基金Supported by the Natural Science Foundation of Guangdong PrOvince （06025657） and Guangdong Provincial Green Chemicals.
文摘Apatite-type lanthanum silicate with special conduction mechanism via interstitial oxygen has attracted considerable interest in recent years. In this work, pure powder of La9.33 2x/3MxSi6O26 （M=Mg, Ca, Sr） is prepared by the sol-gel method with sintering at 1000℃. The powder is characterized by X-ray diffraction （XRD） and scanning electron micrograph （SEM）. The apatite can be obtained at relatively low temperature as compared to the conventional solid-state reaction method. The measurements of conductivity of a series of doped samples La9.33-2x/3MxSi6O26 （M=Ca, Mg, Sr） indicate that the type of dopant and the amount have a significant effect on the conductivity. The greatest decrease in conductivity is observed for Mg doping, following the Ca and the Sr doped apatites. The effect is ultimately attributed to the amount of oxygen interstitials, which is affected by the crystal lattice distortion arising from cation vacancies.
基金This work was financially supported by research projects from Department of Science and Technology of Shandong Province(Nos.2021CXGC010307,2020CXGC010310,ZR2019MEM052,and 2019TSLH0101)The authors acknowledged the assistance of Shandong University Testing and Manufacturing Center for Ad-vanced Materials.H.G.acknowledges the Science and Technol-ogy Project of Hebei Education Department(No.BJK2022068)Hebei Province Introduced Overseas Students Funding Project(No.C20220306).
文摘Rechargeable lithium-oxygen batteries(LOBs)have received incremental attention owing to their high energy density and applicability to mobile devices and electric vehicles.However,the lack of robust,low-cost,and environmentally benign bifunctional catalysts is a major impediment to the commercial application.The introduction of vacancies is one of the effective strategies to enhance the performance of cathode catalysts for lithium-oxygen batteries,but the preparation is complicated.In this work,needle-like microsphere cathode catalysts of nickel-cobalt oxide containing cationic vacancies are constructed by controlling the annealing temperature.It is demonstrated that the presence of cationic vacancies can modulate the electronic structure of the catalyst,reduce the energy barrier for the oxygen electrode re-action,meanwhile enhance the bifunctional catalytic activity.Impressively,the nickel-cobalt oxide-based LOB with cationic vacancies exhibits large specific capacity(12,205 mAh g^(-1)at 200 mA g^(-1))and good durability.This work provides worthwhile insight into the formation and catalytic enhancement mech-anism of transition metal oxide catalysts with cationic vacancies,and to some extent,the creation of efficient and low-cost oxygen electrocatalysts for LOBs.
基金supported by the National Natural Science Foundation of China (No.11547176, No.11704006)Henan College Key Research Project (No.15A140017)
文摘The combination effect of cation vacancies and O2 adsorption on ferromagnetism of Na0.5Bi0.5TiO3（100） surface is studied by using density functional theory. An ideal Na0.5Bi0.5TiO3（100） surface is non-magnetic and the cation vacancy could induce the magnetism. By comparing the formation energies for Na, Bi and Ti vacancy, the Na vacancy is more stable than the others. Therefore, we focus on the configuration and electric structure for the system of O2 molecule adsorption on the Na0.5Bi0.5TiO3（100） surface with a Na vacancy. Among the five physisorption configurations we considered, the most likely adsorption position is Na vacancy. The O2 adsorption enhances the magnetism of the system. The contribution of spin polarization is mainly from the O 2p orbitals. The characteristics of exchange coupling are also calculated, which show that the ferromagnetic coupling is favorable. Compared with the previous calculation results, our calculations could explain the room-temperature ferromagnetism of Na0.5Bi0.5TiO3 nanocrytalline powders more reasonably, because of taking into account adsorbed oxygen and cation vacancies. Moreover, our results also show that adsorption of O2 molecule as well as introduction of cation vacancies may be a promising approach to improve multiferroic materials.
基金supported by the Natural Science Foundation of China Grant No.52272289 and 5240223,and JSPS(Japan Society for the Promotion of Science)of Grant No.22K19088,23H00313,24H02202,and 24H02205。
文摘NiFe-layered double hydroxides(NiFe-LDHs)are among the most promising earth-abundant electrocatalysts for the oxygen evolution reaction(OER)in alkaline media.However,their practical application is hindered by intrinsic activity limitations and poor stability,primarily due to the asymmetric adsorption of oxygen intermediates.To overcome this,the binding strength must be synergistically tuned to a moderate level to optimize catalytic performance.Here,we engineered NiFeCoCr LDH through Co doping to enhance electrical conductivity and controlled Cr leaching to introduce cationic vacancies for modulating intermediate binding strength in NiFe LDH.X-ray absorption near-edge structure and extended X-ray absorption fine structure analyses reveal that NiFe-LDH with Co doping and Cr vacancies modulates the Ni oxidation state and local coordination environment,leading to a balanced electronic structure and enhanced structural complexity around the Ni sites.Additionally,these vacancies can trap OH~-/H_2O species,which can serve as a reservoir for OH~-transfer,facilitating the rapid formation of OER intermediates and enhancing catalytic performance at high current densities.As a result,V_(Cr)-NiFeCo LDH achieves 1.6 A cm^(-2)current density at 1.7 V vs.RHE while maintaining stable operation for over 1000 h at 500 mA cm^(-2).Density functional theory(DFT)calculations validate the synergistic effects of Co doping and Cr-induced vacancies on intermediate binding energies and improved OER kinetics.Overall,this work presents a rational design strategy to simultaneously enhance the activity and durability of NiFe-based OER catalysts for their application in high-performance alkaline water electrolysis.
基金the support of this research by the National Key Research and Development Program of China(2024YFB4106400)the National Natural Science Foundation of China(22179035)the Science Fund for Distinguished Young Scholars of Heilongjiang Province(JQ2022B001)。
文摘Cr leaching is anticipated to extensively advance the activity of Cr-containing catalysts towards the oxygen evolution reaction(OER),but the underlying catalytic enhancement mechanism requires further investigation.Herein,NiFeCr layered double hydroxide(NiFeCr-LDH)is proposed as a proof-of-concept catalyst to elucidate the evolution of Cr species and its enhancement mechanism in OER.The incorporation of Cr(Ⅲ)ions into the lattice of NiFe-LDH is achieved through a meticulously controlled electrodeposition process,which not only promotes Cr leaching but also deepens surface reconstruction.More importantly,experimental and theoretical results demonstrate that protogenetic CrO_(4)^(2-)anions,derived from the oxidation of leached Cr ions,adsorb onto the surface NiFeCr-LDH under the anodic potential to create a CrO_(4)^(2-)-rich electrical double layer(CrO_(4)^(2-)-rich EDL)and function as co-catalyst to trigger OER.CrO_(4)^(2-)-rich EDL integrated with vacancies balances the Gibbs free energies of the reconstructed NiFeCr-LDH for oxygen-containing intermediates,resulting in an exceptionally low overpotential of 286 mV at 500 mA cm^(−2),which outperforms most state-of-the-art metallic catalysts.Additionally,the anion exchange membrane water electrolysis system assembled with NiFeCr-LDH and Pt/C demonstrates 1000-h stability at a current density of 1.0 A cm^(−2)under a voltage of 1.74 V(at 70°C),highlighting its promising potential for practical,large-scale and sustainable applications.
基金supported by the Science,Technology,Innovation Commission of Shenzhen Municipality(GJHZ20220913143204008)Postdoctoral Research Project Funding in Shaanxi Province.
文摘The rapid advancement of metal halide perovskites can be attributed to their exceptional optoelectronic properties and facile solution processing technique.Noteworthy strides have been achieved in the realm of perovskite solar cells(PSCs),with a certified power conversion efficiency(PCE)escalating to 26.7%over the course of a decade,positioning them as promising contenders for next-generation photovoltaic technologies[1].However,the formation of crystal defects,including anion/cation vacancies,Pb–I antisite defects,and uncoordinated Pb^(2+),along the surface and grain boundaries(GBs)of perovskite layers during the solution processing stage poses a significant challenge,compromising the photoelectric performance and stability of PSCs.
文摘The synthesis of silicate oxyapatitesLa10-x（SiO4）6O3-1.5x（x=0. 0.17, 0.33, 0.50 and 0.67） via a sol-gel method at 800 ℃ was reported. The apatite phases were characterized by X-ray diffraction （XRD） and conducting properties were studied by electrochemical impedance spectroscopy （EIS）. It is found that the conductivities are influenced by the amount of cation vacancies and interstitial oxygen. The conductivity of La9.33 （SiO4）6O2 with more cation vacancies is higher than that of La9.5 （SiO4）6O2.25. The conductivity of La10 （SiO4）6O3 with more interstitial oxygen is 7.98 ×10^-3 S·cm^-1, which is about 5 times higher than that of La9.33（SiO4）6O2 at 700℃. The electrical conductivity is almost independent of the oxygen partial pressure from 105 to 1 Pa, which suggests that the oxyapatites exhibit almost pure O^2- ion conduction over a wide range of oxygen partial pressure.
基金supported by the National Natural Science Foundation of China(Grant No.NSF-11174069)the Natural Science Foundation of Hebei Province,China(Grant No.E2011205083)+2 种基金the Key Item Science Foundation of Hebei Province,China(Grant No.10965125D)the Key Item Science Foundation of the Education Department of Hebei Province,China(Grant No.ZD2010129)the Young Scholar Science Foundation of the Education Department of Hebei Province,China(Grant No.QN20131008)
文摘Ag-doped manganite powder samples, La0.7Sr0.1AgxMnO3 6 （x = 0.00, 0.025, 0.05, 0.075, and 0.10） were synthesized using the sol-gel method. X-ray diffraction patterns indicated that the samples had two phases with the R-3c perovskite being the dominant phase and Mn3O4 being the second phase. X-ray energy dispersive spectra indicated that the ratio of Ag to La was very close to that of the nominal composition in the samples. The specific saturation magnetizations at 300 K increased from 32.0 A.mZ/kg when x = 0.00 to 46.8 A-mZ/kg when x = 0.10. The Curie temperature, TC, of the samples increased from 310 K when x = 0.00 to 328 K when x = 0.10. Because the atomic concentration ratios of La, Sr, and Mn in the five samples were all the same and only the Ag concentration changed, the variations of the specific saturation magnetizations at 300 K and the Curie temperatures suggested that the Ag cations have been doped into the A sites of the perovskite phase in the samples.
基金supported by the National Natural Science Foundation of China(grant no.22205125)the Heilongjiang Provincial Natural Science Foundation of China(grant no.LH2022B024)+3 种基金the Outstanding Youth Project of Natural Science Foundation in Heilongjiang Province(grant no.YQ2022E040)the Shandong Provincial Natural Science Foundation(grant no.ZR2022ME166)the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang Province(grant no.UNPYSCT-2020197)the Support Program for Outstanding Young Faculty Basic Research in Provincial Undergraduate Universities in Heilongjiang Province(grant no.YQJH2023098).
文摘Vacancies and lattice strain engineering are considered highly promising strategies to tailor electronic structure.However,the simultaneous construction of controllable cation^(vac)ancies and lattice strain remains an enormous challenge.Herein,NiFe_(2)O_(4)nanosheets synergetically regulated by divalent/trivalent mixed cation^(vac)ancies and controllable lattice tensile strain(TS-Ni^(vac)Fe_(2)^(vac)O_(4)-X,X:quenching temperature)are formulated through controllable chemical etching along with liquid nitrogen quenching method for the first time.Cation^(vac)ancies within TS-Ni^(vac)Fe_(2)^(vac)O_(4)-X could serve as additional insertion points for alkali cations and endow the surface metal active sites with high electrochemical activity.Lattice tensile strain can efficiently modulate the electronic structure to facilitate the catalytic process.Benefiting from the inherent structural advantage,the obtained TS-Ni^(vac)Fe_(2)^(vac)O_(4)-150 with≈0.56%lattice tensile strain demonstrates outstanding hydrogen evolution reaction(61 mV at 10 mA/cm^(2)),desirable oxygen evolution reaction(342 mV at 10 mA/cm^(2))and agreeable overall water splitting performance(1.6 V at 10 mA/cm^(2))as well as remarkable cycling stability,surpassing most previously reported studies.Notably,the simple route is also feasible for NiCo_(2)O_(4)and CoFe_(2)O_(4),demonstrating the general applicability of the strategy toward the advancement of inexpensive and efficient electrocatalysts.
基金Financial support from the National Natural Science Foundation of China(21575016U20A20154+1 种基金22279005)the National Program for Support of Top-notch Young Professionals。
文摘Symmetric six oxygen-coordinated Mn structural units(MnO6)in MnO2 with small Mn–O orbital overlap hamper electron transfer rates during energy storage.Herein,we report a novel bond angle modulation strategy to manipulate Mn–O orbital overlap in MnO2 through the construction of Mn vacancies(MnO2-VMn),aiming at expediting electron transfer,and thus enhancing energy storage performance.Both experimental and theoretical results disclose that the amplification of Mn–O–Mn bond angles exclusively augments the Mn(dx2-y2)-O(py)orbital overlap and triggers the electron redistribution in MnO2-VMn,inducing an augmented Mn dx2-y2 electron occupation.This heightened presence of active electrons in the Mn dx2-y2 orbital paves the way for accelerating electron transfer and ion transfer in MnO2-VMn.Notably,MnO2-VMn delivers an improved specific capacitance of 425 F g−1 at 1 A g−1 and a superior rate capacity of 265 F g−1 at 20 A g−1.Furthermore,an asymmetric supercapacitor(MnO2-VMn//AC ASC)was fabricated,exhibiting a high energy density of 64.3 Wh kg−1 at a power density of 1000 W kg−1.Furthermore,theoretical insights uncover the profound implications of metal–oxygen–metal bond angle regulation on interatomic orbital overlap modulation.These revelations illuminate pathways for the design of advanced energy storage materials.
基金financially supported by the National Key R&D Program of China(No.2021YFB1507403)the National Natural Science Foundation of China(No.52071218)+1 种基金Shenzhen Science and Technology Innovation Commission(No.JCYJ20230808105700001)Shenzhen University 2035 Program for Excellent Research(No.00000218)。
文摘The successful deployment of thermoelectric materials necessitates the concurrent development of highperformance p-type and n-type pairs situated within an identical matrix.Nevertheless,limiting by the low dopant solubility,the conventional doping often cannot transfer the Fermi level to the opposite carrier type.Here,the solubility limit of donor dopants was enhanced to achieve n-type GeSe by inducing additional cationic vacancies through raising crystal symmetry.Converting the intrinsic p-type nature of GeSe to n-type poses significant challenges,primarily due to the exceedingly low dopant solubility within its native orthorhombic structure.To overcome this,the In_(2)Te_(3)alloying was initially employed to transition GeSe from orthorhombic to rhombohedral structure,simultaneously generating a large number of Ge vacancies.Following this,the introduction of Pb acts to mitigate the excessive Ge vacancies,steering the material toward a weak p-type character.Crucially,the elevated Ge vacancy concentration serves to extend the solubility limit of Bi donor dopant,which not only promotes the formation of cubic phase,but also enables the p-n type transition.As a result,a peak zT of 0.18 at 773 K was attained for the n-type cubic Ge_(0.55)Bi_(0.2)Pb_(0.2)5Se(In_(2)Te_(3))_(0.1),marking an 18-fold enhancement in comparison with its n-type orthorhombic counterpart.This work attests to the efficacy of introducing vacancies through enhancing crystal symmetry as an effective means to expand dopant solubility,thereby offering valuable insights into the achievement of compatible p-and n-type chalcogenides within the same matrix.
基金supported by the National Natural Science Foundation of China(52472191 and 52102218)the National KeyResearch and Development Program of China(2020YFA0710303)+4 种基金the Fujian Science&Technology Innovation Laboratory for Optoelectronic Information of China(2021ZZ127)the Minjiang Scholar Professorship(GXRC-21004)the State Key Laboratory of Structure Chemistry(20240010)the Natural Science Foundation of Fujian Province of China(2021J01594)the Fujian Provincial Key Laboratory of Advanced Inorganic Oxygenated Materials(KF202302)。
文摘In this work,cation vacancies induced the tetrahedral distortion,enhancing the second harmonic generation(SHG)response in the diamond-like(DL)structure compounds.Concretely,the high valence and electronegativity of P^(5+)were introduced to substitute the Ge^(4+)in Cd_(4)GeS_(6),which shows a general SHG response of 1.1×AgGaS_(2)(AGS)at 2050 nm.Thus,the isomorphic defective DL Cd_(3.5)PS_(6)was obtained with inherent Cd^(2+)vacancies,leading to an 8.5-fold increase in[CdS_(4)]tetrahedral distortion degree than Cd_(4)GeS_(6).As a result,Cd_(3.5)PS_(6)has a high SHG response of 2×AGS at 2050 nm and a laser-induced damage threshold(LIDT)of 9.4×AGS.Furthermore,equivalent Hg^(2+)substitution concentrates Cd^(2+)vacancies at the Cd(2)site,leading to a 2.66-fold[CdS_(4)]tetrahedral distortion degree than Cd_(3.5)PS_(6).Consequently,Hg_(0.5)Cd_(3)PS_(6)possesses a high SHG response of 2.73×AGS at 2050 nm and LIDT of 5×AGS with a birefringence of 0.076@2050 nm.The results indicate that the cation vacancies and radius scale of mixed atoms provide effective ways to design high-performance nonlinear optical crystals.
基金supported by the National Science Fund for Distinguished Young Scholars(52125309)the National Natural Science Foundation of China(51991343,51920105002,51991340,52188101,and 11974156)+3 种基金Guangdong Innovative and Entrepreneurial Research Team Program(2017ZT07C341 and 2019ZT08C044)the Bureau of Industry and Information Technology of Shenzhen for the “2017 Graphene Manufacturing Innovation Center Project”(201901171523)Shenzhen Basic Research Project(JCYJ20200109144616617 and JCYJ20190809180605522)Shenzhen Science and Technology Program(KQTD20190929173815000 and 20200925161102001)。
文摘Two-dimensional(2D)transition metal chalcogenides(TMCs)are promising for nanoelectronics and energy applications.Among them,the emerging non-layered TMCs are unique due to their unsaturated dangling bonds on the surface and strong intralayer and interlayer bonding.However,the synthesis of non-layered 2D TMCs is challenging and this has made it difficult to study their structures and properties at thin thickness limit.Here,we develop a universal dual-metal precursors method to grow non-layered TMCs in which a mixture of a metal and its chloride serves as the metal source.Taking hexagonal Fe_(1-x)S as an example,the thickness of the Fe_(1-x)S flakes is down to 3 nm with a lateral size of over 100 μm.Importantly,we find ordered cation Fe vacancies in Fe_(1-x)S,which is distinct from layered TMCs like MoS_(2) where anion vacancies are commonly observed.Low-temperature transport measurements and theoretical calculations show that 2D Fe_(1-x)S is a stable semiconductor with a narrow bandgap of60 meV.In addition to Fe_(1-x)S,the method is universal in growing various non-layered 2D TMCs containing ordered cation vacancies,including Fe_(1-x)Se,Co_(1-x)S,Cr_(1-x)S,and V_(1-x)S.This work paves the way to grow and exploit properties of non-layered materials at 2D thickness limit.
基金supported by Japan Society of the Promotion of Science(JSPS)KAKENHI Grants Nos.JP17K19172,JP18H01892,JP19H00883,JP21K19027,JP21H05568,JP21H04619,JP23H02069,and JP23H01869H.A.appreciates Murata Science Foundation and Collaborative Research Project of Laboratory for Materials and Structures,Institute of Innovative Research,Tokyo Institute of Technology.S.O.gratefully acknowledges the Toyota Riken for financial support through a Rising Fellow Program.The computation was carried out using the computer resource offered under the category of General Projects by Research Institute for Information Technology,Kyushu University.
文摘Wurtzite-type ferroelectrics are highly promising for next-generation microelectronic devices due to their ferroelectric properties and integration with exiting semiconductors.However,their high coercive fields,which are close to breakdown electric fields,need to be lowered.To deal with this issue and secure device reliability,much effort has been devoted to exploring novel wurtzite compounds with lower polarization switching barriers and implementing doping strategies.Here,we report first-principles calculations on polarization switching in cation-vacancy ordered wurtziteα-Al2S3,unveiling its uniaxial quadruple-well ferroelectricity and moderate switching barrier,51 meV/cation,which is much lower than that of conventional wurtzite ferroelectrics.There are three important features relevant to the Al vacancies leading to the uncommon quadruple-well ferroelectricity and the moderate switching barrier:mitigation of cation-cation repulsion,structural flexibility that alleviates an in-plane lattice expansion,and formation ofσ-like bonding states consisting of Al 3pz and S 3pz orbitals.Biaxial compressive strain and Ga doping lower the switching barriers by up to 40%.This study encourages experimental investigation of the ferroelectric properties for defective wurtziteα-Al2S3 as a new promising material with unconventional and intriguing ferroelectricity and suggests a potential strategy for reducing switching barriers in wurtzite ferroelectrics:introducing cation vacancies.
基金supported by the Fundamental Research Funds for the Central Universities (531118010127)the National Natural Science Foundation of China (21902047, 51402100, 21825201, 21573066, 21805080, 21972164, U19A2017)the Provincial Natural Science Foundation of Hunan (2016TP1009)。
文摘Ni-based electrocatalysts with strong redox abilities are active for the electrochemical oxidation of 5-hydroxymethylfurfural(HMF). Interface engineering is an efficient way to modulate the electronic structure, tune the intermediate adsorption, and expose more active sites. Herein, we increased the concentration of interfacial sites with rich defects in a 3D hierarchical nanostructured NiO-Co3O4 electrocatalyst and investigated its catalytic performance for HMF electro-oxidation. The interface effect created abundant cation vacancies, modulated the electronic properties of Co and Ni atoms, and raised the oxidation state of Ni species. The NiO-Co3O4 catalysts show superb HMF oxidation activities with a low onset potential of 1.28 VRHE.Meanwhile, in-situ surface-selective vibrational spectroscopy of sum-frequency generation was performed to study the reaction pathway during the oxidation process on the electrocatalysts. The current study offers an efficient way to create cation vacancies and proves the decisive role of cation vacancies in catalyzing the HMF electro-oxidation.
基金This work was financially supported by the National Natu-ral Science Foundation of China(12025503,U1867215,11875211,U1932134,12105208)Hubei Provincial Natural Science Foundation(2019CFA036)+1 种基金the Fundamental Research Funds for the Central Universities(2042021kf0068)China Postdoctoral Science Foundation(No.2020M682469).
文摘With the depletion of fossil fuels and environmental pollution, energy storage and conversion have become the focus of current research. Water splitting and fuel cell technologies have made outstanding contributions to energy conversion. However, the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) have slow kinetics, which limit the capacity of fuel cells. It is of great significance to develop catalysts for the OER and ORR and continuously improve their catalytic performance. Many studies have shown that intrinsic defects, especially vacancies (anion and cation vacancies), can effectively improve the efficiency of electrochemical energy storage and conversion. The introduction of intrinsic defects can generally expose more active sites, enhance conductivity, adjust the electronic state, and promote ion diffusion, thereby enhancing the catalytic performance. This review comprehensively summarizes the latest developments regarding the effects of intrinsic defects on the performance of non-noble metal electrocatalysts. According to the type of intrinsic defect, this article reviews in detail the regulation mechanism, preparation methods and advanced characterization techniques of intrinsic defects in different materials (oxides, non-oxides, etc.). Then, the current difficulties and future development of intrinsic defect regulation are analyzed and discussed thoroughly. Finally, the prospect of intrinsic defects in the field of electrochemical energy storage is further explored.
