Hydrogen fuel cells are expected to play a central role in the next-generation energy paradigm.However,owing to practical limitations,hydrogen is supplied in the form of refined hydrocarbons or alcohols in industrial ...Hydrogen fuel cells are expected to play a central role in the next-generation energy paradigm.However,owing to practical limitations,hydrogen is supplied in the form of refined hydrocarbons or alcohols in industrial applications.Among them,methanol is widely used as a hydrogen source,and CO is inevitably generated during its oxidation process.Even a small amount of CO(∼20 ppm)strongly binds to Pt used as a catalyst,and deactivates it.In addition to CO,surface adsorption of organic cations by binder or ionomer use in alkaline fuel cells is also one of the poisoning issues to be overcome.Herein,we propose FePt bimetallic catalysts that can resist unavoidable CO and organic cation poisoning.Our synthetic strategy,including annealing and acid treatment,allows the catalysts to possess different alloying degrees and surface structures,which in turn induce different levels of resistance to CO and organic-cation poisonings.The correlation between the surface and bulk structures of the catalysts and poisoning resistance was elucidated through X-ray photoemission spectroscopy and electrochemical analysis.The results revealed that an FePt catalyst having an ordered atomic arrangement displayed a better poisoning resistance than that having a disordered arrangement.展开更多
Proton exchange membrane fuel cells (PEMFCs) provide an appealing sustainable energy system,with the solid-electrolyte membrane playing a crucial role in its overall performance.Currently,sulfonated poly(1,4-phenylene...Proton exchange membrane fuel cells (PEMFCs) provide an appealing sustainable energy system,with the solid-electrolyte membrane playing a crucial role in its overall performance.Currently,sulfonated poly(1,4-phenylene ether-ether sulfone)(SPEES),an aromatic hydrocarbon polymer,has garnered considerable attention as an alternative to Nafion polymers.However,the long-term durability and stability of SPEES present a significant challenge.In this context,we introduce a potential solution in the form of an additive,specifically a core–shell-based amine-functionalized iron titanate (A–Fe_(2)TiO_(5)),which holds promise for improving the lifetime,proton conductivity,and power density of SPEES in PEMFCs.The modified SPEES/A–Fe_(2)TiO_(5)composite membranes exhibited notable characteristics,including high water uptake,enhanced thermomechanical stability,and oxidative stability.Notably,the SPEES membrane loaded with 1.2 wt%of A–Fe_(2)TiO_(5)demonstrates a maximum proton conductivity of 155 mS ccm^(-1),a twofold increase compared to the SPEES membrane,at 80°C under 100%relative humidity (RH).Furthermore,the 1.2 wt%of A–Fe_(2)TiO_(5)/SPEES composite membranes exhibited a maximum power density of 397.37 mW cm^(-2)and a current density of 1148 mA cm^(-2)at 60°C under 100%RH,with an opencircuit voltage decay of 0.05 m V/h during 103 h of continuous operation.This study offers significant insights into the development and understanding of innovative SPEES nanocomposite membranes for PEMFC applications.展开更多
The realization of practical solar hydrogen production relies on the development of efficient devices with nontoxic and low-cost materials.Since the predominant contributors for the performance and cost are the cataly...The realization of practical solar hydrogen production relies on the development of efficient devices with nontoxic and low-cost materials.Since the predominant contributors for the performance and cost are the catalyst and the light absorber,it is imperative to develop cost-effective catalysts and absorbers that are compatible with each other for achieving high performance.In this study,a 10%efficient solar-to-hydrogen conversion device was developed through the meticulous integration of low-cost Ni Heazlewoodite-based catalysts for the hydrogen evolution reaction(HER)and ternary bulk heterojunction organic semiconductor(OS)-based light absorbers.Se-incorporated Ni_(3)S_(2)was synthesized using a simple one-step hydrothermal method,which demonstrated a low overpotential and Tafel slope,indicating superior HER activity compared to Ni_(3)S_(2).The theoretical calculation results validate the enhanced HER performance of the Se-incorporated Ni_(3)S_(2)catalyst in alkaline electrolytes.The ternary phase organic light absorber is designed to generate tailored photovoltage and maximized photocurrent,resulting in a photocurrent density of 8.24 mA cm^(-2)under unbiased conditions,which corresponds to 10%solar to hydrogen conversion.Low-temperature photoluminescence spectroscopy results revealed that the enhanced photocurrent density originates from a reduction in both phonon-and vibration-induced inter-and intramolecular non-radiative decay.Our results establish a new benchmark for the emerging OS-based efficient solar hydrogen production based on nontoxic and cost-effective materials.展开更多
A novel polybenzimidazole(PBI)-based trilayer membrane assembly is developed for application in vanadium redox flow battery(VRFB).The membrane comprises a 1μm thin cross-linked poly[2,2′-(p-oxydiphenylene)−5,5′-bib...A novel polybenzimidazole(PBI)-based trilayer membrane assembly is developed for application in vanadium redox flow battery(VRFB).The membrane comprises a 1μm thin cross-linked poly[2,2′-(p-oxydiphenylene)−5,5′-bibenzimidazole](OPBI)sandwiched between two 20μm thick porous OPBI membranes(p-OPBI)without further lamination steps.The trilayer membrane demonstrates exceptional properties,such as high conductivity and low area-specific resistance(ASR)of 51 mS cm^(−1) and 81mΩ cm^(2),respectively.Contact with vanadium electrolyte increases the ASR of trilayer membrane only to 158mΩ cm^(2),while that of Nafion is 193mΩ cm^(2).VO^(2+) permeability is 2.73×10^(-9) cm^(2) min^(−1),about 150 times lower than that of Nafion NR212.In addition,the membrane has high mechanical strength and high chemical stability against VO^(2+).In VRFB,the combination of low resistance and low vanadium permeability results in excellent performance,revealing high Coulombic efficiency(>99%),high energy efficiency(EE;90.8% at current density of 80mA cm^(−2)),and long-term durability.The EE is one of the best reported to date.展开更多
Polyvinylidene fluoride-hexafluoropropylene （PVdF-HFP） / clay nanocomposite membranes were prepared by phase inversion method through controlling retention time to apply for a lithium ion secondary batteries. Increa...Polyvinylidene fluoride-hexafluoropropylene （PVdF-HFP） / clay nanocomposite membranes were prepared by phase inversion method through controlling retention time to apply for a lithium ion secondary batteries. Increased membrane porosity with macrovoids was observed at increasing retention time. Partially intercalated structures of PVdF-HFP/clay nanocomposite membranes were confirmed by X-ray diffraction （XRD） analysis. PVdF-HFP membranes containing various kind of clay showed the increase of membrane modulus compared to the pristine PVdF-HFP membrane.展开更多
Pt-Ni alloy nanocrystals with Pt-enriched shells were prepared by selective etching of surface Ni using sulfuric acid and hydroquinone.The changes in the electronic and geometric structure of the alloy nanoparticles a...Pt-Ni alloy nanocrystals with Pt-enriched shells were prepared by selective etching of surface Ni using sulfuric acid and hydroquinone.The changes in the electronic and geometric structure of the alloy nanoparticles at the surface were elucidated from the electrochemical surface area,the potential of zero total charge(PZTC),and relative surface roughness,which were determined from CO-and CO_(2)-displacement experiments before and after 3000 potential cycles under oxygen reduction reaction conditions.While the highest activity and durability were achieved in hydroquinone-treated Pt–Ni,sulfuric acidtreated one showed the lower activity and durability despite its higher surface Pt concentration and alloying level.Both PZTC and QCO_(2)/QCO ratio(desorption charge of reductively adsorbed CO_(2) normalized by COad-stripping charge)depend on surface roughness.In particular,QCO_(2)/QCO ratio change better reflects the roughness on an atomic scale,and PZTC is also affected by the electronic modification of Pt atoms in surface layers.In this study,a comparative study is presented to find a relationship between surface structure and electrochemical properties,which reveals that surface roughness plays a critical role to improve the electrochemical performance of Pt-Ni alloy catalysts with Pt-rich surfaces.展开更多
An electrolyte model for the solid oxide fuel cell (SOFC) with proton conducting perovskite electrolyte is developed in this study, in which four types of charge carriers including proton, oxygen vacancy (oxide ion), ...An electrolyte model for the solid oxide fuel cell (SOFC) with proton conducting perovskite electrolyte is developed in this study, in which four types of charge carriers including proton, oxygen vacancy (oxide ion), free electron and electron hole are taken into consideration. The electrochemical process within the SOFC with hydrogen as the fuel is theoretically analyzed. With the present model, the effects of some parameters, such as the thickness of electrolyte, operating temperature and gas composition, on the ionic transport (or gas permeation) through the electrolyte and the electrical performance, i.e., the electromotive force (EMF) and internal resistance of the cell, are investigated in detail. The theoretical results are tested partly by comparing with the experimental data obtained from SrCe0.95M0.05O3-α, (M=Yb, Y) cells.展开更多
Proton-hole mixed conductor, SrCeo.95Yb0.05O3-α(SCYb), has the potential to be used as a membrane for dehydrogenation reactions such as methane coupling due to its high C2-selectivity and its simplicity for fabricati...Proton-hole mixed conductor, SrCeo.95Yb0.05O3-α(SCYb), has the potential to be used as a membrane for dehydrogenation reactions such as methane coupling due to its high C2-selectivity and its simplicity for fabricating reactor systems. In addition, the mixed conducting membrane in the hollow fibre geometry is capable of providing high surface area per unit volume. In this study, mechanism of methane coupling reaction on the SCYb membrane was proposed and the kinetic parameters were obtained by regression of experimental data. A mathematical model describing the methane coupling in the SCYb hollow fibre membrane reactor was also developed. With this mathematical model, various operating conditions such as the operation mode, operation pressure and feed concentrations affecting performance of the reactor were investigated. The simulation results show that the cocurrent flow in the reactor exhibits higher conversion of methane and higher yield of ethylene compared to the countercurrent flow. In order to achieve the highest C2 yield, especially of ethylene, pure methane should be used as feed and the operating pressure be 300 kPa. Air can be used as the source of oxygen for the reaction and its optimum feed velocity is twice of the methane feed velocity. The air pressure in the lumen side should be kept the same as or slightly lower than the pressure of shell side.展开更多
The main requirements for battery separators are high porosity which can serve pathways of lithium ion and space for gel electrolytes to impregnate in a membrane and mechanical strength to allow easy handling for batt...The main requirements for battery separators are high porosity which can serve pathways of lithium ion and space for gel electrolytes to impregnate in a membrane and mechanical strength to allow easy handling for battery assembly. Generally, it appears the trade-off relationship between the porosity and mechanical strength of the membrane. PVdF composite membranes containing nano-size clays were used to improve the mechanical strength of the membrane without affecting the membrane porosity. The composite membranes were prepared by phase inversion method controlling the membrane preparation conditions such as retention time. The resultant membranes show increased mechanical properties with similar membrane porosity around 80 % compared to the pristine PVdF membrane. Incorporation of nonoclay can be considered as an effective method to improve the mechanica! strength in porous membrane supports, especially in a separator.展开更多
Scaled-up industrial water electrolysis equipment that can be used with abundant seawater is key for affordable hydrogen production.The search for highly stable,dynamic,and economical electrocatalysts could have a sig...Scaled-up industrial water electrolysis equipment that can be used with abundant seawater is key for affordable hydrogen production.The search for highly stable,dynamic,and economical electrocatalysts could have a significant impact on hydrogen commercialization.Herein,we prepared energy-efficient,scalable,and engineering electronic structure modulated Mn-Ni bimetal oxides(Mn_(0.25)Ni_(0.75)O)through simple hydrothermal followed by calcination method.As-optimized Mn_(0.25)Ni_(0.75)O displayed enhanced oxygen and hydrogen evolution reaction(OER and HER)performance with overpotentials of 266 and115 mV at current densities of 10 mA cm^(-2)in alkaline KOH added seawater electrolyte solution.Additionally,Mn-Ni oxide catalytic benefits were attributed to the calculated electronic configurations and Gibbs free energy for OER,and HER values were estimated using first principles calculations.In real-time practical application,we mimicked industrial operating conditions with modified seawater electrolysis using Mn_(0.25)Ni_(0.75)O‖Mn_(0.25)Ni_(0.75)O under various temperature conditions,which performs superior to the commercial IrO_(2)‖Pt-C couple.These findings demonstrate an inexpensive and facile technique for feasible large-scale hydrogen production.展开更多
The aim of this study is to determine the effect of the main chemical components ofbiomass： cellulose, hemicel- lulose and lignin, on chemical kinetics ofbiomass pyrolysis. The experiments were designed based on a si...The aim of this study is to determine the effect of the main chemical components ofbiomass： cellulose, hemicel- lulose and lignin, on chemical kinetics ofbiomass pyrolysis. The experiments were designed based on a simplex- lattice mixture design. The pyrolysis was observed by using a thermogravimetric analyzer. The curves obtained from the employed analytical method fit the experimental data （R2 〉 0.9）. This indicated that this method has the potential to determine the kinetic parameters such as the activation energy （E~）, frequency factor （A） and re- action order （n） for each point of the experimental design. The results obtained from the simplex-lattice mixture design indicated that cellulose had a significant effect on Ea and A, and the interaction between cellulose and lignin had an important effect on the reaction order, n. The proposed models were then proved to be useful for predicting pyrolysis behavior in real biomass and so could be used as a simple approximation for predicting the overall trend of chemical reaction kinetics.展开更多
A set of metal nanoparticle-decorated titanium dioxide(Mx/TiO_(2);where x is the percent by mass,%)photocatalysts was prepared via the sol-immobilization in order to enhance the simultaneous hydrogen(H_(2))production ...A set of metal nanoparticle-decorated titanium dioxide(Mx/TiO_(2);where x is the percent by mass,%)photocatalysts was prepared via the sol-immobilization in order to enhance the simultaneous hydrogen(H_(2))production and pollutant reduction from real biodiesel wastewater.Effect of the metal nanoparticle(NP)type(M=Ni,Au,Pt or Pd)and,for Pd,the amount(1%–4%)decorated on the surface of thermal treated commercial TiO_(2)(T_(400))was evaluated.The obtained results demonstrated that both the type and amount of decorated metal NPs did not significantly affect the pollutant reduction,measured in terms of the reduction of chemical oxygen demand(COD),biological oxygen demand(BOD)and oil&grease levels,but they affected the H_(2) production rate from both deionized water and biodiesel wastewater,which can be ranked in the order of Pt_(1)/T_(400)>Pd_(1)/T_(400)>Au_(1)/T_(400)>Ni_(1)/T_(400).This was attributed to the high difference in work function between Pt and the parent T400.However,the difference between Pt1/T400 and Pd1/T400 was not great and so from an economic consideration,Pd/TiO_(2) was selected as appropriate for further evaluation.Among the four different Pdx/TiO_(2) photocatalysts,the Pd3/TiO_(2) demonstrated the highest activity and gave a high rate of H_(2) production(up to 135 mmol·h−1)with a COD,BOD and oil&grease reduction of 30.3%,73.7%and 58.0%,respectively.展开更多
A ternary hybrid membrane architecture consisting of sulfonated fluorinated multi-block copolymer （SFMC）, sulfonated （poly ether ether ketone） （SPEEK） and I or 5 wt% graphene oxide （GO） was fabricated through ...A ternary hybrid membrane architecture consisting of sulfonated fluorinated multi-block copolymer （SFMC）, sulfonated （poly ether ether ketone） （SPEEK） and I or 5 wt% graphene oxide （GO） was fabricated through a facile solution casting approach. The simple, but effective monomer sulfonation was performed for SFMC to create compact and rigid hydrophobic backbone structures, while conventional random sulfonation was carried-out for SPEEK. Hydrophilic-hydrophobic-hydrophilic structure of SFMC enhances the compatibility with SPEEK and GO and allows for an unprecedented approach to alter me- chanical strength and proton conductivity of ternary hybrid membrane, as verified from universal test machine （UTM） curves and alternating current （AC） impedance plots. The impact of GO integration on the morphology and roughness of hybrid membrane was scrutinized using field emission scanning electron microscope （FE-SEM） and atomic force microscope （AFM）. Ternary hybrid showed uniform intercalation of GO nanosheets throughout the entire surface of membrane with an increased surface roughness of 8.91 nm. The constructed ternary hybrid membrane revealed excellent water absorption, ion exchange capacity and gas barrier properties, while retaining reasonable dimensional stability. The well-optimized ternary hybrid membrane containing 5 wt% GO revealed a maximum proton conductivity of 111.9 mS/cm, which is higher by a factor of two-fold with respect to that of bare SFMC membrane. The maximum PEMFC power density of 528.07mW/cm2 was yielded by ternary hybrid membrane at a load current density of 1321.1 mA/cm2 when operating the cell at 70 ℃ under 100% relative humidity （RH）. In comparison, a maximum power density of only 182.06 mW/cm2 was exhibited by the bare SFMC membrane at a load current density of 455.56 mA/cm2 under same operating conditions.展开更多
Tailoring atomically dispersed single-atom catalyst(Fe-SAC)holding well-defined coordination structure(Fe-N_(4))along with precise control over morphology is a critical challenge.Herein,we propose a novel acid-amine c...Tailoring atomically dispersed single-atom catalyst(Fe-SAC)holding well-defined coordination structure(Fe-N_(4))along with precise control over morphology is a critical challenge.Herein,we propose a novel acid-amine coupling reaction between metalchelated ionic liquid([1-(3-aminopropyl)3-methylimidazolium tetrachloroferrate(III)][APIM]+[FeCl_(4)]−)and carboxylic groups of carbon allotropes(C=GO,CNT,CNF,and vX-72)to precisely immobilize Fe-N_(x) sites.Out of designed single-atom catalyst(IL-Fe-SAC-C),Fe-N_(4) on graphene(IL-Fe-SAC-Gr)delivered superior oxygen reduction reaction(ORR)activity by holding higher halfwave potential of 0.882 V versus RHE in 1.0 M KOH akin to Pt/C(0.878 V vs.RHE)and surpassing recently reported M–N–C catalysts with superior ethanol tolerance.Thanks to higher graphitization degree,enhanced surface characteristics,and richness in high-density Fe-N_(4) sites of IL-Fe-SAC-Gr confirmed by XPS,X-ray absorption spectroscopy(XAS),and HAADF analysis.The IL-Fe-SAC-Gr catalyst-coated cathode on testing in flexible direct ethanol fuel cells(f-DEFC)delivered higher peak power density of 18mWcm^(−2) by outperforming Pt/C-based cathode by 3.5 times as a result of excellent ethanol tolerance.Further,the developed f-DEFCsuccessfully powered the Internet of Things(IoT)-based health monitoring system.This method demonstrates novel strategy to tailor high-performance single-atom(Fe-SAC-C)sites on desired morphologies to meet specific application requirements with feasibility and versatility.展开更多
This study aims to conduct a sensitivity analysis of closure models and modeling parameters for the Dense Discrete Phase Modeling(DDPM)approach in order to investigate the hydrodynamics of a 3D lab-scale Tapered Fluid...This study aims to conduct a sensitivity analysis of closure models and modeling parameters for the Dense Discrete Phase Modeling(DDPM)approach in order to investigate the hydrodynamics of a 3D lab-scale Tapered Fluidized Bed(TFB).The closure models and model parameters under investigation include the gas-solid drag force,viscous models,particle-particle interaction models,restitution coefficient,specularity coefficient,and rebound coefficient.The primary objective of this sensitivity analysis is to optimize the numerical model's performance.The numerical results,in terms of axial and lateral Solid Volume Fraction(SVF)profiles obtained from the sensitivity analysis,indicate that the drag force and restitution coefficient significantly influence the hydrodynamics of the TFB.Properly selecting these parameters could result in the improved performance of the numerical model.However,the sensitivity of turbulence models,particle-particle interaction models,specularity coefficient,and rebound coefficient has a lesser impact on the hydrodynamics results.This work concludes with the recommendation of a set of closure models and modeling parameters that offer the most accurate prediction of the hydrodynamics of the TFB.展开更多
Relatively large measurement uncertainty severely hindered wide application for laser-induced breakdown spectroscopy(LIBS),therefore it is of great importance to understand the mechanism of signal uncertainty generati...Relatively large measurement uncertainty severely hindered wide application for laser-induced breakdown spectroscopy(LIBS),therefore it is of great importance to understand the mechanism of signal uncertainty generation,including initiation and propagation.It has been found that the Auctuation of plasma morphology was the main reason for signal uncertainty.However,it still remains unclear what mechanism leads to laser-induced plasma morphology fluctuation.In the present work,we employed three fast-imaging cameras to capture three successive plasma images fromn a same laser-induced Titanium alloy plasma,which enables us to understand more clearly of the plasma evolution process especially for the early plasma evolution stage when plasma and surrounding gases interact drastically.Seen from the images,the plasma experienced an increasing morphological fuctuation as delay time increased,transforming from a“stable plasma”before the delay time of 100 ns to a“fuctuating plasma”after the delay time of 300 ns.Notably,the frontier part of plasma showed a significant down-ward motion from the delay time of 150 ns to 200 ns and crashed with the lower part of the plasma,making the plasma fatter and later even splitting the plasma into two parts,which was considered as a critical process for the transformation of“stable plasma”to“unstable plasma”.By calculating the correlation coefficient of plasma image pairs at successive delay times,it was found that the higher the similarity between two plasma at early stage,the more similar at later stage;this implied that the tiny plasma fuctuation earlier than the critical delay time(150-200 ns)was amplifed,causing a large plasma fluctuation at the later stage as well as LIBS measurement uncertainty.The initation of slight fluctuation was linked with Rayleigh-Taylor Instability(RTI)due to the drastic material interpenetration at the plasma-ambient gas interface at earlier stage(before 50 ns).That is,the uncertainty generation of LIBS was proposed as:plasma morphology fluctuation was inevitably trigged by RTI at the early stage and the tiny fuctuation was amplified by the back pressed downward process of plasma frontier material,leading to severe morphology fluctuation as well as LIBS signal uncertainty.展开更多
This study utilized the particle image velocimetry （P1V） technique, non-invasively near the wall, in the developing region, for the measurements of laminar and turbulent properties during circulation of Geldart B ty...This study utilized the particle image velocimetry （P1V） technique, non-invasively near the wall, in the developing region, for the measurements of laminar and turbulent properties during circulation of Geldart B type particles in the U.S. Department of Energy （DOE） National Energy Technology Laboratory （NETL） riser. A novel method was used to measure axial and radial laminar and turbulent solids dispersion coefficients using autocorrelation technique. The instantaneous and hydrodynamic velocities for the solid phase were measured simultaneously in the axial and radial directions using a CCD camera, with the help of a colored rotating transparency. The measured properties, such as laminar and Reynolds stresses, laminar and turbulent granular tempera- tures, laminar and turbulent dispersion coefficients and energy spectra exhibited anisotropy. The mixing in the riser was on the level of clusters. The total granular temperatures were in reasonable agreement with the literature values. However, the axial and radial solids dispersion coefficients measured near the wall were slightly lower than the radially averaged values in the literature.展开更多
A Calcium Looping Process(CLP)is an emerging approach for Carbon Capture and Utilization(CCU).It is essentially a CO_(2) capture process that utilizes calcium oxide(CaO)as a sorbent for the removal of CO_(2).A concent...A Calcium Looping Process(CLP)is an emerging approach for Carbon Capture and Utilization(CCU).It is essentially a CO_(2) capture process that utilizes calcium oxide(CaO)as a sorbent for the removal of CO_(2).A concentrated stream of CO_(2)(96%)that is suitable for storage and reuse is produced in this process.The objective of this work is to use mass and energy integration to couple CLP with industrial facilities and power plants in order to enhance industrial symbiosis and reduce cost via the chemical conversion of CO_(2) into value-added products.Special attention is given to plants that generate large amount of CO_(2) and/or provide excess heat that can be used in driving CLP.A case study is solved to assess the integration of CLP with candidate processes including power plants,cement production,gas-to-liquid(GTL)facility,and chemical plants for the production of ammonia,urea,polymer,methanol and acetic acid.The solution to the case study shows the merits integrating CLP with processing facilities.展开更多
In this work,the sorption enhanced steam reforming (SESR) method was developed for improved hydrogen (H2) production,and the drawbacks of conventional steam reforming processes on H2 yield and purity were overcome.How...In this work,the sorption enhanced steam reforming (SESR) method was developed for improved hydrogen (H2) production,and the drawbacks of conventional steam reforming processes on H2 yield and purity were overcome.However,the SESR process is discontinuous and requires regeneration after sorbent saturation with CO2.The circulating fluidized bed reactor (CFBR) system has previously been proposed for continuous H2 production,with both reforming and sorbent regeneration occurring simultaneously.The main aim of this work was to determine the feasibility and performance of SESR with a proper design and conditions in conjunction with the CFBR system.The reforming riser and bubbling bed regenerator are studied separately but related to each other.Two-dimensional transient models using the Euler-Euler approach and kinetic theory of granular flow were used for fluid dynamic simulations combined with the decarbonation kinetics of dolomite,to investigate a conceptual regenerator system and determine its key conditions.A mixture of the Ni-based catalyst and dolomite from the risers was injected with a flux of 200 kg/(m2 s) and a catalyst to sorbent ratio of 2.54 kg/kg.A double-stage bubbling bed regenerator system was designed with 1.2 m width,0.8 m bed height,a gas inlet velocity of 0.2 m/s and solid preheating at 950 ℃.The used dolomite was regenerated with an assumed CaO conversion of 3%;the almost fresh dolomite was then released with good mixing of the catalyst and sorbent.展开更多
In this work,we demonstrate the power of a simple top-down electrochemical erosion approach to obtain Pt nanoparticle with controlled shapes and sizes(in the range from-2 to-10 nm).Carbon supported nanoparticles with ...In this work,we demonstrate the power of a simple top-down electrochemical erosion approach to obtain Pt nanoparticle with controlled shapes and sizes(in the range from-2 to-10 nm).Carbon supported nanoparticles with narrow size distributions have been synthesized by applying an alternating voltage to macroscopic bulk platinum structures,such as disks or wires.Without using any surfactants,the size and shape of the particles can be changed by adjusting simple parameters such as the applied potential,frequency and electrolyte composition.For instance,application of a sinusoidal AC voltage with lower frequencies results in cubic nanoparticles;whereas higher frequencies lead to predominantly spherical nanoparticles.On the other hand,the amplitude of the,sinusoidal signal was found to affect the particle size;the lower the amplitude of the applied AC signal,the smaller the resulting particle size.Pt/C catalysts prepared by this approach showed 0.76 A/mg mass activity towards the oxygen reduction reaction which is-2 times higher than the state-of-the-art commercial Pt/C catalyst(0.42 A/mg)from Tanaka.In addition to this,we discussed the mechanistic insights about the nanoparticle formation pathways.展开更多
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korean government(Nos.2022M3J1A1063917 and 2021M3H4A3A02086681).
文摘Hydrogen fuel cells are expected to play a central role in the next-generation energy paradigm.However,owing to practical limitations,hydrogen is supplied in the form of refined hydrocarbons or alcohols in industrial applications.Among them,methanol is widely used as a hydrogen source,and CO is inevitably generated during its oxidation process.Even a small amount of CO(∼20 ppm)strongly binds to Pt used as a catalyst,and deactivates it.In addition to CO,surface adsorption of organic cations by binder or ionomer use in alkaline fuel cells is also one of the poisoning issues to be overcome.Herein,we propose FePt bimetallic catalysts that can resist unavoidable CO and organic cation poisoning.Our synthetic strategy,including annealing and acid treatment,allows the catalysts to possess different alloying degrees and surface structures,which in turn induce different levels of resistance to CO and organic-cation poisonings.The correlation between the surface and bulk structures of the catalysts and poisoning resistance was elucidated through X-ray photoemission spectroscopy and electrochemical analysis.The results revealed that an FePt catalyst having an ordered atomic arrangement displayed a better poisoning resistance than that having a disordered arrangement.
基金BK21 FOUR Program by Jeonbuk National University Research Grantsupported by “Regional Innovation Strategy (RIS)” through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (MOE)(2023RIS-008)H2KOREA funded by the Ministry of Education(2024 Hydrogen Industry-002, Innovative Human Resources Development Project for Hydrogen Industry)。
文摘Proton exchange membrane fuel cells (PEMFCs) provide an appealing sustainable energy system,with the solid-electrolyte membrane playing a crucial role in its overall performance.Currently,sulfonated poly(1,4-phenylene ether-ether sulfone)(SPEES),an aromatic hydrocarbon polymer,has garnered considerable attention as an alternative to Nafion polymers.However,the long-term durability and stability of SPEES present a significant challenge.In this context,we introduce a potential solution in the form of an additive,specifically a core–shell-based amine-functionalized iron titanate (A–Fe_(2)TiO_(5)),which holds promise for improving the lifetime,proton conductivity,and power density of SPEES in PEMFCs.The modified SPEES/A–Fe_(2)TiO_(5)composite membranes exhibited notable characteristics,including high water uptake,enhanced thermomechanical stability,and oxidative stability.Notably,the SPEES membrane loaded with 1.2 wt%of A–Fe_(2)TiO_(5)demonstrates a maximum proton conductivity of 155 mS ccm^(-1),a twofold increase compared to the SPEES membrane,at 80°C under 100%relative humidity (RH).Furthermore,the 1.2 wt%of A–Fe_(2)TiO_(5)/SPEES composite membranes exhibited a maximum power density of 397.37 mW cm^(-2)and a current density of 1148 mA cm^(-2)at 60°C under 100%RH,with an opencircuit voltage decay of 0.05 m V/h during 103 h of continuous operation.This study offers significant insights into the development and understanding of innovative SPEES nanocomposite membranes for PEMFC applications.
基金supported by the National R&D Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(Grant No.RS-2023-0025177 and 2021R1A2B5B01002879)The technology Innovation Program funded by the Ministry of Trade Industry and Energy(MOTIE,Korea)(Grant No.RS-2024-00435432)。
文摘The realization of practical solar hydrogen production relies on the development of efficient devices with nontoxic and low-cost materials.Since the predominant contributors for the performance and cost are the catalyst and the light absorber,it is imperative to develop cost-effective catalysts and absorbers that are compatible with each other for achieving high performance.In this study,a 10%efficient solar-to-hydrogen conversion device was developed through the meticulous integration of low-cost Ni Heazlewoodite-based catalysts for the hydrogen evolution reaction(HER)and ternary bulk heterojunction organic semiconductor(OS)-based light absorbers.Se-incorporated Ni_(3)S_(2)was synthesized using a simple one-step hydrothermal method,which demonstrated a low overpotential and Tafel slope,indicating superior HER activity compared to Ni_(3)S_(2).The theoretical calculation results validate the enhanced HER performance of the Se-incorporated Ni_(3)S_(2)catalyst in alkaline electrolytes.The ternary phase organic light absorber is designed to generate tailored photovoltage and maximized photocurrent,resulting in a photocurrent density of 8.24 mA cm^(-2)under unbiased conditions,which corresponds to 10%solar to hydrogen conversion.Low-temperature photoluminescence spectroscopy results revealed that the enhanced photocurrent density originates from a reduction in both phonon-and vibration-induced inter-and intramolecular non-radiative decay.Our results establish a new benchmark for the emerging OS-based efficient solar hydrogen production based on nontoxic and cost-effective materials.
基金supported by KIST (2E31871 and 2E32591)and Innovation Fund Denmark Denmark (DANFLOW—project#9090-00059)Korea Institute for Advancement of Technology (KIAT)through the International Cooperative R&D program (Project No.P0018437)Basic Science Research Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education (2021R1A6A1A03039981).
文摘A novel polybenzimidazole(PBI)-based trilayer membrane assembly is developed for application in vanadium redox flow battery(VRFB).The membrane comprises a 1μm thin cross-linked poly[2,2′-(p-oxydiphenylene)−5,5′-bibenzimidazole](OPBI)sandwiched between two 20μm thick porous OPBI membranes(p-OPBI)without further lamination steps.The trilayer membrane demonstrates exceptional properties,such as high conductivity and low area-specific resistance(ASR)of 51 mS cm^(−1) and 81mΩ cm^(2),respectively.Contact with vanadium electrolyte increases the ASR of trilayer membrane only to 158mΩ cm^(2),while that of Nafion is 193mΩ cm^(2).VO^(2+) permeability is 2.73×10^(-9) cm^(2) min^(−1),about 150 times lower than that of Nafion NR212.In addition,the membrane has high mechanical strength and high chemical stability against VO^(2+).In VRFB,the combination of low resistance and low vanadium permeability results in excellent performance,revealing high Coulombic efficiency(>99%),high energy efficiency(EE;90.8% at current density of 80mA cm^(−2)),and long-term durability.The EE is one of the best reported to date.
基金funded by Fundamental R&D Program for core Technol-ogy of Materials of Korean Ministry of Knowledge Economy
文摘Polyvinylidene fluoride-hexafluoropropylene （PVdF-HFP） / clay nanocomposite membranes were prepared by phase inversion method through controlling retention time to apply for a lithium ion secondary batteries. Increased membrane porosity with macrovoids was observed at increasing retention time. Partially intercalated structures of PVdF-HFP/clay nanocomposite membranes were confirmed by X-ray diffraction （XRD） analysis. PVdF-HFP membranes containing various kind of clay showed the increase of membrane modulus compared to the pristine PVdF-HFP membrane.
基金This study was supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2019R1F1A1062193).
文摘Pt-Ni alloy nanocrystals with Pt-enriched shells were prepared by selective etching of surface Ni using sulfuric acid and hydroquinone.The changes in the electronic and geometric structure of the alloy nanoparticles at the surface were elucidated from the electrochemical surface area,the potential of zero total charge(PZTC),and relative surface roughness,which were determined from CO-and CO_(2)-displacement experiments before and after 3000 potential cycles under oxygen reduction reaction conditions.While the highest activity and durability were achieved in hydroquinone-treated Pt–Ni,sulfuric acidtreated one showed the lower activity and durability despite its higher surface Pt concentration and alloying level.Both PZTC and QCO_(2)/QCO ratio(desorption charge of reductively adsorbed CO_(2) normalized by COad-stripping charge)depend on surface roughness.In particular,QCO_(2)/QCO ratio change better reflects the roughness on an atomic scale,and PZTC is also affected by the electronic modification of Pt atoms in surface layers.In this study,a comparative study is presented to find a relationship between surface structure and electrochemical properties,which reveals that surface roughness plays a critical role to improve the electrochemical performance of Pt-Ni alloy catalysts with Pt-rich surfaces.
文摘An electrolyte model for the solid oxide fuel cell (SOFC) with proton conducting perovskite electrolyte is developed in this study, in which four types of charge carriers including proton, oxygen vacancy (oxide ion), free electron and electron hole are taken into consideration. The electrochemical process within the SOFC with hydrogen as the fuel is theoretically analyzed. With the present model, the effects of some parameters, such as the thickness of electrolyte, operating temperature and gas composition, on the ionic transport (or gas permeation) through the electrolyte and the electrical performance, i.e., the electromotive force (EMF) and internal resistance of the cell, are investigated in detail. The theoretical results are tested partly by comparing with the experimental data obtained from SrCe0.95M0.05O3-α, (M=Yb, Y) cells.
基金Supported by the National Natural Science Foundation of China(No.20076025).
文摘Proton-hole mixed conductor, SrCeo.95Yb0.05O3-α(SCYb), has the potential to be used as a membrane for dehydrogenation reactions such as methane coupling due to its high C2-selectivity and its simplicity for fabricating reactor systems. In addition, the mixed conducting membrane in the hollow fibre geometry is capable of providing high surface area per unit volume. In this study, mechanism of methane coupling reaction on the SCYb membrane was proposed and the kinetic parameters were obtained by regression of experimental data. A mathematical model describing the methane coupling in the SCYb hollow fibre membrane reactor was also developed. With this mathematical model, various operating conditions such as the operation mode, operation pressure and feed concentrations affecting performance of the reactor were investigated. The simulation results show that the cocurrent flow in the reactor exhibits higher conversion of methane and higher yield of ethylene compared to the countercurrent flow. In order to achieve the highest C2 yield, especially of ethylene, pure methane should be used as feed and the operating pressure be 300 kPa. Air can be used as the source of oxygen for the reaction and its optimum feed velocity is twice of the methane feed velocity. The air pressure in the lumen side should be kept the same as or slightly lower than the pressure of shell side.
基金Project supported by the Fundamental R&D Program for Core Technology of Materials of Korean, Ministry of Knowledge EconomyProject supported by the second stage of Brain Korea (BK) 21
文摘The main requirements for battery separators are high porosity which can serve pathways of lithium ion and space for gel electrolytes to impregnate in a membrane and mechanical strength to allow easy handling for battery assembly. Generally, it appears the trade-off relationship between the porosity and mechanical strength of the membrane. PVdF composite membranes containing nano-size clays were used to improve the mechanical strength of the membrane without affecting the membrane porosity. The composite membranes were prepared by phase inversion method controlling the membrane preparation conditions such as retention time. The resultant membranes show increased mechanical properties with similar membrane porosity around 80 % compared to the pristine PVdF membrane. Incorporation of nonoclay can be considered as an effective method to improve the mechanica! strength in porous membrane supports, especially in a separator.
基金supported by the GEONJI Research support programsupported by Basic Science Research through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2021R1I1A1A01050905)+1 种基金supported by grants from the Medical Research Center Program(NRF-2017R1A5A2015061)through the National Research Foundation(NRF),which is funded by the Korean government(MSIP)supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT and Future Planning(NRF-2020R1A2B5B01001458)。
文摘Scaled-up industrial water electrolysis equipment that can be used with abundant seawater is key for affordable hydrogen production.The search for highly stable,dynamic,and economical electrocatalysts could have a significant impact on hydrogen commercialization.Herein,we prepared energy-efficient,scalable,and engineering electronic structure modulated Mn-Ni bimetal oxides(Mn_(0.25)Ni_(0.75)O)through simple hydrothermal followed by calcination method.As-optimized Mn_(0.25)Ni_(0.75)O displayed enhanced oxygen and hydrogen evolution reaction(OER and HER)performance with overpotentials of 266 and115 mV at current densities of 10 mA cm^(-2)in alkaline KOH added seawater electrolyte solution.Additionally,Mn-Ni oxide catalytic benefits were attributed to the calculated electronic configurations and Gibbs free energy for OER,and HER values were estimated using first principles calculations.In real-time practical application,we mimicked industrial operating conditions with modified seawater electrolysis using Mn_(0.25)Ni_(0.75)O‖Mn_(0.25)Ni_(0.75)O under various temperature conditions,which performs superior to the commercial IrO_(2)‖Pt-C couple.These findings demonstrate an inexpensive and facile technique for feasible large-scale hydrogen production.
基金Supported by the Grants from the Thailand Research Fund for fiscal year 2014–2016(TRG5780205)the Grant for Development of New Faculty Staff(Ratchadaphisek Somphot Endowment Fund)of Chulalongkorn Universitythe Center of Excellence on Petrochemical and Materials Technology,Chulalongkorn University
文摘The aim of this study is to determine the effect of the main chemical components ofbiomass： cellulose, hemicel- lulose and lignin, on chemical kinetics ofbiomass pyrolysis. The experiments were designed based on a simplex- lattice mixture design. The pyrolysis was observed by using a thermogravimetric analyzer. The curves obtained from the employed analytical method fit the experimental data （R2 〉 0.9）. This indicated that this method has the potential to determine the kinetic parameters such as the activation energy （E~）, frequency factor （A） and re- action order （n） for each point of the experimental design. The results obtained from the simplex-lattice mixture design indicated that cellulose had a significant effect on Ea and A, and the interaction between cellulose and lignin had an important effect on the reaction order, n. The proposed models were then proved to be useful for predicting pyrolysis behavior in real biomass and so could be used as a simple approximation for predicting the overall trend of chemical reaction kinetics.
文摘A set of metal nanoparticle-decorated titanium dioxide(Mx/TiO_(2);where x is the percent by mass,%)photocatalysts was prepared via the sol-immobilization in order to enhance the simultaneous hydrogen(H_(2))production and pollutant reduction from real biodiesel wastewater.Effect of the metal nanoparticle(NP)type(M=Ni,Au,Pt or Pd)and,for Pd,the amount(1%–4%)decorated on the surface of thermal treated commercial TiO_(2)(T_(400))was evaluated.The obtained results demonstrated that both the type and amount of decorated metal NPs did not significantly affect the pollutant reduction,measured in terms of the reduction of chemical oxygen demand(COD),biological oxygen demand(BOD)and oil&grease levels,but they affected the H_(2) production rate from both deionized water and biodiesel wastewater,which can be ranked in the order of Pt_(1)/T_(400)>Pd_(1)/T_(400)>Au_(1)/T_(400)>Ni_(1)/T_(400).This was attributed to the high difference in work function between Pt and the parent T400.However,the difference between Pt1/T400 and Pd1/T400 was not great and so from an economic consideration,Pd/TiO_(2) was selected as appropriate for further evaluation.Among the four different Pdx/TiO_(2) photocatalysts,the Pd3/TiO_(2) demonstrated the highest activity and gave a high rate of H_(2) production(up to 135 mmol·h−1)with a COD,BOD and oil&grease reduction of 30.3%,73.7%and 58.0%,respectively.
基金supported by the Korea Institute of Energy Technology Evaluation and Planning(KETEP)the Ministry of Trade,Industry&Energy(MOTIE)of the Republic of Korea(No.20164030201070)supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT and future Planning(NRF-2017R1A2B4005230)
文摘A ternary hybrid membrane architecture consisting of sulfonated fluorinated multi-block copolymer （SFMC）, sulfonated （poly ether ether ketone） （SPEEK） and I or 5 wt% graphene oxide （GO） was fabricated through a facile solution casting approach. The simple, but effective monomer sulfonation was performed for SFMC to create compact and rigid hydrophobic backbone structures, while conventional random sulfonation was carried-out for SPEEK. Hydrophilic-hydrophobic-hydrophilic structure of SFMC enhances the compatibility with SPEEK and GO and allows for an unprecedented approach to alter me- chanical strength and proton conductivity of ternary hybrid membrane, as verified from universal test machine （UTM） curves and alternating current （AC） impedance plots. The impact of GO integration on the morphology and roughness of hybrid membrane was scrutinized using field emission scanning electron microscope （FE-SEM） and atomic force microscope （AFM）. Ternary hybrid showed uniform intercalation of GO nanosheets throughout the entire surface of membrane with an increased surface roughness of 8.91 nm. The constructed ternary hybrid membrane revealed excellent water absorption, ion exchange capacity and gas barrier properties, while retaining reasonable dimensional stability. The well-optimized ternary hybrid membrane containing 5 wt% GO revealed a maximum proton conductivity of 111.9 mS/cm, which is higher by a factor of two-fold with respect to that of bare SFMC membrane. The maximum PEMFC power density of 528.07mW/cm2 was yielded by ternary hybrid membrane at a load current density of 1321.1 mA/cm2 when operating the cell at 70 ℃ under 100% relative humidity （RH）. In comparison, a maximum power density of only 182.06 mW/cm2 was exhibited by the bare SFMC membrane at a load current density of 455.56 mA/cm2 under same operating conditions.
基金supported by the Basic Science Research Program(2023R1A2C3004336)Regional Leading Research Center(RS-2024-00405278)through the National Research Foundation of Korea(NRF)grant funded by the Korea Government(MSIT).
文摘Tailoring atomically dispersed single-atom catalyst(Fe-SAC)holding well-defined coordination structure(Fe-N_(4))along with precise control over morphology is a critical challenge.Herein,we propose a novel acid-amine coupling reaction between metalchelated ionic liquid([1-(3-aminopropyl)3-methylimidazolium tetrachloroferrate(III)][APIM]+[FeCl_(4)]−)and carboxylic groups of carbon allotropes(C=GO,CNT,CNF,and vX-72)to precisely immobilize Fe-N_(x) sites.Out of designed single-atom catalyst(IL-Fe-SAC-C),Fe-N_(4) on graphene(IL-Fe-SAC-Gr)delivered superior oxygen reduction reaction(ORR)activity by holding higher halfwave potential of 0.882 V versus RHE in 1.0 M KOH akin to Pt/C(0.878 V vs.RHE)and surpassing recently reported M–N–C catalysts with superior ethanol tolerance.Thanks to higher graphitization degree,enhanced surface characteristics,and richness in high-density Fe-N_(4) sites of IL-Fe-SAC-Gr confirmed by XPS,X-ray absorption spectroscopy(XAS),and HAADF analysis.The IL-Fe-SAC-Gr catalyst-coated cathode on testing in flexible direct ethanol fuel cells(f-DEFC)delivered higher peak power density of 18mWcm^(−2) by outperforming Pt/C-based cathode by 3.5 times as a result of excellent ethanol tolerance.Further,the developed f-DEFCsuccessfully powered the Internet of Things(IoT)-based health monitoring system.This method demonstrates novel strategy to tailor high-performance single-atom(Fe-SAC-C)sites on desired morphologies to meet specific application requirements with feasibility and versatility.
基金supported by the Ratchadapisek Somphot Fund for Postdoctoral Fellowship,Chulalongkorn Universitythe Research Grant from the National Research Council of Thailand(N42A660438)Thailand Science Research and Innovation Fund Chulalongkorn University.
文摘This study aims to conduct a sensitivity analysis of closure models and modeling parameters for the Dense Discrete Phase Modeling(DDPM)approach in order to investigate the hydrodynamics of a 3D lab-scale Tapered Fluidized Bed(TFB).The closure models and model parameters under investigation include the gas-solid drag force,viscous models,particle-particle interaction models,restitution coefficient,specularity coefficient,and rebound coefficient.The primary objective of this sensitivity analysis is to optimize the numerical model's performance.The numerical results,in terms of axial and lateral Solid Volume Fraction(SVF)profiles obtained from the sensitivity analysis,indicate that the drag force and restitution coefficient significantly influence the hydrodynamics of the TFB.Properly selecting these parameters could result in the improved performance of the numerical model.However,the sensitivity of turbulence models,particle-particle interaction models,specularity coefficient,and rebound coefficient has a lesser impact on the hydrodynamics results.This work concludes with the recommendation of a set of closure models and modeling parameters that offer the most accurate prediction of the hydrodynamics of the TFB.
基金The autor thank the financial support from the National Natural Science,Foundation of China(No.61675110)the National Key Research and Development Program Key Projects of China(No.2016YFC0302102).
文摘Relatively large measurement uncertainty severely hindered wide application for laser-induced breakdown spectroscopy(LIBS),therefore it is of great importance to understand the mechanism of signal uncertainty generation,including initiation and propagation.It has been found that the Auctuation of plasma morphology was the main reason for signal uncertainty.However,it still remains unclear what mechanism leads to laser-induced plasma morphology fluctuation.In the present work,we employed three fast-imaging cameras to capture three successive plasma images fromn a same laser-induced Titanium alloy plasma,which enables us to understand more clearly of the plasma evolution process especially for the early plasma evolution stage when plasma and surrounding gases interact drastically.Seen from the images,the plasma experienced an increasing morphological fuctuation as delay time increased,transforming from a“stable plasma”before the delay time of 100 ns to a“fuctuating plasma”after the delay time of 300 ns.Notably,the frontier part of plasma showed a significant down-ward motion from the delay time of 150 ns to 200 ns and crashed with the lower part of the plasma,making the plasma fatter and later even splitting the plasma into two parts,which was considered as a critical process for the transformation of“stable plasma”to“unstable plasma”.By calculating the correlation coefficient of plasma image pairs at successive delay times,it was found that the higher the similarity between two plasma at early stage,the more similar at later stage;this implied that the tiny plasma fuctuation earlier than the critical delay time(150-200 ns)was amplifed,causing a large plasma fluctuation at the later stage as well as LIBS measurement uncertainty.The initation of slight fluctuation was linked with Rayleigh-Taylor Instability(RTI)due to the drastic material interpenetration at the plasma-ambient gas interface at earlier stage(before 50 ns).That is,the uncertainty generation of LIBS was proposed as:plasma morphology fluctuation was inevitably trigged by RTI at the early stage and the tiny fuctuation was amplified by the back pressed downward process of plasma frontier material,leading to severe morphology fluctuation as well as LIBS signal uncertainty.
基金support by the U.S. Department of Energy (DOE) University Grant(DE-FG26-06NT42736)
文摘This study utilized the particle image velocimetry （P1V） technique, non-invasively near the wall, in the developing region, for the measurements of laminar and turbulent properties during circulation of Geldart B type particles in the U.S. Department of Energy （DOE） National Energy Technology Laboratory （NETL） riser. A novel method was used to measure axial and radial laminar and turbulent solids dispersion coefficients using autocorrelation technique. The instantaneous and hydrodynamic velocities for the solid phase were measured simultaneously in the axial and radial directions using a CCD camera, with the help of a colored rotating transparency. The measured properties, such as laminar and Reynolds stresses, laminar and turbulent granular tempera- tures, laminar and turbulent dispersion coefficients and energy spectra exhibited anisotropy. The mixing in the riser was on the level of clusters. The total granular temperatures were in reasonable agreement with the literature values. However, the axial and radial solids dispersion coefficients measured near the wall were slightly lower than the radially averaged values in the literature.
文摘A Calcium Looping Process(CLP)is an emerging approach for Carbon Capture and Utilization(CCU).It is essentially a CO_(2) capture process that utilizes calcium oxide(CaO)as a sorbent for the removal of CO_(2).A concentrated stream of CO_(2)(96%)that is suitable for storage and reuse is produced in this process.The objective of this work is to use mass and energy integration to couple CLP with industrial facilities and power plants in order to enhance industrial symbiosis and reduce cost via the chemical conversion of CO_(2) into value-added products.Special attention is given to plants that generate large amount of CO_(2) and/or provide excess heat that can be used in driving CLP.A case study is solved to assess the integration of CLP with candidate processes including power plants,cement production,gas-to-liquid(GTL)facility,and chemical plants for the production of ammonia,urea,polymer,methanol and acetic acid.The solution to the case study shows the merits integrating CLP with processing facilities.
文摘In this work,the sorption enhanced steam reforming (SESR) method was developed for improved hydrogen (H2) production,and the drawbacks of conventional steam reforming processes on H2 yield and purity were overcome.However,the SESR process is discontinuous and requires regeneration after sorbent saturation with CO2.The circulating fluidized bed reactor (CFBR) system has previously been proposed for continuous H2 production,with both reforming and sorbent regeneration occurring simultaneously.The main aim of this work was to determine the feasibility and performance of SESR with a proper design and conditions in conjunction with the CFBR system.The reforming riser and bubbling bed regenerator are studied separately but related to each other.Two-dimensional transient models using the Euler-Euler approach and kinetic theory of granular flow were used for fluid dynamic simulations combined with the decarbonation kinetics of dolomite,to investigate a conceptual regenerator system and determine its key conditions.A mixture of the Ni-based catalyst and dolomite from the risers was injected with a flux of 200 kg/(m2 s) and a catalyst to sorbent ratio of 2.54 kg/kg.A double-stage bubbling bed regenerator system was designed with 1.2 m width,0.8 m bed height,a gas inlet velocity of 0.2 m/s and solid preheating at 950 ℃.The used dolomite was regenerated with an assumed CaO conversion of 3%;the almost fresh dolomite was then released with good mixing of the catalyst and sorbent.
基金support from Deutsche Forschungsgemeinschaft under Germany s excellence strategy-EXC 2089/1-390776260Germany’s excellence cluster“e-conversion”,DFG project BA 5795/4-1funding from the TUM IGSSE project 11.01 are gratefully acknowledged.We also acknowledge DESY(Hamburg,Germany),a member of the Helmholtz Association HGF,for the provision of experimental facilities.Parts of this research were carried out at PETRA III using beamline P02.1.We acknowledge CzechNanoLab Research Infrastructure supported by MEYS CR (LM2018110) and CEITEC Nano Research Infrastructure for TEM measurements.
文摘In this work,we demonstrate the power of a simple top-down electrochemical erosion approach to obtain Pt nanoparticle with controlled shapes and sizes(in the range from-2 to-10 nm).Carbon supported nanoparticles with narrow size distributions have been synthesized by applying an alternating voltage to macroscopic bulk platinum structures,such as disks or wires.Without using any surfactants,the size and shape of the particles can be changed by adjusting simple parameters such as the applied potential,frequency and electrolyte composition.For instance,application of a sinusoidal AC voltage with lower frequencies results in cubic nanoparticles;whereas higher frequencies lead to predominantly spherical nanoparticles.On the other hand,the amplitude of the,sinusoidal signal was found to affect the particle size;the lower the amplitude of the applied AC signal,the smaller the resulting particle size.Pt/C catalysts prepared by this approach showed 0.76 A/mg mass activity towards the oxygen reduction reaction which is-2 times higher than the state-of-the-art commercial Pt/C catalyst(0.42 A/mg)from Tanaka.In addition to this,we discussed the mechanistic insights about the nanoparticle formation pathways.
