Pt/Mo2C heteronanosheets for superior hydrogen evolution reaction

One of the most primary challenges to achieve large-scale hydrogen generation from water electrolysis is the sluggish kinetics and noble metal dependence of cathodic hydrogen evolution reaction(HER).By considering the excellent water dissociation catalytic activity of Mo2C, abundant Pt/Mo2C interfaces were facilely engineered via galvanic replacement(gr) by using Mo/Mo2C nanosheets as self-sacrificed templates to alter the alkaline HER mechanism on Pt based catalyst. The rational designed interface-rich gr-Pt/Mo2C catalyst exhibited excellent activity with the overpotential to drive 10 mA/cm2 current density decreased by 18.5 mV compared with the commercial Pt/C catalyst. 34.3 mV/dec Tafel slope confirms the Volmer-Tafel HER route on gr-Pt/Mo2C in alkaline condition. Platinum utilization is calculated to be improved by 9.7 times by considered the low Pt loading in the gr-Pt/Mo2C catalyst. With its satisfied stability, the scalable gr-Pt/Mo2C catalyst shows promising application potential in industrial electrolysis systems.

Universal order-parameter and quantum phase transition for two-dimensional q-state quantum Potts model

We investigate quantum phase transitions for q-state quantum Potts models(q=2,3,4)on a square lattice and for the Ising model on a honeycomb lattice by using the infinite projected entangled-pair state algorithm with a simplified updating scheme.We extend the universal order parameter to a two-dimensional lattice system,which allows us to explore quantum phase transitions with symmetry-broken order for any translation-invariant quantum lattice system of the symmetry group G.The universal order parameter is zero in the symmetric phase,and it ranges from zero to unity in the symmetry-broken phase.The ground-state fidelity per lattice site is computed,and a pinch point is identified on the fidelity surface near the critical point.The results offer another example highlighting the connection between(i)critical points for a quantum many-body system undergoing a quantum phase-transition and(ii)pinch points on a fidelity surface.In addition,we discuss three quantum coherence measures:the quantum Jensen–Shannon divergence,the relative entropy of coherence,and the l1norm of coherence,which are singular at the critical point,thereby identifying quantum phase transitions.

Comparison of microstructures and mechanical properties of composite extruded AZ31 sheets

The microstructures and mechanical properties of the composite extruded AZ31/AZ31 and AZ31/4047 Al sheets were investigated and made a comparison to the conventional extruded AZ31 sheet.Owing to the introduced intense shear deformation at the interface during the composite extrusion,grain refinement and tilted texture were detected in AZ31 layers of the AZ31/AZ31 and AZ31/4047 Al sheets,while the conventional extruded AZ31 sheet exhibited a relative coarse,inhomogeneous microstructure and strong basal texture.The compressiontension yield ratio was increased gradually from the AZ31 to the AZ31/AZ31 and AZ31/4047 Al sheets.Besides,the AZ31/4047 Al sheet could successfully accomplish the whole bending forming process at room temperature,while the AZ31 and AZ31/AZ31 sheets were both bend-formed to failure with significant cracks in the outer tensile region under the identical bending parameters.Moreover,under the same bending strain,both the outward offset degree of strain neutral layer and the sheet thickening were more serious in the AZ31/4047 Al composite sheet than those of the AZ31 and AZ31/AZ31 sheets.The foremost reason was the quite wide gap of material properties between Mg alloy AZ31 layer(tensile loading in the outer region)and Al 4047 layer(compressive loading in the inner region).

Coprinus comatus-derived nitrogen-containing biocarbon electrocatalyst with the addition of self-generating graphene-like support for superior oxygen reduction reaction

The development of nitrogen-rich biomassderived carbon catalysts provides an attractive perspective to substitute for Pt-based electrocatalysts for oxygen reduction reaction(ORR). We here report a facile strategy for synthesis of a nitrogen-doped biocarbon/graphene-like composite electrocatalyst by pyrolyzing a solid-state mixture of coprinus comatus biomass and melamine under nitrogen protection. The graphtic carbon nitride formed by polycondensation of melamine at 600 °C acts as a selfsacrificing template to generate the nitrogen-doped graphene-like sheet, which can function as an inserting agent and self-generating support. The composite catalyst exhibits the most promising catalytic activity towards the fourelectron ORR with a half-wave potential of around 0.83 V(vs. RHE), and more excellent stability and tolerance to methanol/ethanol compared to the commercial Pt/C catalyst. It is interestingly found that both a higher content of nitrogen and a larger ratio of graphitic-nitrogen species,which may derive from self-addition of graphene-like support into the catalyst, can effectively improve the electrocatalytic activity. The planar N group may be the nitrogen functionality that is most responsible for maintaining the ORR activity in alkaline medium. This study can largely encourage the exploration of high-performance carbon-based catalysts from economical and sustainable fungus biomass.

Unveiling annealing texture formation and static recrystallization kinetics of hot-rolled Mg-Al-Zn-Mn-Ca alloy

The development of Mg-Al-Zn-Mn-Ca series alloys provides a potential prospect to achieve high strength and formability at room temperature(RT).The formation of elliptical annular texture is treated as a crucial factor for the enhanced RT formability.However,the origin of such an elliptical annular texture formation has been rarely reported.Herein,we unveiled the formation and evolution of elliptical annular texture in the hot-rolled Mg-1.6 Al-0.8 Zn-0.4 Mn-0.5 Ca(AZMX1100,wt.%)alloy after annealing at different temperatures for 1 h,and its static recrystallization(SRX)kinetics in given annealing temperature for different time.The results revealed that the formation of elliptical annular texture in the hot-rolled AZMX1100 alloy after annealing was derived from nucleation-oriented SRX mechanism,which took place in 200-300°C,induced by cracked chain-shaped Al2 Ca phases,contraction twins,intersections of double twins,intersections of double twins and grain boundaries and non-basal slips.On further annealing from300-450°C,the grains with 45°–70°transverse direction(TD)preferentially grew,which made elliptical annular texture extended along the TD.Based on the Johnson-Mehl-Avrami-Kolmogorov(JMAK)model,Avrami exponent n value was estimated to be 0.68–1.02,attributed to non-random SRX nucleation,giving rise to the lower activation energy QRof nucleation of^74.24 k J/mol.Since the co-segregation of Al,Zn and Ca atoms in grain boundaries created a strong interaction of solutes and grain boundaries,the hot-rolled AZMX1100 alloy exhibited the higher activation energy Qg(~115.48 k J/mol)of grain growth.

Photoluminescence properties of Tb^(3+) and Ce^(3+) co-doped Sr_2MgSi_2O_7 phosphors for solid-state lighting

Sr2MgSi2OT：Tb3＋,Ce3＋ phosphors were synthesized by solid-state reaction and placed in a muffle furnace in a reducing at- mosphere at 1300 ~C for 3 h. Photoluminescence properties and energy transfer were investigated. The Ce3＋/Tb3＋ energy transfer was thoroughly investigated by their emission/excitation spectra and photoluminescence lifetime, there was shortened lifetime of Ce3＋ （from 51.31 to 50.06 ns） which could support evidence of energy transfer from Ce3＋ to Tb3＋ in the host. The varied emitted color of Srj.97_yMgSi2OT：0.03Tb3＋,yCe3＋phosphors could be achieved by altering the concentration of Ce3＋, the chromaticity coordinates （x, y） varied from （0.225, 0.376） to （0.172, 0.231）. In Srl.96MgSi207：0.03Tb3＋,0.01 Ce3＋ phosphors, the results indicated that Sr2MgSi207：Tb3＋,Ce3＋ might be useful as tunable phosphors for ultraviolet white-light-emitting diodes.

Synthesis of carbon dots with a tunable photoluminescence and their applications for the detection of acetone and hydrogen peroxide

Carbon dots(CDs) with multi-color emissive properties and a high photoluminescent quantum yield(PLQY) have attracted great attention recently due to their potential applications in chemical,environmental,biological and photo-electronic fields.Solvent-dependent effect in photoluminescence provides a facial and effective approach to tune the emission of CDs.In this study,green emissive nitrogen-doped carbon dots(N-CDs) are synthesized from p-hydroquinone and ethylenediamine through a simple hydrothermal method.The as-prepared N-CDs possess a robust excitation-independent green luminescence and a high PLQY of up to 15.9%.Further spectroscopic characterization indicates that the high PLQY is achieved by the balance of nitrogen doping states and the surface passivation extent in CDs.The N-CDs also exhibit solvent-dependent multi-color emissive property and distinct PLQY in different solvents(the maximum can reach up to 25.3%).Furthermore,the as-prepared N-CDs are applied as fluorescence probes to detect acetone and H2O2 in water.This method has exhibited a low detection limit of acetone(less than 0.1 %) and a quick and linear response to the H_2O_2 with the concentration from 0 to 120 μmol/L.This work broadens the knowledge of applying CDs as probes in the bio and chemical sensing fields.

Near infrared molybdenum oxide quantum dots with high photoluminescence and photothermal performance

The synthesized near infrared molybdenum oxide quantum dots perform excellent red fluorescence imaging performance and photothermal performance,which have 600,650 and 700 nm three unique peaks excited at 540 nm,with a high quantum yield around 20%.Meanwhile,with 808 nm NIR laser excitation,10 mg/mL modified Molybdenum oxide quantum dots can increase temperature up to 72.2℃within 150 s and 77.7℃within 270 s,respectively.

Influence of minor Ce additions on the microstructure and mechanical properties of Mg-1.0Sn-0.6Ca alloy

The microstructure and mechanical properties of Mg-Sn-Ca-Ce alloys with different Ce contents(0.0,0.2,0.5,1.0 wt%)were studied at room temperature.Ce additions to ternary Mg-Sn-Ca alloy resulted in grain refinement as well as a change in the category of second phase from CaMgSn to(Ca,Ce)Mg Sn and Mg12Ce.The volume fraction of second phase increased with rising Ce content,which aggravated the restriction of DRXed grain growth during the extrusion process and eventually led to texture weakening of as-extruded Mg-Sn-Ca based alloys.In terms of plasticity,owing to vigorously activated basal slip and homogeneous distributed tensile strain in tension,the tensile ductility of as-extruded alloys reached the maximum value of 27.6%after adding 0.2 wt%Ce,which enhanced by about 26%than that of ternary MgSn-Ca alloy.However,further Ce additions(0.5 and 1.0 wt%)would coarsen the second phase particles and then impair ductility.The tension-compression yield asymmetry of as-extruded Mg-Sn-Ca ternary alloy was alleviated greatly via Ce additions,due to the joint effects of grain refinement,increased amount of strip distributed second phase particles and texture weakening.

Highly luminescence manganese doped carbon dots

Heteroatom doped carbon dots(CDs)with distinct merits are of great attractions in various fields such as solar cells,catalysis,trace element detection and photothermal therapy.In this work,we successfully synthesized blue-fluorescence and photostability manganese-doped carbon dots(Mn-CDs)with a quantum yield up to 7.5%,which was prepared by a facile one-step hydrothermal method with sodium citrate and manganese chloride.The Mn-CDs is the high mono-dispersity,uniform spherical nanoparticles.The Mn element plays a critical role in achieving a high quantum yield in synthesis of carbon dots,which was confirmed by the structure analysis using XPS and FTIR.Spectroscopic investigations proved that the decent PLQY and luminescence properties of Mn-CDs are due to the heteroatom doped,oxidized carbon-based surface passivation.In addition,the Mn-CDs are demonstrated as promising fluorescent sensors for iron ions with a linear range of 0–500 μmol/L and a detection limit of2.1 nmol/L(turn-off),indicating their great potential as a fluorescent probe for chemical sensing.

Current understanding and applications of the cold sintering process

In traditional ceramic processing techniques,high sintering temperature is necessary to achieve fully dense microstructures.But it can cause various problems including warpage,overfiring,element evaporation,and polymorphic transformation.To overcome these drawbacks,a novel processing technique called“tcold sintering process(CSP)”has been explored by Randall et al.CSP enables densification of ceramics at ultra-low temperature(<300℃)with the assistance o f transient aqueous solution and applied pressure.In CSP,the processing conditions including aqueous solution,pressure,temperature,and sintering duration play critical roles in the densification and properties of ceramics,which will be reviewed.The review will also include the applications of CSP in solid-state rechargeable batteries.Finally,the perspectives about CSP is proposed.

Convenient synthesis of twin-Christmas tree-like PbWO4 microcrystals and their photocatalytic properties

Novel twin-Christmas tree-like PbWO4 microcrystals have been prepared via a convenient aqueous solution route at room temperature under the assistance of 13- cyclodextrin （13-CD）. The product was characterized by XRD, EDX, SEM, TEM, UV-vis and PL and BET techniques. It was found that 13-CD plays an important role in the forming of twin-Christmas tree-like PbWO4 microcrystals. A five-step growth mechanism was proposed to explain the formation of such twin-Christmas tree-like structures. The photocatalytic performance of PbWO4 microcrystals was evaluated by measuring the decomposition rate of methylene blue （MB） and malachite green （MG） solution under the UV irradiation, and the photocatalytic results indicated that as-prepared PbWO4 microcrystals exhibit good and versatile photocatalytic activity as well as excellent recyclability.

Highly ordered Ag-TiO2 nanocomposited arrays with high visible-light photocatalytic activity

TiO2 is active only in the ultraviolet region. To enhance the active ability, a combined method consisting of the anodic oxidation method and the hydrothermal method was developed to prepare highly ordered Ag-TiO2 nanocomposited arrays. The anodic oxidation was used to synthesize amorphous nanotubes with high chemical activity that subsequently served as highly ordered templates in preparing the final sample. The amorphous nanotubes got converted to highly ordered Ag-TiO2 （anatase） arrays in the silver nitrate ＆ glucose aqueous solution via hydrothermal treatment. SEM and TEM results show that the Ag-TiO2 nanocomposite was composed of a large number of Ag nanoparticles and anatase TiO2 nanoparticles, and the morphology of those at the top of the arrays was found different from that of its trunk. The morphology evolution mechanism of the obtained sample was discussed. It is also revealed that the Ag-TiO2 nanocomposite has high visible-light photocatalytic activity.

提高聚合物太阳电池性能的新方法:两步溶解法制备电池活性层（英文）

本文以P3HT:PC_(61)BM和PTB7:PC_(71)BM两种有机光伏体系为研究对象,探讨了光伏材料的"两步"溶解处理对聚合物太阳电池性能的影响.P3HT:PC_(61)BM光活性层的光学与形貌表征揭示了P3HT的有序相结构和给/受体相分离结构可以被"两步"溶解处理进一步优化;瞬态荧光数据表明,P3HT:PC_(61)BM光活性材料经"两步"溶解处理后,激子的分离能力得到增强.经"两步"溶解处理后的器件性能较"一步"溶解处理的器件性能提高了24%.此外,同样的处理方式应用于PTB7:PC_(71)BM体系,可使器件的光伏性能提高8%.因此,光活性材料的"两步"溶解处理是一种简单、有效的提高聚合物光伏性能的优化方法.

Fabrication and photoluminescence characteristics of novel red-emitting Ba_(2)LuNbO_(6):Eu^(3+)double-perovskite phosphors on near UV WLEDs

Red emitting phosphors play a significant role in accelerating the improvement of illumination quality for white light emitting diodes(WLEDs).In this work,by using solid-state reaction method,an efficient novel Ba_(2)LuNbO_(6):Eu^(3+)phosphor with double-perovskite structure was successfully prepared.Here,a series of Ba_(2)LuNbO_(6):Eu^(3+)red phosphors can be efficiently pumped by the near-ultraviolet(UV)light and then present high-brightness at orange emission(598 nm,~5D_(0)→~7 F_(1))and red emission(610 nm,~5D_(0)→~7 F_(2)).The ratio values of 610 to 598 nm in Ba_(2)LuNbO_(6):Eu^(3+)phosphors exceed 1 when the content of Eu^(3+)is larger than 0.4 mol,because the occupation of Eu^(3+)ions is changed from Lu^(3+)ions with symmetric sites to Ba^(2+)ions with asymmetric sites.Besides,the optimized concentration of Eu^(3+)at the~5D_(0)→~7 F_(2)transitions is obtained when x=1,indicating that there is non-concentration quenching in Ba_(2)LuNbO_(6):Eu^(3+)phosphors.Moreover,the CIE chromaticity coordinates of Ba_(2)LuNbO_(6):Eu^(3+)was calculated to be(0.587,0.361),the color purity was calculated to be 72.26%and internal quenching efficiency(IQE)was measured to be 67%.Finally,the thermal stability of Ba_(2)LuNbO_(6):Eu^(3+)phosphors was also studied.Our work demonstrates that the novel double-perovskite red-emitting Ba_(2)LuNbO_(6):Eu^(3+)phosphors are prospective red emitting elements for WLEDs applications.

Diffusion behavior and reactions between Al and Ca in Mg alloys by diffusion couples

The diffusion behavior and reactions between AI and Ca in Mg alloys by diffusion couple method were investigated. Results demonstrate that Al2Ca is the only phase existing in the diffusion reaction layers. The volume fraction of Al2Ca in diffusion reaction layers increases linearly with temperature. The standard enthalpy of formation for intermetallic compounds was rationalized on the basis of the Miedema model. Al-Ca intermetallic compounds were preferable to form in the Mg-Al-Ca ternary system under the same conditions. Over the range of 350-400℃, the structure of Al2Ca is more stable than that of Al4Ca, Al14Ca13and Al3Ca8, The growth constants of the layer I, layer II and entire diffusion reaction layers were determined. The activation energies for the growth of the layer I, layer II and entire diffusion reaction layers were （80.74 ± 3.01 ） kJ/mol, （93.45 ±2.12） kJ/mol and （83.52 ±1.50） kJ/mot, respectively. In layer I and II, AI has higher integrated interdiffusion coefficients D^i^Int,layer layer than Ca. The average effective interdiffusion coefficients D^Al^eff values are higher than D^Ca^eff in the layer I and II.