MicroED as a powerful technique for the structure determination of complex porous materials

Porous materials have garnered significant attention in recent years.Understanding the intrinsic relationship between their structures and properties requires precise knowledge of their atomic structures.Single-crystal X-ray diffraction(SCXRD)has traditionally been the primary method for elucidating such structures,but it demands large,high-quality crystals,often exceeding 5μm in size.The growth of these crystals can be a time-consuming process,especially for one-and two-dimensional materials.To explore structures at the nanoscale,MicroED(microcrystal electron diffraction(ED))offers unprecedented insights into the realm of nanomaterials.This revolutionary technique enables researchers to uncover intricate details within nanoscale structures,promising to reshape our fundamental understanding of materials.In this review,we delve into the applications of MicroED in the study of various porous materials,including zeolites,metal-organic frameworks(MOFs),and covalent organic frameworks(COFs).We emphasize the pivotal role of MicroED in nanomaterial characterization,enabling precise crystallographic analysis and phase identification.

Control of electromechanical performance in 3D printing latticestructured BaTiO_(3) piezoelectric ceramics

Barium titanate(BaTiO_(3))piezoelectric ceramics with triply periodic minimal surface(TPMS)structures have been frequently used in filters,engines,artificial bones,and other fields due to their high specific surface area,high thermal stability,and good heat dissipation.However,only a limited number of studies have analyzed the effect of various parameters,such as different wall thicknesses and porosities of TPMS structures,on ceramic electromechanical performance.In this study,we first employed vat photopolymerization(VPP)three-dimensional(3D)printing technology to fabricate high-performance BaTiO_(3) ceramics.We investigated the slurry composition design and forming process and designed a stepwise sintering postprocessing technique to achieve a density of 96.3%and a compressive strength of 250±25 MPa,with the piezoelectric coefficient(d_(33))reaching 263 pC/N.Subsequently,we explored the influence of three TPMS structures,namely,diamond,gyroid,and Schwarz P,on the piezoelectric and mechanical properties of BaTiO_(3) ceramics,with the gyroid structure identified as exhibiting optimal performance.Finally,we examined the piezoelectric and mechanical properties of BaTiO_(3) ceramics with the gyroid structure of varying wall thicknesses and porosities,thus enabling the modulation of ceramic electromechanical performance.

Three-dimensional MXene-encapsulated porous Ni-NDC nanosheets as anodes for enhanced lithium-ion batteries

Although metal–organic frameworks have been heavily tested as the anode materials for lithium-ion batteries(LIBs),the poorer conductivity,easy collapse of frameworks,and serious volume expansion limit their further application in LIBs.Herein,we report a facile approach to obtain MXene-encapsulated porous Ni-naphthalene dicarboxylic acid(Ni-NDC)nanosheets by hybridizing ultrathin Ti_(3)C_(2)MXene and three-dimensional(3D)Ni-NDC nanosheet aggregates.In the structure of Ni-NDC/MXene hybrids,the interlayer hydrogen-bond interaction between Ni-NDC and MXene can effectively increase the interlayer spacing and further inhibit the oxidation of pure MXene.Hence,the introduction of MXene(a conductive matrix)could further improve the conductivity of Ni-NDC,avoid self-agglomeration,and buffer the volume expansion of Ni-NDC nanosheets.Benefiting from the synergistic effects between Ni-NDC and MXene,Ni-NDC/MXene hybrid electrode exhibits a reversible discharge capacity(579.8 mA∙h∙g^(−1)at 100 mA∙g^(−1)after 100 cycles)and good long-term cycling performance(310 mA∙h∙g^(−1)at 1 A∙g^(−1)after 500 cycles).

Three-dimensional porous electrodes for direct formate fuel cells

The dual-layer electrode for fuel cells is typically prepared by binding discrete catalyst nanoparticles onto a diffusion layer.Such a random packing forms a dense catalyst layer and thus creates a barrier for mass/ion transport,particularly for direct liquid fuel cells.Three-dimensional porous electrodes,a thin nano-porous catalyst layer uniformly distributed on the matrix surface of a foam-like structure,are typically employed to improve the mass/ion transport.Such a three-dimensional porous structure brings two critical advantages:(i)reduced mass/ion transport resistance for the delivery of the reactants via shortening the transport distance and(ii)enlarged electrochemical surface area,via reducing the dead pores,isolated particles and severe aggregations,for interfacial reactions.Moreover,the three-dimensional design is capable of fabricating binder-free electrodes,thereby eliminating the use of ionomers/binders and simplifying the fabrication process.In this work,three types of three-dimensional porous electrode are fabricated,via different preparation methods,for direct formate fuel cells:(i)Pd/C nanoparticles coating on the nickel foam matrix surface(Pd-C/NF)via a dip-coating method,(ii)Pd nanoparticles depositing on the nickel foam matrix surface(Pd/NF)via reduction reaction deposition,and(iii)Pd nanoparticles embedding in the nickel foam matrix(Pd/(in)NF)via replacement reaction deposition.The latter two are binder-free three-dimensional porous electrodes.As a comparison,a conventional dual-layer design,Pd/C nanoparticles painting on the nickel foam layer(Pd-C//NF),is also prepared via direct painting method.It is shown that the use of the three-dimensional Pd-C/NF electrode as the anode in a direct formate fuel cell results in a peak power density of 45.0 mW cm^(-2)at 60℃,which is two times of that achieved by using a conventional dual-layer design(19.5 mW cm^(-2)).This performance improvement is mainly attributed to the unique three-dimensional structure design,which effectively enhances the mass/ion transport through the porous electrode and enlarges the electrochemical surface area(accessible active area)for interfacial reactions.In addition,the delivery of the fuel solution is still sufficient even when the flow rate is as low as 2.0 mL min^(-1).It is also demonstrated that direct formate fuel cells using two binder-free electrodes yield the peak power densities of 13.5 mW cm^(-2)(Pd/(in)NF)and 14.0 mW cm^(-2)(Pd/NF)at 60℃,respectively,both of which are much lower than the power density achieved by using the Pd-C/NF electrode.This is because the electrochemical surface areas of two binderfree electrodes are much smaller than the Pd/C-based electrodes,since the specific area of Pd/C nanoparticles is much larger.

Preparation and surface modification of 3D printed Ti-6Al-4V porous implant

Three-dimensional(3D)printed titanium alloy implants hold enormous potential in orthopedic applications to avoid stress shielding.However,titanium alloy is bioinert,limiting its application and making surface modification a necessity.In this paper,porous implants were treated by acid etching and anodizing to improve the bioactivity,which was evaluated by simulated body fluid(SBF)immersion test.The results showed that,after surface modification,micro-nanocomposite structures were obtained on the titanium surface,and after immersing in SBF for 2 weeks,the implants showed a drastically enhanced apatite forming ability,confirming improved bioactivity.However,the surface structures were different at different positions and it is believed that this phenomenon is closely related to the different current densities of the surfaces during anodic oxidation.Our research evaluates the effect of anodic oxidation at different voltages on the surface modification and provides a reference for improving the bioactivity of the medical porous implant surface prepared by 3 D printing.

Hierarchical porous carbon derived from coal-based carbon foam for high-performance supercapacitors

Hierarchical porous carbon(HPC)from bituminous coal was designed and synthesized through pyrolysis foaming and KOH activation.The obtained HPC(NCF-KOH)were characterized by a high specific surface area(S_(BET))of 3472.41 m^(2)/g,appropriate mesopores with V_(mes)/V_(total)of 57%,and a proper amount of surface oxygen content(10.03%).This NCF-KOH exhibited a high specific capacitance of 487 F/g at 1.0 A/g and a rate capability of 400 F/g at 50 A/g based on the three-electrode configuration.As an electrode for a symmetric capacitor,a specific capacitance of 299 F/g at 0.5 A/g was exhibited,and the specific capacitance retained 96%of the initial capacity at 5 A/g after 10,000 cycles.Furthermore,under the power density of 249.6 W/kg in 6 mol/L KOH,a high energy density of 10.34 Wh/kg was obtained.The excellent charge storage capability benefited from its interconnected hierarchical pore structure with high accessible surface area and the suitable amount of oxygen-containing functional groups.Thus,an effective strategy to synthesize HPC for high-performance supercapacitors serves as a promising way of converting coal into advanced carbon materials.