The promoter is very important for effective catalysts,and the relationship among active species,promoter,and support is a hot topic in the field of catalysis.This work aims to investigate the influence of the promoter on the formation of effective active species.For this purpose,V was leached out from V-loaded TiO2(V/Ti)step by step,and the loaded V was classified into different species based on their performances in the catalytic oxidation of chlorobenzene.As a result,when V/Ti was co-doped with Mo or W,the chlorobenzene conversion rate was increased from 48.1%to 54.0%(Mo)or 61.0%(W)at210℃.The enhancement was attributed to the redistribution of V species.Specifically,7.8%of V was"Inactive"V on V/Ti.This"Inactive"V was transformed into an"Active"species.At the same time,"Highly-active V"amounts were increased from 86.0%(V_3.3/Ti)to 88.1%(WV_3.3/Ti)and 87.1%(MoV_3.3/Ti).According to the mechanism investigation,when W and Mo coexisted with V during the synthesis,V3+was oxidized into V⁵⁺,which is easily invaded into the TiO₂,created more strong acidic sites,and activated more active lattice oxygens.These are all in favor of the effective catalytic oxidation of chlorobenzene.The new understanding of the promoter effect will help to produce a more effective catalyst using the same amount of active species.

Tungsten(W)is considered a critical and strategic material,the recycling of which has proved extremely important due to the substantial amount of W-rich waste and rising demand for W products.This study provides a sound technological approach for efficient utilization of bulk W,achieving a high W destruction rate(rw)of 0.3 g·cm^-2·h^-1via electrochemical oxidation/in situ reduction of W electrodes in oxalic acid under alternating current(AC)with varying symmetries to synthesize WO_3-xnanopowders(NPs).Amorphous-crystalline dual-phase reduced WO_3-xNPs featuring dense and porous nanoarchitectures were synthesized using asymmetrical and symmetrical AC,respectively.The nano scale interconnecting flaky WO_3-xstructure arises from the synergy of high anodic voltage etching and the release of H₂microbubbles,boosting the exfoliation of WO₃flakes.The optimized WO_3-xNP exhibits superior electrochemical and electrochromic properties,attributed to the increased surface capacitance alongside an extra contribution from intercalation pseudocapacitance.The number of WO_3-xlayers deposited by the spin coating technique and the annealing temperature have a significant impact on the electrochemical and electrochromic characteristics of the WO₃film.An increase in the transferred charge density(Q),coloring/bleaching time(t_c/t_b)values,and areal capacitance was observed,alongside a decrease in optical modulation(ΔT)and coloration efficiency(CE)with an increasing number of WO₃layers.WO₃produced at a lower temperature outperforms WO₃treated at 400-500℃,particularly in fast switching,enhanced efficiency,and reversibility.TheΔT of 68.7%,CE of 47.9 cm²·C^-1,areal capacitance of 53.5 mF·cm^-2,and reversibility close to 100%were achieved in H₂SO₄for the optimized WO_3-xfilm.The research aligns with the ongoing development strategy of the circular economy and validates the promising features of the efficient recycling of W-containing spent resources through an environmentally sustainable electrochemical approach.

The urgent need to overcome the strength-ductility trade-off of nickel-aluminum bronze(NAB)in deep-sea engineering motivates the design of a Cu-bearing multi-principal element alloy(MPEA),Cu₃₅Ni₃₅Co₃₀,via magnetic levitation melting.The as-cast Cu₃₅Ni₃₅Co₃₀ MPEA exhibits a dual face-centered cubic(FCC)structure with superior mechanical properties(yield strength:~503 MPa,ultimate tensile strength:~686 MPa,total elongation:~11.0%)over its counterparts fabricated by vacuum arc melting.A single-phase FCC structure was obtained by homogenizing at 1030℃ for 15 h.Cold rolling and postdeformation annealing(PDA)were used to construct heterogeneous grain structures,which were achieved in PDA-treated samples at 1030℃ for 45 s(PDA-1030-45s)and 60 s(PDA-1030-60s).The PDA-1030-45s sample,composed of nano-sized recrystallized grains and residual deformed grains(RDGs),showed the best strength among the PDA-treated samples(a yield strength of~864 MPa,an ultimate tensile strength of~959 MPa,and a total elongation of~13.4%).The PDA-1030-60s sample with micro-sized recrystallized grains and RDGs exhibits an excellent combination of strength and ductility,showing a yield strength of~560 MPa,an ultimate tensile strength of~761 MPa,and a total elongation of~32.9%.These mechanical strengths are superior to those reported by NAB.The dominant strengthening mechanisms of the PDA-1030-45s and the PDA-1030-60s samples are dislocation strengthening and hetero-deformation-induced strengthening,respectively.

Martensitic transformation offers a pathway to overcome the room-temperature brittleness of refractory high-entropy alloys(RHEAs).The resulting extensive formation of the hexagonal close-packed(hcp)α-martensite necessitates deformation coordination via twinning to sustain plasticity during mechanical loading.However,the synergistic formation of multiple twin types and their effect on work hardening remain unclear.Employing advanced characterization techniques,this study identifies three primary martensitic twin systems({1011},{1012},and{1341}),two secondary twin configurations({1011}-{1341}and{1341}-{1011}),and three{1341}twin variants in metastable Ti₂₇Zr₄₀Hf₂₃Ta₁₀RHEAs.The presence of multiple martensitic twins generates dense twin interfaces that refine the grain structure while effectively hindering dislocation motion,thereby enhancing strain hardening capacity.The coexistence of multiple martensitic twins increases the number of independent slip systems within grains and induces variations in slip systems across different regions of the grains.This heterogeneity in slip systems accommodates multi-directional plastic deformation,consequently improving the material's sustained hardening capability.These findings underscore the critical role of synergistic twinning mechanisms in governing the work hardening of metastable martensitic RHEAs.

The methanol oxidation reaction is a critical half-reaction in direct methanol fuel cells(DMFCs),but its efficiency is limited by the low activity and poor stability of traditional electrocatalysts.This study reports the development of a high-performance PtCo/Mo₂CT_xcatalyst for methanol oxidation in DMFCs.Synthesized by depositing PtCo alloy nanoparticles on Mo₂CT_xsheets prepared via cetyltrimethylammonium bromide-assisted etching of Mo2Ga2C,the PtCo/Mo₂CT_xcatalyst achieved enhanced interlayer spacing and excellent dispersion of active sites.The optimized PtCo/Mo₂CT_xcatalyst exhibited remarkable catalytic activity,reaching a mass activity of 2296 mA·mg_Pt^-1—6.5 times that of commercial Pt/C.Electrochemical studies confirmed the catalyst's low charge transfer resistance,high electrochemical surface area,and strong CO antipoisoning ability.Stability tests showed that the catalyst retained 62.26%activity after 1000 cycles.These improvements are attributed to the synergistic effects between Pt and Co,the conductive and layered structure of Mo₂CT_x,making PtCo/Mo₂CT_xa promising,durable anode material for DMFCs in sustainable energy applications.

Successful synthesis of rGO@Gd₂TiIn₂O₇nanocomposite(rGO@GTINC)as an effective electrocatalytic material for hydrazine detection is reported.The desirable rGO@GTINC was constructed under a simple hydrothermal method using key precursors in stoichiometric proportions.Advanced analytical and spectroscopic procedures were used to ascertain the structural and physico-chemical characteristics of rGO@GTINC.Characterization results provided critical insights into the well-defined crystalline structure and improved size uniformity achieved through the successful incorporation of rGO within the nanocomposite,ensuring stability and structural integrity.For electrochemical analysis,as-synthesized rGO@GTINC was modified onto a glassy carbon electrode(GCE),resulting in the GCE/rGO@GTINC configuration.Investigations confirmed that the integration of rGO@GTINC into the working electrode significantly enhanced the sensing performance.The electrochemical qualities of rGO enhanced the electron transfer rate,resulting in a lower peak potential and an increased oxidation peak current.The constructed rGO@GTINC sensor demonstrated an extensive linear range of hydrazine sensing(1-120μmol·L)with a low detection limit of 31 nmol·L^-1.The constructed rGO@GTINC sensor's good recovery rate in the real sample analysis ensures accurate detection and quantification of hydrazine in food samples.The prepared sensor showed acceptable reproducibility,stability,and good selectivity toward hydrazine and provided an effective approach to using electrochemical hydrazine sensing in different food beverages and environmental samples.

To meet the increasing demand for continuously enhancing engineering performance and energy efficiency in a variety of aerospace and energy applications,structural materials with high strength at ultra-high temperatures are urgently required.In the past decade,refractory multi-principal element alloys(RMPEAs),particularly those containing elements with high melting temperatures(T_m)such as W and Ta(hereafter denoted as WTa-RMPEAs),have garnered extensive interest due to their exceptional strengths and thermally stability at high temperatures.Characterized by high T_m,sluggish diffusion,and severe lattice distortion,WTa-RMPEAs exhibit chemical composition fluctuations at different scales,leading to unique mechanical properties and deformation behavior.In this paper,an initial summary is provided of the mechanical properties of typical WTa-RMPEAs at room and high temperatures and the differences in deformation behavior and underlying mechanisms between RMPEAs and conventional alloys are discussed.Additionally,strengthening and toughening strategies and the suggested deformation mechanisms were reviewed.Finally,the challenges in revealing the actual deformation mechanism of WTa-RMPEAs were described,and a brief perspective on the future research of the mechanical behavior of WTa-RMPEAs was proposed.

Oxygen-induced microstructural evolution critically governs the long-term reliability of refractory multi-principal element alloys(RMPEAs)in extreme environments,where oxygen ingress during prolonged high-temperature service can drastically alter micro structural stability and mechanical performance,yet its atomic-scale mechanisms remain poorly understood.Here,oxygen's dual role in NbZrTi-based RMPEAs is systematically revealed through aging experiments at 650℃for 48and 168 h,combined with multiscale characterization.High-oxygen alloys(3 at.%O)exhibited multi-phase precipitation,including Zr-O-enriched hexagonal close-packed and dual body-centered cubic phases(Zr+Ti-O-rich and Nb+Ti-rich),governed by oxygen redistribution and thermodynamic stabilization.Contrary to conventional precipitation hardening,oxygen segregation gradients at the grain boundaries induced lattice distortion mitigation in the matrix,leading to a twostage age-softening behavior:rapid initial hardness reduction(20%within 48 h)followed by a plateau regime.The interplay between oxygen-mediated phase separation and concentration-dependent solute partitioning highlights the delicate balance required to optimize RMPEAs for high-temperature applications.These findings establish oxygen concentration thresholds and grain boundary engineering as critical design parameters for RMPEAs,enabling simultaneous optimization of radiation resistance and century-scale stability in next-generation nuclear reactor structure materials.

Maintaining thermal stability is a key concern for the potential application of multi-principal-element alloys(MPEAs)at elevated temperatures,particularly in the intermediate temperature range.In this regime,the thermodynamic dominance of the entropy term over enthalpy may diminish,while atomic migration remains kinetically active.In this study,the stability of a series of refractory MPEAs(RMPEAs)from the subsystems of Ti-V-Zr-Nb-Hf-Ta is investigated at 550℃for 2-28 days.Although all eleven alloys exhibit a single solid solution phase with a body-centered cubic structure at their homogenized states,only two alloys,VNbTa and TiVNbTa,remain stable after annealing.Decomposition occurs in the other nine alloys under the spinodal manner or the nucleation and growth mechanism,including all three quinary alloys,demonstrating that configurational entropy is not a dominant factor.The phase stabilities can be well understood from the enthalpy perspectives,by combining first-principles calculations and semi-empirical models.By comparing the different contributors of formation enthalpy,the lattice distortion energy is found to be the most critical factor for this alloy system.Furthermore,the phases formed after long-term annealing are generally located at different regions in the space with the axes of chemical,structural,and lattice distortion energies.This work provides a way to interpret and control the stability of RMPEAs in the intermediate temperature regime.

To improve strength and ductility of Ti-Zr-Nb lightweight refractory multi-principal element alloys(LRMPEAs)simultaneously,which is difficult for traditional solution strengthening and second-phase/precipitate strengthening,the compositional inhomogeneity in TiZrNb ternary equimolar LRMPEAs with a single-phased body-centered cubic structure is stimulated and tailored by doping V element.When V is introduced,compositional inhomogeneity shows as the segregation of V and Zr elements form.As the value of x for TiZrNbV_xLRMPEAs increases from 0.3 to 0.6,the mild compositional fluctuation develops to the spinodal decomposition structured three-dimensional framework with a periodicity of~5 nm.Then the dislocations in TiZrNbV_0.6LRMPEA are compactly pinned,a remarkable strengthening effect(~120 MPa)while the Frank-Read sources for dislocation multiplication and cross-slip are stimulated.Thus,an optimal combination of strength and ductility including the yield strength of 883 MPa and the fracture elongation of 26.6%is achieved in TiZrNbV0.6 LRMPEA.This work provides a useful method to enhance the strength of Ti-Zr-Nb LRMPEAs without sacrificing the ductility.This way is expected to be effective for other multi-principal element alloys,including high-entropy alloys and medium-entropy alloys.