Kinetics of Catalyzed Thermal Degradation of Polylactide and Its Application as Sacrificial Templates

Polylactide(PLA)is an outstanding sacrificial template material for the manufacture of microchannels in a thermosetting matrix.However,the initial thermal degradation temperature of pure PLA is relatively high(about 280℃),which limits its use as a sacrificial template.In this report,we found that TBD,an organic base catalyst,can significantly reduce the thermal degradation temperature of PLA.TBD has higher catalytic activity for the thermal degradation of PLA compared with Tin(II)oxalate(Sn(Oxa)),one catalyst reported in the literature.Moreover,the gaseous products catalyzed by TBD for PLA thermal degradation are mainly lactide,and the formation temperature of the monomer is lower and the yield is higher,which may have potential value for PLA recycling.A combined catalyst,S8T2,was composed of 80%low activity catalyst Sn(Oxa)and 20%high activity catalyst TBD,which can catalyze the rapid degradation of PLA without greatly damaging the mechanical properties of PLA.PLA-S8T2 sacrificial fibers can form high-precision one-dimensional microchannels in the epoxy resin matrix,and 3D-printed PLA-S8T2 sacrificial templates can be used to form three-dimensional microchannels in a thermosetting matrix by vaporization of sacrificial components process(VaSC).These features highlight the great potential of PLA-S8T2 as sacrificial template material for the preparation of the complicated microchannels in the thermosetting matrix.

Sacrificial template synthesis of(V_(0.8)Ti_(0.1)Cr_(0.1))_(2)AlC and carbon fiber@(V_(0.8)Ti_(0.1)Cr_(0.1))_(2)AlC microrods for efficient microwave absorption

The morphology of MAX phase powders significantly influences their microwave absorption properties.However,the traditional synthesis via solid-state reactions produces irregular powders,and the preparation of MAX phase powders with specific morphology remains a challenge.Herein,(VTiCr)Al C MAX phase microrods were fabricated for the first time in NaCl/KCl molten salts using vanadium,titanium,chromium,aluminum,and short carbon fibers as precursors.It was found that despite acting as a carbon source,carbon fibers also acted as sacrificial templates.By adjusting the molar ratio of metal powders and short carbon fibers,a series of carbon fiber@(V_(0.8)Ti_(0.1)Cr_(0.1))_(2)AlC microrods with core-sheath structure were also obtained.Carbon fiber@(V_(0.8)Ti_(0.1)Cr_(0.1))_(2)AlC microrods with a molar ratio of 8:2 showed the optimum microwave absorption performance.The reflection loss(RL)value reached up to–63.26 d B at 2.40 mm,and the effective absorption bandwidth(EAB)was about 5.28 GHz with a thickness of2.02 mm.Based on the electromagnetic parameter analysis and theoretical simulation,the enhanced microwave absorption performance was attributed to the synergistic effect of different factors like dielectric loss,magnetic loss,multiple reflection,and scattering.This work offers a facile route to modulate the morphology of MAX phase powders and may accelerate its application as microwave absorbers.

Three-dimensional paper-like graphene framework with highly orientated laminar structure as binder-free supercapacitor electrode

A free-standing paper-like three-dimensional graphene framework（3DGF） with orientated laminar structure and interconnected macropores, was obtained by the hard template-directed ordered assembly. As the sacrificial templates, polystyrene（PS） latex spheres were assembled with graphene oxide（GO） to build up a sandwich type composite film, followed by heat removal of which with a simultaneous reduction of GO. The 3DGF exhibited high specific surface area of 402.5 m2/g, controllable pores and mechanical flexibility, which was employed as the binder-free supercapacitor electrode and shows high specific gravimetric capacitance of 95 F/g at 0.5 A/g, with enhanced rate capability in 3 electrode KOH system.

Immobilization of PANI on Mesoporous Carbon： Preparation and Supercapacitor Performance

Polyaniline(PANI)was effectively immobilized on the surface of ordered mesoporous carbon(OMC)by using Mn_2O_3 as sacrificial template.The observed microstructure and morphology indicate that a thin layer of PANI was coated on OMC uniformly.As a supercapacitor electrode material,the discharge capacity of the optimized PANI/OMC could reach 467 F/g,which is far higher than that of OMC,PANI and Mn_2O_3/OMC.Furthermore,PANI/OMC composites with different content of PANI are obtained by adjusting the amount of Mn_2O_3 on OMC and their properties are characterized.The results show that a thin layer of PANI can improve the capacity of PANI/OMC composites effectively and the further increase of PANI reduces the capacity of PANI/OMC composites.The sacrificial template method presented here is beneficial to coating a layer of polymer on carbon materials,and the content of polymer layer can be controlled by adjusting the amount of Mn_2O_3 in Mn_2O_3/OMC.

Template sacrificial controlled synthesis of hierarchical nanoporous carbon@NiCo_(2)S_(4)microspheres for high-performance hybrid supercapacitors

Binary transition metal sulfides are hotly investigated in advanced energy storage devices because of their ultra-high reversible capacity.Nevertheless,the unsatisfied rate capability and cycling stability still hinder their practical application.Herein,hierarchical nanoporous carbon@NiCo_(2)S_(4)(HNCMs@NCS)composites with coreshell flower-like structures were prepared by in situ growing of NiCo_(2)S_(4) nanosheets on HNCMs through a hydro thermal-as sis ted template sacrificial method.Benefiting from a synergistic effect between the NiCo_(2)S_(4)shell with high specific capacity and the HNCMs with unique porous structure,the synthesized flower-like HNCMs@NCS composites exhibit extraordinary electrochemical performances,including a high capacity of 346.9 mAh·g^(-1)at 1 A·g^(-1),superb rate property with86.4%initial capacity at 30 A·g^(-1)and predominant cycle stability with 81.2%capacity retention after 5000 cycles.Furthermore,the resulting HNCMs@NCS cathode was coupled with the chemical-activated HNCMs(AHNCMs)anode to construct a hybrid supercapacitor device.The asfabricated device exhibits superior energy density(49.9 Wh·kg^(-1)at 802 W·kg^(-1))and ultra-high power density(24 kW·kg^(-1)at 29.5 Wh·kg^(-1)).This fascinating result further demonstrates the tremendous prospect of the synthesized HNCMs@NCS composites as high-performance supercapacitor electrode materials.

Cobalt-nanoparticle catalysts derived from zeolitic imidazolate framework@MXene composites for efficient oxidative self-coupling of benzylamines

In this study,we synthesize a catalyst comprising cobalt nanoparticles supported on MXene by pyrolyzing a composite in a N2 environment.Specifically,the composite comprises a bimetallic Zn/Co zeolitic imidazole framework grown in situ on the outer surface of MXene.The catalytic efficiency of the catalyst is tested for the self-coupling of 4-methoxybenzylamine to produce value-added imine,where atmospheric oxygen(1 atm)is used as the oxidant.Based on the results,the catalyst displayed impressive catalytic activity,achieving 95.4%yield of the desired imine at 383 K for 8 h.Furthermore,the catalyst showed recyclability and tolerance toward benzylamine substrates with various functional groups.The outstanding performance of the catalyst is primarily attributed to the synergetic catalytic effect between the cobalt nanoparticles and MXene support,while also benefiting from the three-dimensional porous structure.Additionally,a preliminary investigation of potential reaction mechanisms is conducted.

The development of MOFs-based nanomaterials in heterogeneous organocatalysis

Metal-organic framework(MOF) is a class of inorganic-organic hybrid material assembled periodically with metal ions and organic ligands. MOFs have always been the focuses in a variety of frontier fields owing to the advantageous properties, such as large BET surface areas, tunable porosity and easyfunctionalized surface structure. Among the various application areas, catalysis is one of the earliest application fields of MOFs-based materials and is one of the fastest-growing topics. In this review, the main roles of MOFs in heterogeneous organocatalysis have been systematically summarized, including used as support materials(or hosts), independent catalysts, and sacrificial templates. Moreover, the application prospects of MOFs in photocatalysis and electrocatalysis frontiers were also mentioned.Finally, the key issues that should be conquered in future were briefly sketched in the final parts of each item. We hope our perspectives could be beneficial for the readers to better understand these topics and issues, and could also provide a direction for the future exploration of some novel types of MOFs-based nanocatalysts with stable structures and functions for heterogeneous catalysis.

Preparation and photoluminescence enhancement of Li^+ and Eu^(3+) co-doped YPO_4 hollow microspheres

Li＋ and Eu3＋ co-doped YPO4 hollow microspheres were successfully synthesized by a sacrificial template method using polystyrene （PS） as template. Techniques of X-ray diffraction （XRD）, scanning electron microscopy （SEM）, as well as transmission electron microscopy （TEM） were employed to characterize the as-synthesized sample. Furthermore, the photoluminescence （PL） characterization of the Li＋ and Eu3＋ co-doped YPO4 microsphere was carried out and the effects of the doping concentration of Li＋ and Eu3＋ active center concentration as well as calcination temperature on the PL properties were studied in detail. The results showed that the incorporation of Li＋ ions into the YPOa：Eu3＋ lattice could induce a remarkable improvement of the PL intensity. The highest emission intensity was observed with the compound of 5%Li＋ and 5%Eu3＋ co-doped YPO4, whose brightness was increased by a factor of more than 2.2 in comparison with that of the YPO4：5%Eu3＋.

In-plane grain boundary induced defect state in hierarchical NiCo-LDH and effect on battery-type charge storage

Domain boundaries are regarded as the effective active sites for electrochemical energy storage materials due to defects enrichment therein.However,layered double hydroxides(LDHs)tend to grow into single crystalline nano sheets due to their unique two-dimentional(2D)lattice structure.Previously,much efforts were made on the designing hierarchical structure to provide more exposed electroactive sites as well as accelerate the mass transfer.Herein,we demonstrate a strategy to introduce low angle grain boundary(LAGB)in the flakes of Ni/Co layered double hydroxides(NiCo-LDHs).These defect-rich nano flakes were self-assembled into hydrangea-like spheres that further constructed hollow cage structure.Both the formation of hierarchical structure and grain boundaries are interpreted with the synergistic effect of Ni2+/Co2+ratio in an“etching-growth”process.The domain boundary defect also results in the preferential formation of oxygen vacancy(Vo).Additionally,density functional theory(DFT)calculation reveals that Co substitution is a critical factor for the formation of adjacent lattice defects,which contributes to the formation of domains boundary.The fabricated battery-type Faradaic NiCo-LDH-2 electrode material exhibits significantly enhanced specific capacitance of 899 C·g^(−1)at a current density of 1 A·g^(−1).NiCo-LDH-2//AC asymmetric capacitor shows a maximum energy density of 101.1 Wh·kg^(−1)at the power density of 1.5 kW·kg^(−1).

3D multicore-shell CoSn nanoboxes encapsulated in porous carbon as anode for lithium-ion batteries

Due to its high theoretical capacity and appropriate potential platform,tin-based alloy materials are expected to be a competitive candidate for the next-generation high performance anodes of lithium-ion batteries.Nevertheless,the immense volume change during the lithium-ion insert process leads to severe disadvantages of structural damage and capacity fade,which limits its practical application.In this work,a three-dimensional(3 D)multicore-shell hollow nanobox encapsulated by carbon layer is obtained via a three-step method of hydrothermal reaction,annealing and alkali etching.During the electrochemical reactions,the CoSn@void@C nanoboxes provide internal space to compensate the volumetric change upon the lithiation of Sn,while the inactive component of Co acts as chemical buffers to withstand the anisotropic expansion of nanoparticles.Owing to the above-mentioned advantages,the elaborated anode delivers an excellent capacity of 788.2 m Ah/g at 100 m A/g after 100 cycles and considerable capacity retention of 519.2 mAh/g even at a high current density of 1 A/g after 300 cycles.The superior stability and high performance indicate its capability as promising anodes for lithium-ion batteries.