Enhancing cathode performance for CO_2 electrolysis with Ce_(0.9)M_(0.1)O_(2-δ)(M=Fe,Co, Ni) catalysts in solid oxide electrolysis cell

Electrochemical conversion with solid oxide electrolysis cells is a promising technology for CO_2 utilization and simultaneously store renewable energy. In this work, Ce_(0.9)M_(0.1)O_(2-δ)(CeM, M=Fe, Co, Ni) catalysts are infiltrated into La_(0.6) Sr_(0.4) Cr_(0.5_ Fe_(0.5) O_(3-δ)–Gd_(0.2) Ce_(0.8) O_(2-δ)(LSCr Fe-GDC) cathode to enhance the electrochemical performance for CO2 electrolysis. Ce Co-LSCr Fe-GDC cell obtains the best performance with a current density of 0.652 A cm-2, followed by Ce Fe-LSCr Fe-GDC and Ce Ni-LSCr Fe-GDC cells with the value of 0.603 and 0.535 A cm~(-2), respectively, about 2.44, 2.26 and 2.01 times higher than that of the LSCr Fe-GDC cell at1.5 V and 800 °C. Electrochemical impedance spectra combined with distributions of relaxed times analysis shows that both CO_2 adsorption process and the dissociation of CO_2 at triple phase boundaries are accelerated by Ce M catalysts, while the latter is the key rate-determining step.     

Co/Fe oxide and Ce_(0.8)Gd_(0.2)O_(2-δ) composite interlayer for solid oxide electrolysis cell

A composite interlayer comprised of gadolinia doped ceria(GDC) and Co/Fe oxide was prepared and investigated for solid oxide electrolysis cell with yttrium stabilized zirconia(YSZ) electrolyte and La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ)(LSCF) anode. The interlayer was constructed of a base layer of GDC and a top layer of discrete Co_3O_4/FeCo_2O_4 particles. The presence of the GDC layer drastically alleviated the undesired reactions between LSCF and YSZ, and the presence of Co/Fe oxide led to further performance improvement. At 800 °C and 45% humidity, the cell with 70% Co/Fe-GDC interlayer achieved 0.98 A/cm~2 at 1.18 V, 14% higher than the cell without Co/Fe oxide. Electrochemical impedance spectroscopy(EIS) revealed that with higher Co/Fe content, both the ohmic resistance and the polarization resistance of the cell were reduced. It is suggested that Co/Fe oxide can react with the Sr species segregated from LSCF and Sr_(1-x)(Co,Fe)O_(3-δ), a compound with high catalytic activity and electronic conductivity. The Sr-capturing ability of Co/Fe oxide in combination with the Sr-blocking ability of GDC layer can effectively suppress the undesired reaction between LSCF and YSZ, and consequently improve the cell performance.     

Towards high-performance tubular-type protonic ceramic electrolysis cells with all-Ni-based functional electrodes

Protonic ceramic electrolysis cells(PCECs), which permit high-temperature electrolysis of water, exhibit various advantages over conventional solid oxide electrolysis cells(SOECs), including cost-effectiveness and the potential to operate at low-/intermediate-temperature ranges with high performance and efficiency. Although many efforts have been made in recent years to improve the electrochemical characteristics of PCECs, certain challenges involved in scaling them up remain unresolved. In the present work, we present a twin approach of combining the tape-calendering method with all-Ni-based functional electrodes with the aim of fabricating a tubular-designed PCEC having an enlarged electrode area(4.6 cm~2). This cell, based on a 25 μm-thick Ba Ce_(0.5) Zr_(0.3) Dy_(0.2) O_(3–δ)proton-conducting electrolyte, a nickelbased cermet and a Pr_(1.95) Ba_(0.05) NiO_(4+) δoxygen electrode, demonstrates a high hydrogen production rate(19 m L min~(–1) at 600 °C), which surpasses the majority of results reported for traditional button-or planar-type PCECs. These findings increase the scope for scaling up solid oxide electrochemical cells and maintaining their operability at reducing temperatures.     

Electrochemical ageing study of mixed lanthanum/praseodymium nickelates La2-xPrxNiO4+δ as oxygen electrodes for solid oxide fuel or electrolysis cells

The chemical and electrochemical stability of lanthanide nickelates La2 NiO4+δ(LNO),Pr2 NiO4+δ(PNO)and their mixed compounds La(2-x)PrxNiO4+δ(LPNOs)with x=0.5,1 or 1.5 is reported.The aim is to promote these materials as efficient electrodes for solid oxide fuel cell(SOFC)and/or solid oxide electrolysis cell(SOEC).La2 NiO4+δand La1.5Pr0.5NiO4+δcompounds are chemically very stable as powders over one month in the temperature range 600-800℃,while the other materials rich in praseodymium progressively decompose into various perovskite-deriving components with additional Pr6 O11.Despite their uneven properties,all these materials are quite efficient and sustainable as electrodes on top of gadolinium doped ceria(GDCBL)//yttrium doped zirconia(8 YSZ)electrolyte,for one month at 700℃without polarization.Under polarization(300 mA·cm-2),the electrochemical performances of LNO,PNO and La1.5Pr0.5NiO4+δ(LP5 NO)quickly degrade in SOFC mode,i.e.for the oxygen reduction reaction,while they show durability in SOEC mode,i.e.for the oxide oxidation reaction.     

Efficient CO_2 Electrolysis with Fluorite Structure Nanoparticles Modified Perovskite Structure La_(0.75)Sr_(0.25)Cr_(0.5)Mn_(0.5)O_(3-δ) Cathode

Perovskite structure La_(0.75)Sr_(0.25)Cr_(0.5)Mn_(0.5)O_(3-δ)(LSCM) cathode with unique structure can electrolyze CO_2 to CO in solid oxide electrolysers(SOEs).However,the cell performance is restricted by its electro-catalysis activity.In this work,fluorite structure nanoparticles(CeO_(2-δ)) are impregnated on LSCM cathode to improve the electro-catalysis activity.X-ray diffraction(XRD),scanning electron microscope(SEM) and X-ray photoelectron spectroscopy(XPS) together approve that the fluorite structure nanoparticles are uniformly distributed on the perovskite structure LSCM scaffold.Electrochemical measurements illustrate that direct CO_2 electrolysis with 10%mol CeO_(2-δ) impregnated LSCM cathode exhibits excellent performance for current density(0.5 A×cm~(-2)) and current efficiency(～95%) at 800 ℃ under 1.6 V.It is believed that the enhanced performance of directed CO_2 electrolysis may be due to the synergetic effect of fluorite structure CeO_(2-δ) nanoparticles and perovskite structure LSCM ceramic electrode.     

Hollow cobalt oxide nanoparticles embedded in nitrogen-doped carbon nanosheets as an efficient bifunctional catalyst for Zn–air battery

Rational design of low-cost, highly electrocatalytic activity, and stable bifunctional electrocatalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER) has been a great significant for metal–air batteries. Herein, an efficient bifunctional electrocatalyst based on hollow cobalt oxide nanoparticles embedded in nitrogen-doped carbon nanosheets(Co/N-Pg) is fabricated for Zn–air batteries. A lowcost biomass peach gum, consisting of carbon, oxygen, and hydrogen without other heteroatoms, was used as carbon source to form carbon matrix hosting hollow cobalt oxide nanoparticles. Meanwhile, the melamine was applied as nitrogen source and template precursor, which can convert to carbon-based template graphitic carbon nitride by polycondensation process. Owing to the unique structure and synergistic effect between hollow cobalt oxide nanoparticles and Co-N-C species, the proposal Co/N-Pg catalyst displays not only prominent bifunctional electrocatalytic activities for ORR and OER, but also excellent durability. Remarkably, the assembled Zn–air battery with Co/N-Pg air electrode exhibited a low discharge-charge voltage gap(0.81 V at 50 mA cm~(-2)) and high peak power density(119 mW cm~(-2)) with long-term cycling stability. This work presents an effective approach for engineering transition metal oxides and nitrogen modified carbon nanosheets to boost the performance of bifunctional electrocatalysts for Zn–air battery.     

High-temperature electrocatalysis and key materials in solid oxide electrolysis cells

Solid oxide electrolysis cells(SOECs)can convert electricity to chemicals with high efficiency at ~600-900℃,and have attracted widespread attention in renewable energy conversion and storage.SOECs operate in the inverse mode of solid oxide fuel cells(SOFCs)and therefore inherit most of the advantages of SOFC materials and energy conversion processes.However,the external bias that drives the electrochemical process will strongly change the chemical environments in both in the cathode and anode,therefore necessitating careful reconsideration of key materials and electrocatalysis processes.More importantly,SOECs provide a unique advantage of electrothermal catalysis,especially in converting stable low-carbon alkanes such as methane to ethylene with high selectivity.Here,we review the state-of-the-art of SOEC research progress in electrothermal catalysis and key materials and provide a future perspective.     

A Novel Route to Synthesize Nano-crystalline Ba0.5Sr0.5Co0.8Fe0.2O3-δ Perovskite Oxide at High Temperature

BSCF, a composite oxide with mixed oxygen ionic and electronic conductivity at high temperature, has received increasing attention since it was first developed as the oxygen permeable membrane and the membrane reactor for partial oxidation of natural gas to syngas by Shao et al.2, 3. It shows high oxygen permeability and catalytic activity for the reduction of the oxygen4-6. Very recently, it is also successfully applied as the cathode material in intermediate temperature solid oxide fuel cel…     

Preparation and Electrochemical Performance of Cobalt-free Cathode Material Ba0.5Sr0.5Fe0.9Nb0.1O3-δ for Intermediate-temperature Solid Oxide Fuel Cells

Perovskite oxide Ba0.5Sr0.5Fe0.9Nb0.1O3-δ（BSFN） as a cobalt-free cathode for intermediate-temperature solid oxide fuel cells（IT-SOFCs） on the Ce0.5Sm0.2O1.9（SDC） and La0.9Sr0.1Ga0.8Mg0.23O3-δ（LSGM） electrolytes was prepared and investigated. The single phase BSFN oxide with a cubic perovskite structure and relatively high elec- trical conductivities was obtained after sintering at 1250℃ for 10 h in air. The BSFN cathode exhibited excellent chemical stability on the SDC and LSGM electrolytes at temperatures below 950 ℃. The area specific resistance of the BSFN cathode on the SDC and LSGM electrolytes were 0.024 and 0.021 Ω·cm2 at 800℃, respectively. The maximum power densities of the single cell with BSFN cathode in 300 μm-thick SDC and LSGM electrolytes achieved 414 and 516 mW/cm2 at 800℃, respectively. These results show that the BSFN material is a promising co- bait-free cathode candidate to be used in IT-SOFCs. A combination of the BSFN cathode and LSGM electrolyte is preferred owing to its excellent electrochemical performance.     

一种新型氧离子导体：La3GaMo2O12

A new oxide ion conductor,La_3GaMo_2O_(12),with a bulk conductivity of 2.7×10~(-2)S·cm~(-1) at 800 ℃ in air at-mosphere was prepared by the traditional solid-state reaction.The room temperature X-ray diffraction data could beindexed on a monoclinic cell with lattice parameters of a=0.5602(2) nm,b=0.3224(1) nm,c=1.5741(1) nm,β=102.555(0)°,V= 0.2775(2) nm~3 and space group Pc(7).Ac impedance measurements in various atmospheres furthersupport that it is an oxide ion conductor.This material was stable in various atmospheres with oxygen partial pres-sure p(O_2)ranging from 1.0×10~5 to 1.0×10~(-7) Pa at 800 ℃.A reversible polymorphic phase transition occurred atelevated temperatures as confirmed by the differential thermal analysis and dilatometric measurement.     

Facile Synthesis of Layered Sodium Manganese Oxide for Application in Asymmetric Supercapacitor

Layered sodium manganese oxides(LSMOs), with two-dimensional channels for ion diffusion, have been regarded as the promising electrode materials in the application of asymmetric supercapacitors(ASCs). In this work, the layered Na_(0.5)Mn_2O_4·1.5H_2O was synthesized through a facile hydrothermal method by controlling the molar ratio of sodium and manganese. When the molar ratio of sodium to manganese is 3:1, Na_(0.5)Mn_2O_4·1.5H_2O has shown the best capacitance of 369 F/g with current density of 0.5 A/g, and maintained a capacitance of 265 F/g after 2000 cycles. The asymmetric supercapacitor consists of the sodium manages oxides as the positive electrode and active carbon(AC) as the negative electrode in 1 mol/L Na_2SO_4 solution. The voltage of the asymmetric supercapacitor has been expanded to 0～2 V with an energy density of 10.13 Wh/kg at a power density of 500 W/kg based on the total weight of both active electrode materials when the mass ratio of AC to Na_(0.5)Mn_2O4·1.5H_2O was 3:1.     

Nanocarbons and their hybrids as catalysts for non-aqueous lithium–oxygen batteries

Rechargeable lithium-oxygen(Li–O_2) batteries have been considered as the most promising candidates for energy storage and conversion devices because of their ultra high energy density. Until now, the critical scientific challenges facing Li–O_2batteries are the absence of advanced electrode architectures and highly efficient electrocatalysts for both oxygen reduction reaction(ORR) and oxygen evolution reaction(OER), which seriously hinder the commercialization of this technology. In the last few years, a number of strategies have been devoted to exploring new catalysts with novel structures to enhance the battery performance. Among various of oxygen electrode catalysts, carbon-based materials have triggered tremendous attention as suitable cathode catalysts for Li–O_2batteries due to the reasonable structures and the balance of catalytic activity, durability and cost. In this review, we summarize the recent advances and basic understandings related to the carbon-based oxygen electrode catalytic materials, including nanostructured carbon materials(one-dimensional(1D) carbon nanotubes and carbon nanofibers, 2D graphene nanosheets, 3D hierarchical architectures and their doped structures), and metal/metal oxide-nanocarbon hybrid materials(nanocarbon supporting metal/metal oxide and nanocarbon encapsulating metal/metal oxide). Finally, several key points and research directions of the future design for highly efficient catalysts for practical Li–O_2batteries are proposed based on the fundamental understandings and achievements of this battery field.     

Cobalt oxide and carbon modified hematite nanorod arrays for improved photoelectrochemical water splitting

Given the proper band gap, low cost and good stability, hematite(α-Fe_2O_3) has been considered as a promising candidate for photoelectrochemical(PEC) water splitting, however suffers from the sluggish surface water oxidation reaction kinetics. In this study, a simple dip-coating process was used to modify the surface of α-Fe_2O_3 nanorod arrays with cobalt oxide(CoO_x) and carbon(C) for the improved PEC performance, with a photocurrent density at 1.6 V(vs. reversible hydrogen electrode, RHE) increased from 0.10 mA/cm~2 for the pristine α-Fe_2O_3 to 0.37 mA/cm~2 for the CoO_x/C modified α-Fe_2O_3 nanorods. As revealed by electrochemical analysis, thanks to the synergistic effect of CoO_x and C, the PEC enhancement could be attributed to the enhanced charge transfer ability, decreased surface charge recombination, and accelerated water oxidation reaction kinetics. This study serves as a good example for improving PEC water splitting performance via a simple method.     

Electrochemical Oxidation of Chlorimuron-ethyl on Ti/SnO2-Sb2O5/PbO2 Anode for Waste Water Treatment

<正>The electrochemical oxidation of chlorimuron-ethyl on Ti/SnO_2-Sb_2O_5/PbO_2 electrode was studied by cyclic voltammetry. The electrochemical behaviour of the electrode in a sodium sulfate solution and in the mixture solution of sodium sulfate and chlorimuron-ethyl was studied.The experimental results of cyclic voltammetry show that the acidic medium was suitable for the efficient electrochemical oxidation of chlorimuron-ethyl.Some electro-generated reagent was formed in the electrolysis process and chlorimuron-ethyl could be oxidized by the electro-generated reagent.A Ti/SnO_2-Sb_2O_5/PbO_2 electrode was used as the anode and the electrolysis experiment was carried out under the optimized conditions.The electrolysis process was monitored by UV-Vis spectrometry and high performance liquid chromatography(HPLC),and the chemical oxygen demand(COD) was determined by the potassium dichromate method.The mechanism of chlorimuron-ethyl to be oxided was studied primarily by the cyclic voltammetry and UV-Vis spectrometry.The results of electrolysis experiment demonstrate the possibility of the electrode to be used as an anode for the electrochemical treatment of chlorimuron-ethyl contained in waste water.     

Facile synthesis of high electrical conductive CoP via solid-state synthetic routes for supercapacitors

Co-P precursor was prepared by a mechanical alloying method and then is controlled to synthesis of Co P phase through an annealing method. The optimal conditions of ball milling and annealing temperature are investigated. The Co P exhibits higher electrical conductivity than graphite and cobalt oxide, showing excellent pseudocapacitive properties due its high electrical conductivity which can result in a fast electron transfer in high rate charge–discharge possess. The as-obtained Co P electrode achieves a high specific capacitance of 447.5 F/g at 1 A/g, and displays an excellent rate capability as well as good cycling stability. Besides, the asymmetric supercapacitor(ASC) based on the Co P as the positive electrode and activated carbon(AC) as the negative electrode was assembled and displayed a high rate capability(60%of the capacitance is retained when the current density increased from 1 A/g to 12 A/g), excellent cycling stability(96.7% of the initial capacitance is retained after 5000 cycles), and a superior specific energy of19 Wh/kg at a power density of 350.8 W/kg. The results suggest that the Co P electrode materials have a great potential for developing high-performance electrochemical energy storage devices.     

Synthesis and Electrochemical Performance of Co3O4/Graphene

Co3O4/reduced graphene oxide composites were synthesized via a simple electrochemical method from graphene oxide and Co（NO3）2·6H2O as raw materials.Co3O4 nanoparticles with sizes of around 30-50 nm were distributed on the surface of graphene nanosheets confirmed by scanning electron microscopy and transmission electron microscopy.Electrochemical properties of Co3O4/graphene composite were tested by cyclic voltammetry,galvanostatic charge-discharge,and electrochemical impedance spectroscopy.The Co3O4/reduced graphene oxide composite was used as the pseudocapacitor electrode in the 2 mol/L NaOH aqueous electrolyte solution.The Co3O4/reduced graphene oxide composite electrode exhibited a specific capacitance of 357 F/g at a current density of 0.5 A/g in a three-electrode system.72％ of capacitance was retained when the current density increased to 3 A/g.The Co3O4/reduced graphene oxide composite prepared electrodes show a high rate capability and excellent long-term stability.After 1000 cycles of charge and discharge,the capacitance is still maintained 87％ at a current density of 1 A/g,indicating that the composite is a oromising alternative electrode material used for supercapacitors.     

Low temperature preparation and fuel cell properties of rare earth doped barium cerate solid electrolytes

The solid electrolytes, BaCe_(0.8) Ln_(0.2)O_(2.9) (Ln: Gd, Sm, Eu), were prepared by the sol-gel method. XRD indicated that a pure orthorhombic phase was formed at 900℃. The synthesis temperature by the sol-gel method was about 600℃ lower than the high temperature solid phase reaction method, The electrical conductivity and impedance spectra were measured and the conduction mechanism was studied. The grain-boundary resistance of the solid electrolyte could be reduced or eliminated by the sol-gel method. The conductivity of BaCe_(0.8)Gd_(0.2)O_(2.9) is 7.87×10~(-2) S·cm~(-1) at 800℃. The open-circuit voltage of hydrogen-oxygen fuel cell using BaCe_(0.8) Gd_(0.2)O_(2.9) as electrolyte was near to 1 V and its maximum power density was 30 mW·cm~(-2).     

PREPARATIVE AND STRUCTURAL STUDIES ON THE SUPERCONDUCTING PHASE YBa_2Cu_3O_(7-d)

Reasonably homogeneous samples were obtained by following the formula Y_(0.334)Ba_(0.666)CuO_(3-y) andusing citric acid as a complex-forming agent to improve the dispersion of the metal oxides. We havealso found that the variant condition in preparative procedure leads to variant deviation from tetrago-nality and that more pronounced deviation gives better superconducting properties. The crystal structure determined from X-ray powder diffraction diagrams confirms the stoichiom-etry of the metal ions and gives the positions of the oxygen atoms. The orthorhombic or pseudo-tetragonal unit cell with a=3.893, b= 3.813 and c= 11.687 A contains YBa_2Cu_3O_7. It is composed ofthree perovskite cubes with three copper atoms at their corners, the two barium atoms at the centers ofthe top and bottom cubes, and the yttrium at the center of the unit cell. The oxygen atoms sit on centersof cube edges. The positions (0 0 1/2) are vacant. The vacancies represented by (0(1/2)0) cause the ar-rangement of atoms to lose tetragonal symmetry, and have far-reaching effect for this phase. The yttriumand barium atoms are coordinated in a cuboctahedron respectively with four equatoria oxygen atoms at(0 0 1/2) and two at (0 1/2 0) removed. In the light of bond valence theory we can infer from the in-teratomic distances Y-O, Ba-O and Cu-O that the occupancy of the oxygen atoms at (1/2 0 0) is wellbelow unity while the positions (0 0 1/2) are vacant, the formula of the phase is YBa_2Cu_3O_(7-d), thefraction of Cu(Ⅱ) and (Ⅲ) for the set of copper at (0 0 0) is respectively d/0.5 and (1-d/0.5), and0.2相似文献   

HIGH TEMPERATURE SUPERCONDUCTOR YBa_2CuaO_(7-x) AS A LITHIUM BATTERY CATHODE

Superconductor YBa_2Cu_3O_(7-x) used as a material for lithium battery was examined in 1NLiClO_4 propylene carbonate/1,2-dimethoxyethane (1:1) solution. YBa_2Cu_3O_(7-x) exhibited 150 mAh/g of discharge capacity at 250 uA/cm~2 discharge current. An ac impedance measurements was carried out, the results have shown that the electrode reaction has low charge-transfer resistance and the chemical diffusion coeffic ient of Li~+ has a value of 10~(-11) cm~2/sec.     

Perovskite Sr_(0.9)Fe_(0.9)Zr_(0.1)O_(3-δ):Redox-stable Structure,Oxygen Vacancy,Electrical Properties and Steam Electrolysis Performance

Many researchers have studied on perovskite oxide for its unique structure.Perovskite oxides,ABO_(3-δ),with different A and B metals have shown wide applications in many fields,in particular solid oxide electrolysers.SrFeO_(3-δ),typical perovskite oxides,in which iron is the mixed-valence cation with the capacity to change the chemical valence,have a wide range of oxygen nonstoichiometry.In this study,Sr_(0.9)Fe_(0.9)Zr_(0.1)O_(3-δ)(SFZO) is synthesized and then treated in 5%H_2/Ar and air at high temperature,exhibiting excellent redox stability.Redox-stable structure,oxygen vacancy and electrical properties of SFZO are investigated.Steam electrolysis is then performed with SFZO cathode under 5%H_2O/5%H_2/Ar and 5%H_2O/Ar atmospheres,respectively.The present results indicate that the SFZO is a novel promising cathode material for solid oxide steam electrolyser.