Directing in-situ self-optimization of single-atom catalysts for improved oxygen evolution

The demand for clean and sustainable energy has encouraged the production of hydrogen from water electrolyzers.To overcome the obstacle to improving the efficiency of water electrolyzers,it is highly desired to fabricate active electrocatalysts for the sluggish oxygen evolution process.However,there is generally an intrinsic gap between the as-prepared and real electrocatalysts due to structure evolution under the oxidative reaction conditions.Here,we combine in-situ anionic leaching and atomic deposition to realize single-atom catalysts with self-optimized structures.The introduced F ions facilitate structural transformation from Co(OH)xF into CoOOH(F),which generates an amorphous edge surface to provide more anchoring sites for Ir single atoms.Meanwhile,the in-situ anionic leaching of F ions elevates the Co valence state of Ir_(1)/CoOOH(F)more significantly than the counterpart without F ions(Ir_(1)/CoOOH),leading to stronger adsorption of oxygenated intermediates.As revealed by electrochemical measurements,the increased Ir loading together with the favored adsorption of*OH intermediates improve the catalytic activity of Ir_(1)/CoOOH(F).Specifically,Ir_(1)/CoOOH(F)delivered a current density of 10 mA cm-2at an overpotential of 238 mV,being lower than 314 mV for Ir_(1)/CoOOH.The results demonstrated the facility of the in-situ optimization process to optimize catalyst structure for improved performance.

Design of Multi-Coupled Laminates with Extension-Twisting Coupling for Application in Adaptive Structures

The multiple coupling of composite laminates has a unique advantage in improving the macro mechanical properties of composite structures.A total of three hygro-thermally stablemulti-coupled laminates with extensiontwisting coupling were presented,which were conducive to the formation of passive adaptive structures.Then,the multi-coupled laminates were used to design the bending-twisting coupled box structure,in which the configuration of laminate and box structure could be extended to variable cross-section configuration.The optimal design of stacking sequence was realized,the optimization objectives of which were to maximize bending-twisting coupling of box structure and extension-twisting coupling of laminate,respectively.The effects of multiple coupling on hygro-thermal stability,coupling,failure strength,buckling load,robustness and other comprehensive mechanical properties of laminates and box structures were analyzed by parametric modeling method.The results show that the extension-twisting coupling of laminate and the bending-twisting coupling of box structures can be greatly improved by 450%and 260%at maximum,respectively.Meanwhile,it would have a negative impact on the failure strength and buckling load,which,however,can be minimized by a reasonable paving method.Multicoupled laminates have good robustness,and the bending-twisting coupling helps improve robustness.Finally,the hygro-thermal stability and mechanical properties were verified by numerical simulation with finite element method.

Comparison between Top and Bottom NiO-pinning Spin Valves: Effect of Interfacial Roughness on Specular Reflection

Top and bottom NiO-pinning spin valves of Si/Ta/NiO/Co/Cu/Co/Ta and Si/Ta/Co/Cu/Co/NiO/Ta were prepared by magnetron sputtering, and X-ray diffraction and giant magnetoresistance （GMR） ratio were measured in the temperature range from 5 to 300 K. For the bottom spin valve, the interracial roughness at NiO/Co is much smaller than that of Co/NiO in the top one. The Co/Cu and Cu/Co interfaces have the same roughness in the bottom and the top spin valves. NiO, Co, and Cu layers have （111） preferred orientations in the top one and random orientations in the bottom one. The GMR ratio of the bottom spin valve is larger than that of the top one at all temperatures and their difference increases with decreasing temperature.

Observation of high ionic conductivity of polyelectrolyte microgels in salt-free solutions

Here, we report an observation that illustrate the potential of polyelectrolyte microgels in salt-free solutions to display a high ionic conductivity. Laser light scattering and ionic conductivity tests on very dilute aqueous dispersions of the microgels indicate that both small size and swollen state of gel particles play vital roles, which should favor the counterions to freely penetrate and leave gel particles, and thus can contribute to the ion-conducting property. Upon discovering this on microgels that are composed of imidazolium-based poly(ionic liquid), we also illustrate the generality of the finding to single lithium-ion polyelectrolyte microgels that are of more technically relevant features for applications, for instance, as injectable liquid “microgel-in-solution” electrolytes of high conductivity(ca. 8.2 × 10^(-2)S/m at 25.0 ℃ for1.0 × 10^(-2)g/m L of microgels in a LiNO_(3)-free 1:1 v/v mixture of 1,2-dioxolane and dimethoxymethane) and high lithium-ion transference number(0.87) for use in the rechargeable lithium-sulfur battery.

Enhancing hydrogen storage properties of MgH_(2) using FeCoNiCrMn high entropy alloy catalysts

Herein,we report the successful preparation of the FeCoNiCrMn high entropy alloy(HEA)loaded MgH_(2) and HEA’s effect on the hydrogen storage properties of Mg/MgH_(2).The HEA shows high catalytic activity toward hydrogen dissociation and recombination reaction,and successfully suppressed activation energy of dehydrogenation reaction from 151.9 to 90.2 kJ mol-1.Moreover,part of Co and Ni can react with Mg,and produce Mg_(2) Co/Mg_(2) CoH 5 and Mg_(2) Ni/Mg_(2) NiH_(4) during the hydrogen storage processes,further en-hancing dehydrogenation reaction through the“hydrogen pumping”mechanism.Asa result,the MgH_(2)-5 wt%HEA composite can release 5.6 wt%of H_(2) at 280℃ within 10 min,and absorb 5.5 wt%H_(2) within 0.5 min at 150℃.The loaded HEA shows robustness against particle aggregation,leading to stable re-versible hydrogen storage processes at least 50 times.These findings show the synergistic effects of HEA on Mg-based hydrogen storage materials,providing an additional degree of freedom for catalyst design.

Structure and strain tunings of topological anomalous Hall effect in cubic noncollinear antiferromagnet Mn3Pt epitaxial films

Antiferromagnets(AFMs)with chiral noncollinear spin structure have attracted great attention in recent years.However,the existing research has mainly focused on hexagonal chiral AFMs,such as Mn3Sn,Mn3Ga,Mn3Ge with low crystalline symmetry.Here,we present our systematical study for the face-centered cubic noncollinear antiferromagnetic Mn3Pt.By varying the alloy composition(x),we have successfully fabricated antiferromagnetic Mn1-xPtx epitaxial films on MgO substrates and have observed a crystalline structure transition from L10 MnPt to L12 Mn3Pt.The Mn3Pt exhibits a large anomalous Hall effect,which is in the same order of magnitude as those of ferromagnetic materials.Moreover,a large thickness-evolved strain effect is revealed in Mn3Pt films by X-ray diffraction(XRD)analysis based on the Scherrer method.Our work explores Mn3Pt as a promising candidate for topological antiferromagnetic spintronics.