Metal–organic frameworks(MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.[1,2]It is challenging to visualize MOFs with transmissi...Metal–organic frameworks(MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.[1,2]It is challenging to visualize MOFs with transmission electron microscopy(TEM) due to their inherent instability under electron beam irradiation. Here, we employ cryo-electron microscopy(cryoEM) to capture images of MOF ZIF-8, revealing inverted-space structural information at a resolution of up to about 1.7A and enhancing its critical electron dose to around 20 e^(-)/A^(2). In addition, it is confirmed by electron-beam irradiation experiments that the high voltage could effectively mitigate the radiolysis, and the structure of ZIF-8 is more stable along the [100] direction under electron beam irradiation. Meanwhile, since the high-resolution electron microscope images are modulated by contrast transfer function(CTF) and it is difficult to determine the positions corresponding to the atomic columns directly from the images. We employ image deconvolution to eliminate the impact of CTF and obtain the structural images of ZIF-8. As a result, the heavy atom Zn and the organic imidazole ring within the organic framework can be distinguished from structural images.展开更多
Electrocatalytic conversion of carbon dioxide(CO_(2))offers an effective method of CO_(2)fixation to mitigate global warming and the energy crisis.However,for supported Ni single-atom catalysts(SACs),which are among t...Electrocatalytic conversion of carbon dioxide(CO_(2))offers an effective method of CO_(2)fixation to mitigate global warming and the energy crisis.However,for supported Ni single-atom catalysts(SACs),which are among the most promising candidates for this application,the relationship between Ni coordination structure and catalytic properties is still under strong debate.Here,we fabricated a series of Ni SACs through precise-engineering of anchor sites on nitrogen-doped carbon(NC)followed by Ni atom anchoring using atomic layer deposition.Among them,a Ni_(1)/NC SAC,with a coordination number(CN)of four but less pyridinic nitrogen(N_(pyri)),achieved over 90%faradaic efϐiciency for CO at potentials from-0.7 to-1.0 V and a mass activity of 6.5 A/mgNi at-0.78 V along with high stability,outperforming other Ni SACs with lower CN and more N_(pyri).Theoretical calculations of various three and four-coordinated Ni_(1)-NxCy structures revealed a linear correlation between the reaction Gibbs free energy for the potential-limiting step and the highest occupied molecular orbital(HOMO)position of Ni-3d orbitals,therein the four-coordinated Ni_(1)-N_(1)C_(3)with the highest HOMO position is identified as the active site for the electrocatalytic CO_(2)-to-CO process,in line with the experimental results.展开更多
Topochemical fluorination introduces significant structural distortions and emerging properties in perovskite oxides via substituting oxygen with fluorine.However,the rapid fluorination process and the similarity betw...Topochemical fluorination introduces significant structural distortions and emerging properties in perovskite oxides via substituting oxygen with fluorine.However,the rapid fluorination process and the similarity between F and O render the O/F site occupation and local lattice evolution during fluorination unclear.Here we investigated the atomic-scale O/F exchange in La2CoO4and quantified the lattice distortion of three ordered structures:La_(2)CoO_(3.5)F,La_(2)CoO_(3)F_(2),and La_(2)CoO_(2.5)F_(3)by utilizing aberration-corrected electron microscopy.Atomic-resolved elemental mapping provides direct evidence for the O/F occupancy in interstitial and apical sites.We revealed that apical F ions induce significant octahedral tilting from 178°to 165°,linearly proportional to the occupancy rate;and cause the obvious change in the fine structure O K edge,meanwhile apical O is exchanged into interstitial sites.The strong octahedral tilt leads to the in-plane elongation of the[CoO_(4)F_(2)]octahedra.These findings elucidate the atomic-scale mechanisms of the entire fluorination process and highlight the significant role of F in tuning the octahedral tilt of functional oxides.展开更多
One of the central tasks in the field of heterogeneous catalysis is to establish structure‐function relationships for these catalysts,especially for precious metals dispersed on the sub‐nanometer scale.Here,we repor...One of the central tasks in the field of heterogeneous catalysis is to establish structure‐function relationships for these catalysts,especially for precious metals dispersed on the sub‐nanometer scale.Here,we report the preparation of MgAl2O4‐supported Pt nanoparticles,amorphous aggregates and single atoms,and evaluate their ability to catalyze the hydrogenation of benzaldehyde.The Pt species were characterized by N2adsorption,X‐ray diffraction(XRD),aberration‐corrected transmission electron microscopy(ACTEM),CO chemisorption and in situ Fourier transform infrared spectroscopy of the chemisorbed CO,as well as by inductively coupled plasma atomic emission spectroscopy.They existed as isolated or neighboring single atoms on the MgAl2O4support,and formed amorphous Pt aggregates and then nanocrystallites with increased Pt loading.On the MgAl2O4support,single Pt atoms were highly active in the selective catalytic hydrogenation of benzaldehyde to benzyl alcohol.The terrace atoms of the Pt particles were more active but less selective;this was presumably due to their ability to form bridged carbonyl adsorbates.The MgAl2O4‐supported single‐atom Pt catalyst is a novel catalyst with a high precious atom efficiency and excellent catalytic hydrogenation ability and selectivity.展开更多
Ino rganic tubular materials have an exceptionally wide range of applications,yet developing a simple and universal method to controllably synthesize them remains challenging.In this work,we report a vaporphase-etchin...Ino rganic tubular materials have an exceptionally wide range of applications,yet developing a simple and universal method to controllably synthesize them remains challenging.In this work,we report a vaporphase-etching hard-template method that can directly fabricate tubes on various thermally stable oxide and sulfide materials.This synthesis method features the introduction of a vapor-phase-etching process to greatly simplify the steps involved in preparing tubular materials and avoids complicated postprocessing procedures.Furthermore,the in-situ heating transmission electron microscopy(TEM)technique is used to observe the dynamic formation process of TiO_(2-x) tubes,indicating that the removal process of the Sb2S3 templates first experienced the Rayleigh instability,then vapor-phase-etching process.When used as an anode for sodium ion batteries,the TiO_(2-x) tube exhibits excellent rate performance of134.6 mA h g^(-1) at the high current density of 10 A g^(-1) and long-term cycling over 7000 cycles.Moreover,the full cell demonstrates excellent cycling performance with capacity retention of 98%after 1000 cycles,indicating that it is a promising anode material for batteries.This method can be expanded to the design and synthesis of other thermally-stable tubular materials such as ZnS,MoS_(2),and SiO_(2).展开更多
We report comprehensive transport, electron microscopy and Raman spectroscopy studies on transition-metal chalcogenides Cu1.89Te single crystals. The metallic Cu1.89Te displays successive metal-semiconductor transitio...We report comprehensive transport, electron microscopy and Raman spectroscopy studies on transition-metal chalcogenides Cu1.89Te single crystals. The metallic Cu1.89Te displays successive metal-semiconductor transitions at low temperatures and almost ideal linear MR when magnetic field up to 33 T. Through the electron diffraction patterns, the stable room-temperature phase is identified as a 3 × 3 × 2 modulated superstructure based on the Nowotny hexagonal structure. The superlattice spots of transmission electron microscopy and scanning tunneling microscopy clearly show the structural transitions from the room-temperature commensurate Ⅰ phase, named as C-Ⅰ phase, to the low temperature commensurate Ⅱ(C-Ⅱ) phase. All the results can be understood in terms of charge density wave(CDW) instability, yielding intuitive evidences for the CDW formations in Cu1.89Te. The additional Raman modes below room temperature further reveal that the zone-folded phonon modes may play an important role on the CDW transitions. Our research sheds light on the novel electron features of Cu1.89Te at low temperature, and may provide potential applications for future nano-devices.展开更多
The microstructure significantly influences the superconducting properties.Herein,the defect structures and atomic arrangements in high-temperature Bi_(2)Sr_(2)CaCu_(2)O8_(+σ) superconducting wire are directly charac...The microstructure significantly influences the superconducting properties.Herein,the defect structures and atomic arrangements in high-temperature Bi_(2)Sr_(2)CaCu_(2)O8_(+σ) superconducting wire are directly characterized via stateof-the-art scanning transmission electron microscopy.Interstitial oxygen atoms are observed in both the charge reservoir layers and grain boundaries in the doped superconductor.Inclusion phases with varied numbers of CuO_(2) layers are found,and twist interfaces with different angles are identified.This study provides insights into the structures of Bi-2212 wire and lays the groundwork for guiding the design of microstructures and optimizing the production methods to enhance superconducting performance.展开更多
Palladium(Pd)‐based catalysts are essential to drive high‐performance Suzuki coupling reactions,which are powerful tools for the synthesis of functional organic compounds.Herein,we developed a solution‐rapid‐annea...Palladium(Pd)‐based catalysts are essential to drive high‐performance Suzuki coupling reactions,which are powerful tools for the synthesis of functional organic compounds.Herein,we developed a solution‐rapid‐annealing process to stabilize nitrogen‐mesoporous carbon supported Pd single‐atom/cluster(Pd/NMC)material,which provided a catalyst with superior performance for Suzuki coupling reactions.In comparison with commercial palladium/carbon(Pd/C)catalysts,the Pd/NMC catalyst exhibited significantly boosted activity(100%selectivity and 95%yield)and excellent stability(almost no decay in activity after 10 reuse cycles)for the Suzuki coupling reactions of chlorobenzenes,together with superior yield and excellent selectivity in the fields of the board scope of the reactants.Moreover,our newly developed rapid annealing process of precursor solutions is applied as a generalized method to stabilize metal clusters(e.g.Pd,Pt,Ru),opening new possibilities in the construction of efficient highly dispersed metal atom and sub‐nanometer cluster catalysts with high performance.展开更多
In thermoelectrics,doping is essential to augment the figure of merit.Traditional strategy,predomina ntly heavy doping,aims to optimize carrier concentration and restrain lattice thermal conductivity.However,this tact...In thermoelectrics,doping is essential to augment the figure of merit.Traditional strategy,predomina ntly heavy doping,aims to optimize carrier concentration and restrain lattice thermal conductivity.However,this tactic can severely hamper carrier transport due to pronounced point defect scattering,particularly in materials with inherently low carrier mean-free-path.Conversely,dilute doping,although minimally affecting carrier mobility,frequently fails to optimize other vital thermoelectric parameters.Herein,we present a more nuanced dilute doping strategy in GeTe,leveraging the multifaceted roles of small-size metal atoms.A mere 4%CuPbSbTe_(3)introduction into GeTe swiftly suppresses rhombohedral distortion and optimizes carrier concentration through the aid of Cu interstitials.Additionally,the formation of multiscale microstructures,including zero-dimensional Cu interstitials,one-dimensional dislocations,two-dimensional planar defects,and three-dimensional nanoscale amorphous GeO_(2)and Cu_(2)GeTe_(3)precipitates,along with the ensuing lattice softening,contributes to an ultralow lattice thermal conductivity.Intriguingly,dilute CuPbSbTe_(3)doping incurs only a marginal decrease in carrier mobility.Subsequent trace Cd doping,employed to alleviate the bipolar effect and align the valence bands,yields an impressive figure-of-merit of 2.03 at 623 K in(Ge_(0.97)Cd_(0.03)Te)_(0.96)(CuPbSbTe_(3))_(0.04).This leads to a high energyconversion efficiency of 7.9%and a significant power density of 3.44 W cm^(-2)at a temperature difference of 500 K.These results underscore the invaluable insights gained into the constructive role of nuanced dilute doping in the concurrent tuning of carrier and phonon transport in GeTe and other thermoelectric materials.展开更多
Recently,photodynamic therapy(PDT)has been extensively applied in clinical and coadjuvant treatment of various kinds of tumors.However,the photosensitizer(PS)of PDT still lack of high production of singlet oxygen(^(1)...Recently,photodynamic therapy(PDT)has been extensively applied in clinical and coadjuvant treatment of various kinds of tumors.However,the photosensitizer(PS)of PDT still lack of high production of singlet oxygen(^(1)O_(2)),low cytotoxicity and high biocompatibility.Herein,we propose a facile method for establishing a new core-shell structured Sn nanocluster@carbon dots(CDs)PS.Firstly,Sn^(4+)@S-CDs complex is synthesized using the sulfur-doped CDs(S-CDs)and SnCl4 as raw materials,and subsequently the new PS(Sn nanocluster@CDs)is obtained after vaporization of Sn4+@S-CDs solution.Remarkably,the obtained Sn nanocluster@CDs show an enhanced fluorescence as well as a higher ^(1)O_(2) quantum yield(QY)than S-CDs.The high ^(1)O_(2) QY(58.3%)irradiated by the LED light(400-700 nm,40 mW/cm^(2)),induce the reduction of 4 T1 cancer cells viability by 25%.More intriguingly,no visible damage happens to healthy cells,with little impact on liver tissue due to renal excretion,both in vitro and in vivo experiments demonstrate that Sn nanocluster@CDs may become a promising PS,owning a high potential for application in PDT.展开更多
Bismuth telluride（Bi2Te3） based alloys, such as p-type Bi（0.5）Sb（1.5）Te3, have been leading candidates for near room temperature thermoelectric applications. In this study, Bi（0.48）Sb（1.52）Te3 bulk materials...Bismuth telluride（Bi2Te3） based alloys, such as p-type Bi（0.5）Sb（1.5）Te3, have been leading candidates for near room temperature thermoelectric applications. In this study, Bi（0.48）Sb（1.52）Te3 bulk materials with MnSb2Se4 were prepared using high-energy ball milling and spark plasma sintering（SPS） process. The addition of MnSb2Se4 to Bi（0.48）Sb（1.52）Te3 increased the hole concentration while slightly decreasing the Seebeck coefficient, thus optimising the electrical transport properties of the bulk material. In addition, the second phases of MnSb2Se4 and Bi（0.48）Sb（1.52）Te3 were observed in the Bi（0.48）Sb（1.52）Te3 matrix. The nanoparticles in the semi-coherent second phase of MnSb2Se4 behaved as scattering centres for phonons,yielding a reduction in the lattice thermal conductivity. Substantial enhancement of the figure of merit, ZT, has been achieved for Bi（0.48）Sb（1.52）Te3 by adding an Mn（0.8）Cu（0.2）Sb2Se4（2mol%） sample, for a wide range of temperatures, with a peak value of 1.43 at 375 K, corresponding to -40% improvement over its Bi（0.48）Sb（1.52）Te3 counterpart. Such enhancement of the thermoelectric（TE） performance of p-type Bi2Te3 based materials is believed to be advantageous for practical applications.展开更多
Finding a real thermoelectric(TE)material that excels in various aspects of TE performance,mechanical properties,TE power generation,and cooling is challenging for its commercialization.Herein,we report a novel multif...Finding a real thermoelectric(TE)material that excels in various aspects of TE performance,mechanical properties,TE power generation,and cooling is challenging for its commercialization.Herein,we report a novel multifunctional Ge0.78Cd0.06Pb0.1Sb0.06Te material with excellent TE performance and mechanical strength,which is utilized to construct candidate TE power generation and cooling devices near room temperature.Specifically,the effectiveness of band convergence,combined with optimized carrier concentration and electronic quality factor,distinctly boosts the Seebeck coefficient,thus greatly improving the power factor.Advanced electron microscopy observation indicates that complex multi-scale hierarchical structures and strain field distributions lead to ultra-low lattice thermal conductivity,and also effectively enhance mechanical properties.High ZT0.6 at 303 K,average ZTave1.18 from 303 to 553 K,and Vickers hardness of200 Hv in Ge0.78Cd0.06Pb0.1Sb0.06Te are obtained synchronously.Particularly,a 7-pair TE cooling device with a maximumΔT of45.9 K at Th=328 K,and a conversion efficiency of5.2%at Th=553 K is achieved in a single-leg device.The present findings demonstrate a unique approach to developing superior multifunctional GeTe-based alloys,opening up a promising avenue for commercial applications.展开更多
Amid escalating global challenges in energy efficiency and environmental sustainability,the utilization of waste heat has gained significant scientific attention.This growing interest has positioned thermoelectric ene...Amid escalating global challenges in energy efficiency and environmental sustainability,the utilization of waste heat has gained significant scientific attention.This growing interest has positioned thermoelectric energy conversion as a pivotal research frontier in materials science,particularly for its potential to transform low-grade thermal energy into usable electricity.Thermoelectric materials hold significant potential in addressing this challenge due to their unique properties,such as the absence of vibration,radiation,and the ability to directly convert heat into electricity.展开更多
Atomically dispersed catalysts have attracted attention in energy conversion applications because their efficiency and chemoselectivity for special catalysis are superior to those of traditional catalysts. However, th...Atomically dispersed catalysts have attracted attention in energy conversion applications because their efficiency and chemoselectivity for special catalysis are superior to those of traditional catalysts. However, they have limitations owing to the extremely low metal-loading content on supports, difficulty in the precise control of the metal location and amount as well as low stability at high temperatures. We prepared a highly doped single metal atom hybrid via a single-step thermal pyrolysis of glucose, dicyandiamide, and inorganic metal salts. High-angle annular dark field-scanning transmission electron microscopy （HAADF-STEM） and X-ray absorption fine structure spectroscopy （XAFS） revealed that nitrogen atoms doped into the graphene matrix were pivotal for metal atom stabilization by generating a metal-Nx coordination structure. Due to the strong anchoring effect of the graphene matrix, the metal loading content was over 4 wt.% in the isolated atomic hybrid （the Pt content was as high as 9.26 wt.% in the Pt-doped hybrid）. Furthermore, the single iron-doped hybrid （Fe@N-doped graphene） showed a remarkable electrocatalytic performance for the oxygen reduction reaction. The peak power density was - 199 mW·cm-2 at a current density of 310 mA·cm-2 and superior to that of a commercial Pt/C catalyst when it was used as a cathode catalyst in assembled zinc-air batteries. This work offered a feasible approach to design and fabricate highly doped single metal atoms （SMAs） catalysts for potential energy applications.展开更多
Metal halide perovskites possess intriguing optoelectronic properties,however,the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integra...Metal halide perovskites possess intriguing optoelectronic properties,however,the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integrated devices.Here,we report a space confinement and antisolvent-assisted crystallization method for the homogeneous perovskite single crystal arrays spanning 100 square centimeter areas.This method enables precise control over the crystal arrays,including different array shapes and resolutions with less than 10%-pixel position variation,tunable pixel dimensions from 2 to 8 pm as well as the in-plane rotation of each pixel.The crystal pixel could serve as a high-quality whispering gallery mode(WGM)microcavity with a quality factor of 2915 and a threshold of 4.14μJ cm^(-2).Through directly on-chip fabrication on the patterned electrodes,a vertical structured photodetector array is demonstrated with stable photoswitching behavior and the capability to image the input patterns,indicating the potential application in the integrated systems of this method.展开更多
Maximizing band degeneracy and minimizing phonon relaxation time are proven to be successful for advancing thermoelectrics.Alloying with monotellurides has been known to be an effective approach for converging the val...Maximizing band degeneracy and minimizing phonon relaxation time are proven to be successful for advancing thermoelectrics.Alloying with monotellurides has been known to be an effective approach for converging the valence bands of PbTe for electronic improvements,while the lattice thermal conductivity of the materials remains available room for being further reduced.It is recently revealed that the broadening of phonon dispersion measures the strength of phonon scattering,and lattice dislocations are particularly effective sources for such broadening through lattice strain fluctuations.In this work,a fine control of MnTe and EuTe alloying enables a significant increase in density of electron states near the valence band edge of PbTe due to involvement of multiple transporting bands,while the creation of dense in-grain dislocations leads to an effective broadening in phonon dispersion for reduced phonon lifetime due to the large strain fluctuations of dislocations as confirmed by synchrotron X-ray diffraction.The synergy of both electronic and thermal improvements successfully leads the average thermoelectric figure of merit to be higher than that ever reported for p-type PbTe at working temperatures.展开更多
Being a typical state of the art heterogeneous catalyst,supported noble metal catalyst often demonstrates enhanced catalytic properties.However,a facile synthetic method for realizing large-scale and low-cost supporte...Being a typical state of the art heterogeneous catalyst,supported noble metal catalyst often demonstrates enhanced catalytic properties.However,a facile synthetic method for realizing large-scale and low-cost supported noble metal catalyst is strictly indispensable.To this end,by making use of the strong metal-support interaction(SMSI)and mechanochemical reaction,we introduce an efficient synthetic route to obtain ultrafine Pt and Ir nanoclusters immobilized on diverse substrates by wet chemical milling.We further demonstrate the scaling-up effect of our approach by large-scale ball-milling production of Pt nanoclusters immobilized on TiO_(2)substrate.The synthesized Pt/Ir@Co_(3)O_(4)catalysts exhibit superior oxygen evolution reaction(OER)performance with only 230 and 290 mV overpotential to achieve current density of 10 and 100 mA·cm^(-2),beating the catalytic performance of Co_(3)O_(4)supported Pt or Ir clusters and commercial Ir/C.It is envisioned that the present work strategically directs facile ways for fabricating supported noble metal heterogeneous catalysts.展开更多
Numerous experiments have demonstrated that the metal atom is the active center of monoatomic catalysts for hydrogen evolution reaction(HER),while the active sites of nonmetal doped atoms are often neglected.By combin...Numerous experiments have demonstrated that the metal atom is the active center of monoatomic catalysts for hydrogen evolution reaction(HER),while the active sites of nonmetal doped atoms are often neglected.By combining theoretical prediction and experimental verification,we designed a unique ternary Ru-N_(4)-P coordination structure constructed by monodispersed Ru atoms supported on N,P dual-doped graphene for highly efficient hydrogen evolution in acid solution.The density functional theory calculations indicate that the charge polarization will lead to the most charge accumulation at P atoms,which results in a distinct nonmetallic P active sites with the moderate H∗adsorption energy.Notably,these P atoms mainly supply highly efficient catalytic sites with ultrasmall absorption energy of 0.007 eV.Correspondingly,the Ru-N_(4)-P demonstrated outstanding HER performance not only in an acidic condition but also in alkaline environment.Notably,the performance of Ru-NPC catalyst at high current is even superior to the commercial Pt/C catalysts,whether in acidic or alkaline medium.Our in situ synchrotron radiation infrared spectra demonstrate that a P-H_(ads) intermediate is continually emerging on the Ru-NPC catalyst,actively proving the nonmetallic P catalytically active site in HER that is very different with previously reported metallic sites.展开更多
Carbon-supported noble-metal-free single-atom catalysts(SACs)have aroused widespread interest due to their green chemistry aspects and excellent performances.Herein,we propose a“ligand regulation strategy”and achiev...Carbon-supported noble-metal-free single-atom catalysts(SACs)have aroused widespread interest due to their green chemistry aspects and excellent performances.Herein,we propose a“ligand regulation strategy”and achieve the successful fabrication of bifunctional SAC/MOF(MOF=metal-organic framework)nanocomposite(abbreviated NiSA/ZIF-300;ZIF=ZIF-8)with exceptional catalytic performance and robustness.The designed NiSA/ZIF-300 has a planar interfacial structure with the Ni atom,involving one S and three N atoms bonded to Ni(Ⅱ),fabricated by controllable pyrolysis of volatile Ni-S fragments.For CO_(2) cycloaddition to styrene epoxide,NiSA/ZIF-300 exhibits ultrahigh activity(turnover number(TON)=1.18×105;turnover frequency(TOF)=9830 molSC·mol_(Ni)^(-1)·h^(-1);SC=styrene carbonate)and durability at 70℃ under 1 atm CO_(2) pressure,which is much superior to Ni complex/ZIF,NiNP/ZIF-300,and most reported catalysts.This study offers a simple method of bifunctional SAC/MOF nanocomposite fabrication and usage,and provides guidance for the precise design of additional original SACs with unique catalytic properties.展开更多
Previous research on the ternary Ti-Fe-Sb system has revealed that stoichiometric TiFeSb cannot exist as a stable compound,whereas a single-phase TiFe_(1.33)Sb alloy with the half-Heusler-like structure has been synth...Previous research on the ternary Ti-Fe-Sb system has revealed that stoichiometric TiFeSb cannot exist as a stable compound,whereas a single-phase TiFe_(1.33)Sb alloy with the half-Heusler-like structure has been synthesized by adding excessive Fe.In this work,we report that TiFeSb can also be stabilized by filling additional Cu to the vacant 4d site of the half-Heusler lattice.Our experiments indicate that the TiFe-Cu_(x)Sb(x=0-0.25)samples exhibit a p-type conduction with extremely high carrier concentration((0.5-2.5)×10^(22)cm^(-3)),while these samples attain very large Seebeck coefficients,over 100 mV/K in the whole measured temperature range for the samples with x=0.15-0.25.In addition,a logarithmic divergence of the temperature-dependent specific heat capacity(CP/T)is observed at low temperatures,implying the strange-metal behavior of TiFeCu_(x)Sb samples.The partial filling of the vacant 4d site results in significantly reduced lattice thermal conductivity,leading to the low total thermal conductivity of 2.8 W·m^(-1)·K^(-1)at 823 K for the TiFeCu_(0.20)Sb sample.Consequently,a dimensionless figure of merit zT of 0.54 at 923 K is realized for TiFeCu_(0.20)Sb,demonstrating that promising thermoelectric materials with intriguing physical properties can be discovered in the composition gap of half-and full-Heusler alloys.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12074409 and 12374021)。
文摘Metal–organic frameworks(MOFs) are crystalline porous materials with tunable properties, exhibiting great potential in gas adsorption, separation and catalysis.[1,2]It is challenging to visualize MOFs with transmission electron microscopy(TEM) due to their inherent instability under electron beam irradiation. Here, we employ cryo-electron microscopy(cryoEM) to capture images of MOF ZIF-8, revealing inverted-space structural information at a resolution of up to about 1.7A and enhancing its critical electron dose to around 20 e^(-)/A^(2). In addition, it is confirmed by electron-beam irradiation experiments that the high voltage could effectively mitigate the radiolysis, and the structure of ZIF-8 is more stable along the [100] direction under electron beam irradiation. Meanwhile, since the high-resolution electron microscope images are modulated by contrast transfer function(CTF) and it is difficult to determine the positions corresponding to the atomic columns directly from the images. We employ image deconvolution to eliminate the impact of CTF and obtain the structural images of ZIF-8. As a result, the heavy atom Zn and the organic imidazole ring within the organic framework can be distinguished from structural images.
文摘Electrocatalytic conversion of carbon dioxide(CO_(2))offers an effective method of CO_(2)fixation to mitigate global warming and the energy crisis.However,for supported Ni single-atom catalysts(SACs),which are among the most promising candidates for this application,the relationship between Ni coordination structure and catalytic properties is still under strong debate.Here,we fabricated a series of Ni SACs through precise-engineering of anchor sites on nitrogen-doped carbon(NC)followed by Ni atom anchoring using atomic layer deposition.Among them,a Ni_(1)/NC SAC,with a coordination number(CN)of four but less pyridinic nitrogen(N_(pyri)),achieved over 90%faradaic efϐiciency for CO at potentials from-0.7 to-1.0 V and a mass activity of 6.5 A/mgNi at-0.78 V along with high stability,outperforming other Ni SACs with lower CN and more N_(pyri).Theoretical calculations of various three and four-coordinated Ni_(1)-NxCy structures revealed a linear correlation between the reaction Gibbs free energy for the potential-limiting step and the highest occupied molecular orbital(HOMO)position of Ni-3d orbitals,therein the four-coordinated Ni_(1)-N_(1)C_(3)with the highest HOMO position is identified as the active site for the electrocatalytic CO_(2)-to-CO process,in line with the experimental results.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.52322212,52025025,5225040212474001)the National Key R&D Program of China(Grant Nos.2022YFA1403203 and 2023YFA1406300)。
文摘Topochemical fluorination introduces significant structural distortions and emerging properties in perovskite oxides via substituting oxygen with fluorine.However,the rapid fluorination process and the similarity between F and O render the O/F site occupation and local lattice evolution during fluorination unclear.Here we investigated the atomic-scale O/F exchange in La2CoO4and quantified the lattice distortion of three ordered structures:La_(2)CoO_(3.5)F,La_(2)CoO_(3)F_(2),and La_(2)CoO_(2.5)F_(3)by utilizing aberration-corrected electron microscopy.Atomic-resolved elemental mapping provides direct evidence for the O/F occupancy in interstitial and apical sites.We revealed that apical F ions induce significant octahedral tilting from 178°to 165°,linearly proportional to the occupancy rate;and cause the obvious change in the fine structure O K edge,meanwhile apical O is exchanged into interstitial sites.The strong octahedral tilt leads to the in-plane elongation of the[CoO_(4)F_(2)]octahedra.These findings elucidate the atomic-scale mechanisms of the entire fluorination process and highlight the significant role of F in tuning the octahedral tilt of functional oxides.
基金supported by the National Natural Science Foundation of China(21403213,21673226,21376236,U1462121)the"Hundred Talents Programme"of the Chinese Academy of Sciences+3 种基金the"Strategic Priority Research Program"of the Chinese Academy of Sciences(XDB17020100)National Key R&D Program of China(2016YFA0202801)Department of Science and Technology of Liaoning province under contract of 2015020086-101the Natural Science Foundation of Hunan Province(2016JJ2128)~~
文摘One of the central tasks in the field of heterogeneous catalysis is to establish structure‐function relationships for these catalysts,especially for precious metals dispersed on the sub‐nanometer scale.Here,we report the preparation of MgAl2O4‐supported Pt nanoparticles,amorphous aggregates and single atoms,and evaluate their ability to catalyze the hydrogenation of benzaldehyde.The Pt species were characterized by N2adsorption,X‐ray diffraction(XRD),aberration‐corrected transmission electron microscopy(ACTEM),CO chemisorption and in situ Fourier transform infrared spectroscopy of the chemisorbed CO,as well as by inductively coupled plasma atomic emission spectroscopy.They existed as isolated or neighboring single atoms on the MgAl2O4support,and formed amorphous Pt aggregates and then nanocrystallites with increased Pt loading.On the MgAl2O4support,single Pt atoms were highly active in the selective catalytic hydrogenation of benzaldehyde to benzyl alcohol.The terrace atoms of the Pt particles were more active but less selective;this was presumably due to their ability to form bridged carbonyl adsorbates.The MgAl2O4‐supported single‐atom Pt catalyst is a novel catalyst with a high precious atom efficiency and excellent catalytic hydrogenation ability and selectivity.
基金financial support from the National Natural Science Foundation of China(21971146 and 22272093)the Taishan Scholarship Fund in Shandong Provinces(ts201511004)+2 种基金the Natural Science Foundation of Shandong Province(ZR2021MB127)the operational support of ANSTO staff for synchrotron-based characterizations(Awarded beamtime:AS212/PD/17323)the support from the Australian Research Council(ARC)(DE200101384 and LP180100722)。
文摘Ino rganic tubular materials have an exceptionally wide range of applications,yet developing a simple and universal method to controllably synthesize them remains challenging.In this work,we report a vaporphase-etching hard-template method that can directly fabricate tubes on various thermally stable oxide and sulfide materials.This synthesis method features the introduction of a vapor-phase-etching process to greatly simplify the steps involved in preparing tubular materials and avoids complicated postprocessing procedures.Furthermore,the in-situ heating transmission electron microscopy(TEM)technique is used to observe the dynamic formation process of TiO_(2-x) tubes,indicating that the removal process of the Sb2S3 templates first experienced the Rayleigh instability,then vapor-phase-etching process.When used as an anode for sodium ion batteries,the TiO_(2-x) tube exhibits excellent rate performance of134.6 mA h g^(-1) at the high current density of 10 A g^(-1) and long-term cycling over 7000 cycles.Moreover,the full cell demonstrates excellent cycling performance with capacity retention of 98%after 1000 cycles,indicating that it is a promising anode material for batteries.This method can be expanded to the design and synthesis of other thermally-stable tubular materials such as ZnS,MoS_(2),and SiO_(2).
基金supported by the National Natural Science Foundation of China(Grant Nos.U19A2093,11904002,U2032214,U2032163,and 11774353)the National Key Research and Development Program of China(Grant No.2017YFA0403502)+1 种基金the Natural Science Foundation of Anhui Province(Grant No.1908085QA15)the Youth Innovation Promotion Association CAS(Grant No.2017483)。
文摘We report comprehensive transport, electron microscopy and Raman spectroscopy studies on transition-metal chalcogenides Cu1.89Te single crystals. The metallic Cu1.89Te displays successive metal-semiconductor transitions at low temperatures and almost ideal linear MR when magnetic field up to 33 T. Through the electron diffraction patterns, the stable room-temperature phase is identified as a 3 × 3 × 2 modulated superstructure based on the Nowotny hexagonal structure. The superlattice spots of transmission electron microscopy and scanning tunneling microscopy clearly show the structural transitions from the room-temperature commensurate Ⅰ phase, named as C-Ⅰ phase, to the low temperature commensurate Ⅱ(C-Ⅱ) phase. All the results can be understood in terms of charge density wave(CDW) instability, yielding intuitive evidences for the CDW formations in Cu1.89Te. The additional Raman modes below room temperature further reveal that the zone-folded phonon modes may play an important role on the CDW transitions. Our research sheds light on the novel electron features of Cu1.89Te at low temperature, and may provide potential applications for future nano-devices.
文摘The microstructure significantly influences the superconducting properties.Herein,the defect structures and atomic arrangements in high-temperature Bi_(2)Sr_(2)CaCu_(2)O8_(+σ) superconducting wire are directly characterized via stateof-the-art scanning transmission electron microscopy.Interstitial oxygen atoms are observed in both the charge reservoir layers and grain boundaries in the doped superconductor.Inclusion phases with varied numbers of CuO_(2) layers are found,and twist interfaces with different angles are identified.This study provides insights into the structures of Bi-2212 wire and lays the groundwork for guiding the design of microstructures and optimizing the production methods to enhance superconducting performance.
文摘Palladium(Pd)‐based catalysts are essential to drive high‐performance Suzuki coupling reactions,which are powerful tools for the synthesis of functional organic compounds.Herein,we developed a solution‐rapid‐annealing process to stabilize nitrogen‐mesoporous carbon supported Pd single‐atom/cluster(Pd/NMC)material,which provided a catalyst with superior performance for Suzuki coupling reactions.In comparison with commercial palladium/carbon(Pd/C)catalysts,the Pd/NMC catalyst exhibited significantly boosted activity(100%selectivity and 95%yield)and excellent stability(almost no decay in activity after 10 reuse cycles)for the Suzuki coupling reactions of chlorobenzenes,together with superior yield and excellent selectivity in the fields of the board scope of the reactants.Moreover,our newly developed rapid annealing process of precursor solutions is applied as a generalized method to stabilize metal clusters(e.g.Pd,Pt,Ru),opening new possibilities in the construction of efficient highly dispersed metal atom and sub‐nanometer cluster catalysts with high performance.
基金supported by the National Key R&D Program of China(2021YFB1507403)the National Natural Science Foundation of China(52071218,and 11874394)+1 种基金the Shenzhen University 2035 Program for Excellent Research(00000218)The University Synergy Innovation Program of Anhui Province(GXXT-2020-003)。
文摘In thermoelectrics,doping is essential to augment the figure of merit.Traditional strategy,predomina ntly heavy doping,aims to optimize carrier concentration and restrain lattice thermal conductivity.However,this tactic can severely hamper carrier transport due to pronounced point defect scattering,particularly in materials with inherently low carrier mean-free-path.Conversely,dilute doping,although minimally affecting carrier mobility,frequently fails to optimize other vital thermoelectric parameters.Herein,we present a more nuanced dilute doping strategy in GeTe,leveraging the multifaceted roles of small-size metal atoms.A mere 4%CuPbSbTe_(3)introduction into GeTe swiftly suppresses rhombohedral distortion and optimizes carrier concentration through the aid of Cu interstitials.Additionally,the formation of multiscale microstructures,including zero-dimensional Cu interstitials,one-dimensional dislocations,two-dimensional planar defects,and three-dimensional nanoscale amorphous GeO_(2)and Cu_(2)GeTe_(3)precipitates,along with the ensuing lattice softening,contributes to an ultralow lattice thermal conductivity.Intriguingly,dilute CuPbSbTe_(3)doping incurs only a marginal decrease in carrier mobility.Subsequent trace Cd doping,employed to alleviate the bipolar effect and align the valence bands,yields an impressive figure-of-merit of 2.03 at 623 K in(Ge_(0.97)Cd_(0.03)Te)_(0.96)(CuPbSbTe_(3))_(0.04).This leads to a high energyconversion efficiency of 7.9%and a significant power density of 3.44 W cm^(-2)at a temperature difference of 500 K.These results underscore the invaluable insights gained into the constructive role of nuanced dilute doping in the concurrent tuning of carrier and phonon transport in GeTe and other thermoelectric materials.
基金financially supported by the National Natural Science Foundation of China(No.51772001)the support from the Key Laboratory of Structure and Functional Regulation of Hybrid Materials(Anhui University),Ministry of Education,Chinathe Key Laboratory of Environment-Friendly Polymer Materials of Anhui Province,Anhui University。
文摘Recently,photodynamic therapy(PDT)has been extensively applied in clinical and coadjuvant treatment of various kinds of tumors.However,the photosensitizer(PS)of PDT still lack of high production of singlet oxygen(^(1)O_(2)),low cytotoxicity and high biocompatibility.Herein,we propose a facile method for establishing a new core-shell structured Sn nanocluster@carbon dots(CDs)PS.Firstly,Sn^(4+)@S-CDs complex is synthesized using the sulfur-doped CDs(S-CDs)and SnCl4 as raw materials,and subsequently the new PS(Sn nanocluster@CDs)is obtained after vaporization of Sn4+@S-CDs solution.Remarkably,the obtained Sn nanocluster@CDs show an enhanced fluorescence as well as a higher ^(1)O_(2) quantum yield(QY)than S-CDs.The high ^(1)O_(2) QY(58.3%)irradiated by the LED light(400-700 nm,40 mW/cm^(2)),induce the reduction of 4 T1 cancer cells viability by 25%.More intriguingly,no visible damage happens to healthy cells,with little impact on liver tissue due to renal excretion,both in vitro and in vivo experiments demonstrate that Sn nanocluster@CDs may become a promising PS,owning a high potential for application in PDT.
基金supported by the National Natural Science Foundation of China(Grant Nos.51472052 and Y6J1421A41)
文摘Bismuth telluride（Bi2Te3） based alloys, such as p-type Bi（0.5）Sb（1.5）Te3, have been leading candidates for near room temperature thermoelectric applications. In this study, Bi（0.48）Sb（1.52）Te3 bulk materials with MnSb2Se4 were prepared using high-energy ball milling and spark plasma sintering（SPS） process. The addition of MnSb2Se4 to Bi（0.48）Sb（1.52）Te3 increased the hole concentration while slightly decreasing the Seebeck coefficient, thus optimising the electrical transport properties of the bulk material. In addition, the second phases of MnSb2Se4 and Bi（0.48）Sb（1.52）Te3 were observed in the Bi（0.48）Sb（1.52）Te3 matrix. The nanoparticles in the semi-coherent second phase of MnSb2Se4 behaved as scattering centres for phonons,yielding a reduction in the lattice thermal conductivity. Substantial enhancement of the figure of merit, ZT, has been achieved for Bi（0.48）Sb（1.52）Te3 by adding an Mn（0.8）Cu（0.2）Sb2Se4（2mol%） sample, for a wide range of temperatures, with a peak value of 1.43 at 375 K, corresponding to -40% improvement over its Bi（0.48）Sb（1.52）Te3 counterpart. Such enhancement of the thermoelectric（TE） performance of p-type Bi2Te3 based materials is believed to be advantageous for practical applications.
基金support from the National Key Research and Development Program of China(Grant Nos.2018YFA0702100 and 2022YFB3803900)the National Natural Science Foundation of China(Grant No.11874394)+2 种基金the Sichuan University Innovation Research Program of China(Grant No.2020SCUNL112)the University Synergy Innovation Program of Anhui Province(No.GXXT-2020-003)Ruihuan Cheng,Chengliang Xia,and Yue Chen are grateful for the research computing facilities offered by ITS,HKU.
文摘Finding a real thermoelectric(TE)material that excels in various aspects of TE performance,mechanical properties,TE power generation,and cooling is challenging for its commercialization.Herein,we report a novel multifunctional Ge0.78Cd0.06Pb0.1Sb0.06Te material with excellent TE performance and mechanical strength,which is utilized to construct candidate TE power generation and cooling devices near room temperature.Specifically,the effectiveness of band convergence,combined with optimized carrier concentration and electronic quality factor,distinctly boosts the Seebeck coefficient,thus greatly improving the power factor.Advanced electron microscopy observation indicates that complex multi-scale hierarchical structures and strain field distributions lead to ultra-low lattice thermal conductivity,and also effectively enhance mechanical properties.High ZT0.6 at 303 K,average ZTave1.18 from 303 to 553 K,and Vickers hardness of200 Hv in Ge0.78Cd0.06Pb0.1Sb0.06Te are obtained synchronously.Particularly,a 7-pair TE cooling device with a maximumΔT of45.9 K at Th=328 K,and a conversion efficiency of5.2%at Th=553 K is achieved in a single-leg device.The present findings demonstrate a unique approach to developing superior multifunctional GeTe-based alloys,opening up a promising avenue for commercial applications.
基金supported by the National Key R&D Program of China(2022YFA1403203)the National Natural Science Foundation of China(12474001)。
文摘Amid escalating global challenges in energy efficiency and environmental sustainability,the utilization of waste heat has gained significant scientific attention.This growing interest has positioned thermoelectric energy conversion as a pivotal research frontier in materials science,particularly for its potential to transform low-grade thermal energy into usable electricity.Thermoelectric materials hold significant potential in addressing this challenge due to their unique properties,such as the absence of vibration,radiation,and the ability to directly convert heat into electricity.
基金This work is financially supported partly by Ministry of Science and Technology （MOST） （Nos. 2017YFA0303500 and 2014CB848900）, the National Natural Science Foundation of China （NSFC） （Nos. U1532112, 11574280 and 11605201 ）, CAS Interdisciplinary Innovation Team and CAS Key Research Program of Frontier Sciences （No. QYZDB-SSW-SLH018）. L. S. acknowledges the recruitment program of global experts, the CAS Hundred Talent Program and Key Laboratory of Advanced Energy Materials Chemistry （Ministry of Education） Nankai University. We thank the Shanghai Synchrotron Radiation Facility （14W1, SSRF）, the Beijing Synchrotron Radiation Facility （1W1B and soft-X-ray endstation, BSRF）, the Hefei Synchrotron Radiation Facility （Photoemission, MCD and Catalysis/ Surface Science Endstations, NSRL）, and the USTC Center for Micro and Nanoscale Research and Fabrication for helps in characterizations.
文摘Atomically dispersed catalysts have attracted attention in energy conversion applications because their efficiency and chemoselectivity for special catalysis are superior to those of traditional catalysts. However, they have limitations owing to the extremely low metal-loading content on supports, difficulty in the precise control of the metal location and amount as well as low stability at high temperatures. We prepared a highly doped single metal atom hybrid via a single-step thermal pyrolysis of glucose, dicyandiamide, and inorganic metal salts. High-angle annular dark field-scanning transmission electron microscopy （HAADF-STEM） and X-ray absorption fine structure spectroscopy （XAFS） revealed that nitrogen atoms doped into the graphene matrix were pivotal for metal atom stabilization by generating a metal-Nx coordination structure. Due to the strong anchoring effect of the graphene matrix, the metal loading content was over 4 wt.% in the isolated atomic hybrid （the Pt content was as high as 9.26 wt.% in the Pt-doped hybrid）. Furthermore, the single iron-doped hybrid （Fe@N-doped graphene） showed a remarkable electrocatalytic performance for the oxygen reduction reaction. The peak power density was - 199 mW·cm-2 at a current density of 310 mA·cm-2 and superior to that of a commercial Pt/C catalyst when it was used as a cathode catalyst in assembled zinc-air batteries. This work offered a feasible approach to design and fabricate highly doped single metal atoms （SMAs） catalysts for potential energy applications.
基金National Natural Science Foundation of China(No.52125205,U20A20166,52192614,52102184)National key R&D program of China(2021YFB3200302,2021YFB3200304)+2 种基金Natural Science Foundation of Bejing Municipality(Z180011,2222088)Shenzhen Science and Technology Program(Grant No.KQTD20170810105439418)GuangDong Basic and Applied Basic Research Foundation(2020A1515110740).
文摘Metal halide perovskites possess intriguing optoelectronic properties,however,the lack of precise control of on-chip fabrication of the large-scale perovskite single crystal arrays restricts its application in integrated devices.Here,we report a space confinement and antisolvent-assisted crystallization method for the homogeneous perovskite single crystal arrays spanning 100 square centimeter areas.This method enables precise control over the crystal arrays,including different array shapes and resolutions with less than 10%-pixel position variation,tunable pixel dimensions from 2 to 8 pm as well as the in-plane rotation of each pixel.The crystal pixel could serve as a high-quality whispering gallery mode(WGM)microcavity with a quality factor of 2915 and a threshold of 4.14μJ cm^(-2).Through directly on-chip fabrication on the patterned electrodes,a vertical structured photodetector array is demonstrated with stable photoswitching behavior and the capability to image the input patterns,indicating the potential application in the integrated systems of this method.
基金This work is supported by the National Key Research and Development Program of China(2018YFB0703600)the National Natural Science Foundation of China(Grant Nos.51861145305 and 51772215)+3 种基金the Fundamental Research Funds for Science and Technology Innovation Plan of Shanghai(18JC1414600)the Fok Ying Tung Education Foundation(Grant No.20170072210001)ZZ and YC are grateful for the financial support from RGC under project numbers 17200017 and 17300018the research computing facilities offered by ITS,HKU.
文摘Maximizing band degeneracy and minimizing phonon relaxation time are proven to be successful for advancing thermoelectrics.Alloying with monotellurides has been known to be an effective approach for converging the valence bands of PbTe for electronic improvements,while the lattice thermal conductivity of the materials remains available room for being further reduced.It is recently revealed that the broadening of phonon dispersion measures the strength of phonon scattering,and lattice dislocations are particularly effective sources for such broadening through lattice strain fluctuations.In this work,a fine control of MnTe and EuTe alloying enables a significant increase in density of electron states near the valence band edge of PbTe due to involvement of multiple transporting bands,while the creation of dense in-grain dislocations leads to an effective broadening in phonon dispersion for reduced phonon lifetime due to the large strain fluctuations of dislocations as confirmed by synchrotron X-ray diffraction.The synergy of both electronic and thermal improvements successfully leads the average thermoelectric figure of merit to be higher than that ever reported for p-type PbTe at working temperatures.
基金This study was supported by the National Natural Science Foundations of China(Nos.51902027,61874014,61874013,51788104,61974011 and 61976025)the Basic Science Center Program of the National Natural Science Foundation of China(No.51788104)+2 种基金National Basic Research of China(Nos.2016YFE0102200 and 2018YFB0104404)Beijing Natural Science Foundation(No.JQ19005)Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications,China).
文摘Being a typical state of the art heterogeneous catalyst,supported noble metal catalyst often demonstrates enhanced catalytic properties.However,a facile synthetic method for realizing large-scale and low-cost supported noble metal catalyst is strictly indispensable.To this end,by making use of the strong metal-support interaction(SMSI)and mechanochemical reaction,we introduce an efficient synthetic route to obtain ultrafine Pt and Ir nanoclusters immobilized on diverse substrates by wet chemical milling.We further demonstrate the scaling-up effect of our approach by large-scale ball-milling production of Pt nanoclusters immobilized on TiO_(2)substrate.The synthesized Pt/Ir@Co_(3)O_(4)catalysts exhibit superior oxygen evolution reaction(OER)performance with only 230 and 290 mV overpotential to achieve current density of 10 and 100 mA·cm^(-2),beating the catalytic performance of Co_(3)O_(4)supported Pt or Ir clusters and commercial Ir/C.It is envisioned that the present work strategically directs facile ways for fabricating supported noble metal heterogeneous catalysts.
基金supported in part by the National Key R&D Program of China(2017YFA0303500),NSFC(U1932201,11574280,21727801,51902303,and 21978278)NSFCMAECI(51861135202)+2 种基金CAS Key Research Program of Frontier Sciences(QYZDB-SSW-SLH018)USTC start-up fund and CAS Interdisciplinary Innovation Team,and Fundamental Research Funds for the Central Universities(Grant No.WK2310000074)L.S.acknowledges the support from Key Laboratory of Advanced Energy Materials Chemistry(Ministry of Education),Nankai University(111 project,B12015).
文摘Numerous experiments have demonstrated that the metal atom is the active center of monoatomic catalysts for hydrogen evolution reaction(HER),while the active sites of nonmetal doped atoms are often neglected.By combining theoretical prediction and experimental verification,we designed a unique ternary Ru-N_(4)-P coordination structure constructed by monodispersed Ru atoms supported on N,P dual-doped graphene for highly efficient hydrogen evolution in acid solution.The density functional theory calculations indicate that the charge polarization will lead to the most charge accumulation at P atoms,which results in a distinct nonmetallic P active sites with the moderate H∗adsorption energy.Notably,these P atoms mainly supply highly efficient catalytic sites with ultrasmall absorption energy of 0.007 eV.Correspondingly,the Ru-N_(4)-P demonstrated outstanding HER performance not only in an acidic condition but also in alkaline environment.Notably,the performance of Ru-NPC catalyst at high current is even superior to the commercial Pt/C catalysts,whether in acidic or alkaline medium.Our in situ synchrotron radiation infrared spectra demonstrate that a P-H_(ads) intermediate is continually emerging on the Ru-NPC catalyst,actively proving the nonmetallic P catalytically active site in HER that is very different with previously reported metallic sites.
基金support by the National Natural Science Foundation of China(Nos.21972001,21871001)the Natural Science Foundation of Anhui Province(No.2008085MB37)the Anhui University,the University of Bordeaux,and the Centre National de la Recherche Scientifique(CNRS).
文摘Carbon-supported noble-metal-free single-atom catalysts(SACs)have aroused widespread interest due to their green chemistry aspects and excellent performances.Herein,we propose a“ligand regulation strategy”and achieve the successful fabrication of bifunctional SAC/MOF(MOF=metal-organic framework)nanocomposite(abbreviated NiSA/ZIF-300;ZIF=ZIF-8)with exceptional catalytic performance and robustness.The designed NiSA/ZIF-300 has a planar interfacial structure with the Ni atom,involving one S and three N atoms bonded to Ni(Ⅱ),fabricated by controllable pyrolysis of volatile Ni-S fragments.For CO_(2) cycloaddition to styrene epoxide,NiSA/ZIF-300 exhibits ultrahigh activity(turnover number(TON)=1.18×105;turnover frequency(TOF)=9830 molSC·mol_(Ni)^(-1)·h^(-1);SC=styrene carbonate)and durability at 70℃ under 1 atm CO_(2) pressure,which is much superior to Ni complex/ZIF,NiNP/ZIF-300,and most reported catalysts.This study offers a simple method of bifunctional SAC/MOF nanocomposite fabrication and usage,and provides guidance for the precise design of additional original SACs with unique catalytic properties.
基金support of the National Key Research and Development Program of China(No.2018YFA0702100)National Natural Science Foundation of China(No.52272226 and 52072234).
文摘Previous research on the ternary Ti-Fe-Sb system has revealed that stoichiometric TiFeSb cannot exist as a stable compound,whereas a single-phase TiFe_(1.33)Sb alloy with the half-Heusler-like structure has been synthesized by adding excessive Fe.In this work,we report that TiFeSb can also be stabilized by filling additional Cu to the vacant 4d site of the half-Heusler lattice.Our experiments indicate that the TiFe-Cu_(x)Sb(x=0-0.25)samples exhibit a p-type conduction with extremely high carrier concentration((0.5-2.5)×10^(22)cm^(-3)),while these samples attain very large Seebeck coefficients,over 100 mV/K in the whole measured temperature range for the samples with x=0.15-0.25.In addition,a logarithmic divergence of the temperature-dependent specific heat capacity(CP/T)is observed at low temperatures,implying the strange-metal behavior of TiFeCu_(x)Sb samples.The partial filling of the vacant 4d site results in significantly reduced lattice thermal conductivity,leading to the low total thermal conductivity of 2.8 W·m^(-1)·K^(-1)at 823 K for the TiFeCu_(0.20)Sb sample.Consequently,a dimensionless figure of merit zT of 0.54 at 923 K is realized for TiFeCu_(0.20)Sb,demonstrating that promising thermoelectric materials with intriguing physical properties can be discovered in the composition gap of half-and full-Heusler alloys.
