Efficient hydrogenolysis of fructose to 1,2-propanediol over bifunctional Ru-WO_(x)-MgO_(y) catalysts under mild reaction conditions via enhancing the chemoselective cleavage of C-C bonds

Selective conversion of fructose to 1,2-propanediol(1,2-PDO)is considered as a sustainable and cost-effective alternative to petroleum-based processes,however,this approach still faces challenges associated with low efficiency and harsh reaction conditions.Here,we have successfully synthesized a novel bifunctional Ru-WO_(x)-MgO_(y) catalyst through a facile'one-pot'solvothermal method.Remarkably,this catalyst exhibits exceptional catalytic performances in the conversion of fructose to 1,2-PDO under mild reaction conditions.The yield of 1,2-PDO is up to 56.2%at 140°C for 4 h under an ultra-low hydrogen pressure of only 0.2 MPa,surpassing the reported results in recent literature(below 51%).Comprehensive characterizations and density functional theory(DFT)calculations reveal that the presence of oxygen vacancies in the Ru-WO_(x)-MgO_(y) catalyst,serving as active acidic sites,facilitates the chemoselective cleavage of C-C bonds in fructose,which leads to the generation of active intermediates and ultimately resulted in the high yield of 1,2-PDO.

Copper-comprising nanocrystals as well-defined electrocatalysts to advance electrochemical CO_(2) reduction

In the continuous development of electrochemical CO_(2) reduction (ECR), Cu-based electrocatalysts have received great attention, due to their unique ability to produce high value-added multicarbon products. Of particular interest are various Cu-comprising nanocrystals, not only because they usually show better catalytic properties than bulk materials, but also because their well-defined structures and highly tunable compositions facilitate in-depth mechanistic studies. This review aims to summarize the latest developments of electrocatalysts for ECR, with a focus on systems using Cu-comprising nanocrystals. We first give a general introduction to the field of ECR, covering the significance of this process, reaction mechanisms, catalyst evaluation criteria, and electrolytic cell configurations. Next, we discuss Cu-comprising nanocrystals developed for ECR by categorizing them into four groups: monometallic copper, copper-containing bimetals/multimetals, copper compounds, and copper–metal oxide hybrids;among these groups, we choose representative examples for detailed discussion on the synthetic methods, structural and compositional reaction sensitivities, and catalyst evolution during ECR. In the last section, we outline the challenges in this field from the fundamental and applicative aspects, and give perspectives on the expansion of catalyst varieties, the identification and preservation of active sites, and the exploration of industrially relevant operations for these nanocrystals. We hope the insights provided in this review will inspire the design and development of next-generation catalysts for ECR.

Low-Dose Electron Microscopy Imaging of Electron Beam-Sensitive Crystalline Materials

As one of the most widely used characterization tools in materials science,(scanning)transmission electron microscopy((S)TEM)has the unique ability to directly image specimens with atomic resolution.Compared to diffraction-based techniques,the main advantage of(S)TEM imaging is that in addition to the periodic average structures of crystalline materials,it can be used to probe nonperiodic local structures such as surfaces,interfaces,dopants,and defects,which have crucial impacts on material properties.However,many crystalline materials are extremely sensitive to electron beam irradiation,which can only withstand dozens(or even fewer)of electrons per square angstrom before they undergo structural damage.Although using electron doses lower than the thresholds can in principle preserve their structures,the thus acquired images are too noisy to be useful.Consequently,high-resolution imaging of the inherent structures of such electron beam-sensitive materials using(S)TEM is a longstanding challenge.In recent years,the advances in electron detectors and image-acquisition methods have enabled high-resolution(S)TEM with ultralow electron doses,largely overcoming this challenge.A series of highly electron beam-sensitive materials that are traditionally considered impossible to be imaged with(S)TEM,including metal organic frameworks(MOFs),covalent organic frameworks(COFs),organic−inorganic hybrid halide perovskites,and supramolecular crystals,have been successfully imaged at atomic resolutions.This technological advance has greatly expanded the application range of electron microscopy.This Account focuses on our recent works pertaining to the high-resolution imaging of electron beam-sensitive materials using very low electron doses.We first explain that the use of direct-detection electron-counting(DDEC)cameras provides the hardware basis for successful low-dose high-resolution TEM(HRTEM).Subsequently,we introduce a suite of methods to address the challenges peculiar to low-dose HRTEM,including rapid search for crystal zone axes,precise alignment of the image stack,and accurate determination of the defocus value.These methods,combined with the use of a DDEC camera,ensure efficient imaging of electron beam-sensitive crystalline materials in the TEM mode.Moreover,we demonstrate that integrated differential phase contrast STEM(iDPC-STEM)is an effective method for acquiring directly interpretable atomic-resolution images under low-dose conditions.In addition,we share our views on the great potential of four-dimensional STEM(4D-STEM)in imaging highly electron beamsensitive materials and provide preliminary simulation results to demonstrate its feasibility.Finally,we discuss the significance of developing(S)TEM specimen preparation techniques applicable for sensitive materials and the advantages of using the cryogenic focused ion beam(cryo-FIB)technique for this purpose.

Boosting alkaline hydrogen evolution performance by constructing ultrasmall Ru clusters/Na^(+),K^(+)-decorated porous carbon composites

The construction of efficient and durable electrocatalysts with highly dispersed metal clusters and hydrophilic surface for alkaline hydrogen evolution reaction(HER)remains a great challenge.Herein,we prepared hydrophilic nanocomposites of Ru clusters(~1.30 nm)anchored on Na^(+),K^(+)-decorated porous carbon(Ru/Na^(+),K^(+)-PC)through hydrothermal method and subsequent annealing treatment at 500℃.The Ru/Na^(+),K^(+)-PC exhibits ultralow overpotential of 7 mV at 10 mA·cm^(-2),mass activity of 15.7 A·mgRu^(-1)at 100 mV,and long-term durability of 20,000 cycles potential cycling and 200 h chronopotentiometric measurement with a negligible decrease in activity,much superior to benchmarked commercial Pt/C.Density functional theory based calculations show that the energy barrier of H-OH bond breaking is efficiently reduced due to the presence of Na and K ions,thus favoring the Volmer step.Furthermore,the Ru/Na^(+),K^(+)-PC effectively employs solar energy for obtaining H_(2)in both alkaline water and seawater electrolyzer.This finding provides a new strategy to construct high-performance and cost-effective alkaline HER electrocatalyst.

Designing ABC-6 family small pore zeolites by epitaxial growth approach

Aluminosilicate small pore zeolites belonging to ABC-6 family play crucially important roles in the high methanol conversion with the high selectivity of light olefins,gas separation and storage,and selective catalytic reduction of NO_(x).In this work,we report a general method,called the epitaxial growth approach,for designing ABC-6 family small pore zeolites.It is mainly realized through the epitaxial growth on the nonporous SOD-type zeolite in the presence of inorganic cations(Na^(+)and K^(+))combined with a variety of organic structure directing agents(OSDAs).In this case,a series of ABC-6 family small pore zeolites such as ERI-,SWY-,LEV-,AFX-,and PTT-type zeolites have been successfully synthesized within a few hours.More importantly,the advanced focused ion beam(FIB)and the low-dose high-resolution transmission electron microscopy(HRTEM)imaging technique have been utilized for unraveling the zeolite heterojunction at the atomic level during the epitaxial growth process.It turns out(222)crystallographic planes of the SOD-type zeolite substrate provide unique pre-building units,which facilitate the growth of targeted ABC-6 family small pore zeolites along its c-axis.Moreover,the morphologies of ERI-type zeolite can also be tuned through the epitaxial growth approach,achieving a longer lifetime in the methanol conversion.

Isoreticular Regulation of Two-Dimensional Redox-Active Covalent Organic Framework Cathodes for Enhanced Lithium-Ion Storage

A challenge facing scientists is the rational synthesis of highly crystalline covalent organic frameworks(COFs),consisting of both n-type and p-type redox-active units,as cathodes for high-performance lithium-ion batteries(LIBs).Herein,we apply reticular chemistry to regulate a COF platform with the kgm topology via an in-situ postsynthetic oxidation strategy.We integrate both n-type and p-type redox-active units into a resulting COF skeleton—TPDA-DQTA-COF,and this COF-based cathode shows an enhanced performance for LIBs compared to the parent TPDA-DMTA-COF.On account of dual redox-active units for PF6−/Li+costorage,the TPDADQTA-COF cathode presents the highly reversible capacity of 308 mAh g−1 at 0.2 A g^(−1) and the high energy density of 800 Wh kg^(−1).The long-term cycling experiment reveals a capacity retention of 91%after 200 cycles at a low current density of 0.5 A g^(−1).The combined Fourier transform infrared and X-ray photoelectron spectroscopy experiments suggest that the in-situ electrochemical oxidation from the C-OH to the C=O group of COFs occurs during the charging process.We believe our study demonstrates that the atomic-level modification of functional groups in COF-based cathode materials has a significant impact on the macroscopic performance of lithium-ion storage,clearly illustrating the structure-property relationship.

PtCu_(3) nanoalloy@porous PWO_(x) composites with oxygen container function as efficient ORR electrocatalysts advance the power density of room-temperature hydrogen-air fuel cells

It is challenging and desirable to construct Pt-based nanocomposites with oxygen storage function as efficient oxygen reduction reaction(ORR)catalysts for practical proton exchange membrane fuel cells(PEMFCs).Herein,we achieve novel porous nanocomposites of PtCu_(3) nanoalloys-embedded in the PWO_(x) matrix(PtCu_(3)@PWO_(x)),which has an oxygen container feature.The PtCu_(3)@PWO_(x)/C exhibits an ultrahigh mass activity(MA)of 3.94 A·mgPt−1 for ORR,which is 26.3 times as high as the commercial Pt/C and the highest value ever reported for PtCu-based binary system.Theoretical calculations reveal that the compressive strain and d-band center downshift of Pt intrinsically contribute to the excellent ORR performance.In H_(2)-air PEMFCs at room temperature,furthermore,the PtCu_(3)@PWO_(x)/C delivers a high power density(218.6 mW·cm^(−2)),much superior to commercial Pt/C(131.6 mW·cm^(−2)).In H_(2)-O_(2) PEMFCs,PtCu_(3)@PWO_(x)/C outputs a maximum power density of 420.1 mW·cm^(−2).This work provides an effective idea for designing oxygen-storing ORR catalysts used for practical room-temperature H_(2)-air fuel cells.

Metal support interaction of defective-rich CuO and Au with enhanced CO low-temperature catalytic oxidation and moisture resistance

Water is considered to be an inhibitor of CO oxidation.The mechanism of retarding the reaction is thought to contribute to the practical application of CO oxidation,which is investigated by constructing the coupling of Au nanoparticles and defective CuO to form metal-support interactions(MSI)and oxygen vacancies(OVs).The introduction of Au forms a new CO adsorption site,which successfully solves the competitive adsorption problem of CO with H2O and O_(2).Due to the coupling of MSI and OVs,the reduced ability of catalyst and the activation and migration ability of oxygen are enhanced simultaneously.Au-CuO has the ability to oxidize CO at room temperature with high stability under a humid environment.Theoretical calculation confirmed the competitive adsorption and the influence of MSI and OVs coupling on the catalyst performance.The mechanism of water resistance in CO catalytic oxidation was also explained.

Highly spectra-stable pure blue perovskite light-emitting diodes based on copper and potassium co-doped quantum dots

Halide perovskite light emitting diodes(LEDs)have gained great progress in recent years.However,mixed-halide perovskites for blue LEDs usually suffer from electroluminescence(EL)spectra shift at a high applied voltage or current density,limiting their efficiency.In this work,we report a strategy of using single-layer perovskite quantum dots(QDs)film to tackle the electroluminescence spectra shift in pure-blue perovskite LEDs and improve the LED efficiency by co-doping copper and potassium in the mixed-halide perovskite QDs.As a result,we obtained pure-blue halide perovskite QD-LEDs with stable EL spectra centred at 469 nm even at a current density of 1,617 mA·cm^(−2).The optimal device presents a maximum external quantum efficiency(EQE)of 2.0%.The average maximum EQE and luminance of the LEDs are 1.49%and 393 cd·m^(−2),increasing 62%and 66%compared with the control LEDs.Our study provides an effective strategy for achieving spectra-stable and highly efficient pure-blue perovskite LEDs.

MnO2-directed synthesis of NiFe-LDH@FeOOH nanosheeet arrays for supercapacitor negative electrode

The complex-architectured NiFe-LDH@FeOOH negative material was first prepared by simple two-step hydrothermal method.In this study,the porous nanostructure of FeOOH nanosheets features a large number of accessible channels to electroactive sites and the two-dimensional layered structure of NiFe-LDH nanosheets have an open spatial structure with high specific surface area,which enhance the diffusion of ions in the active material.Benefited from above advantages,the excellent electrochemical properties were demonstrated.NiFe-LDH@FeOOH nanocomposites present high specific capacitance(1195 F/g at a current density of 1 A/g),lower resistance and well cycling performance(90.36% retention after 1000 cycles).Furthermore,the NiFe-LDH@MnO2//NiFe-LDH@FeOOH supercapacitor exhibits22.68 Wh/kg energy density at 750 W/kg power density,demonstrating potential application in energy storage devices.

Low-coordinated surface sites make truncated Pd tetrahedrons as robust ORR electrocatalysts outperforming Pt for DMFC devices

Developing highly stable and active non-Pt oxygen reduction reaction(ORR)electrocatalysts for power generation device raises great concerns and remains a challenge.Here,we report novel truncated Pd tetrahedrons(T-Pd-Ths)enclosed by{111}facets with excellent uniformity,which have both low-coordinated surface sites and distinct lattice distortions that would induce“local strain”.In alkaline electrolyte,the T-Pd-Ths/C achieves remarkable ORR specific/mass activity(SA/MA)of 2.46 mA·cm^(−2)/1.69 A·mgPd^(−1),which is 12.3/16.9 and 10.7/14.1 times higher than commercial Pd/C and Pt/C,respectively.The T-Pd-Ths/C also exhibits high in-situ carbon monoxide(CO)tolerance and 50,000 cycles durability with an activity loss of 7.69%and morphological stability.The rotating ring-disk electrode(RRDE)measurements show that a 4-electron process occurs on T-PdThs/C.Theoretical calculations demonstrate that the low-coordinated surface sites contribute largely to the enhancement of ORR activity.In actual direct methanol fuel cell(DMFC)device,the T-Pd-Ths/C delivers superior open-circuit voltage(OCV)and peak power density(PPD)to commercial Pt/C from 25 to 80℃,and the maximum PPD can reach up to 163.7 mW·cm−2.This study demonstrates that the T-Pd-Ths/C holds promise as alternatives to Pt for ORR in DMFC device.

Facile Exfoliation of Two-Dimensional Crystalline Monolayer Nanosheets from an Amorphous Metal-Organic Framework

The large-scale preparation ofmonolayer two-dimensional(2D)material remains a great challenge,which hinders its real-world applications.Herein,we report a novel layered metal–organic framework(MOF),IPM-1,whichwas synthesized froma cage-like organic linker,with extremely weak interlaminar interaction.When subjected to external disturbance,IPM-1 degenerated into an intermediate state between the crystalline and amorphous phase,in which the layers retain the inplane two-dimensional periodic structure but aremisaligned in the third dimension,leading to the loss of apparent porosity and crystallinity.This amorphous IPM-1 is readily exfoliated at gramscale into crystalline 2D nanosheets with a thickness of 1.15 nm,excellent thickness homogeneity,lateral size up to 10μm,and restored microporosity.IPM-1 nanosheets exhibit high chemical stability and catalytic activity in the oxidation of alcohol,combining the advantages of both homogeneous and heterogeneous catalyst.This work underscores that MOFs without apparent crystallinity can be ideal precursors for the successful preparation of 2D crystalline monolayer nanosheets.

Interface-rich Au-doped PdBi alloy nanochains as multifunctional oxygen reduction catalysts boost the power density and durability of a direct methanol fuel cell device

The development of cathode oxygen reduction reaction(ORR)catalysts with high characteristics for practical,direct methanol fuel cells(DMFCs)has continuously increased the attention of researchers.In this work,interface-rich Au-doped PdBi(PdBiAu)branched one-dimensional(1D)alloyed nanochains assembled by sub-6.5 nm particles have been prepared,exhibiting an ORR mass activity(MA)of 6.40 A·mgPd^(−1) and long-term durability of 5,000 cycles in an alkaline medium.The MA of PdBiAu nanochains is 46 times and 80 times higher than that of commercial Pt/C(0.14 A·mgPt^(−1))and Pd/C(0.08 A·mgPd^(−1)).The MA of binary PdBi nanochains also reaches 5.71 A·mgPd^(−1).Notably,the PdBiAu nanochains exhibit high in-situ carbon monoxide poisoning resistance and high methanol tolerance.In actual DMFC device tests,the PdBiAu nanochains enhance power density of 140.1 mW·cm^(−2)(in O_(2))/112.4 mW·cm^(−2)(in air)and durability compared with PdBi nanochains and Pt/C.The analysis of the structure–function relationship indicates that the enhanced performance of PdBiAu nanochains is attributed to integrated functions of surficial defect-rich 1D chain structure,improved charge transfer capability,downshift of the d-band center of Pd,as well as the synergistic effect derived from“Pd-Bi”and/or“Pd-Au”dual active sites.