Promotion on electrochemical performance of Ba‐deficient Ba1 − xBi0.05Co0.8Nb0.15O3 − δ cathode for intermediate temperature solid oxide fuel cells

Reducing the operating temperature is the developing trend for solid oxide fuel cells. The key is to develop the cathode with high electrocatalytic activity for oxygen reduction reaction operated at reduced temperatures. Ba‐deficient Ba_1 ? xBi_0.05Co_0.8Nb_0.15O_3 ? δ (Ba_1 ? xBCN, 0 ≤ x ≤ 0.10) are synthesized by solid‐state reaction method and evaluated as novel cathodes for intermediate‐temperature solid oxide fuel cells. Ba_1 ? xBCN is preserved to primitive cubic perovskite phase and meets the compatibility requirement with gadolinium doped ceria oxide (GDC) electrolyte at 950°C. Though the Ba deficiency distorts the cell symmetry, it improves the charge transfer steps rapidly, ascribing to the improvement of oxygen vacancy concentration. The polarization resistance of Ba_0.95BCN is as low as 0.056 Ω cm² in air at 700°C. The peak power density of the single cell with this cathode is as high as 1.41 W cm^?2 at 750°C with wet H₂ as fuel and air as oxidant, indicating the great potential for enhanced performance of Co‐based cathodes with A‐site deficiency.     

Synthesis and application of Fe3O4@nanocellulose/TiCl as a nanofiller for high performance of quasisolid‐based dye‐sensitized solar cells

In this research, to optimize the surface of the photoanode, two different types of surface coatings were used and their effects on the photovoltaic parameters were investigated. Also, to compare the two different electrolytic systems based on liquid and gel‐state electrolyte, the novel magnetic core‐shell nanocellulose/titanium chloride (Fe₃O₄@)NCs/TiCl) nanocomposite was introduced into a polymeric system as a nanofiller to decrease the crystallinity of the polymer and enhance the diffusion of triiodide ions in quasisolid‐state dye‐sensitized solar cells (QS‐DSSCs). For this purpose, Fe₃O₄@)NCs/TiCl was synthesized by coprecipitation of Fe³⁺ and Fe²⁺ ions in the presence of nanocellulose and then used as magnetic support for bonding TiCl₄ to prepare QS‐DSSCs. Containing a 10.0 wt% magnetic nanocomposite, it displayed a higher apparent diffusion coefficient (D_app) for I₃^? ions (4.10 × 10^?6 cm²/s) than the gel polymeric electrolyte (GPE) did (1.35 × 10^?6 cm²/s). GPEs were characterized using various techniques including current density‐voltage curves, AC impedance measurements, and linear sweep voltammetry (LSV). The photovoltaic values for the short‐circuit current density (J_sc), open‐circuit voltage (V_OC), and fill factor (FF) and the energy conversion efficiency (η) of the novel Fe₃O₄@NCs/TiCl nanocomposite–based QS‐DSSCs were 14.90 mA cm^?2, 0.757 V, 64%, and 7.22%, respectively.     

Synthesis and assessment of La0.8Sr0.2ScyMn1−yO3−δ as cathodes for solid-oxide fuel cells on scandium-stabilized zirconia electrolyte

Perovskite-type La_0.8Sr_0.2Sc_yMn_1−yO_3−δ oxides (LSSMy, y = 0.0–0.2) were synthesized and investigated as cathodes for solid-oxide fuel cells (SOFCs) containing a stabilized zirconia electrolyte. The introduction of Sc³⁺ into the B-site of La_0.8Sr_0.2MnO_3−δ (LSM) led to a decrease in the oxides’ thermal expansion coefficients and electrical conductivities. Among the various LSSMy oxides tested, LSSM0.05 possessed the smallest area-specific cathodic polarization resistance, as a result of the suppressive effect of Sc³⁺ on surface SrO segregation and the optimization of the concentration of surface oxygen vacancies. At 850 °C, it was only 0.094 Ω cm² after a current passage of 400 mA cm⁻² for 30 min, significantly lower than that of LSM (0.25 Ω cm²). An anode-supported cell with a LSSM0.05 cathode demonstrated a peak power density of 1300 mW cm⁻² at 850 °C. The corresponding value for the cell with LSM cathode was 450 mW cm⁻² under the same conditions. The LSSM0.05 oxide may potentially be a good cathode material for IT-SOFCs containing doped zirconia electrolytes.     

Enhanced alkaline stability and performance of alkali‐doped quaternized poly(vinyl alcohol) membranes for passive direct ethanol fuel cell

Direct ethanol fuel cells (DEFCs) emerge as the new research energy field since fast production of electricity, high efficiency conversion, and simple fabrication process. The production cost, conductivity properties, and ethanol permeability of membrane were the main problem that limited the DEFC performance and commercialization. In this study, a low cost, good ionic conductivity and low ethanol permeability of an anion exchange membrane based on incorporation KOH‐doped quaternized poly(vinyl alcohol) (QPVA) membrane (designed as QPVA/KOH) is synthesized and cross‐linked with glutaraldehyde solution. The membrane is expected to cut the production cost and enhance the performance. In this work, an optimum of alkali‐doped concentration has influence the membrane performance. The membrane has reveal high chemical stability even doped with 8‐M KOH solution in 100°C. The morphology of membranes remained unbreakable and achieved high range of ionic conductivity (~10^?2 S cm^?1). The membranes present maximum ionic conductivity 1.29 × 10^?2 S cm^?1 at 30°C and 3.07 × 10^?2 S cm^?1 at 70°C. The ethanol permeability of membrane is lower compared with the commercial membranes. Power density of alkaline DEFCs with platinum‐based catalyst by using cross‐linked QPVA/KOH membrane is 5.88 mW cm^?2, which is higher than commercial membranes at 30°C temperature. At 70°C, power density has increased up to 11.28 mW cm^?2 and significantly increased up to 22.82 mW cm^?2 via the nonplatinum‐based catalyst. Moreover, according to the durability test, the performance of passive alkaline DEFC by using cross‐linked QPVA/KOH membrane has maintained at 36.2% level. With such efficiency, the stack current density has been able to stay above 120 mA cm^?2 for over 1000 hours, at 70°C.     

Flexible supercapacitor based on three‐dimensional cellulose/graphite/polyaniline composite

Fast charge‐discharge rate and high areal capacitance, along with high mechanically stability, are the pre‐requisites for flexible supercapacitors to power flexible electronic devices. In this paper, we have used three‐dimensional polyacrylonitrile graphite foam as flexible current collector for electro‐deposition of polyaniline (PANI) nanowires. The graphite foam with PANI was then used to fabricate symmetric supercapacitor. The fabricated supercapacitor in the three‐electrode system shows a high specific capacitance (C_sp) of 357 F.g^?1 and areal capacitance (C_areal) of 7142 mF.cm^?2 in 1 M H₂SO₄ at current density of 80 mA.cm^?2, while using two‐electrode system, it shows C_sp of 256 F.g^?1 and C_areal of 5120 mF.cm^?2 in 1 M H₂SO₄ at current density of 100 mA.cm^?2. The current density of 100 mA.cm^?2 is up to 10 folds higher than reported current densities of many PANI‐based supercapacitors. The high capacitance can be attributed to the spongy network of PANI‐NWs on three‐dimensional graphite surface which provides an easy path for electrolyte ions in active electrode materials. The developed supercapacitor shows specific energy of 64.8 Whkg^?1 and a specific power of 6.1 kWkg^?1 with a marginally decrease of 1.6% in C_sp after 1000^th cycles, along with coulombic efficiency retention of 87% in polyvinyl alcohol/H₂SO₄ gel electrolyte. This flexible supercapacitor exhibits great potential for energy storage application.     

A freestanding MoO2‐decorated carbon nanofibers interlayer for rechargeable lithium sulfur battery

Lithium‐sulfur (Li‐S) battery based on sulfur cathodes is of great interest because of high capacity and abundant sulfur source. But the shuttling effect of polysulfides caused by charge‐discharge process results in low sulfur utilization and poor reversibility. Here, we demonstrate a good approach to improve the utility of sulfur and cycle life by synthesizing carbon nanofibers decorated with MoO₂ nanoparticles (MoO₂‐CNFs membrane), which plays a role of multiinterlayer inserting between the separator and the cathode for Li‐S battery. The S/MoO₂‐CNFs/Li battery showed a discharge capacity of 6.93 mAh cm^?2 (1366 mAh g^?1) in the first cycle at a current density of 0.42 mA cm^?2 and 1006 mAh g^?1 over 150 cycles. Moreover, even at the highest current density (8.4 mA cm^?2), the battery achieved 865 mAh g^?1. The stable electrochemical behaviors of the battery has achieved because of the mesoporous and interconnecting structure of MoO₂‐CNFs, proving high effect for ion transfer and electron conductive. Furthermore, this MoO₂‐CNFs interlayer could trap the polysulfides through strong polar surface interaction and increases the utilization of sulfur by confining the redox reaction to the cathode.     

Enhanced hydrogen evolution reaction on highly stable titania‐supported PdO and Eu2O3 nanocomposites in a strong alkaline solution

In this work, PdO/TiO₂ and Eu₂O₃/TiO₂ nanocomposites (NCs) were synthesized using a new facile, template‐free, and one‐step solvothermal approach and characterized by several instrumentation techniques. X‐ray photoelectron spectroscopy studies revealed the presence of oxidized form of the Pd and Eu nanoparticles within the NC materials (PdO and Eu₂O₃). The two catalysts exhibited remarkable activity for the hydrogen evaluation reaction (HER) in a strong alkaline solution (4.0 M NaOH) with PdO/TiO₂ catalyst being the best, which recorded an exchange current density (j_o) of 0.26 mA cm^?2 and a Tafel slope (β_c) of 125 mV dec^?1. Such parameters are not far from those recorded for a commercial Pt/C catalyst (0.71 mA cm^?2 and 120 mV dec^?1) performed here under the same operating conditions. Eu₂O₃/TiO₂ catalyst recorded j_o and β_c values of 0.05 mA cm^?2 and 135 mV dec^?1. The Tafel slopes 125 and 135 mV dec^?1 calculated on the PdO/TiO₂ and Eu₂O₃/TiO₂ catalysts suggest a HER kinetics controlled by the Volmer step. PdO/TiO₂ catalyzed the HER with a high turnover frequency of 2.3 H₂/s at 0.2 V versus the reversible hydrogen electrode, while Eu₂O₃/TiO₂ catalyst only measured a turnover frequency value of 1.25 H₂/s at the same overpotential. The two catalysts exhibited excellent stability and durability after 10 000 cycles and 72 hours of controlled potential electrolysis at a high cathodic overpotential, reflecting their practical applicability. Scanning electron microscope and X‐ray photoelectron spectroscopy examinations revealed that the morphology and chemistry of both catalysts were not altered as a result of the performed long‐term stability and durability tests.     

A dotted nanowire arrayed by 5 nm sized palladium and nickel composite nanopaticles showing significant electrocatalytic activity towards ethanol oxidation reaction (EOR)

To the best of our knowledge, this is the first time to report the preparation of a dotted nanowire arrayed by 5 nm sized palladium and nickel composite nanoparticles (denoted as Pd_xNi_y NPs) via a hydrothermal method using NU and PdO·H₂O as the starting materials. The samples prepared at the mass ratio of NU to PdO·H₂O 1:1, 1:2 and 2:1 were, respectively, nominated as catalyst c₁, c₂ and c₃. The chemical compositions of all synthesized catalysts were mainly studied by using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), revealing that metallic Ni was one main component of all prepared catalysts. Surprisingly, the main diffraction peaks appearing in the XRD patterns of all prepared catalysts were assigned to the metallic Ni rather than the metallic Pd. Very interestingly, as indicated by the TEM images, a large number of dotted nanowires arrayed by numerous equidistant 5 nm sized nanoparticles were distinctly exhibited in catalyst c₁. More importantly, when being used as electrocatalysts for EOR, all prepared catalysts exhibited an evident electrocatalytic activity towards EOR. In the cyclic voltammetry (CV) test, the peak current density of the forward peak of EOR on catalyst c₁ measured at 50 mV s^?1 was as high as 56.1 mA cm^?2, being almost 9 times higher than that of EOR on catalyst c₃ (6.3 mA cm^?2). Particularly, the polarized current density of EOR on catalyst c₁ at 3600 s, as indicated by the chronoamperometry (CA) experiment, was still maintained to be around 1.47 mA cm^?2, a value higher than the latest reported data of 1.3 mA cm^?2 (measured on the pure Pd/C electrode). Presenting a novel method to prepare dotted nanowires arranged by 5 nm sized nanoparticles and showing the significant eletrocatalytic activities of the newly prepared dotted nanowires towards EOR were the major contributions of this preliminary work.     

A novel experimental study on discharge characteristics of an aluminum‐air battery

In order to explore the discharge characteristics of aluminum‐air battery and find out the best discharge performance of aluminum‐air battery under the optimum working conditions, this paper studies discharge performances of an aluminum‐air battery under various ambient temperature and battery discharge conditions. The relationship between the temperature rise of the battery electrolyte and the discharge current density was studied by an experimental method. Effects of the electrolyte concentration and the ambient temperature on the battery discharge voltage were investigated. In addition, a novel method for calculating the efficiency of the aluminum‐air battery was proposed. Results show that the temperature of the aluminum‐air battery electrolyte gradually increases as its discharge current density increases and the electrolyte temperature rise could reach as high as 10°C after 60 minutes with a constant 35 mA cm^?2 discharge current density. The specific energy and the specific capacity of the aluminum‐air battery first increase and then decrease as the current density increases. When the current density is 25 mA cm^?2, the specific energy has a peak of 3105 Wh kg^?1 for the condition of the chamber temperature 40°C and the electrolyte concentration 2 mol L^?1 (2 M), while the specific capacity has a peak of 2207 Ah kg^?1; furthermore, its efficiencies under various conditions increase first with the current density, reach a peak range of 19.6% to approximately 36% at 25 mA cm^?2, and then decrease. These experimental results could be used as a technical guidance for the optimization in thermal management designs of the aluminum‐air battery under various operating conditions.     

High‐pressure hydrogen storage properties of TixCr1 − yFeyMn1.0 alloys

Ti_xCr_{1 ? y}Fe_yMn_1.0 (x = 1.02, 1.05, 1.1, 0.05 ≤ y ≤ 0.25) alloys were prepared by plasma arc melting and annealing at 1273 K for 2 hours. The XRD results show that the main phase of all alloys is the C14 type Laves phase, and a little secondary phase exists in a mixture of the binary alloy phase. The lattice parameters increase with Ti super‐stoichiometry ratio increasing, whereas smaller lattice parameters emerge with increasing Fe stoichiometry content. Additionally, as the Ti super‐stoichiometry ratio decreases, the pressure‐composition‐temperature measurements indicated that hydrogen absorption and desorption plateau pressures of Ti_xCr_0.9Fe_0.1Mn_1.0 (x = 1.1, 1.05, 1.02) alloys increase from 3.15, 0.67, to 5.94, 1.13 MPa at 233 K, respectively. On the other hand, with the Fe content increasing in Ti_1.05Cr_{1 ? y}Fe_yMn_1.0 (0.1 ≤ y ≤ 0.25) alloys from 0.1 to 0.25, the hydrogen desorption plateau pressures increased from 1.41 to 2.46 MPa at 243 K. The hydrogen desorption plateau slopes reduce to 0.2 with Ti super‐stoichiometry ratio decreasing to 1.02, but the alloys are very difficult to activate for hydrogen absorption and cannot activate when the Fe substituting for Cr exceeds 0.2. The maximum hydrogen storage capacities were more than 1.85 wt% at 201 K. The reversible hydrogen storage capacities can remain more than 1.55 wt% at 271 K. The enthalpy and entropy for all hydride dehydrogenation are in the range of 21.0 to 25.5 kJ/mol H₂ and 116 to 122 J mol^?1 K^?1, respectively. Our results suggest that Ti_1.05Cr_0.75Fe_0.25Mn_1.0 alloy with low enthalpy holds great promise for a high hydrogen pressure hybrid tank in a hydrogen refueling station (45 MPa at 333 K), and the other alloys of low cost may be used for a potable hybrid tank due to high dissociation pressure at 243 K and high volumetric density exceeding 40 kg/m³.     

Property evaluation of Sm1‐xSrxFe0.7Cr0.3O3‐δ perovskites as cathodes for intermediate temperature solid oxide fuel cells

Perovskite‐type (ABO₃) complex oxides of Sm_1‐xSr_xFe_0.7Cr_0.3O_3‐δ (x = 0.5‐0.7) series were prepared by a glycine‐nitrate combustion process. The crystal structure, oxygen nonstoichiometry, electrical conducting, thermal expansion, and electrocatalytic properties of Sm_1‐xSr_xFe_0.7Cr_0.3O_3‐δ perovskites were inspected in view of their use as cathode materials for intermediate temperature solid oxide fuel cells (IT‐SOFCs). Changing the content of Sm³⁺ at the A‐site was demonstrated to be effective in tuning the structure and properties. The variation of the various properties with Sm³⁺ content was explained in relation to the corresponding evolution of the crystal structure and oxygen nonstoichiometry. Sm_0.3Sr_0.7Fe_0.7Cr_0.3O_3‐δ (x = 0.7) was determined to be the optimal composition in the Sm_1‐xSr_xFe_0.7Cr_0.3O_3‐δ series based on a trade‐off between the thermal expansion and electrocatalytic properties. Sm_0.3Sr_0.7Fe_0.7Cr_0.3O_3‐δ ceramic specimen exhibited an electrical conductivity of approximately 40 S·cm^?1 at 800°C and a thermal expansion coefficient of 14.1 × 10^?6 K^?1 averaged in the temperature range from 40°C to 1000°C. At 800°C in air, Sm_0.3Sr_0.7Fe_0.7Cr_0.3O_3‐δ electrode showed a cathodic polarization resistance of 0.19 Ω·cm², a cathodic overpotential of 30 mV at current density of 200 mA·cm^?2, and an exchange current density of 257 mA·cm^?2. It is suggested that Sm_0.3Sr_0.7Fe_0.7Cr_0.3O_3‐δ is a potential candidate material for cathode of IT‐SOFCs in light of its overall properties.     

Performance of an HT‐PEMFC having a catalyst with graphene and multiwalled carbon nanotube support

In this study, the effect of multiwalled carbon nanotube and graphene nanoplatelet‐based catalyst supports on the performance of reformate gas‐fed polybenzimidazole (PBI)‐based high‐temperature proton exchange membrane fuel cell (HT‐PEMFC) was investigated. In addition, the effect of several microwave conditions on the performance of the Pt‐Ru/multiwalled carbon nanotube (MWCNT)–graphene nanoplatelet (GNP) catalyst was assessed. Through X‐ray diffraction, thermal gravimetric analysis, transmission electron microscopy, scanning electron microscopy, and energy dispersive spectroscopy, the catalysts' chemical structure and morphology were characterized. Cyclic voltammetry analysis was used for the electrochemical characterization of catalysts through an electrochemical cell with three electrodes connected to a potentiostat. The results showed that the best performing catalyst is the catalyst produced using 800‐W power for 40 seconds. The electrochemically active surface area values of this catalyst ranged from 54 to 45 m²/g. Single‐cell performance tests of the HT‐PEMFC were then carried out. In these tests, reformate gas mixture, consisting of H₂, CO₂, and CO, was fed to the anode side at 160°C without humidification. These tests for the best performing catalyst yielded peak power density of 0.280 W/cm² and current density (at 0.6 V) of 0.180 A/cm² in the H₂/air environment and peak power density of 0.266 W/cm² and current density (at 0.6 V) of 0.171 A/cm² in the reformate gas/air environment. As a result of the experiments, it was found that Pt‐Ru/MWCNT‐GNP hybrid material is a suitable catalyst for HT‐PEMFC.     

Stability evaluation of ethanol dry reforming on Lanthania‐doped cobalt‐based catalysts for hydrogen‐rich syngas generation

Catalytic stability with time‐on‐stream is an important aspect in ethanol dry reforming (EDR) since catalysts could encounter undesirable deterioration arising from deposited carbon. This work examined the promotional effect of La on 10%Co/Al₂O₃ in terms of activity, stability, and characteristics. Catalysts were characterized by X‐ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), Raman, and X‐ray photoelectron spectroscopy (XPS) measurements whilst catalytic EDR performance of La‐promoted and unpromoted 10%Co/Al₂O₃ prepared via wet impregnation technique was investigated at 973 K for 72 h using a stoichiometric feed ratio (C₂H₅OH/CO₂ = 1/1). La promoter substantially enhanced both metal dispersion and metal surface area from 0.11% to 0.64% and 0.08 to 0.43 m² g^?1, respectively. Ethanol and CO₂ conversions appeared to be stable within 50 to 72 h after experiencing an initial activity drop. The conversion of C₂H₅OH and CO₂ for La‐promoted catalyst was about 1.65 and 1.34 times greater than unpromoted counterpart in this order. The carbonaceous deposition was considerably decreased from 55.6% to 36.8% with La promotion due to La₂O₂CO₃ intermediate formation. Additionally, 3%La‐10%Co/Al₂O₃ possessed greater oxygen vacancies acting as active sites for CO₂ adsorption and hence increasing carbon gasification. Even though graphitic and filamentous carbons were formed on used catalyst surface, La‐addition diminished graphite formation and increased the reactiveness of amorphous carbon.     

High‐performance solid PEO/PPC/LLTO‐nanowires polymer composite electrolyte for solid‐state lithium battery

Solid polymer composite electrolyte (SPCE) with good safety, easy processability, and high ionic conductivity was a promising solution to achieve the development of advanced solid‐state lithium battery. Herein, through electrospinning and subsequent calcination, the Li_0.33La_0.557TiO₃ nanowires (LLTO‐NWs) with high ionic conductivity were synthesized. They were utilized to prepare polymer composite electrolytes which were composed of poly (ethylene oxide) (PEO), poly (propylene carbonate) (PPC), lithium bis (fluorosulfonyl)imide (LiTFSI), and LLTO‐NWs. Their structures, thermal properties, ionic conductivities, ion transference number, electrochemical stability window, as well as their compatibility with lithium metal, were studied. The results displayed that the maximum ionic conductivities of SPCE containing 8 wt.% LLTO‐NWs were 5.66 × 10^?5 S cm^?1 and 4.72 × 10^?4 S cm^?1 at room temperature and 60°C, respectively. The solid‐state LiFePO₄/Li cells assembled with this novel SPCE exhibited an initial reversible discharge capacity of 135 mAh g^?1 and good cycling stability at a charge/discharge current density of 0.5 C at 60°C.     

Electrospun zeolitic imidazolate framework‐derived nitrogen‐doped carbon nanofibers with high performance for lithium‐sulfur batteries

Three‐dimensional (3D) nitrogen‐doped carbon nanofibers (N‐CNFs) which were originating from nitrogen‐containing zeolitic imidazolate framework‐8 (ZIF‐8) were obtained by a combined electrospinning/carbonization technique. The pores uniformly distributed in N‐CNFs result in the improvement of electrical conductivity, increasing of BET surface area (142.82 m² g^?1), and high porosity. The as‐synthesized 3D free‐standing N‐CNFs membrane was applied as the current collector and binder free containing Li₂S₆ catholyte for lithium‐sulfur batteries. As a novel composite cathode, the free‐standing N‐CNFs/Li₂S₆ membrane shows more stable electrochemical behavior than the CNFs/Li₂S₆ membrane, exhibiting a high first‐cycle discharge specific capacity of 1175 mAh g^?1at 0.1 C and keeping discharge specific capacity of 702 mAh g^?1 at higher rate. More importantly, as the sulfur mass in cathodes was increased at 7.11 mg, the N‐CNFs/Li₂S₆ membrane delivered 467 mAh g^?1after 150 cycles at 0.2 C. The excellent electrochemical properties of N‐CNFs/Li₂S₆ membrane can be ascribed to synergistic effects of high porosity and nitrogen‐doping in N‐CNFs from carbonized ZIF‐8, illustrating collective effects of physisorption and chemisorption for lithium polysulfides in discharge‐charge processes.     

Synthesis of high crystalline nickel‐iron hydrotalcite‐like compound as an efficient electrocatalyst for oxygen evolution reaction

The nickel‐iron hydroxide‐like catalyst for oxygen evolution reaction (OER) is prepared by an improved coprecipitation method. The crystallization degree of hydrotalcite‐like compound is high, and the lamellar structure is homogeneous with no agglomeration, which helps to build efficient mass‐transfer layer channel of OH^? ions. The NiFe layered double hydroxide (LDH)/carbon nanotubes (CNTs) electrode shows good performance and stability for OER. The potential of NiFe LDH/CNTs electrode is only 0.592 V (vs HgO/Hg) at 200 mA·cm^?2 in 6 mol·L^?1 potassium hydroxide (KOH) electrolyte, which shows excellent catalytic activity for OER. The NiFe LDH/CNTs electrode works continuously for 620 hours at 200 mA·cm^?2, with the groove voltage only rises 0.1 V.     

Mo doping of layered Li (NixMnyCo1‐x‐y‐zMz)O2 cathode materials for lithium‐ion batteries

We systematically investigated the effects of Mo doping on the structure, morphology, and the electrochemical performance of Li (Ni_xMn_yCo_{1‐x‐y‐z}M_z)O₂ (NMC) cathode materials for Li‐ion batteries. Layered NMC cathodes were synthesized with the ratio of 111, 622, and 226 via spray pyrolysis yielding submicron‐sized aggregates in the shape of hollow spherical particles. We performed X‐ray diffraction analyses to determine the present phases and the ordering in structure. X‐ray diffraction pattern of Mo‐doped 111, 226, and 622 cathodes showed well‐defined [006]/[102] and [108]/[110] doublets, indicating the layered structure, and good hexagonal ordering. Galvanostatic charge/discharge and electrical impedance spectroscopy measurements were carried out to reveal the effect of Mo doping on the electrochemical performance of the cathodes. Charge/discharge measurements after 20 cycles indicated that the Mo‐doped 111 and 622 NMC cathodes performed a capacity retention of 80% and 81% respectively. Present findings reveal the stabilization effect of Mo in layered NMC structure, especially in the case of Ni‐rich NMC cathodes.     

Raman scattering studies of the condensed phase of the HIx feed of the sulfur–iodine thermochemical cycle

The species present in the condensed phase of the HI_x, hydrogen producing, feed in the water‐splitting, sulfur–iodine thermochemical cycle have been investigated using spontaneous Raman scattering. Measurements of I₂‐containing species in the low Raman‐shift region from 50 to 400 cm^?1 in samples of the two aqueous binary systems, I₂/H₂O and HI/H₂O, and the ternary system HI/I₂/H₂O with and without the addition of H₂SO₄ have provided a consistent picture of the aqueous iodine and polyiodide chemistry. Samples were contained in sealed silica ampoules and were heated to temperatures in the range 20–300°C. The results, which cover a wide range of I₂ and HI mole fractions, and x/x_HI mole ratios, in the HI/I₂/H₂O system, reveal the co‐occurrence of H⁺I, H⁺–I^?(I₂), and H⁺–I^?(I₂)₂ solvated species in the condensed phase of HI_x. Thus, while the first is mostly evident by its strong fundamental band with Raman shift in the range from 110 to 115 cm^?1, the other two species appear convoluted in a broad prominent band whose Raman shift ranges between 153 and 172 cm^?1 depending on the x/x_HI mole ratio. These well characterized Raman features are proposed as an in situ diagnostic for process control of the cycle. Copyright © 2010 John Wiley & Sons, Ltd.     

Effect of iron substitution content on structure, thermal expansion behavior and electrochemical properties of La0.5Ba0.5Co1−yFeyO3−δ

Cubic perovskite oxides La_0.5Ba_0.5Co_1−yFe_yO_3−δ (LBCF-y) with Fe content y = 0.1–0.7 were synthesized by sol-gel method and were studied with respect to their oxygen content, defect chemistry, thermal expansion behavior, and electrical and electrochemical properties. LBCF-y had increased oxygen content and cell volumes with higher Fe content. The chemical defects at B-sites of LBCF-y are Fe⁴⁺, Co⁴⁺ and Co³⁺ ions for y = 0.1–0.3, and Fe⁴⁺, Fe³⁺ and Co³⁺ ions for y ≥ 0.5 respectively. Thermal expansion coefficients of LBCF-y oxides firstly increased to a maximum at y = 0.3 then decreased gradually with bigger y. Conductivities of LBCF-y decreased with higher Fe content, and the maximum conductivity was 800 S cm⁻¹ at 500 K for LBCF-0.1 sample. Fe substitutions for Co in LBCF-y cathodes increase the high-frequency resistance associated with oxygen ionic diffusion process while hardly influence the low-frequency gas diffusion process. Very low area-specific resistances, <0.1 Ω cm² at 923 K, were obtained for LBCF-y (y = 0.1–0.7) oxides, demonstrating their potential applications as cathode materials for intermediate-temperature solid oxide fuel cells.     

Effect of americium‐241 source activity on total conversion efficiency of diamond alpha‐voltaic battery

High‐quality diamond intrinsic layer was epitaxially grown on a IIb‐type boron‐doped diamond substrate. The quality of the epitaxy layer was evaluated by Raman spectroscopy and cross‐polarizer images and compared with other samples. The dark current of the diode was analyzed, revealing a rectification ratio as high as 2 × 10⁹ at ±7 V. Current‐voltage characteristics of the converter under the irradiation of different americium‐241 activity sources were investigated. A maximum total conversion efficiency (η_total) of 1.41%, short‐circuit current (I_sc) of 6.68 nA/cm², and open‐circuit voltage (V_oc) of 1.06 V from the diamond alpha‐voltaic battery were obtained under the irradiation of an americium‐241 source with a source activity of 8.85 μCi/cm². The trend for the battery parameters with the increase in the activity of the americium‐241 source was clarified. Parameters I_sc and V_oc increase with the increase in the radioactive source activity. The η_total increases with the increase in the source activity but fluctuates in a certain activity interval with an increase in the fill factor, and then decreases with the increase in radioactive source activity. The research results are significant for the design of nuclear batteries.