Phase-change memory based on matched Ge-Te,Sb-Te,and In-Te octahedrons:Improved electrical performances and robust thermal stability

Phase-change memory(PCM)has been developed for three-dimensional(3D)data storage devices,posing huge challenges to the thermal stability and reliability of PCM.However,the low thermal stability of Ge2Sb2Te5(GST)limits further application.Here,we demonstrate PCM based on In0.9Ge2Sb2Te5(IGST)alloy,showing 180C 10-years data retention,6 ns set speed,one order of magnitude longer life time,and 75%reduced power consumption compared to GST-based device.The In can occupy the cationic positions and the In-Te octahedrons with good phase-change properties can geometrically match well with the host Ge-Te and Sb-Te octahedrons,acting as nucleation centers to boost the set speed and enhance the endurance of IGST device.Introducing stable matched phase-change octahedrons can be a feasible way to achieve practical PCMs.

Effects of Rattling Behavior of K and Cd Atoms along Different Directions in Anisotropic KCdAs on Lattice Thermal Transport and Thermoelectric Properties

We employ advanced first principles methodology,merging self-consistent phonon theory and the Boltzmann transport equation,to comprehensively explore the thermal transport and thermoelectric properties of KCdAs.Notably,the study accounts for the impact of quartic anharmonicity on phonon group velocities in the pursuit of lattice thermal conductivity and investigates 3ph and 4ph scattering processes on phonon lifetimes.Through various methodologies,including examining atomic vibrational modes and analyzing 3ph and 4ph scattering processes,the article unveils microphysical mechanisms contributing to the lowκL within KCdAs.Key features include significant anisotropy in Cd atoms,pronounced anharmonicity in K atoms,and relative vibrations in non-equivalent As atomic layers.Cd atoms,situated between As layers,exhibit rattling modes and strong lattice anharmonicity,contributing to the observed lowκL.Remarkably flat bands near the valence band maximum translate into high PF,aligning with ultralowκL for exceptional thermoelectric performance.Under optimal temperature and carrier concentration doping,outstanding ZT values are achieved:4.25(a(b)-axis,p-type,3×10^(19)cm^(−3),500 K),0.90(c-axis,p-type,5×10^(20)cm^(−3),700 K),1.61(a(b)-axis,n-type,2×10^(18)cm^(−3),700 K),and 3.06(c-axis,n-type,9×10^(17)cm^(−3),700 K).

Three-dimensional porous V2O5 hierarchical octahedrons with adjustable pore architectures for long-life lithium batteries

Three-dimensional （3D） porous V2O5 octahedrons have been successfully fabricated via a solid-state conversion process of freshly prepared ammonium vanadium oxide （AVO） octahedrons. The formation of AVO octahedrons is a result of the selective adsorption of capping reagents and the favourable supersaturation of growth species. Subsequently, 3D porous V2O5 octahedrons were obtained by simple thermolysis of the AVO octahedrons via a calcination treatment. As cathode material for lithium batteries, the porous V2O5 octahedron cathode exhibits a capacity of 96 mAh·g^-1 at high rate up to 2 A·g^-1 in the rang of 2.4 4 V and excellent cyclability with little capacity loss after 500 cycles, which can be ascribed to its high specific surface area and tunable pore architecture. Importantly, this facile solid-state thermal conversion strategy can be easily extended to controllably fabricate other porous metal oxide micro/nano materials with specific surface textures and morphologies.

Anchoring CoP nanoparticles on the octahedral CoO by self-phosphating for enhanced photocatalytic overall water splitting activity under visible light

Designing an effective and stable composite photocatalyst is of significance for the further realization of practical applications. In this study, a series of CoP/CoO composites are successfully prepared by a straight one-step phosphating method. The reasonable design and controllable preparation of CoP/CoO composite make it exhibit improved photocatalytic performance for overall water splitting and excellent stability under visible light irradiation in comparison with pure CoO, which is derived from the CoP nanoparticles well dispersed on the(111) facets of CoO octahedrons, intimate interface between them and efficiently accelerated of photo-induced electrons from CoO to CoP. This study presents a simple method to design highly-effective composite photocatalysts for overall water splitting to meet the energy demand.

Simultaneously Effi cient Solar Light Harvesting and Charge Transfer of Hollow Octahedral Cu_(2)S/CdS p-n Heterostructures for Remarkable Photocatalytic Hydrogen Generation

Solar-driven water splitting is a promising alternative to industrial hydrogen production.This study reports an elaborate design and synthesis of the integration of cadmium sulfi de(CdS)quantum dots and cuprous sulfi de(Cu_(2)S)nanosheets as three-dimensional(3D)hollow octahedral Cu_(2)S/CdS p-n heterostructured architectures by a versatile template and one-pot sulfi dation strategy.3D hierarchical hollow nanostructures can strengthen multiple refl ections of solar light and provide a large specifi c surface area and abundant reaction sites for photocatalytic water splitting.Owing to the construction of the p-n heterostructure as an ideal catalytic model with highly matched band alignment at Cu_(2)S/CdS interfaces,the emerging internal electric fi eld can facilitate the space separation and transfer of photoexcited charges between CdS and Cu_(2)S and also enhance charge dynamics and prolong charge lifetimes.Notably,the unique hollow Cu_(2)S/CdS architectures deliver a largely enhanced visible-light-driven hydrogen generation rate of 4.76 mmol/(g·h),which is nearly 8.5 and 476 times larger than that of pristine CdS and Cu_(2)S catalysts,respectively.This work not only paves the way for the rational design and fabrication of hollow photocatalysts but also clarifi es the crucial role of unique heterostructure in photocatalysis for solar energy conversion.

A New Kind of Conjugate-nested Central Configurations in Consisted of One Regular Tetrahedron and One Regular Octahedron

A new case configuration in R^3, the conjugate-nest consisted of one regular tetrahedron and one regular octahedron is discussed. If the configuration is a central configuration, then all masses of outside layer are equivalent, the masses of inside layer are also equivalent. At the same time the following relation between ρ（r =√3/3ρ is the radius ratio of the sizes） and mass ratio τ=~↑m/m must be satisfied τ=~↑m/m=ρ（ρ＋3）（3＋2ρ＋ρ^2）^-3/2＋ρ（-ρ＋3）（3-2ρ＋ρ^2）^-3/2-4.2^-3/2ρ^-2-^-1ρ^-2/2（1＋ρ）（3＋2ρ＋ρ^2）^-3/2＋2（ρ-1）（3-2ρ＋ρ^2）^-3/2-4（2√2）^-3ρ, and for any mass ratio τ, when mass ratio r is in the open interval （0, 0.03871633950 ... ）, there exist three central configuration solutions（the initial configuration conditions who imply hamagraphic solutions） corresponding radius ratios are r1, r2, and r3, two of them in the interval （2.639300779… , ＋∞） and one is in the interval （0.7379549890…, 1.490942703… ）. when mass ratio τ is in the open interval （130.8164950… , ＋∞）, in the same way there have three corresponding radius ratios, two of them in the interval （0, 0.4211584789... ） and one is in the interval （0.7379549890…, 1.490942703…）. When mass ratio τ is in the open interval （0.03871633950…, 130.8164950…）, there has only one solution r in the interval （0.7379549890…, 1.490942703… ）.

Syntheses, Characterization and Crystal Structures of Two Novel Oxazoline Based Titanium Complexes

Two novel titanium compounds [（E）-N＇-（2,6-diisopropylphenyl）-N-（2-（4,4-dimethyl-4,5-dihydrooxazol-2-yl）phenyl）benzimidamido]titanium trichloride（1） and [N-（2-（4,4-dimethyl-4,5-dihydrooxaz-ol-2-yl）phenyl）-6-（2,4,6-triisopropyl-phenyl） pyridin-2-amido]titanium trichloride（2） were synthesized by reacting the corresponding ligand with diethylaminetitaniumtrichloride in equal molar ratios. The compounds were characterized with 1H, 13 C NMR, elemental analysis and single-crystal X-ray diffraction analysis. The geometry of both compounds is distorted octahedron. The three nitrogen and one chlorine atoms are in the equatorial plane. Compound 1 crystallizes in orthorhombic system, space group P212121 with a = 10.3520（4）, b = 16.5750（7）, c = 17.1530（7） , Z = 4 and V = 2943.2（2）3. Compound 2 crystalizes in the monoclinic system, space group P21/n with a = 15.6400（11）, b = 10.12.60（7）, c = 22.9120（14）, Z = 4 and V = 3558.5（4）3. The synthesized compounds were employed for ethylene polymerization catalysis. Both complexes showed moderate activity when activated with dry methylaluminoxane（d MAO） and complex 1 produced very high molecular weight polyethylene.

Synthesis and Crystal Structure of Cu(II) Complex with 2,9-Bis(n-2',5'-diazaheptanyl)-1,10-phenanthroline

The Cu(II) complex with the ligand 2,9-bis(n-2?5?diazaheptanyl)-1,10-phenan- throline (L) has been synthesized and characterized by single-crystal X-ray diffraction. It crys- tallizes in the monoclinic system, space group P21/n with a = 12.549(4), b = 13.544(4), c = 16.767(5) ? = 107.179(5), C22H32Cl2N6CuO8, Mr = 642.98, V = 2722.5(13) 3, Z = 4, Dc = 1.569 g/cm3, ?= 1.056 mm-1, F(000) =1332, the final R = 0.0733 and wR = 0.1581. The X-ray analysis revealed that the Cu(II) ion is coordinated by six nitrogen atoms of the ligand, in which two nitrogen from phenanthroline and another two from the imine groups near phenanthroline are in the equatorial plane while the two from imine groups at the end of both arms in the axial positions. The coordination geometry can be described as a compressed octahedron.

A Research for a Division of Regular Polyhedron by Rhombic Dodecahedron

Abstract：A space-filling polyhedron is a polyhedron which ＇tile＇ space, analogous to the way of certain polygons tiled the plane. The cube is the unique space-filling platonic solid. If we make line connections the center with the vertices in the certain cube, the cube is divided into six pyramids. And if we glued six pyramids to the faces of the cube, we obtain a ＇rhombic dodecahedron＇. Since cubes are packing a space, rhombic dodecahedra are also space-filling polyhedra and a rhombic dodecahedron is divided into two regular tetrahcdra and one regular octahedron. In this study, we present how rhombic dodecahedron can be split into tetrahedra and octahedron. In this process, we can research a variety of divisions of regular polyhedron.

Effect of coordination structure of aluminum on its activation from minerals and Oxisols during their acidification

The types and contents of phyllosilicate minerals in soils play an important role in soil acidification,as soil acid buffering capacity varies with the composition of the phyllosilicate minerals.In addition to aluminum-oxygen(Al-O)octahedrons,a certain number of Al-O tetrahedrons exist in phyllosilicate minerals due to the isomorphic substitution of silicon ion(Si4+)by aluminum ion(Al3+)in Si-O tetrahedrons of minerals.However,the effect of the two coordination structures of Al on the release of Al during mineral acidification has not yet been investigated.Therefore,the differences in Al activation in phyllosilicate minerals and soils with different Al coordination structures were investigated through constant-p H experiments and27Al magic-angle spinning nuclear magnetic resonance(MAS-NMR)measurements.The results of27Al MAS-NMR spectra showed that kaolinite contained Al-O octahedrons,phlogopite and illite contained Al-O tetrahedrons,and vermiculite composite contained both octahedral and tetrahedral Al.At p H<5.1,the content of Al released from minerals during simulated acidification followed the order:illite>vermiculite composite>phlogopite>kaolinite,which was consistent with the orders of cation exchange capacity and content of tetrahedral Al of the minerals.According to the rate constants,the Al release rates were in the order of phlogopite>illite>vermiculite composite>kaolinite at p H 4.8.Except for phlogopite,the Al release rates in these minerals increased with decreasing suspension p H.Therefore,the Al release contents and rates were greater in phlogopite,illite,and vermiculite composite containing Al-O tetrahedrons than in kaolinite containing only Al-O octahedrons.Two Oxisols derived from basalt with different ages were selected for similar studies.The27Al MAS-NMR spectra of the Oxisols showed that the 0.01-million-year(Ma)Oxisol contained both octahedral and tetrahedral Al,while the 1.33-Ma Oxisol contained only Al-O octahedrons.The contents of both exchangeable and soluble Al released from the 0.01-Ma Oxisol were greater than those from the 1.33-Ma Oxisol when the two soils were acidified to the same p H.The results from minerals and soils confirmed that Al was more readily released into solution and exchangeable sites as soluble and exchangeable Al in Al-O tetrahedrons than in Al-O octahedrons during the acidification of soils and minerals.The findings of this study will provide useful references for investigating the mechanisms of solid phase Al release and for mitigating soil acidification and inhibiting Al activation in different soil types.

Inhibiting oxygen vacancies and twisting NbO_(6) octahedron in erbium modified KNN-based multifunctional ceramics

It is a challenge to obtain highly tunable multifunctional performances in one ferroelectric system by a simple approach to meet the miniaturization,integration,and functionalization requirements of advanced electronic components.Herein,rare earth erbium(Er)modulated 0.9K_(0.5)Na_(0.5)NbO_(3)-0.1Sr(1-x)Er_(x)Ti_((1-x/4))O_(3),(0.9KNN-0.1ST:xEr)transparent-photoluminescent-ferroelectric energy storage multifunctional ceramics are prepared to solve this problem.The effect of lattice distortion and oxygen vacancies by Er doping on the optical and electrical properties is systematically investigated.The Er^(3+)ions can introduce a large distortion of the NbO_(6) octahedron by replacing the A-site in KNN-based ceramics.Thanks to the higher c/a ratio and lower oxygen vacancy content are simultaneously obtained in 0.9KNN-0.1ST:0.1Er ceramics.The effective energy storage density(Wrec)of 0.86 J/cm^(3),excellent near-infrared transmittance of 51.7%(1100 nm)and strong green upconversion photoluminescence are achieved in this multifunctional ceramic.This study provides a solid basis for rare earth ions doped ferroelectric ceramics with tunable multifunctional properties and has significant potential for applications in optoelectronic devices.

On self-affine tiles that are homeomorphic to a ball

Let M be a 3×3 integer matrix which is expanding in the sense that each of its eigenvalues is greater than 1 in modulus and let D?Z^(3)be a digit set containing|det M|elements.Then the unique nonempty compact set T=T(M,D)defined by the set equation MT=T+D is called an integral self-affine tile if its interior is nonempty.If D is of the form D={0,v,...,(|det M|-1)v},we say that T has a collinear digit set.The present paper is devoted to the topology of integral self-affine tiles with collinear digit sets.In particular,we prove that a large class of these tiles is homeomorphic to a closed 3-dimensional ball.Moreover,we show that in this case,T carries a natural CW complex structure that is defined in terms of the intersections of T with its neighbors in the lattice tiling{T+z:z∈Z^(3)}induced by T.This CW complex structure is isomorphic to the CW complex defined by the truncated octahedron.

Atomic-level unveiling secondary recrystallization enabled microand macroscopic polarization enhancement for piezophotocatalytic oxygen activation

Piezoelectric semiconductors bear the bifunctional photocatalysis and piezocatalysis,while the absent or weak internal charge driving force severely restricts its catalytic activity.Developing polarization strategy is desirable,and particularly understanding its mechanism from a microscopic perspective remains scanty.Herein,we report a secondary recrystallization approach to achieving the simultaneous micro-and macroscopic polarization enhancement on Bi2WO6 nanosheets for boosting piezo-photocatalytic oxygen activation,and unravel the mechanism at an atom-level.The secondary recrystallization process not only results in a strengthened distortion of[WO6]octahedra with distortion index enhancement by~20%for a single octahedron,but also enables lateral crystal growth of nanosheets along the ab plane(av.50 to 180 nm),which separately allows the rise in dipole moment of unit cell(e.g.,1.63 D increase along a axis)and the stacking of the distorted[WO6]octahedron to accumulate the unit cell dipole,collectively contributing to the considerably strengthened spontaneous polarization and piezoelectricity.Besides,exposure of large-area{001}front facet enables more efficient capture and conversion of stress into piezo-potential.Therefore,the well-recrystallized Bi2WO6 nanosheets exhibit considerably promoted piezo-photocatalytic reactive oxygen species generation,given the decreased specific surface area.This work presents a feasible methodology to regulate inside-out polarization for guiding carriers transfer behavior,and may advance the solid understanding on the intrinsic mechanism.

Platinum nickel alloy-MXene catalyst with inverse opal structure for enhanced hydrogen evolution in both acidic and alkaline solutions

The development of an efficient Pt-based electrocatalyst in acidic and alkaline electrolytes is of great significance to the field of electrocatalytic hydrogen evolution.Herein,we report a strategy for in situ growth of Pt_(3)Ni truncated octahedrons on Ti3C2Tx nanosheets and then obtain an ordered porous catalyst via a template method.Meanwhile,we use the finite element calculation to clarify the relationship between the component structure and performance and find that the performance of the spherical shell microstructure catalyst is higher than that of the disc structure catalyst,which is also verified by experiments.The experimental analysis shows that the ordered porous catalyst is conducive to enhancing electrocatalytic hydrogen evolution activity in acidic and alkaline electrolytes.In an acidic solution,the overpotential is 25 mV(10 mA·cm^(−2)),and the Tafel slope is 22.86 mV·dec−1.In an alkaline solution,the overpotential is 44.1 mV(10 mA·cm^(−2)),and the Tafel slope is 39.06 mV·dec−1.The synergistic coupling between Ti3C2Tx and Pt_(3)Ni nanoparticles improves the stability of the catalyst.The in situ growth strategy and design of microstructure with its correlation with catalytic performance represent critical steps toward the rational synthesis of catalysts with excellent catalytic activity.

Effect of Sb-induced oxygen octahedral distortion on piezoelectric performance and thermal stability of Pb(In,Nb)O_(3)-Pb(Hf,Ti)O_(3)ceramics

The combination of excellent thermal stability and outstanding electrical performance is of great sig-nificance for piezoelectric ceramics.Herein,we have prepared 0.11Pb(In_(0.5)Nb_(0.5))O_(3)-0.89Pb(Hf_(0.47)Ti_(0.53))O_(3)-Sb_(2)O_(5)(PIN-PHT-x Sb)ceramics by solid-phase method and investigated the effect of oxygen octahedral lattice distortion on microstructure and macroscopic electrical properties.The distortion index of oxygen octahedra is studied by Rietveld refinement,showing that optimal octahedral distortion can soften B-O repulsion,disrupt long-range ordered ferroelectric domains,and enhance local heterogeneities,signifi-cantly increasing piezoelectric properties.Moreover,outstanding thermal stability and ultrahigh piezo-electric response of PIN-PHT-1.2Sb ceramics are realized under the synergistic influence of octahedral distortion,excellent density,and large grain size.Compared with PIN-PHT ceramics,PIN-PHT-1.2Sb ce-ramics exhibit ultrahigh piezoelectric responses(d_(33)=706 pC/N,k_(p)=0.68,ε_(r)=3244),a high Curie temperature(T C)of 300℃,excellent thermal stability,and anti-fatigue properties.

Engineering yolk-shell CuCo_(2)S_(4)@Cu_(2)O Z-scheme nanoreactors for accelerating generation of value-added chemicals and of degradation multi-organic contaminants

The synthesis of solar-driven chemical value-added products and the degradation of pollutants is a promising approach for sustainable development. However, achieving these works via photocatalysts with efficient charge-separation, photo-absorption is challenging. A yolk-shell CuCo_(2)S_(4)@Cu_(2)O Z-scheme nanoreactor (YS-CuCo_(2)S_(4)@Cu_(2) O-NR) with octahedron Cu_(2)O as the core and tubular CuCo2 S4 as the shell, has been synthesized by regulating composition and morphology. YS-CuCo_(2)S_(4)@Cu_(2)O-NR shows superior photocatalytic activities for producing H_(2) O_(2) collaborates by selective oxidation of benzyl alcohol (BA) to high value-added benzaldehyde (BAD)/utilized Fenton-like reaction to degrade multi-pollutants through space-confinement effect, reaching 80% conversion and 99% selectivity of BA, a yield of 12 mM g^(−1) for H_(2)O_(2) and above 90% degradation efficiency for multi-pollutants. A photocatalysis nanoconfinement reactor system is proposed and demonstrated by using yolk-shell to enhance the performance of the chemical reaction. Mechanism studies show that the yolk-shell provides confined space to accelerate redox reaction kinetics;while the inner void promotes light harvesting and keeps yolk Cu_(2) O from deactivation;combined with the Z-scheme charge transfer, engineering Cu^(+) /Cu^(2+) active composition, they are favorable for enhancing the H_(2) O_(2) generation and Fenton-like activity. These findings provide new opportunities for application of yolk-shell Z-scheme metal-oxide-based photocatalysts.

Synthesis and Electrocatalytic Oxygen Reduction Properties of Truncated Octahedral Pt3Ni Nanoparticles

Pt3Ni nanoparticles have been obtained by shape-controlled synthesis and employed as oxygen reduction electrocatalysts for proton exchange membrane fuel cells （PEMFC）. The effects of varying the synthesis parameters such as the types of the capping agent and the reducing agent, and the reaction time have been systematically studied. The as-prepared PtBNi nanoparticles were subjected to a butylamine-based surface treatment in order to prepare carbon-supported electrocatalysts. The Pt3Ni electrocatalysts show an area- specific activity of 0.76 mA/cm2（pt） at 0.9 V in an alkaline electrolyte, which is 4.5 times that of a commercial Pt/C catalyst （0.17 mA/cm2 （Pt））. The mass activity reached 0.30 A/mg（Pt） at 0.9 V, which is about twice that of the commercial Pt/C catalyst. Our results also show that the area-specific activities of these carbon-supported Pt3Ni electrocatalysts depend strongly on the （111） surface fraction, which is consistent with the results of a study based on Pt3Ni extended single-crystal surfaces.

Shape-Controlled Synthesis of Mn_(3)O_(4) Nanocrystals and Their Catalysis of the Degradation of Methylene Blue

Various sizes and shapes of Mn_(3)O_(4) nanocrystals have been prepared in a one-pot synthesis in extremely dilute solution by soft template self-assembly. To better control size and shape, the effects of varying the growth time, reaction temperature, surfactant, and manganese source were examined. The average size of octahedral Mn_(3)O_(4) crystallites was found to be related to the reaction time, while higher reaction temperature (150 °C) and the use of a cetyltrimethylammonium bromide/poly(vinylpyrrolidone) (CTAB/PVP) mixture allowed construction of a better-defined octahedral morphologies. When PVP or poly(ethylene oxide)-poly(propylene oxide) (P123) was used as template, large-scale agglomeration resulting in loss of the octahedral morphology occurred and crystallites with a quasi-spherical shape were obtained. The nano-octahedral crystallites were shown to be an efficient catalyst for the oxidation of methylene blue.

Highly porous Pt-Pb nanostructures as active and ultrastable catalysts for polyhydric alcohol electrooxidations

Highly porous materials have attracted intensive attention in the past decades due to their unique geometrical configuration, unusual structural features, and outstanding physicochemical properties, but the facile creation of porous metal nanomaterias remains a formidable challenge. Most reports focused on using hard templates to create porous metal nanomaterials via sacrificing the templates. Herein, we have created a new class of porous PtPb/Pt nanocrystals(NCs)with well-defined morphology, composition and porosity through a facile chemical etching approach. Due to the highly open three-dimensional(3D) structure and alloy effect, the porous PtPb/Pt NCs exhibit enhanced performances towards polyhydric alcohol electrooxidations with the optimized porous Pt3Pb nanoplates exhibiting superior activities of 1.75 mA cm-2 and 1.19 A mgPt-1 for ethylene glycol oxidation reaction(EGOR) and of 1.46 m A cm-2 and 1.00 A mg-1Pt for glycerol oxidation reaction(GOR) that are much higher than the commercial Pt/C(0.34 mA cm-2 and 0.22 A mgPt-1 for EGOR, 0.30 mA cm-2 and 0.20 A mgPt-1for GOR). In addition, the porous Pt3Pb nanoplates can endure the long-term stability in EG and glycerol oxidation reactions with limited activity and structure change after 20,000 and 5,000 cycles,respectively, showing a highly promising class of porous Ptbased electrocatalysts for direct polyhydric alcohol fuel cells and beyond.

Thermal annealing synthesis of double-shell truncated octahedral Pt-Ni alloys for oxygen reduction reaction of polymer electrolyte membrane fuel cells

Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction(ORR)of polymer electrolyte membrane fuel ceils(PEMFCs),whose tricks lie in welldesigned structures and surface morphologies.In this paper,a novel synthesis of truncated octahedral PtNi_(3.5) alloy catalysts that consist of homogeneous Pt-Ni alloy cores enclosed by NiO-Pt double shells through thermally annealing defective heterogeneous PtNi35 alloys is reported.By tracking the evolution of both compositions and morphologies,the outward segregation of both PtOv and NiO are first observed in Pt-Ni alloys.It is speculated that the diffusion of low-coordination atoms results in the formation of an energetically favorable truncated octahedron while the outward segregation of oxides leads to the formation of NiO-Pt double shells.It is very attractive that after gently removing the NiO outer shell,the dealloyed truncated octahedral core-shell structure demonstrates a greatly enhanced ORR activity.The asobtained truncated octahedral Pt_(2.1)Ni core-shell alloy presents a 3.4-folds mass-specific activity of that for unannealed sample,and its activity preserves 45.4%after 30000 potential cycles of accelerated degradation test(ADT).The peak power density of the dealloyed truncated octahedral Pt2jNi core-shell alloy catalyst based membrane electrolyte assembly(MEA)reaches 679.8 mW/cm^(2),increased by 138.4 mW/cm^(2) relative to that based on commercial Pt/C.