Tandem hydroalkylation and deoxygenation of lignin-derived phenolics to synthesize high-density fuels

Lignin is the most abundant naturally phenolic biomass,and the synthesis of high-performance renewable fuel from lignin has attracted significant attention.We propose the efficient synthesis of high-density fuels using simulated lignin cracked oil in tandem with hydroalkylation and deoxygenation reactions.First,we investigated the reaction pathway for the hydroalkylation of phenol,which competes with the hydrodeoxygenation form cyclohexane.And then,we investigated the effects of metal catalyst types,the loading amount of metallic,acid dosage,and reactant ratio on the reaction results.The phenol hydroalkylation and hydrodeoxygenation were balanced when 180℃ and 5 MPa H_(2)with the alkanes yield of 95%.By extending the substrate to other lignin-derived phenolics and simulated lignin cracked oil,we obtained the polycyclic alkane fuel with high density of 0.918 g·ml^(-1)and calorific value of41.2 MJ·L^(-1).Besides,the fuel has good low-temperature properties(viscosity of 9.3 mm^(2)·s^(-1)at 20℃ and freezing point below-55℃),which is expected to be used as jet fuel.This work provides a promising way for the easy and green production of high-density fuel directly from real lignin oil.

Photoinduced transposed Paternò-Büchi reaction for effective synthesis of high-performance jet fuel

High-energy-density fuels are important for volume-limited aerospace vehicles,but the increase in fuel energy density always leads to poor cryogenic performance.Herein,we investigated the transposed Paternò-Büchi reaction of biomass cyclic ketone and cyclic alkene to synthesize a new kind of alkyl-substituted polycyclic hydrocarbon fuel with high energy density and good cryogenic performance.The triplet-energy-quenching results and phosphorescent emission spectra reveal the sensitization mechanism of the reaction,including photosensitizer excitation,triplettriplet energy transfer,cyclization,and relaxation,and the possible reaction path was revealed by the density functional theory(DFT)calculations.The reaction conditions of photosensitizer type and addition,molar ratio of substrates,reaction temperature,and incident light intensity were optimized,with the target product yield achieving 65.5%.Moreover,the reaction dynamics of the reaction rate versus the light intensity are established.After the hydrogenation-deoxygenation reaction,three fuels with a high density of 0.864-0.938 g·ml^(-1) and a low freezing point of<-55℃ are obtained.This work provides a benign and effective approach to synthesize high-performance fuels.

Conversion of lignin oil and hemicellulose derivative into high-density jet fuel

Synthesizing high-density fuel from lignocellulose can not only achieve green and low-carbon development,but also expand the feedstock source of hydrocarbon fuel.Here,we reported a route of producing high-density fuel from lignin oil and hemicellulose derivative cyclopentanol through alkylation and hydrodeoxygenation,HY with SiO_(2)/Al_(2)O_(3) molar ratio of 5.3 was screened as the alkylation catalyst in the reaction of model phenolic compounds and mixtures,and the reaction conditions were optimized to achieve conversion of phenolic compounds higher than 87%and selectivity of bicyclic and tricyclic products higher than 99%.Then two phenolic pools simulating the composition of two typic lignin oils were studied to validate the alkylation and analyze the competition mechanism of phenolic compounds in mixture system.Finally,real lignin oil from depolymerized of beech powder was tested,and notably80%of phenolic monomers in the oil were converted into fuel precursor.After hydrodeoxygenation,the alkylated product was converted to fuel blend with a density of 0.91 g/mL at 20℃and a freezing point lower than-60℃,very promising as high density fuel.This work provides a facile and energyefficient way of synthesizing high-performance jet fuel directly from lignocellulosic derivatives,which decreases processing energy consumption and improve the utilization rate of feedstock.

Coupling ferromagnetic ordering electron transfer channels and surface reconstructed active species for spintronic electrocatalysis of water oxidation

Sluggish reaction kinetics of oxygen evolution reaction(OER), resulting from multistep proton-coupled electron transfer and spin constriction, limits overall efficiency for most reported catalysts. Herein, using modeled ZnFe_(2-x)Ni_xO_(4)(0 ≤ x ≤ 0.4) spinel oxides, we aim to develop better OER electrocatalyst through combining the construction of ferromagnetic(FM) ordering channels and generation of highly active reconstructed species. The number of symmetry-breaking Fe–O–Ni structure links to the formation of FM ordering electron transfer channels. Meanwhile, as the number of Ni^(3+)increases, more ligand holes are formed, beneficial for redirecting surface reconstruction. The electro-activated ZnFe_(1.6)Ni_(0.4)O_(4) shows the highest specific activity, which is 13 and 2.5 times higher than that of ZnFe_(2)O_(4) and unactivated ZnFe_(1.6)Ni_(0.4)O_(4), and even superior to the benchmark IrO_(2) under the overpotential of 350 mV. Applying external magnetic field can make electron spin more aligned, and the activity can be further improved to 39 times of ZnFe_(2)O_(4). We propose that intriguing FM exchange-field interaction at FM/paramagnetic interfaces can penetrate FM ordering channels into reconstructed oxyhydroxide layers, thereby activating oxyhydroxide layers as spin-filter to accelerate spin-selective electron transfer. This work provides a new guideline to develop highly efficient spintronic catalysts for water oxidation and other spin-forbidden reactions.

Thixotropic composite hydrogels based on agarose and inorganic hybrid gellants

Water can be used as oxidant in conjunction with metal particles to form metal-water propellant to increase the energy of propellant.For this application,water needs to be stored in form of solid and capable of becoming liquid when use.Stable and thixotropic hydrogel has good potential as water-retaining material and oxidant of metal-based propellant.In this study,we prepared organic/inorganic composite hydrogels by combining inorganic gellants hectorite and fumed silica with organic gellant agarose,respectively.The total content of the gellants can be reduced to less than 2%by adding agarose.The influence of agarose on water content,phase transition temperature,centrifugal stability and other basic physical properties of composite hydrogels were discussed.The results show that the composite hydrogels have better thixotropy and stability than pure inorganic hydrogels,and the gel-sol transformation can be realized by applying shear force or heating to the phase transition temperature.The composite hydrogels have good shear thinning ability and improved mechanical stability.Fumed silica/agarose hydrogels have better physical stability,while the thixotropy and shear thinning ability of hectorite/agarose hydrogels are better.

Regulating the interfacial charge transfer and constructing symmetry-breaking sites for the enhanced N_(2) electroreduction activity

The Haber-Bosch process for industrial NH_(3) production is energy-intensive with heavy CO_(2) emissions.Electrochemical N_(2) reduction reaction(NRR)is an attractive carbon-neutral alternative for NH_(3) synthesis,while the challenge associated with N_(2) activation highlights the demand for efficient electrocatalysts.Herein,we demonstrate that PdCu nanoparticles with different Pd/Cu ratios anchored on boron nanosheet(PdCu/B)behave as efficient NRR electrocatalysts toward NH_(3) synthesis.Theoretical and experimental results confirm that the highly efficient NH_(3) synthesis can be achieved by regulating the charge transfer between interfaces and forming a symmetry-breaking site,which not only alleviates the hydrogen evolution but also changes the adsorption configuration of N_(2) and thus optimizes the reaction pathway of NRR over the separated Pd sites.Compared with monometallic Pd/B and Cu/B,the PdCu/B with the optimized Pd/Cu ratio of 1 exhibits superior activity and selectivity for NH_(3) synthesis.This study provides new insight into developing efficient catalysts for small energy molecule catalytic conversion via regulating the charge transfer between interfaces and constructing symmetry-breaking sites.

Metal-oxoacid-mediated oxyhydroxide with proton acceptor to break adsorption energy scaling relation for efficient oxygen evolution

Metal oxyhydroxides(MOOH)generated from irreversible reconstructions of transition metal compounds are intrinsic active species for oxygen evolution reaction,whose activities are still constrained by sluggish deprotonation kinetics and inherent adsorption energy scaling relations.Herein,we construct a tunable proton acceptor(TPA)on oxyhydroxides by in-situ reconstruction of metal oxoacids such as NiC2O4to accelerate deprotonation and break adsorption energy scaling relations during OER.The modified C_(2)O_(4)^(2-)as a TPA can easily extract H of*OH(forming*HC2O4intermediate)and then promote deprotonation by the transmitted hydrogen bond with*OOH along conjugated(H...)O=C-O(-H)chain.As a result,Ni OOH-C2O4shows non-concerted proton-electron transfer and improved deprotonation rate,and delivers a good OER activity(270 mV@10 mA cm-2).The conjugate acidity coefficient(pKa)of the modified oxoacid group can be a descriptor for TPA selection.This TPA strategy can be universally applied to Co-,Fe-,and Ni-based oxyhydroxides to facilitate OER efficiency.

Recent Advances in the Comprehension and Regulation of Lattice Oxygen Oxidation Mechanism in Oxygen Evolution Reaction

Water electrolysis,a process for producing green hydrogen from renewable energy,plays a crucial role in the transition toward a sustainable energy landscape and the realization of the hydrogen economy.Oxygen evolution reaction(OER)is a critical step in water electrolysis and is often limited by its slow kinetics.Two main mechanisms,namely the adsorbate evolution mechanism(AEM)and lattice oxygen oxidation mechanism(LOM),are commonly considered in the context of OER.However,designing efficient catalysts based on either the AEM or the LOM remains a topic of debate,and there is no consensus on whether activity and stability are directly related to a certain mechanism.Considering the above,we discuss the characteristics,advantages,and disadvantages of AEM and LOM.Additionally,we provide insights on leveraging the LOM to develop highly active and stable OER catalysts in future.For instance,it is essential to accurately differentiate between reversible and irreversible lattice oxygen redox reactions to elucidate the LOM.Furthermore,we discuss strategies for effectively activating lattice oxygen to achieve controllable steady-state exchange between lattice oxygen and an electrolyte(OH^(-)or H_(2)O).Additionally,we discuss the use of in situ characterization techniques and theoretical calculations as promising avenues for further elucidating the LOM.

Self-supporting NiFe LDH-MoS_(x) integrated electrode for highly efficient water splitting at the industrial electrolysis conditions

Developing effective and practical electrocatalyst under industrial electrolysis conditions is critical for renewable hydrogen production.Herein,we report the self-supporting NiFe LDH-MoS_(x) integrated electrode for water oxidation under normal alkaline test condition(1 M KOH at 25℃)and simulated industrial electrolysis conditions(5 M KOH at 65℃).Such optimized electrode exhibits excellent oxygen evolution reaction(OER)performance with overpotential of 195 and 290 mV at current density of 100 and 400 mA·cm^(-2) under normal alkaline test condition.Notably,only over-potential of 156 and 201 mV were required to achieve the current density of 100 and 400mA·cm^(-2) under simulated industrial electrolysis conditions.No significant degradations were observed after long-term durability tests for both conditions.When using in two-electrode system,the operational voltages of 1.44 and 1.72 V were required to achieve a current density of 10 and 100 mA·cm^(-2) for the overall water splitting test(NiFe LDH-MoS_(x)/INF||20%Pt/C).Additionally,the operational voltage of employing NiFe LDH-MoS_(x)/INF as both cathode and anode merely require 1.52 V at 50mA·cm^(-2) at simulated industrial electrolysis conditions.Notably,a membrane electrode assembly(MEA)for anion exchange membrane water electrolysis(AEMWEs)using NiFe LDH-MoS_(x)/INF as an anode catalyst exhibited an energy conversion efficiency of 71.8%at current density of 400 mA·cm^(-2)in 1 M KOH at 60℃.Further experimental results reveal that sulfurized substrate not only improved the conductivity of NiFe LDH,but also regulated its electronic configurations and atomic composition,leading to the excellent activity.The easy-obtained and cost-effective integrated electrodes are expected to meet the large-scale application of industrial water electrolysis.

Photocatalytic Synthesis of High-Energy-Density Fuel:Catalysts,Mechanisms,and Challenges

High-energy-density liquid hydrocarbon fuels are generally synthesized using various chemical reactions to improve the performance(e.g.,range,load,speed)of aerospace vehicles.Compared with conventional fuels,such as aviation kerosene and rocket kerosene,these liquid hydrocarbon fuels possess the advantages of high-energy-density and high volumetric calorifi c value;therefore,the fuels have important application value.The photocatalytic process has shown great potential for the synthesis of a diverse range of fuels on account of its unique properties,which include good effi ciency,clean atomic economy,and low energy consumption.These characteristics have led to the emergence of the photocatalytic process as a promising complement and alternative to traditional thermocatalytic reactions for fuel synthesis.Extensive eff ort has been made toward the construction of catalysts for the multiple photocatalytic syntheses of high-energy-density fuels.In this review,we aim to summarize the research progress on the photocatalytic synthesis of high-energy-density fuel by using homogeneous and heterogeneous catalytic reactions.Specifi cally,the synthesis routes,catalysts,mechanistic features,and future challenges for the photocatalytic synthesis of high-energy-density fuel are described in detail.The highlights of this review not only promote the development of the photocatalytic synthesis of high-energy-density fuel but also expand the applications of photocatalysis to other fi elds.

Perspective on synthesis of high-energy-density fuels:From petroleum to coal-based pathway

High-energy–density(HED)fuel is specifically pivotal to improve the performance of volume-limited aircrafts.The widely used HED fuels composed of polycyclic hydrocarbons are mainly synthesized from petroleum feedstocks.In order to ensure abundant supply,alternative resources such as coal should be considered.Herein,we summarize the synthesis methods and properties of typical HED fuels by using petroleum-derived cyclopentadiene(CPD)as key feedstock through dimerization,cycloaddition,hydrogenation and isomerization/photoisomerization reactions,and then propose a blueprint for synthesizing HED fuels from coal.The method to produce CPD from coal is analyzed and feasibility is demonstrated according to theoretical calculations and reported results.This review provides a novel route for synthesis of HED fuels from coal.

Manipulating Spin Polarization of Defected Co_(3)O_(4)for Highly Effi cient Electrocatalysis

Electrocatalytic water splitting is limited by kinetics-sluggish oxygen evolution,in which the activity of catalysts depends on their electronic structure.However,the infl uence of electron spin polarization on catalytic activity is ambiguous.Herein,we successfully regulate the spin polarization of Co_(3)O_(4)catalysts by tuning the concentration of cobalt defects from 0.8 to 14.5%.X-ray absorption spectroscopy spectra and density functional theory calculations confi rm that the spin polarization of Co_(3)O_(4)is positively correlated with the concentration of cobalt defects.Importantly,the enhanced spin polarization can increase hydroxyl group absorption to signifi cantly decrease the Gibbs free energy change value of the OER rate-determining step and regulate the spin polarization of oxygen species through a spin electron-exchange process to easily produce triplet-state O_(2),which can obviously increase electrocatalytic OER activity.In specifi c,Co_(3)O_(4)-50 with 14.5%cobalt defects exhibits the highest spin polarization and shows the best normalized OER activity.This work provides an important strategy to increase the water splitting activity of electrocatalysts via the rational regulation of electron spin polarization.

Low-temperature synthesis of ultrasmall spinel MnxCo3-xO4 nanoparticles for efficient oxygen reduction

Spinel-type manganese-cobalt oxides have been regarded as important class of electrocatalysts for oxygen reduction reaction(ORR).However,they are usually synthesized through oxidation-precipitation under aqueous ammonia and then crystallization at high temperature(150–180℃),which not only increases the energy consumption but also induces the growth of particles that is unfavorable for ORR.Herein,through a facile precipitation-dehydration method,ultrasmall spinel manganese-cobalt oxide nanoparticles(~5 nm)homogeneously dispersed on conductive carbon black(MnxCo3-xO4/C)were fabricated at low temperature(60℃).And the bimetallic composite oxide(Mn1.5Co1.5O4/C)with cubic spinel structure and high Mn content exhibits remarkable enhancement of ORR activity and stability compared with single metal oxide(both Mn3O4/C and Co3O4/C).The essential reason for the enhancement of activity can be attributed to the presence of the mixed Mn^3+ and Mn^4+ cations in Mn1.5Co1.5O4/C.Moreover,the ORR activity of Mn1.5Co1.5O4/C is comparable to that of commercial 20 wt% Pt/C,and the relative current density only decreases 1.4% after 12 h test,exceeding that of Pt/C and most reported manganese-cobalt oxide electrocatalysts.

Donor‐acceptor carbon nitride with electron‐withdrawing chlorine group to promote exciton dissociation

Carbon nitride(C_(3)N_(4))is promising for photocatalytic hydrogen production,but photogenerated electrons and holes in C_(3)N_(4)usually tend to exist as excitons due to intrinsic Coulomb interactions making its photocatalytic activity unsatisfactory.Herein,a well‐designed intramolecular C_(3)N_(4)‐based donor‐acceptor(D‐A)photocatalytic system was constructed to promote exciton dissociation.Due to its good chemical compatibility with melamine and appropriate sublimation property,2‐amino‐4,6‐dichloropyrimidine unit was chosen as the monomer to react with melamine to construct intramolecular D‐A system(CNCl_(x)).The hydrogen evolution rate of CNCl_(0.15)is 15.3 times higher than that of bulk C_(3)N_(4)under visible light irradiation,with apparent quantum efficiency of 13.6%at 420 nm.The enhanced activity is attributed to introduced electron‐withdrawing−Cl group as terminal group in the resulted CNCl_(x) samples,which can build internal electric field to promote the exciton dissociation into free electron and hole.In addition,lower work function value of CNCl_(x) samples indicates that internal electric field can help free electrons and holes transfer to the surface of CNCl_(x) samples for photocatalytic reaction.

Micro-nanoarchitectonic of aluminum-hydrogel propellant with static stability and dynamic rheology

The aluminum-water system is a promising propellant due to high energy and low signal characteristics,and the gel form is easier to store and utilize.In this work,hydrogels of water and aluminum particles were prepared using the low-molecular-weight gellant agarose.The various physical properties of gel systems,including the water loss rate,phase transition temperature,and centrifugal stability at different gellant and aluminum contents,were examined.Rheological properties were assessed through shear thinning tests,thixotropy tests,strain sweep analysis,and frequency sweep experiments.The microstructure of the gel was obtained through scanning electron microscopy images.The results show that the aluminum-hydrogel network structure is composed of micron-scale aluminum and agarose nanosheets,and the unique micro-nanostructure endows the gel with excellent mechanical strength and thermal stability,which improve with increasing gellant and aluminum contents.Notably,the gel with 2% agarose and 20% aluminum had the best performance;the storage modulus reached 90647 Pa,which was within the linear viscoelastic region,and the maximum withstand pressure was 111.2 kPa,which was 118.8% greater than that of the pure hydrogel.Additionally,the gel demonstrates remarkable shear thinning behavior and can undergo gel-sol transformation upon shearing or heating to exceeding 114℃.

Chiral phenethylamine synergistic tricarboxylic acid modified β-cyclodextrin immobilized on porous silica for enantioseparation

In this work, a series of chiral phenethylamine synergistic tricarboxylic acid modified β-cyclodextrin bonded stationary phase for high performance liquid chromatography(HPLC) were synthesized via a simple one-pot synthesis approach. Various racemates(aryl alcohols, flavanones, triazoles, benzoin, etc.) were well separated on the tricarboxylic acid modified chiral stationary phases in both normal and reversed modes with good reproducibility and stability, and the influence of mobile phase composition on resolution(R_(s)) were deeply investigated. The RSD values of Rsfor repeatability and column-to-column were below 1.28% and 3.05%, respectively. Hence, the fabrication of tricarboxylic acid modified chiral stationary phase(CSPs) is a new efficient strategy to improve the application of β-cyclodextrin as CSPs in the field of chromatography.

Fe/Co-based nanoparticles encapsulated in heteroatom-doped carbon electrocatalysts for oxygen reduction reaction

It is crucial to develop low-cost and highly efficient catalysts for oxygen reduction reaction(ORR)which is the key process in electrochemical energy conversion and storage devices.Transition metal-based nanoparticles/carbon materials are an important class of non-noble metal catalysts that have attracted considerable research interest.The topic of this review is mainly focused on carbon encapsulated Fe/Cobased nanoparticles catalysts for ORR,and these catalysts are summarized in categories of metals,oxides,carbides,phosphides,sulfides and hybrid nanoparticles.The structures and morphologies of the carbon matrix as well as compositions of nanoparticles have great influence on the catalytic performance.Numerous catalysts display excellent ORR activity and stability in alkaline media but only a few are efficient in acidic media.In addition,challenges and further strategies on the development of this type of carbon encapsulated nanoparticles catalysts are also proposed.

Engineering interfacial band bending over bismuth vanadate/carbon nitride by work function regulation for efficient solar-driven water splitting

Nature-inspired artificial Z-scheme photocatalyst offers great promise in solar overall water splitting,but its rational design,construction and interfacial charge transfer mechanism remain ambiguous.Here,we design an approach of engineering interfacial band bending via work function regulation,which realizes directional charge transfer at interface and affords direct Z-scheme pathway.Taking BiVO_(4)as prototype,its oxygen vacancy concentration is reduced by slowing down the crystallization rate,thereby changing the work function from smaller to larger than that of polymeric carbon nitride(PCN).Consequently,the photoinduced charge transfer pathway of BiVO_(4)/PCN is switched from type-Ⅱto Z-scheme as evidenced by synchronous illuminated X-ray photoelectron spectroscopy(XPS)and femtosecond transient absorption spectroscopy.Specifically,the direct Z-scheme BiVO_(4)/PCN shows superior photocatalytic performance in water splitting.This work provides deep insights and guidelines to constructing heterojunction photocatalysts for solar utilization.

Framework Zr Stabilized PtSn/Zr-MCM-41 as a Promising Catalyst for Non-oxidative Ethane Dehydrogenation

Non-oxidative ethane dehydrogenation is a promising route to produce ethene.Herein,PtSn supported catalysts were investigated to achieve better ethane dehydrogenation performance by introduction of different Zr promoters,i.e.,framework Zr and ZrO_(2),to mesoporous MCM-41.In-situ XRD,TEM and CO chemisorption show that aggregation of metal particles and phase segregation of Pt_(3)Sn to Pt and PtSn_(3) at high temperature occur for PtSn/M,leading to bad ethane dehydrogenation activity.Strong interaction be-tween ZrO_(2) and PtSn species,as proved by XPS,results in restrained metal particles,which promotes the initial reactivity.However,Pt phase generated on surface is disadvantageous for the desorption of produced ethene as indicated by CO-IR and C_(3)H_(6)-TPD,and pyridine-IR and NH_(3)-TPD indicate strong acidity generated.Both deactivate the catalyst rapidly by deep dehydrogenation and coking.Moderate interaction between PtSn species and Si-O-Zr with much weaker acidity is formed when framework Zr is incorporated into MCM-41,which benefits the dispersion of metal particles,formation of Pt_(3)Sn/Pt species and stabilization of metal species from phase segregation.Outstanding initial ethane conversion and ethene selectivity of ca.99%were achieved for the optimal PtSn/ZrM,which is more coking-tolerant and stable by generating graphitic carbon mainly on support instead of active metals.

Chiral pillar[n]arenes:Conformation inversion,material preparation and applications

Chiral pillar[n]arenes have shown great research value and application prospect in construction of chiral materials and chiral applications,due to their inherent planar chiral configurations,chiral recognition ability,easy modification and highly symmetric hydrophobic cavity.This review systematically summarized the conformation inversion factors of planar chiral pillar[5]arenes(pR/p S),such as solvents,temperature,substituent size,alkyl chains,chiral and achiral guest molecules.We firstly introduced the applications of chiral pillar[n]arenes for constructing chiral materials and pointed out that planar conformation inversion showed a great potential role in constructing chiral materials.Then,we mainly concluded the chiral applications of chiral and planar chiral pillar[n]arenes like chiral enantiomer analysis by circular dichroism,electrochemistry or chiral fluorescence sensing.From this review,we found that the inherent planar chiral conformation of chiral pillar[n]arenes have played a very important role in chiral field in the future.