Cu^(2+)in copper-based catalysts can facilitate the hydrogenation of the CH_(4)production pathway via the electrochemical carbon dioxide reduction reaction(ECRR).However,Cu^(2+)species in copper oxides are unstable an...Cu^(2+)in copper-based catalysts can facilitate the hydrogenation of the CH_(4)production pathway via the electrochemical carbon dioxide reduction reaction(ECRR).However,Cu^(2+)species in copper oxides are unstable and have been revealed to reduce to Cu^(0)under the applied cathodic potential.In this work,we reported an A-site modulation strategy to stabilize Cu^(2+)in perovskite for efficient ECRR to CH_(4).After the introduction of Ca^(2+)in La_(2)CuO_(4),the obtained LaCa_(0.4)CuO_(3-δ)is stable during ECRR.We achieved a59.6%±3.8%CH4faradaic efficiency at-1.30 V versus reversible hydrogen electrode in H-cell and a partial current density of 155.0 m A/cm^(2)in membrane electrode assembly.DFT calculations and in situ Raman spectroscopy show that Cu^(2+)facilitates the hydrogenation of*CH_(2)O to*CH_(3)O and the further production of CH_(4).This work introduces an efficient strategy to stabilize Cu^(2+)and provides an understanding of Cu^(2+)in promoting ECRR to CH_(4).展开更多
The compositional flexibility and structural stability of SrTiO_(3)-based perovskite oxides present a promising approach to tailor their electrical and thermal transport properties.In this work,a series of(Ca_(0.25)Nd...The compositional flexibility and structural stability of SrTiO_(3)-based perovskite oxides present a promising approach to tailor their electrical and thermal transport properties.In this work,a series of(Ca_(0.25)Nd_(0.25)Sr_(0.35)Ba_(0.15))1-xTiO_(3)±δceramics with varying A-site deficiencies were designed by integrating entropy engineering and defect chemistry,and their microstructural characteristics and transport properties were systematically investigated.All samples exhibited a stable single-phase Pm3m cubic structure with uniformly distributed constituent elements.The introduction of A-site vacancies created favorable pathways for ion diffusion during the sintering process and facilitated grain growth.A-site deficiencies significantly increased carrier concentration by promoting the formation of oxygen vacancies and Ti^(3+),while also enhancing carrier mobility by improving structural symmetry and reducing grain boundary scattering,leading to the improved power factor.The multiscale defects resulting from entropy engineering including point defects,strain fields,and high-density grain boundaries contributed to the reduced thermal conductivity of all samples.By synergistically optimizing the entropy and defect engineering,the sample with x=0.09 achieved a peak figure of merit(ZT)of 0.21 at 900 K,representing a 32%enhancement compared with that of the x=0.03 sample.This work underscores the significance of the combined strategy of entropy engineering and defect chemistry in manipulating the transport properties of SrTiO_(3)-based thermoelectric oxides.展开更多
With the rapid development of electronic technology,how to effectively eliminate electromagnetic pollu-tion has become a serious problem.Perovskite oxides have shown great potential in the field of electro-magnetic wa...With the rapid development of electronic technology,how to effectively eliminate electromagnetic pollu-tion has become a serious problem.Perovskite oxides have shown great potential in the field of electro-magnetic wave absorption due to their unique structure and excellent physicochemical properties.Herein,by rationally manipulating the A-site ion substitution strategy,the theoretically directed doping of Sr ions into La ionic sites was utilized and the layered MoS_(2) was loaded by the hydrothermal process to modify its surface.Consequently,the introduced polarization phenomenon improved the dielectric performance of the perovskite oxides,achieving a collaborative dielectric/magnetic loss mechanism.Accordingly,the prepared La0.7Sr0.3FeO3(LSFO)/MoS_(2) as coating filler in the epoxy resin coating system can obtain the minimum reflection loss of-67.09 dB at 1.9 mm and the maximum effective absorption bandwidth of 7.28 GHz at 2.3 mm.More importantly,it also exhibits excellent absorption performance for multi-band electromagnetic waves,covering a wide range of specified frequency bands.It provides inspiration for ex-ploring novel perovskite oxide-based electromagnetic wave absorbing coatings and broadens the choice of ideal candidate materials for designing highly efficient,multi-band absorbers to cope with sophisticated electromagnetic environments.展开更多
Ba0.9R0.1Co0.TFe0.225Ta0.07503-δ （BRCFT, R = Ca, La or Sr） membranes were synthesized by a solid-state reaction. Metal cation Ca2＋, La3＋ or Sr2＋ doping on A-site partially substituted Ba2＋ in BaCoo.TFe0.225Ta0....Ba0.9R0.1Co0.TFe0.225Ta0.07503-δ （BRCFT, R = Ca, La or Sr） membranes were synthesized by a solid-state reaction. Metal cation Ca2＋, La3＋ or Sr2＋ doping on A-site partially substituted Ba2＋ in BaCoo.TFe0.225Ta0.07503-δ oxides, and its subsequent effects on phase structure stability, oxygen permeability and oxygen desorption were systematically investigated by XRD, TG-DSC, Hz-TPR, O2-TPD techniques and oxygen permeation experiments. The partial substitution with Ca2＋, La3＋ or Sr2＋, whose ionic radii are smaller than that of Ba2＋, succeeded in stabilizing the cubic perovskite structure without formation of impurity phases, as revealed by XRD analysis. Oxygen-involving experi- ments showed that BRCFT with A-site fully occupied by Ba2＋ exhibited good oxygen permeation flux under He flow, reaching about 2.3 mL.min-l .cm-2 at 900 with I mm thickness. Of all the membranes, BLCFT membrane showed better chemical stability in CO2, owing to the reduction in alkalinity of the mixed conductor oxide by La doping. In addition, we also found the stability of the perovskite structure under reducing atmospheres was strengthened by increasing the size of A-site cation （Ba2＋〉La3＋〉SrZ＋〉Ca2＋）.展开更多
High-temperature CO_(2)electrolysis via solid oxide electrolysis cells(CO_(2)-SOECs)has drawn special attention due to the high energy convention efficiency,fast electrode kinetics,and great potential in carbon cyclin...High-temperature CO_(2)electrolysis via solid oxide electrolysis cells(CO_(2)-SOECs)has drawn special attention due to the high energy convention efficiency,fast electrode kinetics,and great potential in carbon cycling.However,the development of cathode materials with high catalytic activity and chemical stability for pure CO_(2)electrolysis is still a great challenge.In this work,A-site cation deficient dual-phase material,namely(Pr_(0.4)Ca_(0.6))_(x)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN,x=1,0.95,and 0.9),has been designed as the fuel electrode for a pure CO_(2)-SOEC,which presents superior electrochemical performance.Among all these compositions,(Pr_(0.4)Ca_(0.6))_(0.95)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN95)exhibited the lowest polarization resistance of 0.458Ωcm^(2)at open-circuit voltage and 800℃.The application of PCFN95 as the cathode in a single cell yields an impressive electrolysis current density of 1.76 A cm^(-2)at 1.5 V and 800℃,which is 76%higher than that of single cells with stoichiometric Pr_(0.4)Ca_(0.6)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN100)cathode.The effects of A-site deficiency on materials'phase structure and physicochemical properties are also systematically investigated.Such an enhancement in electrochemical performance is attributed to the promotion of effective CO_(2)adsorption,as well as the improved electrode kinetics resulting from the A-site deficiency.展开更多
The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently d...The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La Cu3Fe4O（12） and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La Mn3Cr4O（12） with cubic perovskite structure. The Cu–Fe intermetallic charge transfer（LaCu3（3＋）Fe4（3＋）O（12）→ LaCu3（2＋）Fe4（3.75＋）O（12）） leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La Mn3Cr4O（12） is a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.展开更多
La0.7-xSmx＋0.02Ca0.3CrO3-δ （0≤x≤0.4） powders with A-site excessive perovskite structure were synthesized by auto-ignition process and characterized. X-ray diffraction （XRD） patterns of samples after sintering ...La0.7-xSmx＋0.02Ca0.3CrO3-δ （0≤x≤0.4） powders with A-site excessive perovskite structure were synthesized by auto-ignition process and characterized. X-ray diffraction （XRD） patterns of samples after sintering at 1400℃ for 4 h were indexed as tetragonal structure. The relative densities were all above 96% although decreased slightly with the increasing content of samarium, indicating that the excessive A-site element was helpful to enhance their sinterability. Conductivities of the specimens in air increased with increasing content of samarium. The conductivity of La0.6Sm0.12Ca0.3CrO3_swas 33.6 S/cm in air at 700℃ which was about 1.7 times as high as that of La0.7Ca0.3CrO3-δ （20.1 S/cm）. Average thermal expansion coefficients （TECS） of the specimens increased from 11.06×10^-6 to 12.72×10^-6 K^-1 when x increased from 0 to 0.4, and they were close to that of Y doped ZrO2 （YSZ）.La0.7-xSmx＋0.02Ca0.3CrO3-δ （0.1≤x≤0.3） were good choices for intermediate temperature solid oxide fuel cells （IT-SOFCs） interconnect materials.展开更多
The R/Ba-ordered and R-site mixed compound Y0.5La0.5BaMn2O6 is synthesized, in which （Y, La） and Ba are regularly arranged, while Y and La randomly occupy the R-site. Y0.5La0.5BaMn2O6 has a tetragonal unit cell with...The R/Ba-ordered and R-site mixed compound Y0.5La0.5BaMn2O6 is synthesized, in which （Y, La） and Ba are regularly arranged, while Y and La randomly occupy the R-site. Y0.5La0.5BaMn2O6 has a tetragonal unit cell with a space group of P4/mmm. A structural transition between tetragonal and orthorhombic is observed at about 325 K by X-ray powder diffraction （XRD）. Thermal magnetic measurement shows the occurrence of an antiferromagnetic transition at the temperature TN～190 K. Anomalies in magnetization, resistivity and lattice parameters observed around 340 K indicate a charge/orbital order transition accompanying the structural phase transition. The R-site randomness effect is discussed to interpret the different properties of Y0.5La0.5BaMn2O6 between NdBaMn2O6 and SmBaMn2O6.展开更多
Sr0.9Ba0.1Ti0.8Nb0.2O3 ceramics （x=0, 0.01, 0.02 and 0.05） are prepared by solid state reaction, whose thermoelectric properties are investigated from 323K to 1073K. By introducing A-site nonstoichiometry, the absol...Sr0.9Ba0.1Ti0.8Nb0.2O3 ceramics （x=0, 0.01, 0.02 and 0.05） are prepared by solid state reaction, whose thermoelectric properties are investigated from 323K to 1073K. By introducing A-site nonstoichiometry, the absolute Seebeck coefficient is enhanced, while the electrical resistivity is surprisingly reduced due to the significantly enhanced carrier mobility. These results are dramatic in thermoelectric materials, effectively enhancing the power factor. Moreover, the thermal conductivity is reduced, thus the thermoelectric performance of Sr0.9Ba0.1Ti0.8Nb0.2O3 ceramic is significantly enhanced by A-site nonstoiehiometry.展开更多
Although intermediate temperature solid oxide fuel cells(IT-SOFCs)show great potential to address energy conversion challenges,the sluggish oxygen reduction reaction(ORR)kinetics of cathode materials has severely hind...Although intermediate temperature solid oxide fuel cells(IT-SOFCs)show great potential to address energy conversion challenges,the sluggish oxygen reduction reaction(ORR)kinetics of cathode materials has severely hindered extended applications.Herein,we have demonstrated that Bi^(3+)doping on the A-site synergistically regulates the phase transition and electron spin state in La_(0.3)Bi_(0.3)Ca_(0.4)FeO_(3-δ)(LBCF3)for improved performance.An orthorhombic to cubic phase transition occurred with Bi^(3+)doping increases oxygen vacancy concentration and thus increases oxygen ion migration capacity.Simultaneously,the change of Fe from low to medium electron spin state strengths O_(2)adsorption and improves catalytic performances.Consequently,a peak power density improvement up to 48%(from 1.21 to 1.79 W·cm^(-2))at 800℃ is realized in the anodesupported single cell using LBCF3 as cathode,which remains stable for over 270 h at 750℃.展开更多
Novel A-site deficient(1-x-y)Bi_(0.5)Na_(0.5)TiO_(3-x)BaTiO_(3-y)Bi_(0.2)Sr_(0.7)TiO_(3)lead-free relaxor ferroelectrics have been explored for energy storage property.Particularly slim polarization hysteresis(P-E)loo...Novel A-site deficient(1-x-y)Bi_(0.5)Na_(0.5)TiO_(3-x)BaTiO_(3-y)Bi_(0.2)Sr_(0.7)TiO_(3)lead-free relaxor ferroelectrics have been explored for energy storage property.Particularly slim polarization hysteresis(P-E)loops are observed in 0.655Bi_(0.5)Na_(0.5)TiO_(3)-0.065BaTiO_(3)-0.28Bi_(0.2)Sr_(0.7)□_(0.1)TiO_(3)(6.5BNBT-BST)at ambient temperature resulting in a giant recoverable energy density(W_(rec)=1.5 J cm^(-3))and extremely high efficiency(η=90%)at 100 kV cm^(-1),which are closed related to the track of P-E loops.As the addition of Bi_(0.2)Sr_(0.7)TiO_(3)(BST)content,the ergodic relaxor phase becomes dominant with dynamic polar nanoregions attributed to the absence of ferroelectric domain in the relaxor phase.Furthermore,the recoverable energy density exhibits small variation in elevated temperature where the depressed polarization is compensated by almost hysteresis free loops(ηup to 97%).The achievement of these characteristics in P-E loops provides that Bi_(0.2)Sr_(0.7)TiO_(3)tailoring by A-site vacancies is a potential route when designing new relaxor ferroelectrics for energy-storage applications.展开更多
The major factors limiting the electrochemical performance of a perovskite cathode for ceramic-based fuel cells are the sluggish oxygen reduction reaction(ORR)kinetics and poor durability,which are largely determined ...The major factors limiting the electrochemical performance of a perovskite cathode for ceramic-based fuel cells are the sluggish oxygen reduction reaction(ORR)kinetics and poor durability,which are largely determined by the Asite elements.In this work,to enhance the ORR activity and stability,we present an effective strategy of tuning the A-site dopant in a layered double perovskite oxide of Ba_(0.8)Gd_(0.8)Pr_(0.4)-Co_(2)O(6-δ)(BGPC).When applied as a cathode on a La_(0.8)Sr_(0.2)-Ga_(0.8)Mg_(0.2)O_(3-δ)(LSGM)electrolyte-supported cell,it demonstrates high electrochemical performance,achieving an areaspecific resistance(ASR)of 0.170Ωcm^(2),and a peak power density(PPD)of 1.189 W cm^(-2)at 800℃,better than those acquired from a state-of-the-art(La_(0.6)Sr_(0.4))_(0.95)Co_(0.2)Fe_(0.8)O_(3-δ)(LS95 CF)-based cathode.The single cells with the BGPC cathode exhibit better performance and stability(a degradation rate of 0.074%h^(-1))than the cells with the LS95 CF cathode(a PPD of 1.079 W cm^(-2)at 800℃and a degradation rate of0.13%h^(-1))under the same operating conditions.By the electrochemical performance evaluation and characterizations,it is suggested that A-site tuning on a double-perovskite oxide can be a promising strategy to enhance the electrode activity and durability of fuel cells.展开更多
Main observation and conclusion Perovskites(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(x=0.02,0.05,0.1 denoted as BSCF-0.98,BSCF-0.95,BSCF-0.9,respectively)with A-site cation defects are synthesized by simple and...Main observation and conclusion Perovskites(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(x=0.02,0.05,0.1 denoted as BSCF-0.98,BSCF-0.95,BSCF-0.9,respectively)with A-site cation defects are synthesized by simple and efficient sol-gel method and are proved to have better OER catalytic effect than the well-known(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)oxides.BSCF-0.95 exhibits the best OER catalytic activity in the series perovskite.The current density of BSCF-0.95 is about 56%higher than that of BSCF oxide at a potential of 1.7 V.The experimental studies have shown that compared with BSCF,BSCF-0.95 oxide has a larger electrochemical surface area(ECSA),a higher content of O_(2)^(2–)species related to surface oxygen vacancies,and faster charge transfer rate,which may be the factors for the enhancement of OER activity.The theoretical calculation results prove that the center positions of the O 2p-band of perovskite with A-site cation defects are closer to the Fermi level than BSCF oxide,which agrees with the OER performance trend of the material.展开更多
Lead free 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics were prepared by conventional solid-state mixed oxide route with the A-site stoichiometry modified to incorporate donor-doping(through Bi-excess)and accept...Lead free 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics were prepared by conventional solid-state mixed oxide route with the A-site stoichiometry modified to incorporate donor-doping(through Bi-excess)and acceptor-doping(through Na-excess).Both stoichiometric and nonstoichiometric ceramics exhibited a single perovskite phase with pseudo-cubic symmetry.A significant improvement in the dielectric properties was observed in Bi-excess compositions and a deterioration in the dielectric properties was observed in Na-excess compositions.Impedance spectroscopy was utilized to analyze the effects of A-site nonstoichiometry on conduction mechanisms.Compositions with Bi-excess resulted in an electrically homogeneous microstructure with an increase in resistivity by3-4 orders of magnitude and an associated activation energy of 1.57 eV which was close to half of the optical bandgap.In contrast,an electrically heterogeneous microstructure was observed in both the stoichiometric and Na-excess compositions.In addition,the Na-excess compositions exhibited low resistivities(ρ-10^(3)Ω-cm)with characteristic peaks in the impedance data comparable to the recent observations of oxide ion conduction in(Bi_(0.5)Na_(0.5))TiO_(3).Long term annealing studies were also conducted at 800℃to identify changes in crystal structure and electrical properties.The results of this study demonstrates that the dielectric and electrical properties of 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics are very sensitive to Bi/Na stoichiometry.展开更多
In the present work,the crystal structure,ferroelectric and dielectric properties of the dense single-phase Li_(2)CaTa_(2)O_(7) ceramics with A-site ordered double-layer Ruddlesden-Popper structures have been investig...In the present work,the crystal structure,ferroelectric and dielectric properties of the dense single-phase Li_(2)CaTa_(2)O_(7) ceramics with A-site ordered double-layer Ruddlesden-Popper structures have been investigated by the experiments and first-principles calculations.A polar Pna21 phase was determined by the Rietveld refinement against the X-ray diffraction pattern at room temperature,and it was confirmed by its lowest calculated energy and rigid phonon modes.The ferroelectricity was found by observing the ferroelectric hysteresis loop at room temperature,and its remanent polarization was similar to the value calculated from the Berry phase and Born effective charge approaches.The ferroelectricity is a nonconventional proper one since its polarization is induced from the displacement of oxygen anions instead of tantalum cations based on the individual atomic polarization.A first-order transition from an antiferroelectric to paraelectric phase around 900 K was found by the DSC and variable-temperature dielectric measurements.From the present work,the room-temperature ferroelectricity is experimental confirmed in the present ceramics,inspiring the search for new ferroelectricity in the ceramics with A-site ordered Ruddlesden-Popper structures.展开更多
Organic-inorganic halide perovskites have emerged as excellent candidates for low-cost photovoltaics and optoelectronics.While the predominant recent trend in designing perovskites for efficient and stable solar cells...Organic-inorganic halide perovskites have emerged as excellent candidates for low-cost photovoltaics and optoelectronics.While the predominant recent trend in designing perovskites for efficient and stable solar cells has been to mix different A-site cations,the role of A-site cations is still limited to tune the lattice and bandgap of perovskites.Herein we compare the optoelectronic properties of acetamidinum(Ace)and guanidinium(Gua)mixed methylammonium lead iodide perovskites and shed a light on the hidden role of A-site cation on the carrier mobility of mixed-cation lead iodide perovskites.The cations do not affect the bandgap of the perovskites since the orbitals from Ace and Gua do not contribute to the band edges of the material.However,the mobility of the Ace mixed perovskite is significantly enhanced to be an order of magnitude higher than that of the pristine perovskite.We apply the Ace mixed perovskite in hole-conductor-free printable mesoscopic perovskite solar cells and obtain a stabilized PCE of over 18%(certified 17.7%),which is the highest certified efficiency so far.展开更多
Three kinds of metal atoms with different valence electronic configurations,Bi(6s^(2)6p^(3)),Y(4d^(1)5s^(2)),and Ce(4f^(1)5d^(1)6s^(2)),were selected to investigate the effect of A-site(La^(3+))doping on electronic ba...Three kinds of metal atoms with different valence electronic configurations,Bi(6s^(2)6p^(3)),Y(4d^(1)5s^(2)),and Ce(4f^(1)5d^(1)6s^(2)),were selected to investigate the effect of A-site(La^(3+))doping on electronic band structure,photoelectric properties,and photocatalytic performance of LaFeO_(3) perovskite.It was identified that the Bi doped LaFeO_(3) presented significantly improved photocatalytic activity towards the reduction of CO_(2),while the Y or Ce doped LaFeO_(3) displayed decreased photocatalytic activity compared to the pristine LaFeO_(3).It was revealed that doping of all the three metal atoms resulted in narrowed band gap and thus extended light absorption of LaFeO_(3) by lowering its conduction band minimum(CBM).The recombination rate and mobility of the charge carriers were represented by the relative effective mass(D)between holes and electrons for pristine and A-site doped LaFeO_(3).The doping of Bi resulted in increased D value,attributed to the Bi 6s electron states at the valence band maximum(VBM),and thus promoted separation and transfer of the charge carriers and improved photocatalytic activity of LaFeO_(3).In contrast,the doping of Ce resulted in significantly decreased D value,induced by the highly localized Ce 4f hole states at the CBM,and thus higher recombination rate of the charge carriers and decreased photocatalytic activity of LaFeO_(3).Furthermore,the Y doped LaFeO_(3) with a slightly decreased D value presented slightly increased recombination rate of the charge carriers and thus decreased photocatalytic activity.Such a work provides new insights into the A-site doping in LaFeO_(3) perovskite,which should be helpful for optimizing the electronic band structure and activity of perovskite-type photocatalysts at atomic level.展开更多
Solid-oxide fuel cells(SOFCs)offer great promise for producing electricity using a wide variety of fuels such as natural gas,coal gas and gasified carbonaceous solids;however,conventional nickel-based anodes face grea...Solid-oxide fuel cells(SOFCs)offer great promise for producing electricity using a wide variety of fuels such as natural gas,coal gas and gasified carbonaceous solids;however,conventional nickel-based anodes face great challenges due to contaminants in readily available fuels,especially sulphur-containing compounds.Thus,the development of new anode materials that can suppress sulphur poisoning is crucial to the realization of fuel-flexible and cost-effective SOFCs.In this work,La_(0.1)Sr_(1.9)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)(LSFNM)and Pr_(0.1)Sr_(1.9)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)(PSFNM)materials have been synthesized using a sol-gel method in air and investigated as anode mater-ials for SOFCs.Metallic nanoparticle-decorated ceramic anodes were obtained by the reduction of LSFNM and PSFNM in H_(2)at 850℃,forming a Ruddlesden-Popper oxide with exsolved FeNi3 bimetallic nanoparticles.The electrochemical performance of the Sr_(2)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)ceramic anode was greatly enhanced by La doping of A-sites,resulting in a 44%decrease in the polarization resistance in reducing atmosphere.The maximum power densities of Sr-and Mg-doped LaGaO_(3)(LSGM)(300μm)electrolyte-supported single cells with LSFNM as the anode reached 1.371 W cm^(-2)in H_(2)and 1.306 W cm^(-2)in 50 ppm H_(2)S-H_(2)at 850℃.Meanwhile,PSFNM showed improved sulphur tolerance,which could be fully recovered after six cycles from H_(2)to 50 ppm H_(2)S-H_(2)operation.This study indicates that LSFNM and PSFNM are promising high-performance anodes for SOFCs.展开更多
Hybrid improper ferroelectricity has been extensively reported through theoretical prediction and experimental investigation in the oxides with Ruddlesden-Popper(R-P)structures.However,the experimentally reported ferr...Hybrid improper ferroelectricity has been extensively reported through theoretical prediction and experimental investigation in the oxides with Ruddlesden-Popper(R-P)structures.However,the experimentally reported ferroelectric materials based on triple-layer R-P structures are rare,and the weak ferroelectricity impedes its practical application.In the present work,the single-phase Li_(2)Nd_(2)Ti_(3)O_(10)ceramics with A-site cation ordered triple-layer R-P structure was obtained by spark plasma sintering technique,and the crystal structure of P2_(1)ab symmetry was revealed by neutron powder diffraction and transmission electron microscope analysis.Furthermore,the switchable ferroelectricity in Li_(2)Nd_(2)Ti_(3)O_(10)ceramics has been observed at room temperature,and the saturated polarization-electric field hysteresis loop was obtained with P_(r)=0.4μC/cm^(2)under the electric field of 250 kV/cm.The phase transition behavior of Li_(2)Nd_(2)Ti_(3)O_(10)oxides was revealed by the temperature-dependence Raman and dielectric spectra combined with the piezoelectric property.展开更多
Low-dimensional hybrid halide perovskites represent a promising class of materials in optoelectronic applications because of strong broad self-trapped exciton(STE)emissions.However,there exists a limitation in designi...Low-dimensional hybrid halide perovskites represent a promising class of materials in optoelectronic applications because of strong broad self-trapped exciton(STE)emissions.However,there exists a limitation in designing the ideal A-site cation that makes the material satisfy the structure tolerance and exhibit STE emission raised by the appropriate electron–phonon coupling effect.To overcome this dilemma,we developed an inorganic metal-organic dimethyl sulfoxide(DMSO)coordinating strategy to synthesize a series of zero-dimensional(0D)Sb-based halide perovskites including Na_(3)SbBr_(6)·DMSO_(6)(1),AlSbBr_(6)·DMSO_(6)(2),AlSbCl_(6)·DMSO_(6)(3),GaSbCl_(6)·DMSO_(6)(4),Mn_(2)Sb_(2)Br10·DMSO_(13)(5)and MgSbBr_(5)·DMSO_(7)(6),in which the distinctive coordinating A-site cation[Am-DMSO_(6)]n+efficiently separate the[SbXz]polyhedrons.Advantageously,these materials all exhibit broadband-emissions with full widths at half maxima(FWHM)of 95–184 nm,and the highest photoluminescent quantum yield(PLQY)of 3 reaches 92%.Notably,compounds 2–4 are able to remain stable after storage of more than 120 d.First-principles calculations indicate that the origin of the efficient STE emission can be attribted to the localized distortion in[SbXz]polyhedron upon optical excitation.Experimental and calculational results demonstrate that the proposed coordinating strategy provides a way to efficiently expand the variety of novel high-performance STE emitters and continuously regulate their emission behaviors.展开更多
基金financial support from the National Natural Science Foundation of China(Nos.22308246,22478278)Central Government Guides the Special Fund Projects of Local Scientific and Technological Development(No.YDZJSX20231A015)the Fundamental Research Program of Shanxi Province(No.202203021212266)。
文摘Cu^(2+)in copper-based catalysts can facilitate the hydrogenation of the CH_(4)production pathway via the electrochemical carbon dioxide reduction reaction(ECRR).However,Cu^(2+)species in copper oxides are unstable and have been revealed to reduce to Cu^(0)under the applied cathodic potential.In this work,we reported an A-site modulation strategy to stabilize Cu^(2+)in perovskite for efficient ECRR to CH_(4).After the introduction of Ca^(2+)in La_(2)CuO_(4),the obtained LaCa_(0.4)CuO_(3-δ)is stable during ECRR.We achieved a59.6%±3.8%CH4faradaic efficiency at-1.30 V versus reversible hydrogen electrode in H-cell and a partial current density of 155.0 m A/cm^(2)in membrane electrode assembly.DFT calculations and in situ Raman spectroscopy show that Cu^(2+)facilitates the hydrogenation of*CH_(2)O to*CH_(3)O and the further production of CH_(4).This work introduces an efficient strategy to stabilize Cu^(2+)and provides an understanding of Cu^(2+)in promoting ECRR to CH_(4).
基金supported by the National Natural Science Foundation of China(No.52130203)the Natural Science Foundation of Shandong Province(No.ZR2022QB159).
文摘The compositional flexibility and structural stability of SrTiO_(3)-based perovskite oxides present a promising approach to tailor their electrical and thermal transport properties.In this work,a series of(Ca_(0.25)Nd_(0.25)Sr_(0.35)Ba_(0.15))1-xTiO_(3)±δceramics with varying A-site deficiencies were designed by integrating entropy engineering and defect chemistry,and their microstructural characteristics and transport properties were systematically investigated.All samples exhibited a stable single-phase Pm3m cubic structure with uniformly distributed constituent elements.The introduction of A-site vacancies created favorable pathways for ion diffusion during the sintering process and facilitated grain growth.A-site deficiencies significantly increased carrier concentration by promoting the formation of oxygen vacancies and Ti^(3+),while also enhancing carrier mobility by improving structural symmetry and reducing grain boundary scattering,leading to the improved power factor.The multiscale defects resulting from entropy engineering including point defects,strain fields,and high-density grain boundaries contributed to the reduced thermal conductivity of all samples.By synergistically optimizing the entropy and defect engineering,the sample with x=0.09 achieved a peak figure of merit(ZT)of 0.21 at 900 K,representing a 32%enhancement compared with that of the x=0.03 sample.This work underscores the significance of the combined strategy of entropy engineering and defect chemistry in manipulating the transport properties of SrTiO_(3)-based thermoelectric oxides.
基金National Natural Science Foundation of China(No.52301192)Natural Science Foundation of Shandong Province(No.ZR2019YQ24)+2 种基金Taishan Scholars and Young Experts Program of Shandong Province(No.tsqn202103057)Qingchuang Talents Induction Program of Shandong Higher Education Institution(Research and Innovation Team of Structural Functional Polymer Composites)Special Financial of Shandong Province(Structural Design of High-efficiency Electromag-netic Wave-absorbing Composite Materials and Construction of Shandong Provincial Talent Teams).
文摘With the rapid development of electronic technology,how to effectively eliminate electromagnetic pollu-tion has become a serious problem.Perovskite oxides have shown great potential in the field of electro-magnetic wave absorption due to their unique structure and excellent physicochemical properties.Herein,by rationally manipulating the A-site ion substitution strategy,the theoretically directed doping of Sr ions into La ionic sites was utilized and the layered MoS_(2) was loaded by the hydrothermal process to modify its surface.Consequently,the introduced polarization phenomenon improved the dielectric performance of the perovskite oxides,achieving a collaborative dielectric/magnetic loss mechanism.Accordingly,the prepared La0.7Sr0.3FeO3(LSFO)/MoS_(2) as coating filler in the epoxy resin coating system can obtain the minimum reflection loss of-67.09 dB at 1.9 mm and the maximum effective absorption bandwidth of 7.28 GHz at 2.3 mm.More importantly,it also exhibits excellent absorption performance for multi-band electromagnetic waves,covering a wide range of specified frequency bands.It provides inspiration for ex-ploring novel perovskite oxide-based electromagnetic wave absorbing coatings and broadens the choice of ideal candidate materials for designing highly efficient,multi-band absorbers to cope with sophisticated electromagnetic environments.
基金supported by the National Natural Science Foundation of China(51004069)the National Science Fund for Distinguished Young Scholars(51225401)+1 种基金China Postdoctoral Science Foundation(201104254)the Innovation Program of Shanghai Municipal Education Commission and Shanghai University(14YZ013 and SDCX2012002)
文摘Ba0.9R0.1Co0.TFe0.225Ta0.07503-δ （BRCFT, R = Ca, La or Sr） membranes were synthesized by a solid-state reaction. Metal cation Ca2＋, La3＋ or Sr2＋ doping on A-site partially substituted Ba2＋ in BaCoo.TFe0.225Ta0.07503-δ oxides, and its subsequent effects on phase structure stability, oxygen permeability and oxygen desorption were systematically investigated by XRD, TG-DSC, Hz-TPR, O2-TPD techniques and oxygen permeation experiments. The partial substitution with Ca2＋, La3＋ or Sr2＋, whose ionic radii are smaller than that of Ba2＋, succeeded in stabilizing the cubic perovskite structure without formation of impurity phases, as revealed by XRD analysis. Oxygen-involving experi- ments showed that BRCFT with A-site fully occupied by Ba2＋ exhibited good oxygen permeation flux under He flow, reaching about 2.3 mL.min-l .cm-2 at 900 with I mm thickness. Of all the membranes, BLCFT membrane showed better chemical stability in CO2, owing to the reduction in alkalinity of the mixed conductor oxide by La doping. In addition, we also found the stability of the perovskite structure under reducing atmospheres was strengthened by increasing the size of A-site cation （Ba2＋〉La3＋〉SrZ＋〉Ca2＋）.
基金supported by the U.S.Department of Energy’s Office of Energy Efficiency and Renewable Energy(EERE)under the Industrial Efficiency&Decarbonization Office award number[DE-EE0009427]the funding support by the U.S.Department of Energy(USDOE),Office of Energy Efficiency and Renewable Energy(EERE),Advanced Manufacturing Office(AMO),under DOE Idaho Operations Office under Contract No.DEAC07-05ID14517
文摘High-temperature CO_(2)electrolysis via solid oxide electrolysis cells(CO_(2)-SOECs)has drawn special attention due to the high energy convention efficiency,fast electrode kinetics,and great potential in carbon cycling.However,the development of cathode materials with high catalytic activity and chemical stability for pure CO_(2)electrolysis is still a great challenge.In this work,A-site cation deficient dual-phase material,namely(Pr_(0.4)Ca_(0.6))_(x)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN,x=1,0.95,and 0.9),has been designed as the fuel electrode for a pure CO_(2)-SOEC,which presents superior electrochemical performance.Among all these compositions,(Pr_(0.4)Ca_(0.6))_(0.95)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN95)exhibited the lowest polarization resistance of 0.458Ωcm^(2)at open-circuit voltage and 800℃.The application of PCFN95 as the cathode in a single cell yields an impressive electrolysis current density of 1.76 A cm^(-2)at 1.5 V and 800℃,which is 76%higher than that of single cells with stoichiometric Pr_(0.4)Ca_(0.6)Fe_(0.8)Ni_(0.2)O_(3-δ)(PCFN100)cathode.The effects of A-site deficiency on materials'phase structure and physicochemical properties are also systematically investigated.Such an enhancement in electrochemical performance is attributed to the promotion of effective CO_(2)adsorption,as well as the improved electrode kinetics resulting from the A-site deficiency.
基金Project supported by the National Basic Research Program of China(Grant No.2014CB921500)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB07030300)the National Natural Science Foundation of China(Grant No.11574378)
文摘The A-site ordered perovskite oxides with chemical formula AA＇3B4O（12）display many intriguing physical properties due to the introduction of transition metals at both A and B sites. Here, research on the recently discovered intermetallic charge transfer occurring between A-site Cu and B-site Fe ions in La Cu3Fe4O（12） and its analogues is reviewed, along with work on the magnetoelectric multiferroicity observed in La Mn3Cr4O（12） with cubic perovskite structure. The Cu–Fe intermetallic charge transfer（LaCu3（3＋）Fe4（3＋）O（12）→ LaCu3（2＋）Fe4（3.75＋）O（12）） leads to a first-order isostructural phase transition accompanied by drastic variations in magnetism and electrical transport properties. The La Mn3Cr4O（12） is a novel spindriven multiferroic system with strong magnetoelectric coupling effects. The compound is the first example of cubic perovskite multiferroics to be found. It opens up a new arena for studying unexpected multiferroic mechanisms.
基金supported by the National Natural Science Foundation of China (50572099)
文摘La0.7-xSmx＋0.02Ca0.3CrO3-δ （0≤x≤0.4） powders with A-site excessive perovskite structure were synthesized by auto-ignition process and characterized. X-ray diffraction （XRD） patterns of samples after sintering at 1400℃ for 4 h were indexed as tetragonal structure. The relative densities were all above 96% although decreased slightly with the increasing content of samarium, indicating that the excessive A-site element was helpful to enhance their sinterability. Conductivities of the specimens in air increased with increasing content of samarium. The conductivity of La0.6Sm0.12Ca0.3CrO3_swas 33.6 S/cm in air at 700℃ which was about 1.7 times as high as that of La0.7Ca0.3CrO3-δ （20.1 S/cm）. Average thermal expansion coefficients （TECS） of the specimens increased from 11.06×10^-6 to 12.72×10^-6 K^-1 when x increased from 0 to 0.4, and they were close to that of Y doped ZrO2 （YSZ）.La0.7-xSmx＋0.02Ca0.3CrO3-δ （0.1≤x≤0.3） were good choices for intermediate temperature solid oxide fuel cells （IT-SOFCs） interconnect materials.
基金the National Natural Science Foundation of China(Grant Nos.50872148,51072225,and 11074295)the Natural Science Foundation of Guangxi Province,China(Grant No.2012GXNSFGA060002)
文摘The R/Ba-ordered and R-site mixed compound Y0.5La0.5BaMn2O6 is synthesized, in which （Y, La） and Ba are regularly arranged, while Y and La randomly occupy the R-site. Y0.5La0.5BaMn2O6 has a tetragonal unit cell with a space group of P4/mmm. A structural transition between tetragonal and orthorhombic is observed at about 325 K by X-ray powder diffraction （XRD）. Thermal magnetic measurement shows the occurrence of an antiferromagnetic transition at the temperature TN～190 K. Anomalies in magnetization, resistivity and lattice parameters observed around 340 K indicate a charge/orbital order transition accompanying the structural phase transition. The R-site randomness effect is discussed to interpret the different properties of Y0.5La0.5BaMn2O6 between NdBaMn2O6 and SmBaMn2O6.
基金Supported by the National Basic Research Program of China under Grant No 2013CB632506the National Natural Science Foundation of China under Grant Nos 51202132,51002087 and 11374186the Independent Innovation Foundation of Shandong University under Grant No IIFSDU 2012TS028
文摘Sr0.9Ba0.1Ti0.8Nb0.2O3 ceramics （x=0, 0.01, 0.02 and 0.05） are prepared by solid state reaction, whose thermoelectric properties are investigated from 323K to 1073K. By introducing A-site nonstoichiometry, the absolute Seebeck coefficient is enhanced, while the electrical resistivity is surprisingly reduced due to the significantly enhanced carrier mobility. These results are dramatic in thermoelectric materials, effectively enhancing the power factor. Moreover, the thermal conductivity is reduced, thus the thermoelectric performance of Sr0.9Ba0.1Ti0.8Nb0.2O3 ceramic is significantly enhanced by A-site nonstoiehiometry.
基金supported by the Xinjiang Autonomous Region Key Research Project(No.2022D01D31)the Start-up Grant of Xinjiang University,the Basic Research Fund for Autonomous Region Universities(No.XJEDU2024P015)the Natural Science Foundation of Xinjiang Uygur Autonomous Region(No.2022D01C668).
文摘Although intermediate temperature solid oxide fuel cells(IT-SOFCs)show great potential to address energy conversion challenges,the sluggish oxygen reduction reaction(ORR)kinetics of cathode materials has severely hindered extended applications.Herein,we have demonstrated that Bi^(3+)doping on the A-site synergistically regulates the phase transition and electron spin state in La_(0.3)Bi_(0.3)Ca_(0.4)FeO_(3-δ)(LBCF3)for improved performance.An orthorhombic to cubic phase transition occurred with Bi^(3+)doping increases oxygen vacancy concentration and thus increases oxygen ion migration capacity.Simultaneously,the change of Fe from low to medium electron spin state strengths O_(2)adsorption and improves catalytic performances.Consequently,a peak power density improvement up to 48%(from 1.21 to 1.79 W·cm^(-2))at 800℃ is realized in the anodesupported single cell using LBCF3 as cathode,which remains stable for over 270 h at 750℃.
基金This work was supported by the National Natural Science Foundation(51602252,51702249,51372197 and 51672092)the Key Innovation Team of Shaanxi Province(2014KCT-04)+4 种基金the fund of the State Key Laboratory of Solidification Processing in NWPU(SKLSP201624)the China Postdoctoral Science Foundation(2017M613065)the Shaanxi Province Science Foundation(2017JQ5072)the Outstanding Youth Science Fund of Xi'an University of Science and Technology(2018YQ2-11)the Shanghai talent development fund(2017128).
文摘Novel A-site deficient(1-x-y)Bi_(0.5)Na_(0.5)TiO_(3-x)BaTiO_(3-y)Bi_(0.2)Sr_(0.7)TiO_(3)lead-free relaxor ferroelectrics have been explored for energy storage property.Particularly slim polarization hysteresis(P-E)loops are observed in 0.655Bi_(0.5)Na_(0.5)TiO_(3)-0.065BaTiO_(3)-0.28Bi_(0.2)Sr_(0.7)□_(0.1)TiO_(3)(6.5BNBT-BST)at ambient temperature resulting in a giant recoverable energy density(W_(rec)=1.5 J cm^(-3))and extremely high efficiency(η=90%)at 100 kV cm^(-1),which are closed related to the track of P-E loops.As the addition of Bi_(0.2)Sr_(0.7)TiO_(3)(BST)content,the ergodic relaxor phase becomes dominant with dynamic polar nanoregions attributed to the absence of ferroelectric domain in the relaxor phase.Furthermore,the recoverable energy density exhibits small variation in elevated temperature where the depressed polarization is compensated by almost hysteresis free loops(ηup to 97%).The achievement of these characteristics in P-E loops provides that Bi_(0.2)Sr_(0.7)TiO_(3)tailoring by A-site vacancies is a potential route when designing new relaxor ferroelectrics for energy-storage applications.
基金supported by the National Natural Science Foundation of China(22179039 and 22005105)the Pearl River Talent Recruitment Program(2019QN01C693 and 2021ZT09L392)the Natural Science Foundation of Guangdong Province(2021A1515010395)。
文摘The major factors limiting the electrochemical performance of a perovskite cathode for ceramic-based fuel cells are the sluggish oxygen reduction reaction(ORR)kinetics and poor durability,which are largely determined by the Asite elements.In this work,to enhance the ORR activity and stability,we present an effective strategy of tuning the A-site dopant in a layered double perovskite oxide of Ba_(0.8)Gd_(0.8)Pr_(0.4)-Co_(2)O(6-δ)(BGPC).When applied as a cathode on a La_(0.8)Sr_(0.2)-Ga_(0.8)Mg_(0.2)O_(3-δ)(LSGM)electrolyte-supported cell,it demonstrates high electrochemical performance,achieving an areaspecific resistance(ASR)of 0.170Ωcm^(2),and a peak power density(PPD)of 1.189 W cm^(-2)at 800℃,better than those acquired from a state-of-the-art(La_(0.6)Sr_(0.4))_(0.95)Co_(0.2)Fe_(0.8)O_(3-δ)(LS95 CF)-based cathode.The single cells with the BGPC cathode exhibit better performance and stability(a degradation rate of 0.074%h^(-1))than the cells with the LS95 CF cathode(a PPD of 1.079 W cm^(-2)at 800℃and a degradation rate of0.13%h^(-1))under the same operating conditions.By the electrochemical performance evaluation and characterizations,it is suggested that A-site tuning on a double-perovskite oxide can be a promising strategy to enhance the electrode activity and durability of fuel cells.
基金supported by the National Natural Science Foundation of China(No.21671182)the Fundamental Research Funds for the Central Universities(WK3430000005))The calculations were performed on the supercomputing center of the University of Science and Technology of China(USTC-SCC).
文摘Main observation and conclusion Perovskites(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(x=0.02,0.05,0.1 denoted as BSCF-0.98,BSCF-0.95,BSCF-0.9,respectively)with A-site cation defects are synthesized by simple and efficient sol-gel method and are proved to have better OER catalytic effect than the well-known(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)oxides.BSCF-0.95 exhibits the best OER catalytic activity in the series perovskite.The current density of BSCF-0.95 is about 56%higher than that of BSCF oxide at a potential of 1.7 V.The experimental studies have shown that compared with BSCF,BSCF-0.95 oxide has a larger electrochemical surface area(ECSA),a higher content of O_(2)^(2–)species related to surface oxygen vacancies,and faster charge transfer rate,which may be the factors for the enhancement of OER activity.The theoretical calculation results prove that the center positions of the O 2p-band of perovskite with A-site cation defects are closer to the Fermi level than BSCF oxide,which agrees with the OER performance trend of the material.
文摘Lead free 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics were prepared by conventional solid-state mixed oxide route with the A-site stoichiometry modified to incorporate donor-doping(through Bi-excess)and acceptor-doping(through Na-excess).Both stoichiometric and nonstoichiometric ceramics exhibited a single perovskite phase with pseudo-cubic symmetry.A significant improvement in the dielectric properties was observed in Bi-excess compositions and a deterioration in the dielectric properties was observed in Na-excess compositions.Impedance spectroscopy was utilized to analyze the effects of A-site nonstoichiometry on conduction mechanisms.Compositions with Bi-excess resulted in an electrically homogeneous microstructure with an increase in resistivity by3-4 orders of magnitude and an associated activation energy of 1.57 eV which was close to half of the optical bandgap.In contrast,an electrically heterogeneous microstructure was observed in both the stoichiometric and Na-excess compositions.In addition,the Na-excess compositions exhibited low resistivities(ρ-10^(3)Ω-cm)with characteristic peaks in the impedance data comparable to the recent observations of oxide ion conduction in(Bi_(0.5)Na_(0.5))TiO_(3).Long term annealing studies were also conducted at 800℃to identify changes in crystal structure and electrical properties.The results of this study demonstrates that the dielectric and electrical properties of 0.94(Bi_(0.5)Na_(0.5))TiO_(3)-0.06BaTiO_(3)ceramics are very sensitive to Bi/Na stoichiometry.
基金financially supported by the National Natural Science Foundation of China under Grant Nos.51772266,51790493 and 51961145105the Natural Science Foundation of Zhejiang Province under Grand No.LY20E020012+1 种基金the National Key R&D Program of China under Grant No.2016YFA0300101the Scientific Research Fund of Zhejiang Provincial Education Department under Grant No.Y201941595.
文摘In the present work,the crystal structure,ferroelectric and dielectric properties of the dense single-phase Li_(2)CaTa_(2)O_(7) ceramics with A-site ordered double-layer Ruddlesden-Popper structures have been investigated by the experiments and first-principles calculations.A polar Pna21 phase was determined by the Rietveld refinement against the X-ray diffraction pattern at room temperature,and it was confirmed by its lowest calculated energy and rigid phonon modes.The ferroelectricity was found by observing the ferroelectric hysteresis loop at room temperature,and its remanent polarization was similar to the value calculated from the Berry phase and Born effective charge approaches.The ferroelectricity is a nonconventional proper one since its polarization is induced from the displacement of oxygen anions instead of tantalum cations based on the individual atomic polarization.A first-order transition from an antiferroelectric to paraelectric phase around 900 K was found by the DSC and variable-temperature dielectric measurements.From the present work,the room-temperature ferroelectricity is experimental confirmed in the present ceramics,inspiring the search for new ferroelectricity in the ceramics with A-site ordered Ruddlesden-Popper structures.
基金the National Natural Science Foundation of China(Grant No.22075094)the National Key Research and Development Program of China(Grant No.2016YFA0201101)the Fundamental Research Funds for the Central Universities。
文摘Organic-inorganic halide perovskites have emerged as excellent candidates for low-cost photovoltaics and optoelectronics.While the predominant recent trend in designing perovskites for efficient and stable solar cells has been to mix different A-site cations,the role of A-site cations is still limited to tune the lattice and bandgap of perovskites.Herein we compare the optoelectronic properties of acetamidinum(Ace)and guanidinium(Gua)mixed methylammonium lead iodide perovskites and shed a light on the hidden role of A-site cation on the carrier mobility of mixed-cation lead iodide perovskites.The cations do not affect the bandgap of the perovskites since the orbitals from Ace and Gua do not contribute to the band edges of the material.However,the mobility of the Ace mixed perovskite is significantly enhanced to be an order of magnitude higher than that of the pristine perovskite.We apply the Ace mixed perovskite in hole-conductor-free printable mesoscopic perovskite solar cells and obtain a stabilized PCE of over 18%(certified 17.7%),which is the highest certified efficiency so far.
基金supported by the National Natural Science Foundation of China(No.21773089).
文摘Three kinds of metal atoms with different valence electronic configurations,Bi(6s^(2)6p^(3)),Y(4d^(1)5s^(2)),and Ce(4f^(1)5d^(1)6s^(2)),were selected to investigate the effect of A-site(La^(3+))doping on electronic band structure,photoelectric properties,and photocatalytic performance of LaFeO_(3) perovskite.It was identified that the Bi doped LaFeO_(3) presented significantly improved photocatalytic activity towards the reduction of CO_(2),while the Y or Ce doped LaFeO_(3) displayed decreased photocatalytic activity compared to the pristine LaFeO_(3).It was revealed that doping of all the three metal atoms resulted in narrowed band gap and thus extended light absorption of LaFeO_(3) by lowering its conduction band minimum(CBM).The recombination rate and mobility of the charge carriers were represented by the relative effective mass(D)between holes and electrons for pristine and A-site doped LaFeO_(3).The doping of Bi resulted in increased D value,attributed to the Bi 6s electron states at the valence band maximum(VBM),and thus promoted separation and transfer of the charge carriers and improved photocatalytic activity of LaFeO_(3).In contrast,the doping of Ce resulted in significantly decreased D value,induced by the highly localized Ce 4f hole states at the CBM,and thus higher recombination rate of the charge carriers and decreased photocatalytic activity of LaFeO_(3).Furthermore,the Y doped LaFeO_(3) with a slightly decreased D value presented slightly increased recombination rate of the charge carriers and thus decreased photocatalytic activity.Such a work provides new insights into the A-site doping in LaFeO_(3) perovskite,which should be helpful for optimizing the electronic band structure and activity of perovskite-type photocatalysts at atomic level.
基金supported by the US National Science Foundation (DMR-1832809)Idaho National Laboratory,Laboratory Directed Research&Development program under the Department of Energy Idaho Operations Office (DE-AC07-051D14517).
文摘Solid-oxide fuel cells(SOFCs)offer great promise for producing electricity using a wide variety of fuels such as natural gas,coal gas and gasified carbonaceous solids;however,conventional nickel-based anodes face great challenges due to contaminants in readily available fuels,especially sulphur-containing compounds.Thus,the development of new anode materials that can suppress sulphur poisoning is crucial to the realization of fuel-flexible and cost-effective SOFCs.In this work,La_(0.1)Sr_(1.9)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)(LSFNM)and Pr_(0.1)Sr_(1.9)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)(PSFNM)materials have been synthesized using a sol-gel method in air and investigated as anode mater-ials for SOFCs.Metallic nanoparticle-decorated ceramic anodes were obtained by the reduction of LSFNM and PSFNM in H_(2)at 850℃,forming a Ruddlesden-Popper oxide with exsolved FeNi3 bimetallic nanoparticles.The electrochemical performance of the Sr_(2)Fe_(1.4)Ni_(0.1)Mo_(0.5)O_(6-δ)ceramic anode was greatly enhanced by La doping of A-sites,resulting in a 44%decrease in the polarization resistance in reducing atmosphere.The maximum power densities of Sr-and Mg-doped LaGaO_(3)(LSGM)(300μm)electrolyte-supported single cells with LSFNM as the anode reached 1.371 W cm^(-2)in H_(2)and 1.306 W cm^(-2)in 50 ppm H_(2)S-H_(2)at 850℃.Meanwhile,PSFNM showed improved sulphur tolerance,which could be fully recovered after six cycles from H_(2)to 50 ppm H_(2)S-H_(2)operation.This study indicates that LSFNM and PSFNM are promising high-performance anodes for SOFCs.
基金supported by the National Key R&D Program of China under Grant No.2022YFB3807602the National Natural Science Foundation of China under Grant No.52172131the outstanding doctoral dissertation funding of Zhejiang University under Grant No.422048A.
文摘Hybrid improper ferroelectricity has been extensively reported through theoretical prediction and experimental investigation in the oxides with Ruddlesden-Popper(R-P)structures.However,the experimentally reported ferroelectric materials based on triple-layer R-P structures are rare,and the weak ferroelectricity impedes its practical application.In the present work,the single-phase Li_(2)Nd_(2)Ti_(3)O_(10)ceramics with A-site cation ordered triple-layer R-P structure was obtained by spark plasma sintering technique,and the crystal structure of P2_(1)ab symmetry was revealed by neutron powder diffraction and transmission electron microscope analysis.Furthermore,the switchable ferroelectricity in Li_(2)Nd_(2)Ti_(3)O_(10)ceramics has been observed at room temperature,and the saturated polarization-electric field hysteresis loop was obtained with P_(r)=0.4μC/cm^(2)under the electric field of 250 kV/cm.The phase transition behavior of Li_(2)Nd_(2)Ti_(3)O_(10)oxides was revealed by the temperature-dependence Raman and dielectric spectra combined with the piezoelectric property.
基金supported by the National Natural Science Foundation of China(Nos.21821004 and U21A2082).
文摘Low-dimensional hybrid halide perovskites represent a promising class of materials in optoelectronic applications because of strong broad self-trapped exciton(STE)emissions.However,there exists a limitation in designing the ideal A-site cation that makes the material satisfy the structure tolerance and exhibit STE emission raised by the appropriate electron–phonon coupling effect.To overcome this dilemma,we developed an inorganic metal-organic dimethyl sulfoxide(DMSO)coordinating strategy to synthesize a series of zero-dimensional(0D)Sb-based halide perovskites including Na_(3)SbBr_(6)·DMSO_(6)(1),AlSbBr_(6)·DMSO_(6)(2),AlSbCl_(6)·DMSO_(6)(3),GaSbCl_(6)·DMSO_(6)(4),Mn_(2)Sb_(2)Br10·DMSO_(13)(5)and MgSbBr_(5)·DMSO_(7)(6),in which the distinctive coordinating A-site cation[Am-DMSO_(6)]n+efficiently separate the[SbXz]polyhedrons.Advantageously,these materials all exhibit broadband-emissions with full widths at half maxima(FWHM)of 95–184 nm,and the highest photoluminescent quantum yield(PLQY)of 3 reaches 92%.Notably,compounds 2–4 are able to remain stable after storage of more than 120 d.First-principles calculations indicate that the origin of the efficient STE emission can be attribted to the localized distortion in[SbXz]polyhedron upon optical excitation.Experimental and calculational results demonstrate that the proposed coordinating strategy provides a way to efficiently expand the variety of novel high-performance STE emitters and continuously regulate their emission behaviors.
