As a promising cathode material for aqueous zinc-ion batteries,1T-MoS_(2)has been extensively investigated because of its facile two-dimensional ion-diffusion channels and high electrical ***,the limited number of ava...
详细信息
As a promising cathode material for aqueous zinc-ion batteries,1T-MoS_(2)has been extensively investigated because of its facile two-dimensional ion-diffusion channels and high electrical ***,the limited number of available Zn storage sites,i.e.,limited capacity,hinders its application because the inserted Zn^(2+),which form strong electrostatic interactions with 1T-MoS_(2),preventing subsequent Zn^(2+)***,the approach of enlarging the interlayer distance to reduce electrostatic interactions has been commonly used to enhance the capacity and reduce Zn^(2+)migration ***,an enlarged interlayer spacing can weaken the van der Waals force between 1T-MoS_(2)monolayers,easily disrupting the structural ***,to address this issue,an effective strategy based on Fe doping is proposed for 1T-MoS_(2)(Fe-1T-MoS_(2)).The theoretical calculations reveal that Fe doping can simultaneously moderate the rate of decrease in the adsorption energy after gradually increasing the number of stored atoms,and enhance the electron delocalization on metal-O ***,the experiment results show that Fe doping can simultaneously activate more Zn storage sites,thus enhancing the capacity,and stabilize the structural stability for improved cycling ***,Fe-1T-MoS_(2)exhibits a larger capacity(189 mAh·g^(-1)at 0.1 A·g^(-1))and superior cycling stability(78%capacity retention after 400 cycles at 2 A·g^(-1))than pure 1T-MoS_(2).This work may open up a new avenue for constructing high-performance MoS_(2)-based cathodes.
Micrometer-sized diamonds were incorporated into silicon nitride(Si_(3)N_(4))matrix to manufacture high-performance Si_(3)N_(4)-based composites using spark plasma sintering at 1500℃under 50 *** effects of the diamon...
详细信息
Micrometer-sized diamonds were incorporated into silicon nitride(Si_(3)N_(4))matrix to manufacture high-performance Si_(3)N_(4)-based composites using spark plasma sintering at 1500℃under 50 *** effects of the diamond content on the phase composition,microstructure,mechanical properties and thermal conductivity of the composites were *** results showed that the addition of diamond could effectively improve the hardness of the *** thermal conductivity of Si_(3)N_(4)increased to 52.97 W/m·k at the maximum with the addition of 15 wt%diamond,which was 27.5%higher than that of the monolithic Si_(3)N_(4).At this point,the fracture toughness was 7.54 MPa·m^(1/2).Due to the addition of diamond,the composite material generated a new substance,MgSiN2,which effectively combined Si_(3)N_(4)with ***2 might improve the hardness and thermal conductivity of the materials.
Flexible piezoelectric materials capable of withstanding large deformation play key roles in flexible electronics. Ferroelectric ceramics with a high piezoelectric coefficient are inherently brittle, whereas polar pol...
详细信息
Flexible piezoelectric materials capable of withstanding large deformation play key roles in flexible electronics. Ferroelectric ceramics with a high piezoelectric coefficient are inherently brittle, whereas polar polymers exhibit a low piezoelectric coefficient. Here we report a highly stretchable/compressible piezoelectric composite composed of ferroelectric ceramic skeleton, elastomer matrix and relaxor ferroelectric-based hybrid at the ceramic/matrix interface as dielectric transition layers, exhibiting a giant piezoelectric coefficient of 250 picometers per volt, high electromechanical coupling factor keff of 65%,ultralow acoustic impedance of 3MRyl and high cyclic stability under 50% compression strain. The superior flexibility and piezoelectric properties are attributed to the electric polarization and mechanical load transfer paths formed by the ceramic skeleton, and dielectric mismatch mitigation between ceramic fillers and elastomer matrix by the dielectric transition layer. The synergistic fusion of ultrahigh piezoelectric properties and superior flexibility in these polymer composites is expected to drive emerging applications in flexible smart electronics.
In this work,Ag/Ag_(2)Se composite films with excellent thermoelectric(TE)properties and flexibility are prepared based on a simple one-pot *** adjusting the nominal ratios of Ag/Se,an optimal Ag/Ag_(2)Se composite fi...
详细信息
In this work,Ag/Ag_(2)Se composite films with excellent thermoelectric(TE)properties and flexibility are prepared based on a simple one-pot *** adjusting the nominal ratios of Ag/Se,an optimal Ag/Ag_(2)Se composite film shows a large power factor of~2275 μW m^(-1) K^(-2) at 300 *** an outstand-ing TE performance of the composite film is due to the unique microstructure and the synergistic effect between the Ag and Ag_(2)***,the composite film also shows outstanding flexibility(~91.8%of the initial electrical conductivity is maintained,and the S is unchanged after 1500 bending cycles with a bending radius of 4 mm).Furthermore,a 4-leg flexible TE generator assembled with the optimal film produces a voltage of 14.06 mV and 4.96 μW at a temperature difference of 30.4 *** work provides a new inspiration for the preparation of flexible Ag_(2)Se-based films with excellent TE performance near room temperature.
Water dissociation process is generally regarded as the rate-limiting step for alkaline hydrogen evolution reaction(HER),and severely inhibits the catalytic efficiency of Pt based *** overcome this problem,the in-situ...
详细信息
Water dissociation process is generally regarded as the rate-limiting step for alkaline hydrogen evolution reaction(HER),and severely inhibits the catalytic efficiency of Pt based *** overcome this problem,the in-situ constructed interfaces of PtCo alloy and amorphous cobalt oxide(CoO_(x))on the carbon powder are *** amorphous CoO_(x)at Pt-Co/CoO_(x)interfaces not only provide active sites for water dissociation to facilitate Volmer step,but also produce the strong electronic transfer with ***,the obtained interfacial catalysts exhibit outstanding alkaline HER performance with a Tafel slope of 29.3 mV·dec^(−1)and an ultralow overpotential of only 28 mV at 10 mA·cm^(−2).Density functional theory(DFT)reveals that the electronic accumulation on the interfacial Co atom in Pt-Co/CoO_(x)constructing the novel active site for water *** to the Pt-Co,all of the energy barriers for water adsorption,water dissociation and hydrogen adsorption/desorption are reduced in Pt-Co/CoO_(x)interfaces,suggesting a boosted HER kinetics for alkaline HER.
Precisely tuning the spacing of the active centers on the atomic scale is of great significance to improve the catalytic activity and deepen the understanding of the catalytic mechanism,but still remains a ***,we deve...
详细信息
Precisely tuning the spacing of the active centers on the atomic scale is of great significance to improve the catalytic activity and deepen the understanding of the catalytic mechanism,but still remains a ***,we develop a strategy to dilute catalytically active metal interatomic spacing(d_(M-M))with light atoms and discover the unusual adsorption *** example,by elevating the content of boron as interstitial atoms,the atomic spacing of osmium(d_(Os-Os))gradually increases from 2.73 to 2.96?.More importantly,we find that,with the increase in dOs-Os,the hydrogen adsorption-distance relationship is reversed via downshifting d-band states,which breaks the traditional cognition,thereby optimizing the H adsorption and H_2O dissociation on the electrode surface during the catalytic process;this finally leads to a nearly linear increase in hydrogen evolution reaction ***,the maximum dOs-Os of 2.96?presents the optimal HER activity(8 mV@10 mA cm^(-2))in alkaline media as well as suppressed O adsorption and thus promoted *** is believed that this novel atomic-level distance modulation strategy of catalytic sites and the reversed hydrogen adsorption-distance relationship can shew new insights for optimal design of highly efficient catalysts.
Transition metal oxides with layered structure have been widely used as cathode materials for lithium-ion batteries(LIBs)which have relatively high energy density,large capacity and long ***,in the long-term electroch...
详细信息
Transition metal oxides with layered structure have been widely used as cathode materials for lithium-ion batteries(LIBs)which have relatively high energy density,large capacity and long ***,in the long-term electrochemical cycle,the inevitable degradation of performance of LIBs due to structural degradation in cathodes severely restricts their large-scale practical *** the underlying mechanism of structural degradation is the most critical scientific ***,in situ transmission electron microscopy(TEM)has become a useful tool to study the structural and compositional evolutions at atomic scale in electrochemical reactions,which provided a unique and in-depth understanding of the structural *** this review,we discuss the recent advances in the in situ TEM,focusing on its role in revealing the structural degradation mechanisms in the four key places:(1)the interface between the cathodes and electrolyte;(2)the cathode surface;(3)the particle interior and(4)those induced by thermal *** insight gained by the in-situ TEM which is still developing at its fast pace is unique and expected to provide guidance for designing better layered cathode materials.
Nano-structured silicon(Si)has demonstrated high capacity for lithium storage;however,it suffers from unsatisfactory cycling stability caused by large volume change and poor interface ***,it is very important to const...
详细信息
Nano-structured silicon(Si)has demonstrated high capacity for lithium storage;however,it suffers from unsatisfactory cycling stability caused by large volume change and poor interface ***,it is very important to construct functional coatings on nano-structured Si to buffer the volume change and improve the interface ***,we successfully construct V_(2)O_(3) and carbon(C)dual-layer coatings on Si nanoparticles with ultrathin and uniform thickness using a facile spray drying and chemical vapour deposition *** as-prepared Si@V_(2)O_(3)@C manifests a high specific capacity of 2230 mAh g^(-1) after 100 cycles under the current density of 200 mA g^(-1),showing its promising application prospect in lithium *** situ electrochemical impedance spectroscopy(EIS)results at different lithiation states and different cycles show a more stable interface resistance of Si@V_(2)O_(3)@C than pristine *** V_(2)O_(3) and C dual coating layers not only ensure the Si nanoparticles with high structural stability by buffering volume expansion and preventing electrolyte penetration,but also guarantee a superior electron transport rate because of the metallic V_(2)O_(3) as well as the highly conductive carbon layers.
As the main limiting step of overall water splitting,oxygen evolution reaction(OER)is urgent to be enhanced by developing efficient catalysts to promote the process of electrolytic *** on theoretical analysis,the Ni-m...
详细信息
As the main limiting step of overall water splitting,oxygen evolution reaction(OER)is urgent to be enhanced by developing efficient catalysts to promote the process of electrolytic *** on theoretical analysis,the Ni-metal-organic framework(Ni-MOF)and NiFe-layered double hydroxide(NiFe-LDH)(NiFe-LDH/MOF)heterostructure can optimize the energy barrier of the OER process and decrease the adsorption energy of oxygen-containing intermediates,effectively accelerating the OER ***,layered NiFe-LDH/MOF heterostructures are in situ constructed through a facile two-step reaction process,with substantial oxygen defects and lattice defects that further improve the catalytic *** a result,only 208 and 275 mV OER overpotentials are needed for NiFe-LDH/MOF to drive the current densities of 20 and 100 mA·cm^(-2)in 1 M KOH solutions,and even maintain catalytic stability of 100 h at 20 mA·cm^(-2).When applied to seawater oxidation,only 235 and 307 mV OER overpotentials are required to achieve the current densities of 20 and 100 mA·cm^(-2),respectively,with almost no attenuation for 100 h stability test at 20 mA·cm^(-2),all better than commercial RuO_(2).This work provides the theoretical and experimental basis and a new idea for efficiently driving fresh water and seawater cracking by heterostructure and defect coupling design toward catalysts.
Compositions and morphologies of Pt-based electrocatalysts have great impact on the electrocatalytic activity and stability of oxygen reduction reaction(ORR).Herein,we report a novel design of one-dimensional(1D)Pt-Pd...
详细信息
Compositions and morphologies of Pt-based electrocatalysts have great impact on the electrocatalytic activity and stability of oxygen reduction reaction(ORR).Herein,we report a novel design of one-dimensional(1D)Pt-Pd dendritic nanotubular heterostructures(DTHs)by controlling the degree of Pt 2+-Pt reduction reaction and Pd-Pt galvanic replacement reaction with uniform Pd nanowires as sacrificial *** obtained Pt-Pd bimetallic DTHs catalyst exhibited uniform and dense Pt dendritic nanobranches on the surface of 1D hollow Pt-Pd alloy nanotubes,possessing superior catalytic activity for ORR compared to state-of-the-art commercial Pt/C ***,the Pt_(4)Pd DTHs catalyst showed efficient mass activity(MA,1.05 A mg_(Pt)^(−1))and specific activity(SA,1.25 mA cm_(Pt)^(−2))at 0.9 V(***),and the catalyst exhibited high stability with 90.4%MA retention after 20000 potential *** Pt-Pd bimetallic DTHs configuration combines the advantages of 1D hollow nanostructures and dense Pt dendritic nanobranches,which results in rich electrochemical active surface sites,fast charge transport,and multiple dendritic anchoring points contact on carbon support,thus boosting its catalytic activity and stability towards electrocatalysis.
暂无评论