A review on electrocatalytic CO_(2) conversion via C-C and C-N coupling

Electrochemical C-C and C-N coupling reactions with the conversion of abundant and inexpensive small molecules,such as CO_(2) and nitrogencontaining species,are considered a promising route for increasing the value of CO_(2) reduction products.The development of high-performance catalysts is the key to the both electrocatalytic reactions.In this review,we present a systematic summary of the reaction systems for electrocatalytic CO_(2) reduction,along with the coupling mechanisms of C-C and C-N bonds over outstanding electrocatalytic materials recently developed.The key intermediate species and reaction pathways related to the coupling as well as the catalyst-structure relationship will be also discussed,aiming to provide insights and guidance for designing efficient CO_(2) reduction systems.

Boosting overall saline water splitting by constructing a strain-engineered high-entropy electrocatalyst

High-entropy materials(HEMs),which are newly manufactured compounds that contain five or more metal cations,can be a platform with desired properties,including improved electrocatalytic performance owing to the inherent complexity.Here,a strain engineering methodology is proposed to design transition-metal-based HEM by Li manipulation(LiTM)with tunable lattice strain,thus tailoring the electronic structure and boosting electrocatalytic performance.As confirmed by the experiments and calculation results,tensile strain in the LiTM after Li manipulation can optimize the d-band center and increase the electrical conductivity.Accordingly,the asprepared LiTM-25 demonstrates optimized oxygen evolution reaction and hydrogen evolution reaction activity in alkaline saline water,requiring ultralow overpotentials of 265 and 42 mV at 10 mA cm−2,respectively.More strikingly,LiTM-25 retains 94.6%activity after 80 h of a durability test when assembled as an anion-exchange membrane water electrolyzer.Finally,in order to show the general efficacy of strain engineering,we incorporate Li into electrocatalysts with higher entropies as well.

Construction of a Cu@hollow TS-1 nanoreactor based on a hierarchical full-spectrum solar light utilization strategy for photothermal synergistic artificial photosynthesis

The artificial photosynthesis technology has been recognized as a promising solution for CO_(2) utilization.Photothermal catalysis has been proposed as a novel strategy to promote the efficiency of artificial photosynthesis by coupling both photochemistry and thermochemistry.However,strategies for maximizing the use of solar spectra with different frequencies in photothermal catalysis are urgently needed.Here,a hierarchical full-spectrum solar light utilization strategy is proposed.Based on this strategy,a Cu@hollow titanium silicalite-1 zeolite(TS-1)nanoreactor with spatially separated photo/thermal catalytic sites is designed to realize high-efficiency photothermal catalytic artificial photosynthesis.The space-time yield of alcohol products over the optimal catalyst reached 64.4μmol g−1 h−1,with the selectivity of CH3CH2OH of 69.5%.This rationally designed hierarchical utilization strategy for solar light can be summarized as follows:(1)high-energy ultraviolet light is utilized to drive the initial and difficult CO_(2) activation step on the TS-1 shell;(2)visible light can induce the localized surface plasmon resonance effect on plasmonic Cu to generate hot electrons for H2O dissociation and subsequent reaction steps;and(3)low-energy near-infrared light is converted into heat by the simulated greenhouse effect by cavities to accelerate the carrier dynamics.This work provides some scientific and experimental bases for research on novel,highly efficient photothermal catalysts for artificial photosynthesis.

Defect engineered nickel hydroxide nanosheets for advanced pseudocapacitor electrodes

While the past years have witnessed great achievement in pseudocapacitors,the inauguration of electrode materials of high-performance still remains a formidable challenge.Moreover,the capacity and rate capability of the electrode depends largely on its electrical conductivity,which ensures fast charge transfer kinetics in both the grain bulk and grain boundaries.Here,nickel hydroxides with oxygen vacancies are facilely fabricated via a hydrothermal method.The active materials exhibit a high specific capacitance of 3250 F·g^(−1)and a high areal of capacitance of 14.98 F·cm^(−2)at 4.6 mA·cm^(−2).The asymmetric supercapacitor device based on our material delivers a high energy density of~71.6 Wh·kg^(−1)and a power density of~17,300 W·kg^(−1)and could retain~95%of their initial capacitance even after 30,000 cycles.In addition,the defect-rich hydroxides demonstrate higher electrical conductivity as well as dielectric constant,which is responsible for the superior pseudocapacitive performance.Our new scientific strategy in terms of taking the advantages of oxygen vacancies might open up new opportunities for qualified pseudocapacitive materials of overall high performances not only for nickel hydroxides but also for other metal hydroxides/oxides.

Optical properties and irradiation resistance of novel high-entropy oxide glasses La_(2)O_(3)-TiO_(2)-Nb_(2)O_(5)-WO_(3)-M_(2)O_(3)(M=B/Ga/In)

A new class of high-entropy oxide glasses 20LaO_(3/2)-20TiO_(2)-20NbO_(5/2)-20WO_(3)-20MO_(3/2)(M=B/Ga/In)were designed and successfully fabricated by aerodynamic containerless processing.The results show that one can control the properties and increase the functionality of glass by changing the type of M.The Vicker's hardness reaches the highest value of 6.45 GPa for glass M=B.The best thermal stability and the glass forming ability,measured using the glass-transition temperature T_(g) and the temperature gap ΔT respectively,are found in glass M=In,with T_(g)=740℃ and ΔT=72℃.The optical properties show that the as-prepared glasses exhibit good transparency and high refractive index.Especially for glass M=In,its transmittance reaches almost 78% from visible to IR region,and the value is nearly unchanged after electron beam irradiation,indicating good irradiation resistance of this high-entropy oxide glass.Furthermore,the glass M=In has the highest refractive index(n_(d)=2.46) and low wavelength dispersion(v_(d)=45.6).These results demonstrate that the conceptual design of high-entropy materials is adaptable to high performance oxide glasses,which should be promising host materials for optical applications such as smart phones with digital cameras and endoscopes.

High-entropy enhanced room-temperature ferroelectricity in rare-earth orthoferrites

Single-phase multiferroic materials of rare-earth orthoferrites with magnetism and ferroelectricity are of great technological importance in storage devices.However,the polarization(P)of these materials is generally weak(0.01μC-cm^(-2)),and the ferroelectricity is reported to exist below room temperature(25℃).Here,(Bi_(0.2)La_(0.2)Y_(0.2)Dy_(0.2)Tb_(0.2))FeO_(3)(BLYDTFO)high-entropy oxides that exhibit a saturation P of 5.3μC.cm^(-2)at the electric field(E)of 45 kV·cm^(-1)at room temperature was designed and fabricated by the conventional solid-phase method.The results show that configurational entropy introduces atomic disorder and a larger tilt of BO6 octahedron,which facilitates noncentrosymmetric distortion and ferroelectricity at room temperature compared with other single components(LaFeO_(3),YFeO_(3),DyFeO_(3),and TbFeO_(3)).This high-entropy approach expands the compositional window of the rare-earth orthoferrites to enhance the ferroelectricity in multiferroic applications.

High-entropy ceramics:Present status,challenges,and a look forward

High-entropy ceramics (HECs) are solid solutions of inorganic compounds with one or more Wyckoff sites shared by equal or near-equal atomic ratios of multi-principal elements.Although in the infant stage,the emerging of this new family of materials has brought new opportunities for material design and property tailoring.Distinct from metals,the diversity in crystal structure and electronic structure of ceramics provides huge space for properties tuning through band structure engineering and phonon engineering.Aside from strengthening,hardening,and low thermal conductivity that have already been found in high-entropy alloys,new properties like colossal dielectric constant,super ionic conductivity,severe anisotropic thermal expansion coefficient,strong electromagnetic wave absorption,etc.,have been discovered in HECs.As a response to the rapid development in this nascent field,this article gives a comprehensive review on the structure features,theoretical methods for stability and property prediction,processing routes,novel properties,and prospective applications of HECs.The challenges on processing,characterization,and property predictions are also emphasized.Finally,future directions for new material exploration,novel processing,fundamental understanding,in-depth characterization,and database assessments are given.

Effect of tempering temperature on the microstructure and properties of ultrahigh-strength stainless steel

The microstructure, precipitation and mechanical properties of Ferrium S53 steel, a secondary hardening ultrahigh-strength stainless steel with 10% Cr developed by QuesTek Innovations LLC, upon tem pering were studied by scanning electron microscopy (SEM), transm ission electron microscopy (TEM), X-ray diffraction (XRD), and tensile and impact tests. Based on these results, the influence of the tem pering temperature on the microstructure and properties was discussed. The results show th at decom position occurred when the retained austenite was tem pered above 440 ℃ and that the hardening peak at 482 ℃ was caused by the joint strengthening of the precipitates and martensite transformation. Due to the high Cr content, the trigonal M7C3 carbide precipitated w hen the steel was tem pered at 400 ℃, and M7C3 and M2C (5 -10 nm in size) coexisted w hen it was tem pered at 482 ℃. When the steel was tem pered at 630 ℃, M2C and M23C6 carbides precipitated, and the sizes w ere greater than 50 nm and 500 nm, respectively, but no M7C3 carbide formed. When the tempering tem perature was above 540 ℃, austenitization and large-size precipitates w ere the main factors affecting the strength and toughness.

Enhancing electrical conductivity of single-atom doped Co_(3)O_(4) nanosheet arrays at grain boundary by phosphor doping strategy for efficient water splitting

High electrical conductivity guarantees a rapid electron transfer and thus plays an important role in electrocatalysis.In particular,for the single atom catalysts(SACs),to facilitate interaction between the single atom and supports,precisely engineering the conductivity represents a promising strategy to design SACs with high electrochemical efficiency.Here we show rhodium(Rh)SAC anchored on Co_(3)O_(4) nanosheets arrays on nickel foam(NF),which is modified by a facile phosphorus(P-doped Rh SACCo_(3)O_(4)/NF),possessing an appropriate electronic structure and high conductivity for electrocatalytic reaction.With the introduction of P atom in the lattice,the electrocatalyst demonstrates outstanding alkaline oxygen evolution reaction(OER)activity with 50 mA·cm^(−2) under overpotential of 268 mV,6 times higher than that of Ir/C/NF.More interestingly,the P-doped Rh SAC-Co_(3)O_(4)/NF can get 50 mA·cm^(−2) at only 1.77 V for overall water splitting.Both electrical conductivity studies and density functional theory(DFT)calculations reveal that the high conductivity at grain boundary improves the charge transfer efficiency of the Rh catalytic center.Furthermore,other noble-metal(Ir,Pd,and Ru)doped Co_(3)O_(4) nanosheets arrays are prepared to exhibit the general efficacy of the phosphorus doping strategy.

Influence of ammonium sulfate on YAG nanopowders and Yb：YAG ceramics synthesized by a novel homogeneous co-precipitation method

Homogeneous and dispersed Y3 Al5 O12（yttrium aluminum garnet,YAG） nanopowders were synthesized via a homogeneous co-precipitation method from the mixed solutions of yttrium nitrate,aluminum nitrate and a small amount of ammonium sulfate using hot urea as the precipitant.The method has the superiorities that co-precipitation of cations is ensured and continuous decomposition of the hot urea is achieved to obtain the narrow size distribution particles.The addition of small amount of ammonium sulfate surfactant,although has no influence on YAG garnet phase formation,has significant effect on dispersion,particles distribution and sinterability of the resultant YAG and Yb：YAG powders.Compared with the undoped sample,the green body of Yb：YAG doped with ammonium sulfate has higher total shrinkage,linear shrinkage rate and relative density through sintering at 1600 ℃.The resultant Yb：YAG powders can be sintered into transparent ceramics at 1700 ℃ through vacuum sintering.The influence of the sulfate ions on characteristics of the resultant powders was thoroughly studied.