In operando-formed interface between silver and perovskite oxide for efficient electroreduction of carbon dioxide to carbon monoxide

Electrochemical carbon dioxide(CO_(2))reduction(ECR)is a promising technology to produce valuable fuels and feedstocks from CO_(2).Despite large efforts to develop ECR catalysts,the investigation of the catalytic performance and electrochemical behavior of complex metal oxides,especially perovskite oxides,is rarely reported.Here,the inorganic perovskite oxide Ag-doped(La_(0.8)Sr_(0.2))_(0.95)Ag_(0.05)MnO_(3-δ)(LSA0.05M)is reported as an efficient electrocatalyst for ECR to CO for the first time,which exhibits a Faradaic efficiency(FE)of 84.3%,a remarkable mass activity of 75Ag^(-1)(normalized to the mass of Ag),and stability of 130 h at a moderate overpotential of 0.79 V.The LSA0.05M catalyst experiences structure reconstruction during ECR,creating the in operando-formed interface between the perovskite and the evolved Ag phase.The evolved Ag is uniformly distributed with a small particle size on the perovskite surface.Theoretical calculations indicate the reconstruction of LSA0.05M during ECR and reveal that the perovskite-Ag interface provides adsorption sites for CO_(2) and accelerates the desorption of the*CO intermediate to enhance ECR.This study presents a novel high-performance perovskite catalyst for ECR andmay inspire the future design of electrocatalysts via the in operando formation of metal-metal oxide interfaces.

Deciphering the superior thermoelectric property of posttreatment-free PEDOT:PSS/IL hybrid by X-ray and neutron scattering characterization

In this work,a polymer and ionic liquid(IL)hybrid with superior thermoelectric performance is prepared via a system design of the chemical composition,molar ratio of the constituent molecules and manipulating the structure in solution and dried films.The solution-casted hybrid film,consisting of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)and 1-ethyl-3-methylimidazolium tricyanomethanide(EMIM:TCM),shows the highest power factor of 175μW m^(−1) K^(−2) in the polymer hybrid prepared by a post-treatment-free method.With a set of complementary structure characterization methods,it is found that EMIM:TCM can induce the structure reorganization of PEDOT:PSS in solution from a core-shell model to a rod-like model,during which PEDOT partially separates from PSS that eases the conductive network formation.In addition,the oxidation level of PEDOT:PSS is reduced by adding EMIM:TCM.Based on which,the PEDOT:PSS/IL hybrid shows the best performance in optimizing the conductivity(1163 S cm^(−1))and Seebeck coefficient(38.8μV K^(−1))simultaneously.

Proton dynamics in phosphotungstic acid impregnated mesoporous silica proton exchange membrane materials

Phosphotungstic acid is an excellent proton conductor that can be incorporated into porous supports, and nanocomposite proton exchange membrane materials made from mesoporous silica impregnated with phosphotungstic acid have been suggested for use in fuels cells operating> 100 ℃. In this work, quasielastic neutron scattering was used to study proton self-diffusion in mesoporous disordered and P6 mm symmetry silica impregnated with two concentrations of phosphotungstic acid. Overall, the silica structure had a significantly greater effect on proton conduction and diffusion than phosphotungstic acid concentration, with higher proton conduction occurring for the P6 mm symmetry silica samples. Quasielastic neutron scattering revealed two populations of protons diffusing through each sample, and that proton conduction is limited by the slower of these populations, which diffuse via a jump-diffusion mechanism. Whilst the fundamental jump-diffusion mechanism by which these slower protons moved was found to be similar for both silica supports and phosphotungstic acid concentrations, the faster diffusion occurring in P6 mm structured silica arises from a lower residence time of protons moving between sites in the jump-diffusion model, suggesting a lower energy barrier.

Magneto-Elastic Coupling in a Sinusoidal Modulated Magnet Cr_(2)GaN

We use neutron powder diffraction to investigate the magnetic and crystalline structure of Cr_(2)GaN.A magnetic phase transition is identified at T≈170 K,whereas no trace of structural transition is observed down to 6 K.Combining Rietveld refinement with irreducible representations,the spin configuration of Cr ions in Cr_(2)GaN is depicted as an incommensurate sinusoidal modulated structure characterized by a propagating vector k=(0.365,0.365,0).Upon warming up to the paramagnetic state,the magnetic order parameter closely resembles to the temperature dependence of c-axis lattice parameter,suggesting strong magneto-elastic coupling in this compound.Therefore,Cr_(2)Ga N provides a potential platform for exploration of magnetically tuned properties such as magnetoelectric,magnetostrictive and magnetocaloric effects,as well as their applications.

Soft phonon modes and diffuse scattering in Pb(In_(1/2)Nb_(1/2))O_(3)-Pb(Mg_(1/3)Nb_(2/3))O_(3)-PbTiO_(3)relaxor ferroelectrics

0.29Pb(In_(1/2)Nb_(1/2))O_(3)-0.45Pb(Mg_(1/3)Nb_(2/3))O_(3)-0.26PbTiO_(3)single crystals have been studied using tripleaxis based elastic and inelastic neutron scattering.Elastic diffuse scattering reveals the presence of polar nano-regions(PNR's)in this system,which emerge at the Burns temperature(TB~630 K)and then grow continuously in population and correlation size down to 100 K.At 300 K,characteristic“butterfly”and ellipsoid shaped diffuse scattering patterns are observed in the HK0 scattering plane.Electrical poling along the[110]direction produces a marked asymmetry in the diffuse scattering patterns,with the parallel-to-the-field components enhanced while the perpendicular-to-the-field components suppressed.Several low-energy phonon branches along the[100]and[110]directions have been measured.Most significantly,the PNR-acoustic phonon coupling is confirmed for the[110]transverse acoustic(TA)phonons polarized along the[1-10]real space direction and the[100]TA phonons.This coupling appears to be anisotropic and correlated with the PNRs'distribution,and also affected by the relative length scales of the PNRs and phonon wave vectors.The well-known“waterfall”phenomenon is observed on the[100]and[110]transverse optical(TO)branches,near the zone center.The optical phonons exhibit a lowest-energy,zone center soft TO mode,whose squared energy increases linearly with decreasing temperature below TB.

Spin excitations and spin wave gap in the ferromagnetic Weyl semimetal Co3Sn2S2

We report a comprehensive neutron scattering study on the spin excitations in the magnetic Weyl semimetal Co3Sn2S2 with a quasi-two-dimensional structure.Both in-plane and out-of-plane dispersions of the spin waves were revealed in the ferromagnetic state.Similarly,dispersive but damped spin excitations were found in the paramagnetic state.The effective exchange interactions were estimated using a semi-classical Heisenberg model to consistently reproduce the experimental TCand spin stiffness.However,a full spin wave gap below Eg=2.3 meV was observed at T=4 K.This value was considerably larger than the estimated magnetic anisotropy energy(~0.6 meV),and its temperature dependence indicated a significant contribution from the Weyl fermions.These results suggest that Co3Sn2S2 is a three-dimensional correlated system with a large spin stiffness,and the low-energy spin dynamics can interplay with the topological electron states.

Continuous chemical redistribution following amorphous-to-crystalline structural ordering in a Zr-Cu-Al bulk metallic glass

Bulk metallic glasses(BMGs)are thermodynamically metastable.As such,crystallization occurs when a BMG is thermally annealed at a temperature above the glass transition temperature.While extensive studies have been performed on the crystallization kinetics of BMGs,most of them have focused on the amorphous-to-crystalline structural ordering,and little attention has been paid to chemical distribution and its relationship with the structural ordering during the crystallization process.In this paper,a new approach,with simultaneous differential scanning calorimetry(DSC)and small angle neutron scatter-ing(SANS)measurements,was applied to study in situ the crystallization of a Zr_(45.5)Cu_(45.5)Al_(9)BMG upon isothermal annealing at a temperature in the supercooled liquid region.Quantitative analysis of the DSC and SANS data showed that the structural evolution during isothermal annealing could be classified into three stages:(Ⅰ)incubation;(Ⅱ)amorphous-to-crystalline structural ordering;(Ⅲ)continuous chemical redistribution.This finding was validated by composition analysis with atom probe tomography(APT),which further identified a transition region formed by expelling Al into the matrix.The transition re-gion,with a composition of(Cu,Al)_(50)Zr_(50),served as an intermediate step facilitating the formation of a thermodynamically stable crystalline phase with a composition of(Cu,Al)_(10)Zr_(7).

Quantitative and structural analysis of isotopically labelled natural crosslinks in type I skin collagen using LC-HRMS and SANS

Collagen structure in biological tissues imparts its intrinsic physical properties by the formation of several covalent crosslinks.For the first time,two major crosslinks in the skin dihydroxylysinonorleucine(HLNL)and histidinohydroxymerodesmosine(HHMD),were isotopically labelled and then analysed by liquid-chromatography high-resolution accurate-mass mass spectrometry(LC-HRMS)and small-angle neutron scattering(SANS).The isotopic labelling followed by LC-HRMS confirmed the presence of one imino group in both HLNL and HHMD,making them more susceptible to degrade at low pH.The structural changes in collagen due to extreme changes in the pH and chrome tanning were highlighted by the SANS contrast variation between isotopic labelled and unlabelled crosslinks.This provided a better understanding of the interaction of natural crosslinks with the chromium sulphate in collagen suggesting that the development of a benign crosslinking method can help retain the intrinsic physical properties of the leather.This analytical method can also be applied to study artificial crosslinking in other collagenous tissues for biomedical applications.