查看更多>>摘要：Semiconductors have been widely used in many high-tech fields such as photo-and electro-catalysis,ion bat-teries,and solar cells.In addition to the earliest discovered elemental and compound semiconductors,such as monocrystalline silicon and metal oxides,new types of compound semiconductors have been discovered.Among them,metal hydroxyfluorides(MOHF)are an emerging type of semiconductor that are easy to synthesize and inexpensive.However,many of their properties and applications are not well understood.Nevertheless,some MOHF materials,such as ZnOHF and CoOHF,have been sufficiently developed,and their applications have been extensively explored.This review focuses on a new compound semiconductor,MOHF,with ZnOHF and CoOHF as the typical.After a short introduction to their physical and chemical properties,their common applications are illustrated with several examples.Subsequently,other less-researched MOHF and MOHF-like materials,as well as their applications,are discussed.Moreover,the expectations and development directions of MOHFs are briefly summarized.
查看更多>>摘要：Proton exchange membrane fuel cells(PEMFCs),which have the advantages of high-power density,zero emission,and low noise,are considered ideal electrochemical conversion systems for converting hydrogen(H2)and oxy-gen(O2)/air into electricity.However,the oxygen reduction reaction(ORR),which is accompanied by multiple electrons,results in voltage loss and low conversion efficiency of PEMFCs.Currently,PEMFCs mainly use high-load precious platinum(Pt)to promote the ORR process;however,the high cost of Pt hinders the widespread commercialization of PEMFCs.Over the past few years,metal-nitrogen-carbon single-atom catalysts(M-N-C SACs)have attracted considerable attention and have been recognized as potential Pt-based catalysts owing to their outstanding ORR activity.This review briefly introduces the components of PEMFCs.Second,we discuss the catalytic mechanisms of the M-N-C SACs for the ORR.Third,the latest advances in noble,non-noble,and heteroatom-doped M-N-C SACs used as ORR and PEMFCs cathode catalysts are systematically reviewed.In sum-mary,we have outlined the current challenges and proposed a future perspective of M-N-C SACs for PEMFCs cathodes.
查看更多>>摘要：Lignocellulosic biomass is a critical renewable carbon resource,but most of its utilization is inefficient,and elec-trocatalytic oxidation is a promising method of upgrading lignocellulose into value-added fuels and chemicals under mild operating conditions.Recently,efforts to enable conversion with a high efficiency and low energy con-sumption have been reported,but understanding the reaction mechanisms and realizing scaled-up applications of the electrooxidation of lignocellulosic biomass are still in their early stages.A timely overview of recently reported general reaction mechanisms,particularly the strategies developed for use in improving the reaction efficiencies,is necessary to inspire research regarding the highly efficient utilization of lignocellulose.Herein,we summa-rize the strategies developed to improve electrocatalytic performance in oxidative lignocellulose conversion.The organized summary includes strategies ranging from designing efficient electrocatalysts and adding functional co-catalysts or electrolytes to employing advanced electrolyzers.A comprehensive overview of representative examples should provide universal principles to yield insight into the reaction processes and guide the design of efficient electrocatalytic systems.Finally,the challenges and opportunities in developing the electrocatalytic oxidative upgrading of lignocellulosic biomass in the near future are proposed.
查看更多>>摘要：The enhancement in the efficiency of triplet-triplet annihilation upconversion(TTA-UC)is mainly determined by the triplet energy transfer(TET)and triplet-triplet annihilation(TTA)between the sensitizers and annihilators.The TET process works efficiently by adjusting the concentration ratio of the sensitizers and annihilators.The efficiency of TTA is determined by the properties of the annihilator.Because TTA is a Dexter-type energy transfer and is affected by the diffusion rate,the energy levels of the excited states and the molecular size are both crucial in TTA.In this study,four isomerized dimers of 9,10-diphenlanthracene(DPA)and anthracene(An)were designed and prepared as annihilators for TTA-UC.The singlet and triplet energy levels could be adjusted by altering the connection position while maintaining the molecular weight and size.When PtOEP was used as the sensitizer,the maximum upconversion efficiency of 9-[4-(9-anthracenyl)phenyl]-10-phenylanthracene(9DPA-9An)was～11.18％.This is four times higher than that of 9,10-diphenyl-2,9'-bianthracene(2DPA-9An,2.63％).The calculation of the energies of T1 and the higher triplet state(T3,because E(T2)is similar to the E(T1)of these dimers)for these dimers has provided insights into the underlying reasons.These indicated that the energy gap value of 2 × E(T1)-E(T3)is the determining factor for TTA efficiency.This work may provide a better understanding of the excited-state energy levels,which is crucial for designing novel annihilators to enhance the TTA-UC efficiency.
查看更多>>摘要：A set of novel red phosphors Li8CaLa2Ta2O13∶xEu3+(LCLTO∶xEu3+)were successfully prepared using a solid-state reaction method.The properties of the prepared samples,including phase purity,elemental composition,and morphology,were systematically investigated using X-ray diffraction,scanning electron microscopy,and diffuse reflectance spectroscopy analyses.The 610 nm maximum emission peak is attributed to the 5D0→7F2 transition of Eu3+ion under 394 nm irradiation.Among all the LCLTO∶xEu3+phosphors,LCLTO∶0.6Eu3+showed the strongest emission intensity because of the concentration quenching effect of the electric dipole-dipole in-teraction among the Eu3+ions,which was also demonstrated by the decay curves.Remarkably,the emission intensity of the optimal LCLTO∶0.6Eu3+phosphor,which exhibited a high internal quantum efficiency of 49.30％and excellent color purity of 96.79％,was approximately 2.29 times higher than that of commercial Y2O3∶Eu3+red phosphors.The thermal stability of the LCLTO∶0.6Eu3+sample with good color stability was meticulously inves-tigated.The fabricated white-light-emitting diode(WLED)exhibited a superior color-rendering index of Ra=82 and chromaticity coordinates of(0.3260,0.3639),suggesting that LCLTO∶0.6Eu3+has potential applicability in developing efficient and high-quality WLEDs.Moreover,the prepared LCLTO∶0.6Eu3+/PDMS composite film demonstrated exceptional flexural resistance and chemical stability,indicating considerable promise for practical anti-counterfeiting applications.
查看更多>>摘要：Nanozymes are nanomaterials with intrinsic enzyme-mimic activity,but their large-scale application is generally limited by their low catalytic activity.Herein,we demonstrated that highly exposed Cu active sites on two-dimensional(2D)nitrogen-doped carbon(Cux/NC)can serve as efficient peroxidase-like(POD)catalysts with high atomic utilization.Specially,the uniformly distributed Cu active sites could react with H2O2 to produce singlet oxygen(1O2)under acidic conditions,which can efficiently oxidizes colorless 3,3',5,5'-tetramethylbenzidine(TMB)to blue oxidized TMB(oxTMB).Among various Cux/NC nanozymes studied,the Cu0.14/NC exhibited smaller maximum catalytic velocities(Vmax)and Menten constant(Km)for TMB and H2O2.Benefiting from the highly active peroxidase-like activity,the Cu0.14/NC nanozyme could be successfully applied for the hydroquinone(HQ)and ascorbic acid(AA)detection applications through the inhibitory effect of HQ and AA.More interestingly,α-glucosidase(α-Glu)detection sensing platform could be constructed based on HQ as a signal transmitter,with the detection range ranging from 0 to 12 U/L and the minimum detection limit being 0.68 U/L.This work provides not only an idea for the rational design of highly exposed Cu active sites but also fabricate an effective detection sensing platform for HQ,AA,and α-Glu detection.
查看更多>>摘要：The rapidly increasing usage of electric technology during the last decades has facilitated the fabrication of high-efficiency microwave absorption(MA)materials(MAMs).In this study,hierarchical NiCo layered double hydroxide(LDH)/carbon fiber(CF)nanocomposites were constructed via simple hydrothermal production,and their MA properties were evaluated.Benefiting from interfacial polarization,defect-induced polarization,and multiple reflections induced by the hierarchical sheets,the LDH/CF composites delivered a better MA perfor-mance than that by pure CF and LDH.The addition ratio of the LDH also played a vital role in determining the impedance matching and microwave absorption performance.Specifically,the optimized LDH/CF composites demonstrated an exceptional reflection loss(RL)of-62.47 dB with a thickness of 2.22 mm,and an effective absorption bandwidth(EAB)covering 6.4 GHz(11.6-18.0 GHz)at a 20 wt.％filling ratio,which outperformed the reported CF-based microwave absorbers.Owing to this superior MA,the as-prepared LDH/CF composites demonstrated to be significantly promising for advancing the usage of CF-based MAMs.
查看更多>>摘要：Nickel diselenide(NiSe2),which has a high theoretical capacity,has attracted considerable attention as a promis-ing anode material for sodium-ion batteries(SIBs).Nevertheless,the intrinsically low conductivity,large volume variation,and significant aggregation of NiSe2 during sodiation/desodiation remain significant obstacles to its application.Herein,we report flower-like Fe-doped NiSe2/C hybrid spheres(denoted as Fe-NiSe2/C)fabricated by a glucose intercalation strategy for efficient sodium storage.These Fe-NiSe2/C hybrid spheres are composed of thin porous carbon nanosheets decorated with Fe-NiSe2 nanoparticles.In situ introduced carbon nanosheets derived from intercalated glucose accompanied by moderate Fe doping in NiSe2 nanoparticles can provide ac-celerated ion/electron transfer kinetics through fast ion channels in the flower-like architecture and intimately contacted interfaces between NiSe2 and carbon nanosheets as well as maintain structural integrity by alleviating volume variation.Consequently,the optimal anode of the Fe-NiSe2/C hybrid spheres delivered a high discharge capacity of 415 mAh g-1 at 0.5 A g-1,outstanding rate capability(243 mAh g-1 at 5 A g-1),and significantly enhanced cycling stability(388 mAh g-1 at 1 A g-1 over 200 cycles).This work offers an efficient and valu-able strategy for realizing tailored heteroatom doping in transition metal selenides,accompanied by an in situ combination of conductive carbonaceous networks for advanced alkali metal ion batteries.
查看更多>>摘要：Introduction of aromatic acid derivatives(AADs)into zwitterionic surfactants is an efficient method to prepare wormlike micelles with pH-controllable viscosity;however,the coincident molecular origin of AAD/zwitterionic surfactant binary mixtures remains unclear.Herein,the self-assembly of hydroxyl derivatives of benzoic acid(BA)and cetyldimethyl betaine(BS-16)mixtures in water was systematically assessed,and various factors,such as the molecular structure,molar ratio of AAD and BS-16,and solution pH,were investigated.The structure-property relationship of AAD/BS-16 binary mixtures was established,which provided the molecular origin for the effect of AAD on micellar microstructures and the pH-induced morphological transitions.The ortho-substituted hydroxyl moiety in the BA molecule facilitated the formation of larger wormlike micelles,whereas the effect of the meta-substituted moiety was less significant.The para-substituted hydroxyl moiety in BA did not favor micellar growth.This moiety exhibited similar characteristics to the increasing hydroxyl moiety number in the AAD molecules or solution pH where the negative effects of steric hindrance and electrostatic interactions of molecules in micelles are dominant.
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