Based on experimental results in which VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at%V nanocomposite, a VH/MgH2 in- terface is designed and constituted in this work. A first-princ...Based on experimental results in which VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at%V nanocomposite, a VH/MgH2 in- terface is designed and constituted in this work. A first-principles plane-wave pseudopo- tential method based on Density Functional Theory (DFT) has been used to investigate the vanadium alloying effects on the dehydrogenating properties of magnesium hydride, i.e., MgH2. A low absolute value of the negative heat of formation of VH/MgH2 interface compared with that of MgH2 indicates that vanadium hydrides befit to improve the dehydrogenating properties of MgH2. Based on the analysis of the density of states (DOS) and the total valence electron density distribution of MgH2 before and after V alloying, it was found that the improvement of the dehydrogenating properties of MgH2 caused by V alloying originates from the increasing of the valence electrons at Fermi level (EF) and the decreasing of the HOMO-LUMO gap ( Δ E H ?L) after V alloying. The catalysis effect of V on dehydrogenating kinetics of MgH2 may attribute to a stronger bonding between V and H atoms than that between Mg and H atoms, which leads to nucleation of the α-Mg at the VH/MgH2 interface in the MgH2-V systems easier than that in pure MgH2 phase.展开更多
Organoboron compounds have become important intermediates for the construction of new compounds in synthetic chemistry and pharmaceutical chemistry,and it has been found that pinacol biborate(B_(2)pin_(2))as the boron...Organoboron compounds have become important intermediates for the construction of new compounds in synthetic chemistry and pharmaceutical chemistry,and it has been found that pinacol biborate(B_(2)pin_(2))as the boron source and Cu^(Ⅱ) organophosphorus complex(L)as the catalyst can effectively realize the hydrogen-reduced borylation products and dehydrohydrated borylation products of aryl olefins.The reaction regioselectivity involvingβ-C positions of aryl olefins can be controlled by regulating the ligand and additive types.The formation mechanism of the product is conducted at LCu^(Ⅰ)Bpin formed from Cu^(Ⅱ),L and B_(2)pin_(2).Subsequently the substrate aryl olefins undergo addition reaction to form the active intermediate PhCH(LCu^(Ⅰ))CH_(2)Bpin.Followed by the metathesis of the active intermediate with water to form hydrogen reduction products,the same active intermediate can be oxidized with 2,2,6,6-tetramethylpiperidoxyl(TEMPO)to form trans dehydrogenation products.展开更多
The dehydrogenation of alkanes has emerged as a vital complementary process to address the increasing global demand for olefins.A key challenge remains in the construction of novel active centers that offer superior a...The dehydrogenation of alkanes has emerged as a vital complementary process to address the increasing global demand for olefins.A key challenge remains in the construction of novel active centers that offer superior activity,stability,and cost-effectiveness.Herein,tricoordinated cobalt atoms were successfully fabricated through an in-situ ligand-protected synthesis by introducing tungsten atoms into zeolite frameworks.These unsaturated Co species efficiently activate C-H bonds while suppressing C-C bond cleavage,resulting in exceptional catalytic activity and olefin selectivity in both propane and ethane dehydrogenation reactions.The optimized Co_(0.2%)@0.01W-S-1 catalyst demonstrated an impressive propylene formation rate of 15.2 molC_(3H6)gcC h^(-1)at 823 K and an ethylene formation rate of 240.3mol_(C2H4)g_(Co)^(-1)h^(-1)at 913 K,with propylene and ethylene selectivities of 99.0%and 97.5%,respectively.These results not only significantly surpass conventional tetracoordinated Co catalysts but also rival some Pt-based catalysts under similar conditions.Importantly,the catalyst exhibited excellent stability in dehydrogenation reactions,with no significant loss in catalytic activity after five consecutive regeneration cycles.This work offers valuable insights into the design of zeolite-supported non-precious metal catalysts with high activity and durability for efficient alkane dehydrogenation.展开更多
Non-oxidative dehydrogenation of propane(PDH)is an important route for large-scale on purpose propene production.Although cobalt-based catalysts are promising alternatives to currently used platinum-or chromium oxide-...Non-oxidative dehydrogenation of propane(PDH)is an important route for large-scale on purpose propene production.Although cobalt-based catalysts are promising alternatives to currently used platinum-or chromium oxide-based catalysts,their further developments are hindered by the uncertainties related to the kind of the active sites involved in the desired and side reactions.To contribute to closing such a gap,we systematically investigate the role of oxidized CoO_(x) and metallic Co0 species in the PDH reaction over catalysts based in Silicalite-1 with supported CoO_(x) species differing in their redox properties.C_(3)H_(8) pulse experiments with sub-millisecond and second resolution at pulse sizes of about 13 and 2200 nmol,respectively,combined with in-depth catalyst characterization and PDH tests at different propane conversions enabled us to understand how the reaction-induced reduction of CoO_(x) affects product selectivity.Propane readily reacts with CoO_(x) to yield propene,carbon oxides and water.The formed Co0 species show high activity to coking and cracking reactions.However,if the size of such species is below 2 nm,these undesired reactions are significantly hindered due to the coverage of the active sites by carbon-containing species.The remaining uncovered surface Co0 sites selectively dehydrogenate propane to propene.The best-performing catalyst showed higher activity than a commercial-like K-CrOx/Al_(2)O_(3) and operated durable in a series of 10 dehydrogenation/regeneration cycles under industrial relevant conditions.The space time yield of propene formation of 0.97 kg·h^(-1)·kgcat^(-1) was achieved at 550℃,52%equilibrium propane conversion and 95% propene selectivity.展开更多
Modifying the electronic density of states and the synergistic effect of the active centers by introducing a second metal present an efficient strategy to tune physi/chemi-sorption,probably lead to improving catalytic...Modifying the electronic density of states and the synergistic effect of the active centers by introducing a second metal present an efficient strategy to tune physi/chemi-sorption,probably lead to improving catalytic performances.Herein,bimetallic Ni_(3)Mo/Al_(2)O_(3)catalyst was demonstrated and exhibited over 5 times more active than Pt/Al_(2)O_(3)toward the ethane dehydrogenation(EDH)as well as 2-10 times activity enhancement compared with their monometallic Ni and Mo counterparts and other Ni-based bimetallic nanoparticles.Kinetic studies revealed that the activation energy over Ni_(3)Mo/Al_(2)O_(3)(111 kJ mol^(-1))was much lower than that of Ni(157 kJ mol^(-1))and Mo(171 kJ·mol^(-1)).DFT calculations showed ethane was adsorbed on the Ni or Mo surface in a more parallel configuration,whereas over Ni_(3)Mo it adopted an inclined configuration.This change promoted ethane adsorption and pre-activation of the C-H bond,thereby benefiting the ethane dehydrogenation process on the Ni_(3)Mo surface.展开更多
The bicarbonate-formate(HCO_(3)−–HCO_(2)−)interconversion provides a promising cycle for a conveniently accessible hydrogen storage system via reversible dehydrogenation and hydrogenation processes.Existing catalytic...The bicarbonate-formate(HCO_(3)−–HCO_(2)−)interconversion provides a promising cycle for a conveniently accessible hydrogen storage system via reversible dehydrogenation and hydrogenation processes.Existing catalytic systems often use organic solvents,tedious optimization as well as manipulation of pH values,solvent,pressure and various additives.Herein,we present an operational,robust,safe and cost-effective catalytic system for hydrogen storage and liberation.We have established a unique catalytic system with two different solid organometallic assemblies(NHC-Ru and NHC-Ir)that facilitate the reversible transformation between sodium formate and bicarbonate in aqueous solutions collaboratively and efficiently.Notably,the NHC-Ru catalyst is privileged for the hydrogenation of sodium bicarbonate,whereas the NHC-Ir component enables the dehydrogenation of sodium formate,all in a single reaction vessel.What sets this system apart is its simplicity.The H_(2)discharging and recharging is simply regulated by heating the mixture with or without H_(2).Remarkably,this process requires no extra additives or supplementary treatments.Moreover,the reversible hydrogen storage system is durable and can be reused for over 30 cycles without a discernible decline in activity and selectivity.The strategic paradigm in this study shows significant practical potential in hydrogen fuel cell applications.展开更多
Photocatalytic water splitting using natural solar light is considered as a sustainable approach to generate H_(2) and O_(2).While H_(2) has high market value,the by-product of water splitting,oxygen,is less valuable....Photocatalytic water splitting using natural solar light is considered as a sustainable approach to generate H_(2) and O_(2).While H_(2) has high market value,the by-product of water splitting,oxygen,is less valuable.To make H_(2) produced by means of photocatalysis more economically competitive to that generated from methane,its generation is studied together with synthesis of organic compounds that have higher market value.This review summarizes and analyzes critically dehydrogenation reactions that were developed since 1980s.Photocatalytic dehydrogenation reactions are classified and the results are collected in the online database.Performance of homogeneous and heterogenous photocatalysts in dehydrogenation reactions,such as yield rates of organic products on analytical and preparative scales,and quantum efficiencies are compared.Current limitations of the existing methods and photocatalytic systems are identified and directions for the future developments are outlined.展开更多
Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally ...Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally friendly and cost-effective alternatives.In this study,we developed a facile impregnation method to fabricate unsaturated Co single-atoms with a tricoordinated Co_(1)O_(3)H_(x) structure by regulating silanol nests in purely siliceous Beta zeolites.Detailed PDH catalytic tests and characterizations revealed a positive correlation between the presence of silanol nests and enhanced catalytic activity.Additionally,the unsaturated Co single-atoms exhibited a carbon deposition rate more than an order of magnitude slower than that of Co nanoparticles.Notably,the optimized Co_(0.3%)/deAl-meso-Beta catalyst achieved a record-high propylene formation rate of 21.2 mmol_(C3H6) g_(cat)^(-1) h^(-1),with an exceptional propylene selectivity of 99.1%at 550℃.Moreover,the Co_(0.3%)/deAl-meso-Beta catalyst demonstrated excellent stability,with negligible deactivation after 5 consecutive regeneration cycles.This study emphasizes the pivotal role of silanol nests of zeolites in stabilizing and modulating the coordination environment of metallic active sites,providing valuable insights for the design of high-activity,high-stability,and low-cost PDH catalysts.展开更多
Herein,we report the multi-metal atomic catalysts for solid-state dehydrogenation of MgH_(2).It aims to reveal the multi-element synergy in catalysts for solid-state hydrogen storage.The kinetic measurements and fitti...Herein,we report the multi-metal atomic catalysts for solid-state dehydrogenation of MgH_(2).It aims to reveal the multi-element synergy in catalysts for solid-state hydrogen storage.The kinetic measurements and fitting reveal two mechanisms:one shows a maximum rate at the early stage,such as V and Cr;the other needs a temperature-sensitive preparation time for its maximum rate,such as Ni.The combina-tion of two catalyst components demonstrates the best kinetics:V and Cr boost the initial dehydrogena-tion,and Ni benefits the further hydrogen transfer which alleviates the rate of decay.This work provides guidelines for the design of multi-element doped catalysts for MgH_(2) dehydrogenation.展开更多
The single-atom M-N-C(M typically being Co or Fe)is a prominent material with exceptional reactivity in areas of catalysis for sustainable energy.However,the formation of metal nanoparticles in M-N-C materials is coup...The single-atom M-N-C(M typically being Co or Fe)is a prominent material with exceptional reactivity in areas of catalysis for sustainable energy.However,the formation of metal nanoparticles in M-N-C materials is coupled with hightemperature calcination conditions,limiting the density of M-Nx active sites and thus restricting the catalytic performance of such catalysts.Herein,we describe an effective decoupling strategy to construct high-density M-Nx active sites by generating polyfurfuryl alcohol in the MOF precursor,effectively preventing the formation of metal nanoparticles even with up to 6.377%cobalt loading.This catalyst showed a high H_(2) production rate of 778mLgcat^(−1) h^(−1) when used in the dehydrogenation reaction of formic acid.In addition to the high density of the active site,a curved carbon surface in the structure is also thought to be the reason for the high performance of the catalyst.展开更多
Recent studies have revealed the extraordinary performance of zirconium oxide in propane dehydrogenation,which is attributed to the excellent reactivity of the coordinatively unsaturated zirconium sites(Zr_(cus))aroun...Recent studies have revealed the extraordinary performance of zirconium oxide in propane dehydrogenation,which is attributed to the excellent reactivity of the coordinatively unsaturated zirconium sites(Zr_(cus))around the oxygen vacancies.The origin of the enhanced catalytic activity of ZrO_(2)with defective tetrahedral Zr sites was examined by direct comparison with its pristine counterpart in the current study.Electronic-structure analysis revealed that electrons from oxygen removal were localized within vacancies on the defective surface,which directly attacked the C-H bond in propane.The involvement of localized electrons activates the C-H bond via back-donation to the antibonding orbital on the defective surface;conversely,charge is transferred from propane to the pristine surfaces.The barrier for the first C-H bond activation is clearly significantly reduced on the defective surfaces compared to that on the pristine surfaces,which verifies the superior activity of Zr_(cus).Notably,however,the desorption of both propene and hydrogen molecules from Zr_(cus)is more difficult due to strong binding.The calculated turnover frequency(TOF)for propene formation demonstrates that the pristine surfaces exhibit better catalytic performance at lower temperatures,whereas the defective surfaces have a larger TOF at high temperatures.However,the rate-determining step and reaction order on the defective surface differ from those on the pristine surface,which corroborates that the catalysts follow different mechanisms.A further optimization strategy was proposed to address the remaining bottlenecks in propane dehydrogenation on zirconium oxide.展开更多
In response to the increasing demand of ethylene,electrochemical ethane nonoxidative dehydrogenation(EENDH)to ethylene by protonic ceramic electrolysis cells(PCECs)is developed.However,existing anode materials exhibit...In response to the increasing demand of ethylene,electrochemical ethane nonoxidative dehydrogenation(EENDH)to ethylene by protonic ceramic electrolysis cells(PCECs)is developed.However,existing anode materials exhibit poor proton conductivity and limited catalytic activity.Herein,a novel Sr_(1.95)Fe_(1.4)Co_(0.1)Mo_(0.4)Zr_(0.1)O_(6-δ)(SFCMZ)anode is prepared as PCECs anode for EENDH.Zr doping increases the oxygen vacancies and enhances the proton conductivity of SFCMZ.Moreover,an alloy-oxide heterostructure(Co Fe@SFCMZ)is formed through in-situ exsolution of Co Fe alloy nanoparticles under reduction conditions,generating abundant oxygen vacancies and improving its catalytic activity.Co Fe@SFCMZ cell achieves an electrolysis current density of 0.87 A/cm^(2) at 700℃ under 1.6 V,with an ethane conversion rate of 34.22%and corresponding ethylene selectivity of 93.4%.These results demonstrate that Co Fe@SFCMZ anode exhibits excellent electrocatalytic activity,suggesting promising applications for EENDH.展开更多
Crystalized CeO_(2)structures were typically considered potential photocatalysts due to their great capacity to alter the active sites’size and ability to absorb light.However,the controllable fabrication of well-def...Crystalized CeO_(2)structures were typically considered potential photocatalysts due to their great capacity to alter the active sites’size and ability to absorb light.However,the controllable fabrication of well-defined hierarchical structures of CeO_(2)with high reactive facets is significant and challenging.Herein,a series of CeO_(2)supports including hierarchical flower-like(F-CeO_(2)),ball-like(B-CeO_(2)),cube-like(C-CeO_(2)),and rod-like CeO_(2)(R-CeO_(2))supports were prepared by hydrothermal method(BCeO_(2),R-CeO_(2)and C-CeO_(2))or ice-bath method(F-CeO_(2))respectively.V atoms were selected as the active atoms and loaded on these supports.Their structure-activity relationship in photo-assisted thermal propane dehydrogenation(PTPDH)was investigated systematically.The samples were characterized by Xray diffraction,scanning electron microscopy,transmission electron microscopy,N2 adsorption-desorption isotherms,and Fourier transform infrared spectrum.Results show that R-CeO_(2)support exhibits the biggest surface area thus achieving the best dispersion of VOx species.UV-vis spectrum and photoluminescence spectrum indicate that V/F-CeO_(2)has the best light adsorption property and V/R-CeO_(2)has the best carrier migration capacity.The activity tests demonstrate that the V/R-CeO_(2)has the largest net growth rate and the V/F-CeO_(2)has the biggest relative growth ratio.Furthermore,the non-thermal effect was confirmed by the kinetic method,which lowers the propane reaction orders,selectively promoting the first C-H bond activation.The light radiation TPSR experiment confirmed this point.DFT calculations show a good linear relationship between the energy barrier and the exchanged electron number.It inspires the design of high-reactive facets for boosting the intrinsic activity of the C-H bond in photoassisted thermal chemical processes.展开更多
Propane dehydrogenation(PDH)is a vital industrial process for producing propene,utilizing primarily Cr-based or Pt-based catalysts.These catalysts often suffer from challenges such as the toxicity of Cr,the high costs...Propane dehydrogenation(PDH)is a vital industrial process for producing propene,utilizing primarily Cr-based or Pt-based catalysts.These catalysts often suffer from challenges such as the toxicity of Cr,the high costs of noble metals like Pt,and deactivation issues due to sintering or coke formation at elevated temperatures.We introduce an exceptional Ru-based catalyst,Ru nanoparticles anchored on a nitrogendoped carbon matrix(Ru@NC),which achieves a propane conversion rate of 32.2%and a propene selectivity of 93.1%at 550°C,with minimal coke deposition and a low deactivation rate of 0.0065 h^(-1).Characterizations using techniques like TEM and XPS,along with carefully-designed controlled experiments,reveal that the notable performance of Ru@NC stems from the modified electronic state of Ru by nitrogen dopant and the microporous nature of the matrix,positioning it as a top contender among state-of-the-art PDH catalysts.展开更多
Owing to high thermal stability and large reaction enthalpy,Mg H_(2) has high reaction temperatures and sluggish reaction kinetics in the dehydrogenation process,which consumes lots of energy.To achieve hydrogen relea...Owing to high thermal stability and large reaction enthalpy,Mg H_(2) has high reaction temperatures and sluggish reaction kinetics in the dehydrogenation process,which consumes lots of energy.To achieve hydrogen release with low energy consumption,accelerated reaction rate,and high heating uniformity,this paper proposes a novel method of graphite responsive microwave-assisted thermal management with NaTiO_(x)H catalyst.A multi-physics model of the 5 wt%NaTiO_(x)H catalyzed Mg H_(2) reactor integrated with a microwave generator is developed to investigate the reaction,heat and mass transfer process of hydrogen release.It is found that the graphite responsive microwave heating method could improve the temperature uniformity of reaction bed,reduce the energy consumption by at least 10.71%and save the hydrogen release time by 53.49% compared with the traditional electric heating method.Moreover,the hydrogen desorption thermodynamics could be improved with the increase of microwave power.The hydrogen release time is shortened by 19.55%with the increase of 20 W microwave power.Meanwhile,it is also concluded that the microwave excitation frequency of 2.1 GHz and the graphite content of 2 wt%have better heating performance.Therefore,it can be verified that the graphite responsive microwave heating helps to low-energy and accelerated hydrogen release from MgH_(2) hydrogen storage reactor.展开更多
Dispersing metals from nanoparticles to clusters is often achieved using ligand protection methods,which exhibit unique properties such as suppressing structure-sensitive side reactions.However,this method is limited ...Dispersing metals from nanoparticles to clusters is often achieved using ligand protection methods,which exhibit unique properties such as suppressing structure-sensitive side reactions.However,this method is limited by the use of different metal precursor salts corresponding to different ligands.An alternative approach,the ion exchange(IE)method,can overcome this limitation to some extent.Nevertheless,there is still an urgent need to address the stabilization of metals(especially precious metals)by using IE method.Here,we reported a Pt cluster catalyst prepared mainly by anchoring Pt atoms via O located near the framework Zn in zincosilicate zeolites and riveted by zeolite surface rings after reduction(reduced Pt/Zn-3-IE).The catalyst can achieve an initial propane conversion of 26%in a pure propane atmosphere at 550℃and shows little deactivation even after 7.5 d of operation.Moreover,the alteration of catalyst by the introduction of framework Zn was also highlighted and interpreted.展开更多
Transition metal cobalt exhibits strong activation capabilities for alkanes,however,the instability of Co sites leads to sintering and coke deposition,resulting in rapid deactivation.Hierarchical zeolites,with their d...Transition metal cobalt exhibits strong activation capabilities for alkanes,however,the instability of Co sites leads to sintering and coke deposition,resulting in rapid deactivation.Hierarchical zeolites,with their diverse pore structures and high surface areas,are used to effectively anchor metals and enhance coke tolerance.Herein,a post-treatment method using an alkaline solution was employed to synthesize meso-microporous zeolite supports,which were subsequently loaded with Co species for propane dehydrogenation catalyst.The results indicate that the application of NaOH,an inorganic base,produces supports with a larger mesopore volume and more abundant hydroxyl nests compared to TPAOH,an organic base.UV-vis,Raman,and XPS analyses reveal that Co in the 0.5Co/SN-1-0.05 catalyst is mainly in the form of tetrahedral Co^(2+),which effectively activates C-H bonds.In contrast,the 0.5Co/S-1 catalyst contains mainly Co_(3)O_(4)species.Co^(2+)supported on hierarchical zeolites shows better propane conversion(58.6%)and propylene selectivity(>96%)compared to pure silica zeolites.Coke characterization indicates that hierarchical zeolites accumulate more coke,but it is mostly in the form of easily removable disordered carbon.The mesopores in the microporous zeolite support help disperse the active Co metal and facilitate coke removal during dehydrogenation,effectively preventing deactivation from sintering and coke coverage.展开更多
Magnesium-based hydrogen storage materials are promising candidates for hydrogen storage due to their high storage density and environmentally friendly properties.However,the high dehydrogenation enthalpy change(appro...Magnesium-based hydrogen storage materials are promising candidates for hydrogen storage due to their high storage density and environmentally friendly properties.However,the high dehydrogenation enthalpy change(approximately 75 kJ/mol H_(2))and high dehydrogenation temperature(573 K at 0.1 MPa)of MgH_(2),limits the engineering application of Mg/MgH_(2) as a hydrogen storage material.This work reviews the prediction models and methods of enthalpy changes for hydriding/dehydriding(H/D)reactions in order to find out the ideas and ways to reduce them.The mechanism behind the improvement methods mainly includes two aspects,weakening Mg-H bond and compensating heat of reaction.Proceed from this,the experimental methods and enthalpy data as well as calculated values of enthalpy changes were compared systematically.Elements such as Ti,Nb,V,etc.,with a small electronegativity difference compared to Mg,can reduce the hydrogenation and dehydrogenation enthalpy changes by forming strong Metal-H or Metal-Mg bonds.In addition,this review concludes with an outlook on the remaining challenge issues and prospects.展开更多
Aiming to provide optimal solutions to the sluggish kinetics of Mg(BH_(4))_(2),this study proposes,for the first time,a novel machine learning model to predict dehydrogenation behaviors of modified Mg(BH_(4))_(2).Nota...Aiming to provide optimal solutions to the sluggish kinetics of Mg(BH_(4))_(2),this study proposes,for the first time,a novel machine learning model to predict dehydrogenation behaviors of modified Mg(BH_(4))_(2).Notably,numerous data points are collected from temperatureprogrammed,isothermal,and cyclic dehydrogenation behaviors,a neural network model is proposed by using multi-head attention mechanisms,which exhibits the highest predictive performance compared to traditional machine learning models.The study also ranks different variables influencing dehydrogenation processes,employing interpretable analysis to identify critical variable thresholds,offering guidance for the experimental parameter design.The model can also be adapted to scenarios involving co-doping of hydrides and catalysts in Mg(BH_(4))_(2) system and proved high accuracy and scalability in predicting dehydrogenation curves under diverse conditions.Employing the model,performance predictions for a series of undeveloped Mg(BH_(4))_(2) co-doping systems can be made,and superior dehydrogenation catalytic effects of fluorinated graphite(FGi)are uncovered.Real-world experimental validation of the optimal Mg(BH_(4))_(2)-LiBH_(4)-FGi system confirms consistency with model predictions,and performance enhancement attributes to experimental parameter optimization.Further characterizations provide mechanistic insights into the synergistic interactions of FGi and LiBH_(4).This work paves the way for advancing utilization of machine learning in the high-capacity hydrogen storage field.展开更多
The selective activation of C-H bonds is pivotal in catalysis for converting hydrocarbons into value-added chemicals.Ethylbenzene dehydrogenation to styrene is crucial process to produce polystyrene and its derivative...The selective activation of C-H bonds is pivotal in catalysis for converting hydrocarbons into value-added chemicals.Ethylbenzene dehydrogenation to styrene is crucial process to produce polystyrene and its derivatives used in synthetic materials.Herein,K-Cr@Y with zeolite-encaged isolated O=Cr(VI)=O species modified by extraframework potassium ions is constructed,showing remarkable performance in CO_(2)-promoted ethylbenzene dehydrogenation with initial ethylbenzene conversion of 66%and styrene selectivity of 96%,outperforming other M-Cr@Y catalysts(M=Li,Na,Rb,Cs).Extraframework potassium ions can modulate the electron density of zeolite-encaged Cr(VI)species and therefore facilitate C–H bond activation in ethylbenzene molecules.The gradual reduction of zeolite-encaged O=Cr(VI)=O to less active Cr(IV)=O species by dihydrogen during ethylbenzene dehydrogenation is evidenced by comprehensive characterization results,and Cr(IV)=O can be re-oxidized to O=Cr(VI)=O species upon simple calcination regeneration.The results from in situ DRIFT spectroscopy elucidate the critical promotion role of CO_(2)in ethylbenzene dehydrogenation over K-Cr@Y by retarding the over-reduction of zeolite-encaged Cr species to inactive Cr(III)species and suppressing coke deposition.This study advances the rational design of non-noble metal catalysts for CO_(2)-promoted ethylbenzene dehydrogenation with zeolite-encaged high valence transition metal ions modulated by extraframework cations.展开更多
文摘Based on experimental results in which VH0.81/MgH2 interface was found during the process of mechanically milling MgH2+5at%V nanocomposite, a VH/MgH2 in- terface is designed and constituted in this work. A first-principles plane-wave pseudopo- tential method based on Density Functional Theory (DFT) has been used to investigate the vanadium alloying effects on the dehydrogenating properties of magnesium hydride, i.e., MgH2. A low absolute value of the negative heat of formation of VH/MgH2 interface compared with that of MgH2 indicates that vanadium hydrides befit to improve the dehydrogenating properties of MgH2. Based on the analysis of the density of states (DOS) and the total valence electron density distribution of MgH2 before and after V alloying, it was found that the improvement of the dehydrogenating properties of MgH2 caused by V alloying originates from the increasing of the valence electrons at Fermi level (EF) and the decreasing of the HOMO-LUMO gap ( Δ E H ?L) after V alloying. The catalysis effect of V on dehydrogenating kinetics of MgH2 may attribute to a stronger bonding between V and H atoms than that between Mg and H atoms, which leads to nucleation of the α-Mg at the VH/MgH2 interface in the MgH2-V systems easier than that in pure MgH2 phase.
文摘Organoboron compounds have become important intermediates for the construction of new compounds in synthetic chemistry and pharmaceutical chemistry,and it has been found that pinacol biborate(B_(2)pin_(2))as the boron source and Cu^(Ⅱ) organophosphorus complex(L)as the catalyst can effectively realize the hydrogen-reduced borylation products and dehydrohydrated borylation products of aryl olefins.The reaction regioselectivity involvingβ-C positions of aryl olefins can be controlled by regulating the ligand and additive types.The formation mechanism of the product is conducted at LCu^(Ⅰ)Bpin formed from Cu^(Ⅱ),L and B_(2)pin_(2).Subsequently the substrate aryl olefins undergo addition reaction to form the active intermediate PhCH(LCu^(Ⅰ))CH_(2)Bpin.Followed by the metathesis of the active intermediate with water to form hydrogen reduction products,the same active intermediate can be oxidized with 2,2,6,6-tetramethylpiperidoxyl(TEMPO)to form trans dehydrogenation products.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1506000)Gusu Innovation and Entrepreneurship Leading Talents Program(ZXL2022497)+5 种基金Jiangsu Distinguished Professor programfinancial support by National Natural Science Foundation of China(Grant No.22301057)Natural Science Foundation of Hebei Province(Grant No.B2023201065)Science Research Project of Hebei Education Department(Grant No.BJK2024103)supported by the Open Research Fund of Shanghai Key Laboratory of High-resolution Electron MicroscopyOpen Project of State Key Laboratory of Supramolecular Structure and Materials(sklssm2024019),ShanghaiTech University。
文摘The dehydrogenation of alkanes has emerged as a vital complementary process to address the increasing global demand for olefins.A key challenge remains in the construction of novel active centers that offer superior activity,stability,and cost-effectiveness.Herein,tricoordinated cobalt atoms were successfully fabricated through an in-situ ligand-protected synthesis by introducing tungsten atoms into zeolite frameworks.These unsaturated Co species efficiently activate C-H bonds while suppressing C-C bond cleavage,resulting in exceptional catalytic activity and olefin selectivity in both propane and ethane dehydrogenation reactions.The optimized Co_(0.2%)@0.01W-S-1 catalyst demonstrated an impressive propylene formation rate of 15.2 molC_(3H6)gcC h^(-1)at 823 K and an ethylene formation rate of 240.3mol_(C2H4)g_(Co)^(-1)h^(-1)at 913 K,with propylene and ethylene selectivities of 99.0%and 97.5%,respectively.These results not only significantly surpass conventional tetracoordinated Co catalysts but also rival some Pt-based catalysts under similar conditions.Importantly,the catalyst exhibited excellent stability in dehydrogenation reactions,with no significant loss in catalytic activity after five consecutive regeneration cycles.This work offers valuable insights into the design of zeolite-supported non-precious metal catalysts with high activity and durability for efficient alkane dehydrogenation.
文摘Non-oxidative dehydrogenation of propane(PDH)is an important route for large-scale on purpose propene production.Although cobalt-based catalysts are promising alternatives to currently used platinum-or chromium oxide-based catalysts,their further developments are hindered by the uncertainties related to the kind of the active sites involved in the desired and side reactions.To contribute to closing such a gap,we systematically investigate the role of oxidized CoO_(x) and metallic Co0 species in the PDH reaction over catalysts based in Silicalite-1 with supported CoO_(x) species differing in their redox properties.C_(3)H_(8) pulse experiments with sub-millisecond and second resolution at pulse sizes of about 13 and 2200 nmol,respectively,combined with in-depth catalyst characterization and PDH tests at different propane conversions enabled us to understand how the reaction-induced reduction of CoO_(x) affects product selectivity.Propane readily reacts with CoO_(x) to yield propene,carbon oxides and water.The formed Co0 species show high activity to coking and cracking reactions.However,if the size of such species is below 2 nm,these undesired reactions are significantly hindered due to the coverage of the active sites by carbon-containing species.The remaining uncovered surface Co0 sites selectively dehydrogenate propane to propene.The best-performing catalyst showed higher activity than a commercial-like K-CrOx/Al_(2)O_(3) and operated durable in a series of 10 dehydrogenation/regeneration cycles under industrial relevant conditions.The space time yield of propene formation of 0.97 kg·h^(-1)·kgcat^(-1) was achieved at 550℃,52%equilibrium propane conversion and 95% propene selectivity.
文摘Modifying the electronic density of states and the synergistic effect of the active centers by introducing a second metal present an efficient strategy to tune physi/chemi-sorption,probably lead to improving catalytic performances.Herein,bimetallic Ni_(3)Mo/Al_(2)O_(3)catalyst was demonstrated and exhibited over 5 times more active than Pt/Al_(2)O_(3)toward the ethane dehydrogenation(EDH)as well as 2-10 times activity enhancement compared with their monometallic Ni and Mo counterparts and other Ni-based bimetallic nanoparticles.Kinetic studies revealed that the activation energy over Ni_(3)Mo/Al_(2)O_(3)(111 kJ mol^(-1))was much lower than that of Ni(157 kJ mol^(-1))and Mo(171 kJ·mol^(-1)).DFT calculations showed ethane was adsorbed on the Ni or Mo surface in a more parallel configuration,whereas over Ni_(3)Mo it adopted an inclined configuration.This change promoted ethane adsorption and pre-activation of the C-H bond,thereby benefiting the ethane dehydrogenation process on the Ni_(3)Mo surface.
基金Financial support from the National Natural Science Foundation of China(No.22271060)。
文摘The bicarbonate-formate(HCO_(3)−–HCO_(2)−)interconversion provides a promising cycle for a conveniently accessible hydrogen storage system via reversible dehydrogenation and hydrogenation processes.Existing catalytic systems often use organic solvents,tedious optimization as well as manipulation of pH values,solvent,pressure and various additives.Herein,we present an operational,robust,safe and cost-effective catalytic system for hydrogen storage and liberation.We have established a unique catalytic system with two different solid organometallic assemblies(NHC-Ru and NHC-Ir)that facilitate the reversible transformation between sodium formate and bicarbonate in aqueous solutions collaboratively and efficiently.Notably,the NHC-Ru catalyst is privileged for the hydrogenation of sodium bicarbonate,whereas the NHC-Ir component enables the dehydrogenation of sodium formate,all in a single reaction vessel.What sets this system apart is its simplicity.The H_(2)discharging and recharging is simply regulated by heating the mixture with or without H_(2).Remarkably,this process requires no extra additives or supplementary treatments.Moreover,the reversible hydrogen storage system is durable and can be reused for over 30 cycles without a discernible decline in activity and selectivity.The strategic paradigm in this study shows significant practical potential in hydrogen fuel cell applications.
文摘Photocatalytic water splitting using natural solar light is considered as a sustainable approach to generate H_(2) and O_(2).While H_(2) has high market value,the by-product of water splitting,oxygen,is less valuable.To make H_(2) produced by means of photocatalysis more economically competitive to that generated from methane,its generation is studied together with synthesis of organic compounds that have higher market value.This review summarizes and analyzes critically dehydrogenation reactions that were developed since 1980s.Photocatalytic dehydrogenation reactions are classified and the results are collected in the online database.Performance of homogeneous and heterogenous photocatalysts in dehydrogenation reactions,such as yield rates of organic products on analytical and preparative scales,and quantum efficiencies are compared.Current limitations of the existing methods and photocatalytic systems are identified and directions for the future developments are outlined.
文摘Propane dehydrogenation(PDH)has emerged as a key on-purpose technology for the production of propylene,but it often depends on toxic chromium and expensive platinum catalysts,highlighting the need for environmentally friendly and cost-effective alternatives.In this study,we developed a facile impregnation method to fabricate unsaturated Co single-atoms with a tricoordinated Co_(1)O_(3)H_(x) structure by regulating silanol nests in purely siliceous Beta zeolites.Detailed PDH catalytic tests and characterizations revealed a positive correlation between the presence of silanol nests and enhanced catalytic activity.Additionally,the unsaturated Co single-atoms exhibited a carbon deposition rate more than an order of magnitude slower than that of Co nanoparticles.Notably,the optimized Co_(0.3%)/deAl-meso-Beta catalyst achieved a record-high propylene formation rate of 21.2 mmol_(C3H6) g_(cat)^(-1) h^(-1),with an exceptional propylene selectivity of 99.1%at 550℃.Moreover,the Co_(0.3%)/deAl-meso-Beta catalyst demonstrated excellent stability,with negligible deactivation after 5 consecutive regeneration cycles.This study emphasizes the pivotal role of silanol nests of zeolites in stabilizing and modulating the coordination environment of metallic active sites,providing valuable insights for the design of high-activity,high-stability,and low-cost PDH catalysts.
基金Yijing Wang acknowledges the funding support of the National Key Research and Development Program of China(No.2021YFB4000604)the National Natural Science Foundation of China(No.52271220)+6 种基金the Higher Education Discipline Innovation Project(No.B12015)“the Fundamental Research Funds for the Central Universities”Huaiyu Shao acknowledges the funding support of the Multi-Year Research Grant(MYRG)from the University of Macao(No.MYRG2022-00105-IAPME)the Joint Scientific Research Project Funding by the National Natural Science Foundation of China and the Macao Science and Technology Development Fund(No.0090/2022/AFJ)the Macao Science and Technology Development Fund(FDCT)for funding No.006/2022/ALC of the Macao Centre for Research and Development in Advanced Materials(No.2022-2024)the Natural Science Foundation of Guangdong Province(Grant No.2023A1515010765)the Shenzhen-Hong Kong-Macao Science and Technology Innovation Project(Category C).
文摘Herein,we report the multi-metal atomic catalysts for solid-state dehydrogenation of MgH_(2).It aims to reveal the multi-element synergy in catalysts for solid-state hydrogen storage.The kinetic measurements and fitting reveal two mechanisms:one shows a maximum rate at the early stage,such as V and Cr;the other needs a temperature-sensitive preparation time for its maximum rate,such as Ni.The combina-tion of two catalyst components demonstrates the best kinetics:V and Cr boost the initial dehydrogena-tion,and Ni benefits the further hydrogen transfer which alleviates the rate of decay.This work provides guidelines for the design of multi-element doped catalysts for MgH_(2) dehydrogenation.
基金National Natural Science Foundation of China,Grant/Award Numbers:21603054,31671930Innovation and entrepreneurship training program for college students of Hebei Agricultural University,Grant/Award Numbers:2019085,s202010086046+2 种基金Scientific Research Development Fund project of Hebei Agricultural University,Grant/Award Number:JY2020028the Natural Science Foundation of Hebei Province,Grant/Award Numbers:B2016204131,B2016204136Young Topnotch Talents Foundation of Hebei Provincial Universities,Grant/Award Number:BJ2016027.
文摘The single-atom M-N-C(M typically being Co or Fe)is a prominent material with exceptional reactivity in areas of catalysis for sustainable energy.However,the formation of metal nanoparticles in M-N-C materials is coupled with hightemperature calcination conditions,limiting the density of M-Nx active sites and thus restricting the catalytic performance of such catalysts.Herein,we describe an effective decoupling strategy to construct high-density M-Nx active sites by generating polyfurfuryl alcohol in the MOF precursor,effectively preventing the formation of metal nanoparticles even with up to 6.377%cobalt loading.This catalyst showed a high H_(2) production rate of 778mLgcat^(−1) h^(−1) when used in the dehydrogenation reaction of formic acid.In addition to the high density of the active site,a curved carbon surface in the structure is also thought to be the reason for the high performance of the catalyst.
文摘Recent studies have revealed the extraordinary performance of zirconium oxide in propane dehydrogenation,which is attributed to the excellent reactivity of the coordinatively unsaturated zirconium sites(Zr_(cus))around the oxygen vacancies.The origin of the enhanced catalytic activity of ZrO_(2)with defective tetrahedral Zr sites was examined by direct comparison with its pristine counterpart in the current study.Electronic-structure analysis revealed that electrons from oxygen removal were localized within vacancies on the defective surface,which directly attacked the C-H bond in propane.The involvement of localized electrons activates the C-H bond via back-donation to the antibonding orbital on the defective surface;conversely,charge is transferred from propane to the pristine surfaces.The barrier for the first C-H bond activation is clearly significantly reduced on the defective surfaces compared to that on the pristine surfaces,which verifies the superior activity of Zr_(cus).Notably,however,the desorption of both propene and hydrogen molecules from Zr_(cus)is more difficult due to strong binding.The calculated turnover frequency(TOF)for propene formation demonstrates that the pristine surfaces exhibit better catalytic performance at lower temperatures,whereas the defective surfaces have a larger TOF at high temperatures.However,the rate-determining step and reaction order on the defective surface differ from those on the pristine surface,which corroborates that the catalysts follow different mechanisms.A further optimization strategy was proposed to address the remaining bottlenecks in propane dehydrogenation on zirconium oxide.
基金financially supported by the National Natural Science Foundation of China(Nos.52272190 and 22178023)the National Key R&D Program of China(No.2021YFB4001401)。
文摘In response to the increasing demand of ethylene,electrochemical ethane nonoxidative dehydrogenation(EENDH)to ethylene by protonic ceramic electrolysis cells(PCECs)is developed.However,existing anode materials exhibit poor proton conductivity and limited catalytic activity.Herein,a novel Sr_(1.95)Fe_(1.4)Co_(0.1)Mo_(0.4)Zr_(0.1)O_(6-δ)(SFCMZ)anode is prepared as PCECs anode for EENDH.Zr doping increases the oxygen vacancies and enhances the proton conductivity of SFCMZ.Moreover,an alloy-oxide heterostructure(Co Fe@SFCMZ)is formed through in-situ exsolution of Co Fe alloy nanoparticles under reduction conditions,generating abundant oxygen vacancies and improving its catalytic activity.Co Fe@SFCMZ cell achieves an electrolysis current density of 0.87 A/cm^(2) at 700℃ under 1.6 V,with an ethane conversion rate of 34.22%and corresponding ethylene selectivity of 93.4%.These results demonstrate that Co Fe@SFCMZ anode exhibits excellent electrocatalytic activity,suggesting promising applications for EENDH.
基金the National Key R&D Program of China(Nos.2021YFA1501301,2021YFC2901100)the National Natural Science Foundation of China(Nos.22178381,22035009).
文摘Crystalized CeO_(2)structures were typically considered potential photocatalysts due to their great capacity to alter the active sites’size and ability to absorb light.However,the controllable fabrication of well-defined hierarchical structures of CeO_(2)with high reactive facets is significant and challenging.Herein,a series of CeO_(2)supports including hierarchical flower-like(F-CeO_(2)),ball-like(B-CeO_(2)),cube-like(C-CeO_(2)),and rod-like CeO_(2)(R-CeO_(2))supports were prepared by hydrothermal method(BCeO_(2),R-CeO_(2)and C-CeO_(2))or ice-bath method(F-CeO_(2))respectively.V atoms were selected as the active atoms and loaded on these supports.Their structure-activity relationship in photo-assisted thermal propane dehydrogenation(PTPDH)was investigated systematically.The samples were characterized by Xray diffraction,scanning electron microscopy,transmission electron microscopy,N2 adsorption-desorption isotherms,and Fourier transform infrared spectrum.Results show that R-CeO_(2)support exhibits the biggest surface area thus achieving the best dispersion of VOx species.UV-vis spectrum and photoluminescence spectrum indicate that V/F-CeO_(2)has the best light adsorption property and V/R-CeO_(2)has the best carrier migration capacity.The activity tests demonstrate that the V/R-CeO_(2)has the largest net growth rate and the V/F-CeO_(2)has the biggest relative growth ratio.Furthermore,the non-thermal effect was confirmed by the kinetic method,which lowers the propane reaction orders,selectively promoting the first C-H bond activation.The light radiation TPSR experiment confirmed this point.DFT calculations show a good linear relationship between the energy barrier and the exchanged electron number.It inspires the design of high-reactive facets for boosting the intrinsic activity of the C-H bond in photoassisted thermal chemical processes.
基金supported by the National Key Research and Development Project of China(No.2022YFE0113800)the National Natural Science Foundation of China(No.22102013)+2 种基金Natural Science Foundation of Chongqing(No.cstc2021jcyj-msxmX0945)Venture and Innovation Support Program for Chongqing Overseas Returnees(No.cx2020107)Thousand Talents Program for Distinguished Young Scholars,Postdoctoral Fellowship Program of CPSF(No.GZB20230910)。
文摘Propane dehydrogenation(PDH)is a vital industrial process for producing propene,utilizing primarily Cr-based or Pt-based catalysts.These catalysts often suffer from challenges such as the toxicity of Cr,the high costs of noble metals like Pt,and deactivation issues due to sintering or coke formation at elevated temperatures.We introduce an exceptional Ru-based catalyst,Ru nanoparticles anchored on a nitrogendoped carbon matrix(Ru@NC),which achieves a propane conversion rate of 32.2%and a propene selectivity of 93.1%at 550°C,with minimal coke deposition and a low deactivation rate of 0.0065 h^(-1).Characterizations using techniques like TEM and XPS,along with carefully-designed controlled experiments,reveal that the notable performance of Ru@NC stems from the modified electronic state of Ru by nitrogen dopant and the microporous nature of the matrix,positioning it as a top contender among state-of-the-art PDH catalysts.
基金supported by the National Key R&D Program of China(2023YFB3809103)the National Natural Science Foundation of China(No.52176203)+2 种基金the Key R&D Project of Shaanxi Province,China(No.2023KXJ-283)the Key R&D Project of Shaanxi Province,China(No.2024CY2-GJHX-19)the“Young Talent Support Plan”of Xi’an Jiaotong University(No.QB-A-JZB2015004)。
文摘Owing to high thermal stability and large reaction enthalpy,Mg H_(2) has high reaction temperatures and sluggish reaction kinetics in the dehydrogenation process,which consumes lots of energy.To achieve hydrogen release with low energy consumption,accelerated reaction rate,and high heating uniformity,this paper proposes a novel method of graphite responsive microwave-assisted thermal management with NaTiO_(x)H catalyst.A multi-physics model of the 5 wt%NaTiO_(x)H catalyzed Mg H_(2) reactor integrated with a microwave generator is developed to investigate the reaction,heat and mass transfer process of hydrogen release.It is found that the graphite responsive microwave heating method could improve the temperature uniformity of reaction bed,reduce the energy consumption by at least 10.71%and save the hydrogen release time by 53.49% compared with the traditional electric heating method.Moreover,the hydrogen desorption thermodynamics could be improved with the increase of microwave power.The hydrogen release time is shortened by 19.55%with the increase of 20 W microwave power.Meanwhile,it is also concluded that the microwave excitation frequency of 2.1 GHz and the graphite content of 2 wt%have better heating performance.Therefore,it can be verified that the graphite responsive microwave heating helps to low-energy and accelerated hydrogen release from MgH_(2) hydrogen storage reactor.
文摘Dispersing metals from nanoparticles to clusters is often achieved using ligand protection methods,which exhibit unique properties such as suppressing structure-sensitive side reactions.However,this method is limited by the use of different metal precursor salts corresponding to different ligands.An alternative approach,the ion exchange(IE)method,can overcome this limitation to some extent.Nevertheless,there is still an urgent need to address the stabilization of metals(especially precious metals)by using IE method.Here,we reported a Pt cluster catalyst prepared mainly by anchoring Pt atoms via O located near the framework Zn in zincosilicate zeolites and riveted by zeolite surface rings after reduction(reduced Pt/Zn-3-IE).The catalyst can achieve an initial propane conversion of 26%in a pure propane atmosphere at 550℃and shows little deactivation even after 7.5 d of operation.Moreover,the alteration of catalyst by the introduction of framework Zn was also highlighted and interpreted.
基金supported by the National Natural Science Foundation of China(Nos.22035009,22178381)the National Key R&D Program of China(Nos.2021YFA1501301,2021YFC2901100)the State Key Laboratory of Heavy Oil Processing(No.2021-03).
文摘Transition metal cobalt exhibits strong activation capabilities for alkanes,however,the instability of Co sites leads to sintering and coke deposition,resulting in rapid deactivation.Hierarchical zeolites,with their diverse pore structures and high surface areas,are used to effectively anchor metals and enhance coke tolerance.Herein,a post-treatment method using an alkaline solution was employed to synthesize meso-microporous zeolite supports,which were subsequently loaded with Co species for propane dehydrogenation catalyst.The results indicate that the application of NaOH,an inorganic base,produces supports with a larger mesopore volume and more abundant hydroxyl nests compared to TPAOH,an organic base.UV-vis,Raman,and XPS analyses reveal that Co in the 0.5Co/SN-1-0.05 catalyst is mainly in the form of tetrahedral Co^(2+),which effectively activates C-H bonds.In contrast,the 0.5Co/S-1 catalyst contains mainly Co_(3)O_(4)species.Co^(2+)supported on hierarchical zeolites shows better propane conversion(58.6%)and propylene selectivity(>96%)compared to pure silica zeolites.Coke characterization indicates that hierarchical zeolites accumulate more coke,but it is mostly in the form of easily removable disordered carbon.The mesopores in the microporous zeolite support help disperse the active Co metal and facilitate coke removal during dehydrogenation,effectively preventing deactivation from sintering and coke coverage.
基金financially supported by the National Key Research and Development Program of China(No.2023YFB3809101)the National Natural Science Foundation of China(No.U23A20128)the Chongqing Science and Technology Commission of China(CSTC2024YCJHBGZXM0041).
文摘Magnesium-based hydrogen storage materials are promising candidates for hydrogen storage due to their high storage density and environmentally friendly properties.However,the high dehydrogenation enthalpy change(approximately 75 kJ/mol H_(2))and high dehydrogenation temperature(573 K at 0.1 MPa)of MgH_(2),limits the engineering application of Mg/MgH_(2) as a hydrogen storage material.This work reviews the prediction models and methods of enthalpy changes for hydriding/dehydriding(H/D)reactions in order to find out the ideas and ways to reduce them.The mechanism behind the improvement methods mainly includes two aspects,weakening Mg-H bond and compensating heat of reaction.Proceed from this,the experimental methods and enthalpy data as well as calculated values of enthalpy changes were compared systematically.Elements such as Ti,Nb,V,etc.,with a small electronegativity difference compared to Mg,can reduce the hydrogenation and dehydrogenation enthalpy changes by forming strong Metal-H or Metal-Mg bonds.In addition,this review concludes with an outlook on the remaining challenge issues and prospects.
基金the National Natural Science Foundation of China(No.52171223 and U20A20237).
文摘Aiming to provide optimal solutions to the sluggish kinetics of Mg(BH_(4))_(2),this study proposes,for the first time,a novel machine learning model to predict dehydrogenation behaviors of modified Mg(BH_(4))_(2).Notably,numerous data points are collected from temperatureprogrammed,isothermal,and cyclic dehydrogenation behaviors,a neural network model is proposed by using multi-head attention mechanisms,which exhibits the highest predictive performance compared to traditional machine learning models.The study also ranks different variables influencing dehydrogenation processes,employing interpretable analysis to identify critical variable thresholds,offering guidance for the experimental parameter design.The model can also be adapted to scenarios involving co-doping of hydrides and catalysts in Mg(BH_(4))_(2) system and proved high accuracy and scalability in predicting dehydrogenation curves under diverse conditions.Employing the model,performance predictions for a series of undeveloped Mg(BH_(4))_(2) co-doping systems can be made,and superior dehydrogenation catalytic effects of fluorinated graphite(FGi)are uncovered.Real-world experimental validation of the optimal Mg(BH_(4))_(2)-LiBH_(4)-FGi system confirms consistency with model predictions,and performance enhancement attributes to experimental parameter optimization.Further characterizations provide mechanistic insights into the synergistic interactions of FGi and LiBH_(4).This work paves the way for advancing utilization of machine learning in the high-capacity hydrogen storage field.
文摘The selective activation of C-H bonds is pivotal in catalysis for converting hydrocarbons into value-added chemicals.Ethylbenzene dehydrogenation to styrene is crucial process to produce polystyrene and its derivatives used in synthetic materials.Herein,K-Cr@Y with zeolite-encaged isolated O=Cr(VI)=O species modified by extraframework potassium ions is constructed,showing remarkable performance in CO_(2)-promoted ethylbenzene dehydrogenation with initial ethylbenzene conversion of 66%and styrene selectivity of 96%,outperforming other M-Cr@Y catalysts(M=Li,Na,Rb,Cs).Extraframework potassium ions can modulate the electron density of zeolite-encaged Cr(VI)species and therefore facilitate C–H bond activation in ethylbenzene molecules.The gradual reduction of zeolite-encaged O=Cr(VI)=O to less active Cr(IV)=O species by dihydrogen during ethylbenzene dehydrogenation is evidenced by comprehensive characterization results,and Cr(IV)=O can be re-oxidized to O=Cr(VI)=O species upon simple calcination regeneration.The results from in situ DRIFT spectroscopy elucidate the critical promotion role of CO_(2)in ethylbenzene dehydrogenation over K-Cr@Y by retarding the over-reduction of zeolite-encaged Cr species to inactive Cr(III)species and suppressing coke deposition.This study advances the rational design of non-noble metal catalysts for CO_(2)-promoted ethylbenzene dehydrogenation with zeolite-encaged high valence transition metal ions modulated by extraframework cations.
