Global energy consumption in the last half century has rapidly increased and is expected to continue to grow over the next 50 years,however,with significant differences.The past increase was stimulated by relatively &...Global energy consumption in the last half century has rapidly increased and is expected to continue to grow over the next 50 years,however,with significant differences.The past increase was stimulated by relatively "cheap" fossil fuels and increased rates of industrialization in North America,Europe and Japan;yet while energy consumption in these countries continues to increase,additional factors make the picture for the next 50 years more complex.These additional complicating factors include China and India's rapid increase in energy use as they represent about a third of the world's population;the expected depletion of oil resources in the near future;and,the effect of human activities on global climate change.On the positive side,the renewable energy(RE) technologies of wind,bio-fuels,solar thermal and photovoltaics(PV) are finally showing maturity and the ultimate promise of cost competitiveness.展开更多
Introducing Ni in Ru oxide is a promising approach to enhance the catalytic activity for the oxygen evolution reaction(OER).However,the role of Ni(which has a poor intrinsic activity)is not fully understood.Here,a Ru ...Introducing Ni in Ru oxide is a promising approach to enhance the catalytic activity for the oxygen evolution reaction(OER).However,the role of Ni(which has a poor intrinsic activity)is not fully understood.Here,a Ru NiO_(x)electrode fabricated via a modified dip coating method exhibited excellent OER performance in acidic media,and neutral media for CO_(2)reduction reaction.We combined in-situ/operando X-ray absorption near-edge structure and on-line inductively coupled plasma mass spectrometry studies to unveil the role of the Ni introduced in the Ru oxide.We propose that the Ni not only transforms the electronic structure of the Ru oxide,but also produces a large number of oxygen vacancies by distorting the oxygen lattice structure at low overpotentials,increasing the participation of lattice oxygen for OER.This work demonstrates the real behavior of bimetallic oxide materials under applied potentials and provides new insights into the development of efficient electrocatalysts.展开更多
The polymeric gel electrolytes are attractive owing to their higher ionic conductivities than those of dry polymer electrolytes and lowered water activity for enlarged potential window.However,the ionic conductivity a...The polymeric gel electrolytes are attractive owing to their higher ionic conductivities than those of dry polymer electrolytes and lowered water activity for enlarged potential window.However,the ionic conductivity and mechanical strength of the Na-ion conducting polymeric gel electrolytes are limited by below 20 mS cm−1 and 2.2 MPa.Herein,we demonstrate Na-ion conducting and flexible polymeric hydrogel electrolytes of the chemically coupled poly(diallyldimethylammonium chloride)-dextrin-N,N′-methylene-bisacrylamide film immersed in NaClO_(4) solution(ex-DDA-Dex+NaClO_(4))for flexible sodium-ion hybrid capacitors(f-NIHC).In particular,the anion exchange reaction and synergistic interaction of ex-DDA-Dex with the optimum ClO_(4)−enable to greatly improve the ionic conductivity up to 27.63 mS cm−1 at 25◦C and electrochemical stability window up to 2.6 V,whereas the double networking structure leads to achieve both the mechanical strength(7.48 MPa)and softness of hydrogel electrolytes.Therefore,the f-NIHCs with the ex-DDA-Dex+NaClO_(4) achieved high specific and high-rate capacities of 192.04 F g^(−1)at 500 mA g^(−1)and 116.06 F g^(−1)at 10000 mA g^(−1),respectively,delivering a large energy density of 120.03Wh kg^(−1)at 906Wkg^(−1)and long cyclability of 70%over 500 cycles as well as demonstrating functional operation under mechanical stresses.展开更多
Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H...Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H values on the catalytic activity of La AlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts.When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2 O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.展开更多
The conversion of carbon dioxide(CO2)to valuable fuels and chemicals offers a new pathway for sustainable and clean carbon fixation.Recently,the focus has been on electrochemical CO2 reduction on heterogeneous electro...The conversion of carbon dioxide(CO2)to valuable fuels and chemicals offers a new pathway for sustainable and clean carbon fixation.Recently,the focus has been on electrochemical CO2 reduction on heterogeneous electrode catalysts,leading to remarkable achievements in the reaction performance.To date,CO2 to carbon monoxide(CO)conversion is considered as the most promising candidate reaction for the industrial market,owing to its high efficiency and reasonable technoeconomic feasibility.Moreover,CO has been proposed as a key intermediate species for further reduced hydrocarbons,which can pave the way for various fuel production.This study sets out to describe recent progress on the electrochemical CO2 reduction to CO in a heterogeneously catalyzed system.The review includes understanding of the catalytic material employed and engineering strategies implemented by adjusting the binding energy of key adsorbates.These material design approaches,such as nanostructuring,alloying,doping,and so forth,have pioneered breakouts in the intrinsic catalytic nature of transition metal elements.Moreover,recent advances in systematic design are summarized,with focus on practical industrial applications.Finally,perspectives on the design of electrocatalyst materials for CO production by electrochemical CO2 reduction are presented.展开更多
The hydration of cement generates heat due to the exothermic nature of the hydration process. Poor heat dissipation in mass concrete results in a temperature gradient between the inner core and the outer surface of th...The hydration of cement generates heat due to the exothermic nature of the hydration process. Poor heat dissipation in mass concrete results in a temperature gradient between the inner core and the outer surface of the element. High temperature gradients generate tensile stresses that may exceed the tensile strength of concrete thus leading to thermal cracking. The present paper is an attempt to understand the thermal (heat sink property) and microstructural changes in the hydrated graphene-Portland cement composites. Thermal diffusivity and electrical conductivity of the hydrated graphene-cement composite were measured at various graphene to cement ratios. The mass-volume method was implemented to measure the density of the hydrated graphene-cement composite. Particle size distribution of Portland cement was measured by using a laser scattering particle size analyzer. Heat of hydration of Portland cement was assessed by using a TAMAIR isothermal conduction calorimeter. Scanning electron microscopy (SEM) was implemented to study microstructural changes of the hydrated graphene-cement composites. The mineralogy of graphene-cement and the hydrated graphene-cement composites was investigated by using X-ray diffraction. The findings indicate that incorporation of graphene enhances the thermal properties of the hydrated cement indicating a potential for reduction in early age thermal cracking and durability improvement of the concrete structures.展开更多
Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesd...Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesden-Pop-per-type strontium ferrite (Sr3Fe2O7) toward the oxygen evolution reaction (OER). Owing to the temperature-dependent efficiency of the charge disproportionation of Fe4+, the OER activity of Sr3Fe2O7 varied with the temperature, and the onset potential for the OER at a neutral pH underwent a negative shift of approximately 200 mV by increasing the temperature for the stabilization of Fe4+. When metal substitution was made to Sr3Fe2O7 for stabilizing Fe4+ at room temperature, the temperature dependence of the OER activity disappeared and the OER was driven at a small overpotential without increasing the temperature, indicating that the stabilization of Fe4+ is substantially important for achieving high OER activity.展开更多
Graphene-Polypyrrole (G/PPy) was synthesized by chemical oxidative polymerization method, and electrochemical impedance spectroscopy (EIS) analysis was employed to study the frequency response characteristics of super...Graphene-Polypyrrole (G/PPy) was synthesized by chemical oxidative polymerization method, and electrochemical impedance spectroscopy (EIS) analysis was employed to study the frequency response characteristics of supercapacitors based on G/PPy conducting polymer nanocomposite. It is found that a uniform G/PPy nanocomposite is formed with polypyrrole (PPy) being homogeneously surrounded by graphene nanosheets. The porous structure allowed electrolyte and ions diffusion in synthesized G/PPy nanocomposite. The metallic conductivity of Graphene-polypyrrole exhibited higher knee frequency at 125 Hz than the knee frequency of pristine PPy at 36 Hz. The high knee frequency of G/PPy supercapacitor is indicative of high power application and long cycle life. The G/PPy nanocomposite based supercapacitor with 1MH2SO4 as the electrolyte showed specific capacitances of 270 F/g at 0.1 Hz and112 F/g at 125 Hz.展开更多
Silver (Ag) and silver antimonate (AgSbO3) composites with different amounts of Sb3+ were synthesized by normal sintering with the aim of realizing a thermoelectric material. The electrical conductivity (σ) increased...Silver (Ag) and silver antimonate (AgSbO3) composites with different amounts of Sb3+ were synthesized by normal sintering with the aim of realizing a thermoelectric material. The electrical conductivity (σ) increased in the sample containing larger amount of Sb3+, whereas Seebeck coefficient (S) decreased. Producing Sb3+ caused the generation of oxygen vacancies in the material, and thus the corresponding donor levels are created in the bandgap, providing more conduction electrons. The conductive Ag particles would contribute to the conduction path as bypasses for carrier transport. The thermal conductivity (κ) was slightly lower in the presence of Ag defects in AgSbO3.展开更多
Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric prop...Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric properties (electrical conductivity (σ), Seebeck coefficient (S), Figure of merit (ZT) and calculated thermal conductivity (κ) by S, σ, ZT, and absolute temperature (T)) of bismuth-based rhodium oxides ((Bi1-x,Pbx) 2Sr2Rh2Oy, x = 0 and 0.02, hereafter BSR and BPSR, respectively) were investigated. In comparison with Bi2Sr2Co2Oy (BSC) at 700°C, S and κ enhanced (increased S, 110 (BSR) and 105 μV K-1 (BPSR) from 85 μV K-1 (BSC) and decreased κ, 0.32 (BSR) and 0.50 W m-1 K-1 (BPSR) from 1.75 W m-1 K-1 (BSC)), whereas σ decreased (15 (BSR) and 31 S cm-1 (BPSR) from 70 S cm-1 (BSC)). BPSR reached the highest ZT value of 0.067 at 700°C, compared to those of 0.056 (BSR) and 0.027 (BSC).展开更多
Visible light-induced two-step overall water-splitting was achieved by combining two types of photocatalysts, which were prepared by introducing foreign elements into rutile titanium dioxide (TiO2) and strontium titan...Visible light-induced two-step overall water-splitting was achieved by combining two types of photocatalysts, which were prepared by introducing foreign elements into rutile titanium dioxide (TiO2) and strontium titanate (SrTiO3) with a controlled electronic band structure. Rutile TiO2 and SrTiO3 were doped with chromium and tantalum (Cr,Ta-TiO2) and with rhodium (Rh-SrTiO3), respectively, to introduce visible-light sensitivity. Under irradiation with only visible light from a 420-nm LED lamp, the simultaneous liberation of hydrogen and oxygen with a molar ratio of ~2:1 was achieved with these two types of photocatalysts in the presence of iodate ion/iodide ion as a redox mediator.展开更多
The alpha (α)-hematite (Fe2O3) as photoanode has been used for photoelectrochemical applications due to low bandgap, low cost, high chemical stability, nontoxicity, and abundance in nature. The doping with various tr...The alpha (α)-hematite (Fe2O3) as photoanode has been used for photoelectrochemical applications due to low bandgap, low cost, high chemical stability, nontoxicity, and abundance in nature. The doping with various transition metals, formation of nanostructured and nanocomposite of α-Fe2O3 have been attempted to enrich the carrier mobility, surface kinetics and carrier diffusion properties. The manuscript is an attempt to improve the photoelectrochemical properties of α-Fe2O3 by formation of nanocomposite with dichalcogenide (molybdenum disulfide (MoS2) nanomaterials. The nanocomposite of MoS2-α-Fe2O3 have been synthesized by varying the amount of MoS2 in sol-gel synthesis process. The nanocomposite MoS2-α-Fe2O3 materials were characterized using UV-visible, FTIR, SEM, X-ray diffraction, Raman and particle analyzer. The photoelectrochemical properties were investigated using cyclic voltammetry and chronoamperometry studies. The optical and structural properties of MoS2-α-Fe2O3 nanocomposite have been found to be dependent on MoS2 doping. The band gap has shifted whereas;the structure is more prominent as flower-like morphology, which is a result of doping of MoS2. The photocurrent is more pronounced with and without light exposition to MoS2-α-Fe2O3 based electrode in photoelectrochemical cell. We have understood the photoelectrochemical water splitting using nanocomposite α-Fe2O3-MoS2 through schematic representation based on experimental results. The enhanced photoelectrochemical properties of nanocomposite α-Fe2O3-MoS2 films have been observed as compared to pristine α-Fe2O3 and transition metal doped α-Fe2O3 nanostructured films.展开更多
Visible light-sensitive photocatalyst was developed by combining n-type silicon (n-Si) and tungsten trioxide (WO3, n-Si/WO3), yielding an ohmic contact in between. In this system, the ohmic contact acted as an electro...Visible light-sensitive photocatalyst was developed by combining n-type silicon (n-Si) and tungsten trioxide (WO3, n-Si/WO3), yielding an ohmic contact in between. In this system, the ohmic contact acted as an electron-and-hole mediator for the transfer of electrons and holes in the conduction band (CB) of WO3 and in the valence band (VB) of n-Si, respectively. Utilizing thus- constructed n-Si/WO3, the decomposition of 2-propanolto CO2 via acetone was achieved under visible light irradiation, by the contribution of holes in the VB of WO3 to decompose 2-propanol and the consumption of electrons in the CB of n-Si to reduce O2. The combination of p-type Si (p-Si) and WO3 (p-Si/ WO3), not the ohmic contact but the rectifying contact, was much less effective, compared to n-Si/WO3.展开更多
The phenol photocatalytic degradation was investigated using heterogeneous catalyst Ag-doped ZnO nanowires under UV irradiation. Ag-ZnO nanowires were immobilized on borosilicate glass via a simple hydrothermal techni...The phenol photocatalytic degradation was investigated using heterogeneous catalyst Ag-doped ZnO nanowires under UV irradiation. Ag-ZnO nanowires were immobilized on borosilicate glass via a simple hydrothermal technique. Preliminary photodegradation studies were performed with Ag-ZnO nanowires at various concentrations of phenol (10 - 60 mg/L) at undiluted pH. After determination of the optimal initial concentration (30 mg/L), additional parameters including pH and light intensity were investigated to optimize photodegradation of phenol for large-scale application. The experimental results illustrate that the kinetics of degradation of phenol are pseudo-first order. Based on the relationship, experimental model and empirical correlation were generated and compared for validity. The experimental data were found to fit a cubic model (linear in UV irradiation intensity, I, and cubic in pH), over ranges of 10 - 60 W (UV lamp power) and 2.7 - 11.0 (pH) with a coefficient of determination (R2) of 0.9934. This model, of the form K(I, pH) = c00 + c10I + c01pH + c11IpH + c02pH2 + c12IpH2 + c03pH3 was found to yield a better fit than simpler (quadratic) or more complex (quartic) polynomial-based models considered. The model parameters cij and corresponding 95% confidence intervals were obtained.展开更多
With the development of fuel cells,multi-stack fuel cell system(MFCS)for high power application has shown tremendous development potential owing to their obvious advantages including high efficiency,durability,reliabi...With the development of fuel cells,multi-stack fuel cell system(MFCS)for high power application has shown tremendous development potential owing to their obvious advantages including high efficiency,durability,reliability,and pollution-free.Accordingly,the state-of-the-art of MFCS is summarized and analyzed to advance its research.Firstly,the MFCS applications are presented in high-power scenarios,especially in transportation applications.Then,to further investigate the MFCS,MFCS including hydrogen and air subsystem,thermal and water subsystem,multi-stack architecture,and prognostics and health monitoring are reviewed.It is noted that prognostics and health monitoring are investigated rarely in MFCS compared with previous research.In addition,the efficiency and durability of MFCS are not only related to the application field and design principle but also the energy management strategy(EMS).The reason is that the EMS is crucial for lifespan,cost,and efficiency in the multi-stack fuel cell system.Finally,the challenge and development potential of MFCS is proposed to provide insights and guidelines for future research.展开更多
The development of proton,oxygen-ion,and electron mixed conducting materials,known as triple-conduction materials,as cathodes for proton-conducting solid oxide fuel cells(H-SOFCs)is highly desired because they can inc...The development of proton,oxygen-ion,and electron mixed conducting materials,known as triple-conduction materials,as cathodes for proton-conducting solid oxide fuel cells(H-SOFCs)is highly desired because they can increase fuel cell performance by extending the reaction active area.Although oxygen-ion and electron conductions can be measured directly,proton conduction in these oxides is usually estimated indirectly.Because of the instability of cathode materials in a reducing environment,direct measurement of proton conduction in cathode oxide is difficult.The La0.8Sr0.2Sc0.5Fe0.5O3–δ(LSSF)cathode material is proposed for H-SOFCs in this study,which can survive in an H_(2)-containing atmosphere,allowing measurement of proton conduction in LSSF by hydrogen permeation technology.Furthermore,LSSF is discovered to be a unique proton and electron mixed-conductive material with limited oxygen diffusion capability that is specifically designed for H-SOFCs.The LSSF is an appealing cathode choice for H-SOFCs due to its outstanding CO_(2)tolerance and matched thermal expansion coefficient,producing a record-high performance of 2032 mW cm^(−2)at 700℃and good long-term stability under operational conditions.The current study reveals that a new type of proton–electron mixed conducting cathode can provide promising performance for H-SOFCs,opening the way for developing high-performance cathodes.展开更多
Defect engineering is a promising strategy for supported catalysts to improve the catalytic activity and durability.Here,we selected the Cmatrix enriched with topological defects to serve as the substrate material,in ...Defect engineering is a promising strategy for supported catalysts to improve the catalytic activity and durability.Here,we selected the Cmatrix enriched with topological defects to serve as the substrate material,in which the topological defects can act as anchoring centers to trapPt nanoparticles for driving the O_(2) reduction reactions(ORRs).Both experimental characterizations and theoretical simulations revealed the strong Ptdefect interaction with enhanced charge transfer on the interface.Despite a low Pt loading,the supported catalyst can still achieve a remarkable 55 mV positive shift of half-wave potential toward ORR in O_(2)-saturated 0.1 M HClO_(4) electrolyte compared with the commercial Pt catalyst on graphitized C.Moreover,the degeneration after 5,000 voltage cycles was negligible.This finding indicates that the presence of strong interaction between Pt and topological C defects can not only stabilize Pt nanoparticles but also optimize the electronic structures of Pt/C catalysts toward ORR.展开更多
文摘Global energy consumption in the last half century has rapidly increased and is expected to continue to grow over the next 50 years,however,with significant differences.The past increase was stimulated by relatively "cheap" fossil fuels and increased rates of industrialization in North America,Europe and Japan;yet while energy consumption in these countries continues to increase,additional factors make the picture for the next 50 years more complex.These additional complicating factors include China and India's rapid increase in energy use as they represent about a third of the world's population;the expected depletion of oil resources in the near future;and,the effect of human activities on global climate change.On the positive side,the renewable energy(RE) technologies of wind,bio-fuels,solar thermal and photovoltaics(PV) are finally showing maturity and the ultimate promise of cost competitiveness.
基金supported by institutional program grants from the Korea Institute of Science and Technology and Korea Institute of Energy Technology Evaluation and Planning(KETEP)granted financial resource from the Ministry of Trade,Industry&Energy,Republic of Korea(No.20224C10300020)“Carbon to X Project”(2020M3H7A1098229)through the National Research Foundation(NRF)funded by the Ministry of Science and ICT,Republic of Korea+1 种基金supported by the National Research Council of Science&Technology(NST)grant by the Korean government(MSIT)(No.CAP21011-100)National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(NRF-2021R1A2C2093467)。
文摘Introducing Ni in Ru oxide is a promising approach to enhance the catalytic activity for the oxygen evolution reaction(OER).However,the role of Ni(which has a poor intrinsic activity)is not fully understood.Here,a Ru NiO_(x)electrode fabricated via a modified dip coating method exhibited excellent OER performance in acidic media,and neutral media for CO_(2)reduction reaction.We combined in-situ/operando X-ray absorption near-edge structure and on-line inductively coupled plasma mass spectrometry studies to unveil the role of the Ni introduced in the Ru oxide.We propose that the Ni not only transforms the electronic structure of the Ru oxide,but also produces a large number of oxygen vacancies by distorting the oxygen lattice structure at low overpotentials,increasing the participation of lattice oxygen for OER.This work demonstrates the real behavior of bimetallic oxide materials under applied potentials and provides new insights into the development of efficient electrocatalysts.
基金National Research Foundation,Grant/Award Number:NRF-2020R1A3B2079803Korea Institute for Advancement of Technology,Grant/Award Number:P0026069。
文摘The polymeric gel electrolytes are attractive owing to their higher ionic conductivities than those of dry polymer electrolytes and lowered water activity for enlarged potential window.However,the ionic conductivity and mechanical strength of the Na-ion conducting polymeric gel electrolytes are limited by below 20 mS cm−1 and 2.2 MPa.Herein,we demonstrate Na-ion conducting and flexible polymeric hydrogel electrolytes of the chemically coupled poly(diallyldimethylammonium chloride)-dextrin-N,N′-methylene-bisacrylamide film immersed in NaClO_(4) solution(ex-DDA-Dex+NaClO_(4))for flexible sodium-ion hybrid capacitors(f-NIHC).In particular,the anion exchange reaction and synergistic interaction of ex-DDA-Dex with the optimum ClO_(4)−enable to greatly improve the ionic conductivity up to 27.63 mS cm−1 at 25◦C and electrochemical stability window up to 2.6 V,whereas the double networking structure leads to achieve both the mechanical strength(7.48 MPa)and softness of hydrogel electrolytes.Therefore,the f-NIHCs with the ex-DDA-Dex+NaClO_(4) achieved high specific and high-rate capacities of 192.04 F g^(−1)at 500 mA g^(−1)and 116.06 F g^(−1)at 10000 mA g^(−1),respectively,delivering a large energy density of 120.03Wh kg^(−1)at 906Wkg^(−1)and long cyclability of 70%over 500 cycles as well as demonstrating functional operation under mechanical stresses.
基金supported by C1 Gas Refinery Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT&Future Planning(2015M3D3A1A01064908)
文摘Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H values on the catalytic activity of La AlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts.When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2 O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.
基金The authors acknowledge the support from the Korea Institute of Science and Technology(KIST)institutional program and YU-KIST convergence programpartially from National Research Foundation(NRF)funded by the Korean Government(No.2019R1A2C2005521).
文摘The conversion of carbon dioxide(CO2)to valuable fuels and chemicals offers a new pathway for sustainable and clean carbon fixation.Recently,the focus has been on electrochemical CO2 reduction on heterogeneous electrode catalysts,leading to remarkable achievements in the reaction performance.To date,CO2 to carbon monoxide(CO)conversion is considered as the most promising candidate reaction for the industrial market,owing to its high efficiency and reasonable technoeconomic feasibility.Moreover,CO has been proposed as a key intermediate species for further reduced hydrocarbons,which can pave the way for various fuel production.This study sets out to describe recent progress on the electrochemical CO2 reduction to CO in a heterogeneously catalyzed system.The review includes understanding of the catalytic material employed and engineering strategies implemented by adjusting the binding energy of key adsorbates.These material design approaches,such as nanostructuring,alloying,doping,and so forth,have pioneered breakouts in the intrinsic catalytic nature of transition metal elements.Moreover,recent advances in systematic design are summarized,with focus on practical industrial applications.Finally,perspectives on the design of electrocatalyst materials for CO production by electrochemical CO2 reduction are presented.
文摘The hydration of cement generates heat due to the exothermic nature of the hydration process. Poor heat dissipation in mass concrete results in a temperature gradient between the inner core and the outer surface of the element. High temperature gradients generate tensile stresses that may exceed the tensile strength of concrete thus leading to thermal cracking. The present paper is an attempt to understand the thermal (heat sink property) and microstructural changes in the hydrated graphene-Portland cement composites. Thermal diffusivity and electrical conductivity of the hydrated graphene-cement composite were measured at various graphene to cement ratios. The mass-volume method was implemented to measure the density of the hydrated graphene-cement composite. Particle size distribution of Portland cement was measured by using a laser scattering particle size analyzer. Heat of hydration of Portland cement was assessed by using a TAMAIR isothermal conduction calorimeter. Scanning electron microscopy (SEM) was implemented to study microstructural changes of the hydrated graphene-cement composites. The mineralogy of graphene-cement and the hydrated graphene-cement composites was investigated by using X-ray diffraction. The findings indicate that incorporation of graphene enhances the thermal properties of the hydrated cement indicating a potential for reduction in early age thermal cracking and durability improvement of the concrete structures.
文摘Development of active iron based water oxidation for designing an ideal artificial photosynthesis devices operating under benign neutral pH is highly demanded. We investigated the electrocatalytic activity of Ruddlesden-Pop-per-type strontium ferrite (Sr3Fe2O7) toward the oxygen evolution reaction (OER). Owing to the temperature-dependent efficiency of the charge disproportionation of Fe4+, the OER activity of Sr3Fe2O7 varied with the temperature, and the onset potential for the OER at a neutral pH underwent a negative shift of approximately 200 mV by increasing the temperature for the stabilization of Fe4+. When metal substitution was made to Sr3Fe2O7 for stabilizing Fe4+ at room temperature, the temperature dependence of the OER activity disappeared and the OER was driven at a small overpotential without increasing the temperature, indicating that the stabilization of Fe4+ is substantially important for achieving high OER activity.
文摘Graphene-Polypyrrole (G/PPy) was synthesized by chemical oxidative polymerization method, and electrochemical impedance spectroscopy (EIS) analysis was employed to study the frequency response characteristics of supercapacitors based on G/PPy conducting polymer nanocomposite. It is found that a uniform G/PPy nanocomposite is formed with polypyrrole (PPy) being homogeneously surrounded by graphene nanosheets. The porous structure allowed electrolyte and ions diffusion in synthesized G/PPy nanocomposite. The metallic conductivity of Graphene-polypyrrole exhibited higher knee frequency at 125 Hz than the knee frequency of pristine PPy at 36 Hz. The high knee frequency of G/PPy supercapacitor is indicative of high power application and long cycle life. The G/PPy nanocomposite based supercapacitor with 1MH2SO4 as the electrolyte showed specific capacitances of 270 F/g at 0.1 Hz and112 F/g at 125 Hz.
文摘Silver (Ag) and silver antimonate (AgSbO3) composites with different amounts of Sb3+ were synthesized by normal sintering with the aim of realizing a thermoelectric material. The electrical conductivity (σ) increased in the sample containing larger amount of Sb3+, whereas Seebeck coefficient (S) decreased. Producing Sb3+ caused the generation of oxygen vacancies in the material, and thus the corresponding donor levels are created in the bandgap, providing more conduction electrons. The conductive Ag particles would contribute to the conduction path as bypasses for carrier transport. The thermal conductivity (κ) was slightly lower in the presence of Ag defects in AgSbO3.
文摘Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric properties (electrical conductivity (σ), Seebeck coefficient (S), Figure of merit (ZT) and calculated thermal conductivity (κ) by S, σ, ZT, and absolute temperature (T)) of bismuth-based rhodium oxides ((Bi1-x,Pbx) 2Sr2Rh2Oy, x = 0 and 0.02, hereafter BSR and BPSR, respectively) were investigated. In comparison with Bi2Sr2Co2Oy (BSC) at 700°C, S and κ enhanced (increased S, 110 (BSR) and 105 μV K-1 (BPSR) from 85 μV K-1 (BSC) and decreased κ, 0.32 (BSR) and 0.50 W m-1 K-1 (BPSR) from 1.75 W m-1 K-1 (BSC)), whereas σ decreased (15 (BSR) and 31 S cm-1 (BPSR) from 70 S cm-1 (BSC)). BPSR reached the highest ZT value of 0.067 at 700°C, compared to those of 0.056 (BSR) and 0.027 (BSC).
文摘Visible light-induced two-step overall water-splitting was achieved by combining two types of photocatalysts, which were prepared by introducing foreign elements into rutile titanium dioxide (TiO2) and strontium titanate (SrTiO3) with a controlled electronic band structure. Rutile TiO2 and SrTiO3 were doped with chromium and tantalum (Cr,Ta-TiO2) and with rhodium (Rh-SrTiO3), respectively, to introduce visible-light sensitivity. Under irradiation with only visible light from a 420-nm LED lamp, the simultaneous liberation of hydrogen and oxygen with a molar ratio of ~2:1 was achieved with these two types of photocatalysts in the presence of iodate ion/iodide ion as a redox mediator.
文摘The alpha (α)-hematite (Fe2O3) as photoanode has been used for photoelectrochemical applications due to low bandgap, low cost, high chemical stability, nontoxicity, and abundance in nature. The doping with various transition metals, formation of nanostructured and nanocomposite of α-Fe2O3 have been attempted to enrich the carrier mobility, surface kinetics and carrier diffusion properties. The manuscript is an attempt to improve the photoelectrochemical properties of α-Fe2O3 by formation of nanocomposite with dichalcogenide (molybdenum disulfide (MoS2) nanomaterials. The nanocomposite of MoS2-α-Fe2O3 have been synthesized by varying the amount of MoS2 in sol-gel synthesis process. The nanocomposite MoS2-α-Fe2O3 materials were characterized using UV-visible, FTIR, SEM, X-ray diffraction, Raman and particle analyzer. The photoelectrochemical properties were investigated using cyclic voltammetry and chronoamperometry studies. The optical and structural properties of MoS2-α-Fe2O3 nanocomposite have been found to be dependent on MoS2 doping. The band gap has shifted whereas;the structure is more prominent as flower-like morphology, which is a result of doping of MoS2. The photocurrent is more pronounced with and without light exposition to MoS2-α-Fe2O3 based electrode in photoelectrochemical cell. We have understood the photoelectrochemical water splitting using nanocomposite α-Fe2O3-MoS2 through schematic representation based on experimental results. The enhanced photoelectrochemical properties of nanocomposite α-Fe2O3-MoS2 films have been observed as compared to pristine α-Fe2O3 and transition metal doped α-Fe2O3 nanostructured films.
文摘Visible light-sensitive photocatalyst was developed by combining n-type silicon (n-Si) and tungsten trioxide (WO3, n-Si/WO3), yielding an ohmic contact in between. In this system, the ohmic contact acted as an electron-and-hole mediator for the transfer of electrons and holes in the conduction band (CB) of WO3 and in the valence band (VB) of n-Si, respectively. Utilizing thus- constructed n-Si/WO3, the decomposition of 2-propanolto CO2 via acetone was achieved under visible light irradiation, by the contribution of holes in the VB of WO3 to decompose 2-propanol and the consumption of electrons in the CB of n-Si to reduce O2. The combination of p-type Si (p-Si) and WO3 (p-Si/ WO3), not the ohmic contact but the rectifying contact, was much less effective, compared to n-Si/WO3.
文摘The phenol photocatalytic degradation was investigated using heterogeneous catalyst Ag-doped ZnO nanowires under UV irradiation. Ag-ZnO nanowires were immobilized on borosilicate glass via a simple hydrothermal technique. Preliminary photodegradation studies were performed with Ag-ZnO nanowires at various concentrations of phenol (10 - 60 mg/L) at undiluted pH. After determination of the optimal initial concentration (30 mg/L), additional parameters including pH and light intensity were investigated to optimize photodegradation of phenol for large-scale application. The experimental results illustrate that the kinetics of degradation of phenol are pseudo-first order. Based on the relationship, experimental model and empirical correlation were generated and compared for validity. The experimental data were found to fit a cubic model (linear in UV irradiation intensity, I, and cubic in pH), over ranges of 10 - 60 W (UV lamp power) and 2.7 - 11.0 (pH) with a coefficient of determination (R2) of 0.9934. This model, of the form K(I, pH) = c00 + c10I + c01pH + c11IpH + c02pH2 + c12IpH2 + c03pH3 was found to yield a better fit than simpler (quadratic) or more complex (quartic) polynomial-based models considered. The model parameters cij and corresponding 95% confidence intervals were obtained.
基金This paper is supported in part by funding from State Key Laboratory of Mechanical transmission in Chongqing University(No.:SKLMT-ZZKT-2022R02,No.:2022CDJDX-004 and No.:SKLMT-ZZKT-2022M085)Chongqing Postdoctoral Research Project(Special Grant:2021XM3107)the key technological research funding of Sichuan Province(2021YFG0071).
文摘With the development of fuel cells,multi-stack fuel cell system(MFCS)for high power application has shown tremendous development potential owing to their obvious advantages including high efficiency,durability,reliability,and pollution-free.Accordingly,the state-of-the-art of MFCS is summarized and analyzed to advance its research.Firstly,the MFCS applications are presented in high-power scenarios,especially in transportation applications.Then,to further investigate the MFCS,MFCS including hydrogen and air subsystem,thermal and water subsystem,multi-stack architecture,and prognostics and health monitoring are reviewed.It is noted that prognostics and health monitoring are investigated rarely in MFCS compared with previous research.In addition,the efficiency and durability of MFCS are not only related to the application field and design principle but also the energy management strategy(EMS).The reason is that the EMS is crucial for lifespan,cost,and efficiency in the multi-stack fuel cell system.Finally,the challenge and development potential of MFCS is proposed to provide insights and guidelines for future research.
基金National Natural Science Foundation of China,Grant/Award Numbers:52272216,51972183Hundred Youth Talents Program of HunanStartup Funding for Talents at University of South China。
文摘The development of proton,oxygen-ion,and electron mixed conducting materials,known as triple-conduction materials,as cathodes for proton-conducting solid oxide fuel cells(H-SOFCs)is highly desired because they can increase fuel cell performance by extending the reaction active area.Although oxygen-ion and electron conductions can be measured directly,proton conduction in these oxides is usually estimated indirectly.Because of the instability of cathode materials in a reducing environment,direct measurement of proton conduction in cathode oxide is difficult.The La0.8Sr0.2Sc0.5Fe0.5O3–δ(LSSF)cathode material is proposed for H-SOFCs in this study,which can survive in an H_(2)-containing atmosphere,allowing measurement of proton conduction in LSSF by hydrogen permeation technology.Furthermore,LSSF is discovered to be a unique proton and electron mixed-conductive material with limited oxygen diffusion capability that is specifically designed for H-SOFCs.The LSSF is an appealing cathode choice for H-SOFCs due to its outstanding CO_(2)tolerance and matched thermal expansion coefficient,producing a record-high performance of 2032 mW cm^(−2)at 700℃and good long-term stability under operational conditions.The current study reveals that a new type of proton–electron mixed conducting cathode can provide promising performance for H-SOFCs,opening the way for developing high-performance cathodes.
基金supported by National Natural Science Foundation of China(nos.52002378 and 51872306)Natural Science Foundation of Zhejiang Provincial(nos.LQ19B030002,LD21E020001,and LY21B030006)+3 种基金the From 0 to 1 Innovative program of CAS(no.ZDBS-LY-JSC021)K.C.Wong Education Foundation(GJTD-2019-13)Ningbo S&T Innovation 2025 Major Special Program(nos.2019B10046,2020Z059,2020Z107,and 2019B10041)Ningbo Natural Science Foundation(no.2019A610019).
文摘Defect engineering is a promising strategy for supported catalysts to improve the catalytic activity and durability.Here,we selected the Cmatrix enriched with topological defects to serve as the substrate material,in which the topological defects can act as anchoring centers to trapPt nanoparticles for driving the O_(2) reduction reactions(ORRs).Both experimental characterizations and theoretical simulations revealed the strong Ptdefect interaction with enhanced charge transfer on the interface.Despite a low Pt loading,the supported catalyst can still achieve a remarkable 55 mV positive shift of half-wave potential toward ORR in O_(2)-saturated 0.1 M HClO_(4) electrolyte compared with the commercial Pt catalyst on graphitized C.Moreover,the degeneration after 5,000 voltage cycles was negligible.This finding indicates that the presence of strong interaction between Pt and topological C defects can not only stabilize Pt nanoparticles but also optimize the electronic structures of Pt/C catalysts toward ORR.
