Structural characterization and electrochemical properties of RF-sputtered nanocrystalline Co3O4 thin-film anode

Nanocrystalline Co₃O₄ thin-film anodes were deposited on Pt-coated silicon and 304 stainless steel by radio frequency (RF) magnetron sputtering. The as-deposited and annealed cobalt oxide thin films showed smooth and crack-free morphologies. Both the as-deposited and annealed films exhibited spinel Co₃O₄ phase with nanocrystalline structure. High-temperature annealing enhanced the crystallinity of RF-sputtered cobalt oxide films due to rearrangement of cobalt and oxygen atoms. Electrochemical characterization of RF-sputtered films was carried out by cyclic voltammetry and charge/discharge tests in the voltage range of 0.3–3.0 V. Cyclic voltammetry plots showed that the RF-sputtered Co₃O₄ thin films were electrochemically active. X-ray photoelectron spectrometer (XPS) showed that the fresh cobalt oxide films had two peaks of Co₃O₄. In addition to the binding energy of cobalt oxide, the XPS spectrum of discharged film presented two additional binding energies correspond to Co metal. The first discharge capacities of as-deposited, 300, 500, and 700 °C-annealed films were 722.8, 772.5, 868.4, and 1059.9 μAh cm⁻² μm⁻¹, respectively. High-temperature annealing could enhance the capacity and cycle retention obviously. After 25 cycles discharging, the annealed films showed better cycle retention than as-deposited film. The 700 °C-annealed film exhibited excellent discharge capacity approximated to the theoretical capacity.     

Hydrogen production from sodium borohydride originated compounds: Fabrication of electrospun nano-crystalline Co3O4 catalyst and its activity

Electrospun nanofibers are prepared through electrospinning followed by post-treatment and preferred to use in catalytic applications. The electrospinning provides advantages for active catalysts design based on activity profiles and features of catalyst. In the present study, we fabricated nano-crystalline cobalt oxide (Co₃O₄) catalyst by electrospinning technique followed by thermal conditioning. Polyacrylonitrile (PAN) based Co as-spun mats (Co/NMs) with homogeneous diameter were prepared by electrospinnig process under several conditions as applied voltage (15–25 kV), working distance (5–7.5 cm) with the feed rate of 1 ml min⁻¹. The calcination process as a post-treatment was applied at different temperatures (232 °C, 289 °C and 450 °C) to obtain electrospun nano-crystalline Co₃O₄ catalyst. Co/NMs catalysts were characterized by XRD, SEM, TEM, XPS, FT-IR, TG/DTG, and ICP-MS techniques. The parametrically study was performed for evaluating the hydrogen production activity of catalyst from sodium borohydride (NaBH₄, SBH) and its originated compounds as ammonia borane (NH₃BH₃, AB) and methyl-amine borane (CH₃NH₂BH₃, MeAB). The relation between the internal-external properties and catalytic activities of catalysts for hydrogen production was investigated. The beadless Co/NMs-1 catalyst with homogeneous diameter was obtained under electrospinnig process conditions at 15 kV applied voltage and 7.5 cm working distance. All catalysts showed activity for hydrogen production, also the significant effect of post treatment process was observed on the catalytic activity as given order: Co/NMs-1₄₅₀ > Co/NMs-1₂₈₉ > Co/NMs-1 > Co/NMs-1₂₃₂. Furthermore, mesoporous Co₃O₄ cubic crystals (26 nm) in fibrous architecture was prepared by 450 °C-post-treatment. Hydrogen production rates were recorded at 60 °C as 2.08, 2.20, and 6.39 l H₂.g_cat⁻¹min⁻¹ for NaBH₄, CH₃NH₂BH₃, and NH₃BH₃, respectively.     

FeCo alloys in-situ formed in Co/Co2P/N-doped carbon as a durable catalyst for boosting bio-electrons-driven oxygen reduction in microbial fuel cells

Non-noble metal catalyst with high catalytic activity and stability towards oxygen reduction reaction (ORR) is critical for durable bioelectricity generation in air-cathode microbial fuel cells (MFCs). Herein, nitrogen-doped (iron-cobalt alloy)/cobalt/cobalt phosphide/partly-graphitized carbon ((FeCo)/Co/Co₂P/NPGC) catalysts are prepared by using cornstalks via a facile method. Carbonization temperature exerts a great effect on catalyst structure and ORR activity. FeCo alloys are in-situ formed in the catalysts above 900 °C, which are considered as the highly-active component in catalyzing ORR. AC-MFC with FeCo/Co/Co₂P/NPGC (950 °C) cathode shows the highest power density of 997.74 ± 5 mW m^?2, which only declines 8.65% after 90 d operation. The highest Coulombic efficiency (23.3%) and the lowest charge transfer resistance (22.89 Ω) are obtained by FeCo/Co/Co₂P/NPGC (950 °C) cathode, indicating that it has a high bio-electrons recycling rate. Highly porous structure (539.50 m² g^?1) can provide the interconnected channels to facilitate the transport of O₂. FeCo alloys promote charge transfer and catalytic decomposition of H₂O₂ to ?OH and ?O₂^?, which inhibits cathodic biofilm growth to improve ORR durability. Synergies between metallic components (FeCo/Co/Co₂P) and N-doped carbon energetically improve the ORR catalytic activity of (FeCo)/Co/Co₂P/NPGC catalysts, which have the potential to be widely used as catalysts in MFCs.     

Differences in the effects of Co and CoO on the performance of Ni(OH)2 electrode in Ni/MH power battery

The effects of metallic cobalt (Co) and cobalt monoxide (CoO), as additives in positive electrodes, on the electrochemical performance of nickel/metal hydride (Ni/MH) power batteries are studied. Commercial Co and CoO are charged at 50 °C in 6 M KOH solution. The oxidation mechanism of cobalt materials is investigated by observing structural and morphological evolutions during charging. A pure Co₃O₄-type phase is formed when the starting material is CoO. When Co is used, a cobalt oxyhydroxide (CoOOH) phase is present, together with a tricobalt tetroxide (Co₃O₄) phase. In both cases, the cobalt concentration in the electrolyte decreases during oxidation. The final product is dependent on the solubility of cobalt and the kinetics of the reaction that consumes cobalt tetrahydroxide [Co(OH)₄]²⁻. The highly compact CoOOH phase, which works well between the nickel foam frame and nickel hydroxide [Ni(OH)₂] particles, enhances the power performance of Ni/MH power battery. The Co₃O₄ phase, which works well in connecting Ni(OH)₂ particles, improves the capacitive performance of Ni/MH power battery.     

The coralline cobalt oxides compound of multiple valence states deriving from flower-like layered double hydroxide for efficient hydrogen generation from hydrolysis of NaBH4

Efficient hydrogen storage, transportation and generation are key-technology for future hydrogen economy. Sodium borohydride (NaBH₄) stands out as promising hydrogen energy carrier with merits of high volumetric density and environmentally benign hydrolysis products. Flower-like layered double hydroxide α-Co(OH)₂ with intercalation of B species was synthesized via hydrothermal crystallization method using sodium tetraphenylboron as source of B and alkaline, which makes it different from the previous supporting materials. Pure or mixed cobalt oxides with different valence states containing B (CoO/B, Co₃O₄/B, Co+CoO/B, CoO+Co₃O₄/B) were subtly prepared via controlling calcination temperature, time and atmosphere for sodium borohydride hydrolysis. Coral-like CoO+Co₃O₄/B displayed superior hydrogen generation rate (6478 ml_H2·min^?1·g^?1_metal) with arrhenius activation energies of 41.14 kJ/mol for NaBH₄ hydrolysis in alkaline solutions compared to those reported pure precious metals. The out-standing catalytic performance of CoO+Co₃O₄/B may be attributed to electron transfer among cobalt oxide. DFT calculation indicates NaBH₄ hydrolysis undergoes a reaction path on CoO+Co₃O₄ surface with lower relative energies.     

A high-performance ternary ferrite-spinel material for hydrogen storage via chemical looping redox cycles

Chemical looping has been proposed as an emerging technology for large-scale hydrogen storage with the advantages of high volumetric hydrogen storage density, environmental compatibility, and safety. However, to ensure sufficient redox activity, conventional oxygen carrier materials must be operated at a temperature higher than 800 °C, leading to the rapid deterioration on the storage capacity over several cycles. In this work, we report a ternary ferrite-spinel material Cu_0.5Co_0.5Fe₂O₄ for chemical looping hydrogen storage and production. The material exhibits high volumetric hydrogen storage density (65.58 g·L⁻¹) and average hydrogen production rate (142 μmol·g⁻¹·min⁻¹) at 550 °C. The performance is maintained with negligible deactivation over repetitive redox cycles. The high performance can be attributed to the ability of Cu and Co to improve the reduction and the reversible phase change during the oxidation stage at moderate temperatures. The performance of the Cu_0.5Co_0.5Fe₂O₄ is comparable to the state-of-the-art Rh-FeO_x containing rare earth metals, which enables its potential in industry application.     

Functionalized Co3O4 graphitic nanoparticles: A high performance electrocatalyst for the oxygen evolution reaction

We describe a novel synthesis technique for the production of graphitic carbon functionalized Co₃O₄ (G/Co₃O₄), which involves the rapid decomposition of cobalt nitrate in the presence of citric acid. Upon immobilization of the G/Co₃O₄ upon Screen-Printed macroElectrodes (G/Co₃O₄-SPEs) the G/Co₃O₄-SPEs were found to exhibit remarkable electrocatalytic properties towards the Oxygen Reduction Reaction (OER). A detailed investigation has been carried out on the influence that the graphitization of the citric acid has, during the course of preparation of Co₃O_4, upon the ability of the G/Co₃O₄ to catalyse the OER within alkaline conditions (1.0 M KOH). The graphitization of citric acid ensures the uniform distribution of Co₃O₄ and enhanced conductivity with maximal exposure of active sites, which are the key parameters to delivering enhanced electrochemical activity. The G/Co₃O₄-SPEs exhibits an overpotential of 304 mV (recorded at 10 mA cm⁻²), a Tafel slope of 110 mV dec⁻¹ and remain stable in its signal output (achievable current density) at varying temperatures (5–50 °C), and after 10 h of chronoamperometry in 1.0 M KOH. The G/Co₃O₄-SPE's OER activity was found to be superior to that of bulk and nano Co₃O₄. The results exhibited within this study will enable production of high-performance and environmentally benign electrocatalysts towards the OER for use within water splitting devices.     

Study of the electro-oxidation of CoO and Co(OH)2 at 90 °C in alkaline medium

Cobalt is usually post-added as CoO or Co(OH)₂ to nickel hydroxide at the positive electrode (nickel oxide electrode) of alkaline batteries, to form a conductive network. In the present work, we focus on the transformation of CoO and Co(OH)₂ phases when oxidized at 90 °C. The Co₃O₄ phase is the majority product of such a reaction, with CoOOH as a secondary product. It is shown that the Co₃O₄ phase results from the reaction of the CoOOH phase, formed by electrochemical oxidation of Co(OH)₂, with Co²⁺ species in the electrolyte, which is made possible by temperature. This process requires a global migration of the cobalt phases towards the current collector.     

Methanol steam reforming over highly efficient CuO–Al2O3 nanocatalysts synthesized by the solid-state mechanochemical method

CH₃OH steam reforming is an attractive way to produce hydrogen with high efficiency. In this study, CuO.xAl₂O₃ (x = 1, 2, 3, and 4) were fabricated based on the solid-state route, and the calcined samples were employed in methanol steam reforming at atmospheric pressure and in the temperature range of 200–450 °C. The results revealed that all samples have a high BET area (173–275 m² g⁻¹), and their crystallinity was reduced by increasing the alumina content in the catalyst formulation. The catalytic activity tests showed that the CH₃OH conversion and H₂ selectivity decreased by rising the Al₂O₃·CuO molar ratio. The methanol conversion enhanced from 13% to 85% by increasing the reaction temperature from 200 °C to 450 °C over the CuO·Al₂O₃ catalyst, due to the higher reducibility of this catalyst at lower temperatures compared to other prepared samples. The influence of calcination temperature (300–500 °C), GHSV (28,000–48000 ml h⁻¹. g⁻¹_cat), feed ratio (C:W = 1:1 to 1:9), and reduction temperature (250–450 °C) was also determined on the yield of the chosen sample. The results revealed that the maximum methanol conversion decreased from 90 to 79% by raising the calcination temperature from 300 to 500 °C due to the reduction of surface area and sintering of species at high calcination temperatures.     

Effect of coatings on long term behaviour of a commercial stainless steel for solid oxide electrolyser cell interconnect application in H2/H2O atmosphere

K41X (AISI 441) stainless steel evidenced a high electrical conductivity after 3000 h ageing in H₂/H₂O side when used as interconnect for solid oxide electrolyser cells (SOEC) working at 800 °C. Perovskite (La_1 − xSr_xMnO_3 − δ) and spinel (Co₃O₄) oxides coatings were applied on the surface of the ferritic steel for ageing at 800 °C for 3000 h. Both coatings improved the behaviour of the steel and give interesting opportunities to use the K41X steel as interconnect for hydrogen production via high temperature steam electrolysis. Co₃O₄ reduced into Co leading to a very good Area Specific Resistance (ASR) parameter, 0.038 Ω cm². Despite a good ASR (0.06 Ω cm²), La_1 − xSr_xMnO_3 − δ was less promising because it partially decomposed into MnO and La₂O₃ during ageing in H₂/H₂O atmosphere.     

MnxCo3-xO4 spinel oxides as efficient oxygen evolution reaction catalysts in alkaline media

The design of efficient electrocatalysts for oxygen evolution reaction (OER) is an essential task in developing sustainable water splitting technology for the production of hydrogen. In this work, manganese cobalt spinel oxides with a general formula of Mn_xCo_3-xO₄ (x = 0, 0.5, 1, 1.5, 2) were synthesised via a soft chemistry method. Non-equilibrium mixed powder compositions were produced, resulting in high electrocatalytic activity. The oxygen evolution reaction was evaluated in an alkaline medium (1 M KOH). It was shown that the addition of Mn (up to x ≤ 1) to the cubic Co₃O₄ phase results in an increase of the electrocatalytic performance. The lowest overpotential was obtained for the composition designated as MnCo₂O₄, which exhibited a dual-phase structure (∼30% Co₃O₄ + 70% Mn_1.4Co_1.6O₄): the benchmark current density of 10 mA cm⁻² was achieved at the relatively low overpotential of 327 mV. The corresponding Tafel slope was determined to be ∼79 mV dec⁻¹. Stabilities of the electrodes were tested for 25 h, showing degradation of the MnCo₂O₄ powder, but no degradation, or even a slight activation for other spinels.     

Tailoring La2-XAXNi1-YBYO4+δ cathode performance by simultaneous A and B doping for IT-SOFC

The present work focuses on the study of different Ruddlesden-Popper based cathode materials for Solid Oxide Fuel Cells at Intermediate Temperature (IT-SOFC). The partial substitution of La and Ni by Pr and Co, respectively, were studied in the La_2-XPr_XNi_1-YCo_YO_4+δ system, with the purpose of enhancing their mixed ionic-electronic conductivity and the electrocatalytic activity for the O₂-reduction while the crystal structure was preserved. All synthesized compounds were characterized by electrochemical impedance spectroscopy (EIS), DC conductivity measurements, X-Ray diffraction (XRD), iodometric titration and scanning electron microscopy (SEM). XRD analyses by Rietveld refinement revealed the influence of the ionic radius on the crystalline phase for the different dopants, i.e., variation of the cell parameters and M−O bond lengths. The substitution in both La and Ni sites improves La₂NiO_4+δ electrochemical properties as IT-SOFC cathode, since higher conductivity and lower polarization resistance were obtained. Finally, La_1.5Pr_0.5Ni_0.8Co_0.2O_4+δ cathode exhibited the lowest electrode polarization resistance and activation energy values in the temperature range of 450–900 °C. La_1.5Pr_0.5Ni_0.8Co_0.2O_4+δ was applied on an anode supported cell and a maximum power density of ~400 mW cm⁻² was obtained at 700 °C using pure hydrogen and air.     

Remarkable charge separation and photocatalytic efficiency enhancement through TiO2(B)/anatase hetrophase junctions of TiO2 nanobelts

Light harvesting and charge separation are both significant to the photocatalysis, but it is challenging to synchronously realize both in a single-component material. The surface coarsened TiO₂ nanobelts with TiO₂(B)/anatase hetrophase junctions and large BET surface area are prepared via a hydrothermal/annealing method. The presence of surface coarsened nanobelt structure enhances the light absorption through reflection/refraction of light. The TiO₂(B)/anatase hetrophase junctions can efficiently promote the separation of photoinduced electrons and holes pairs and therefore decrease the charge recombination. The large BET surface area provides abundant active sites for the absorption and diffusion of reactants. As a consequence, the obtained TiO₂ nanobelts exhibit an enhanced photocatalytic H₂ evolution activity at the optimal annealing temperature (450 °C) with Pt as co-catalysts (0.786 mmol h⁻¹g⁻¹), exceeding that of pure anatase TiO₂ nanobelts (TiO₂ nanobelts-600 °C, 0.265 mmol h⁻¹g⁻¹). Interestingly, TiO₂ nanobelts-450 °C still show a high hydrogen evolution rate of 0.601 mmol h⁻¹g⁻¹ in the absence of co-catalysts.     

An optimized synthesis route for high performance composite cathode based on a layered perovskite oxide of PrBa0.92Co2O6-δ with cationic deficiency

For Solid Oxide Fuel Cells (SOFCs) to become an economically attractive energy conversion technology, cathode materials with high catalytic activity over oxygen reduction reaction (ORR) and low cost are desired. In this work, a composite cathode material of PrBa_0.92Co₂O_6-δ-40 wt%Ce_0.8Sm_0.2O_1.9(OPCC) based on a layered perovskite oxide of PrBa_0.92Co₂O_6-δ with Ba²⁺-deficiency at A-sites has been successfully synthesized with a facile and effective one-pot sol-gel method, which was comparatively studied with the counterpart BMCC synthesized with the traditional ball-milling method and the single phase cathode of PrBa_0.92Co₂O_6-δ. Among the three cathodes, OPCC showed the lowest area specific resistances (ASRs) in both air and oxygen atmospheres, indicating the highest ORR catalytic activity. Such performance improvement for OPCC was closely related to its optimized microstructures obtained with the liquid-mixing one-pot synthesis method and existence of Ce_0.8Sm_0.2O_1.9 that has a high ionic conductivity. I-V and I-P curves were measured for the anode-supported single cells with the three cathodes, and the OPCC-based cell showed the highest peak power densities with typical value of 1011  mW cm⁻² at 750 °C in contrast to 783  mW cm⁻² for the BMCC-based cell and 574  mW cm⁻² for the PrBa_0.92Co₂O_6-δ-based cell respectively. The OPCC-based cell also showed a stable performance with no obvious degradation over 100 h at 700 °C.     

Co−O−P composite nanocatalysts for hydrogen generation from the hydrolysis of alkaline sodium borohydride solution

In recent years, catalytic hydrolysis of sodium borohydride is considered to be a promising approach for hydrogen generation towards fuel cell devices, and highly efficient and noble-metal-free catalysts have attracted increasing attention. In our present work, Co₃O₄ nanocubes are synthesized by solvothermal method, and then vapor-phase phosphorization treatment is carried out for the preparation of novel Co−O−P composite nanocatalysts composed of multiple active centers including Co, CoO, and Co₂P. For catalyst characterization, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD) and X-ray photoelectric spectroscopy (XPS) are conducted. Optimal conditions for catalyst preparation and application were investigated in detail. At room temperature (25 °C), maximum hydrogen generation rate (HGR) is measured to be 4.85 L min⁻¹ g⁻¹ using a 4 wt% NaBH₄ − 8 wt% NaOH solution, which is much higher than that of conventional catalysts with single component reported in literature. It is found that HGR remarkably increases with the increasing of reaction temperature, and apparent activation energy for catalytic hydrolysis of NaBH₄ is calculated to be 63 kJ mol⁻¹. After reusing for five times, the Co−O−P composite nanocatalysts still retains 78% of the initial activity.     

Enhanced electrochemical performance of supercapattery derived from sulphur-reduced graphene oxide/cobalt oxide composite and activated carbon from peanut shells

Sulphur-reduced graphene oxide/cobalt oxide composites (RGO-S/Co₃O₄) were successfully synthesized by varying mass loading of Co₃O₄ through a simple hydrothermal method. Structural, morphological, chemical compositional and surface area/pore-size distribution analysis of the materials were obtained by using XRD, Raman spectroscopy, SEM, TEM, EDX, FTIR, XPS and BET techniques, which reveal an effective synthesis of the RGO-S/Co₃O₄ composites. Electrochemical performance of the materials was evaluated using a three- and two-electrode system in 1 M KOH electrolyte. An optimized RGO-S/200 mg Co₃O₄ composite displayed the highest specific capacity of 171.8 mA h g⁻¹ and superior cycling stability of 99.7% for over 5000 cycles at 1 and 5 A g⁻¹, respectively, in a three-electrode system. A fabricated supercapattery device utilizing RGO-S/200 mg Co₃O₄ (positive electrode) and activated carbon from peanut shells (AC-PS) (negative electrode), revealed a high specific energy and power of 45.8 W h kg⁻¹ and 725 W kg⁻¹, respectively, at 1 A g⁻¹. The device retained 83.4% of its initial capacitance for over 10, 000 cycles with a columbic efficiency of 99.5%. Also, a capacitance retention of 71.6% was preserved after being subjected to a voltage holding test of over 150 h at its maximum potential of 1.45 V.     

3D flower-like polypyrrole-derived N-doped porous carbon coupled cobalt oxide as efficient oxygen evolution electrocatalyst

For electrochemical splitting of water, highly active and non-precious metal electrocatalysts towards the oxygen evolution reaction (OER) are direly needed to address the cost and stability issues. Herein, polypyrrole (PPy) with 3D flower-like structure has been prepared to obtain N-doped porous carbon sheets (N–C) and to implant with cobalt oxides (Co₃O₄) via simple and cost-effective hydrothermal reaction. Benefitting from the 3D flower-like porous carbon structure, Co₃O₄/N–C demonstrates enlarged surface area replenished with more electrocatalytic active sites. What's more, Co₃O₄ nanoparticles are evenly dispersed onto the N-doped carbon surface which effectively prevents their aggregation and detachment. These exclusive structural features render amazing catalytic activity for Co₃O₄/N–C towards OER with an onset potential of ~1.31 V (vs RHE), low overpotential of 120 mV at 10 mA cm⁻² and a Tafel slope of only 33 mV dec⁻¹ in basic media. This work presents a simple approach to meet an ideal catalytic material with better morphology and advantageous properties for the possible energy and environmental applications.     

Electrochemical performances of LiNiCoMn bifunctional electrode for low temperature solid oxide fuel cells

Lithium transition metal oxides LiNi_0.83Co_0.11Mn_0.06O₂ (NCM-83) and LiNi_0.8Co_0.1Mn_0.1O₂ (NCM-811) are prepared and acted as cathodes and bifunctional electrodes for low temperature solid oxide fuel cells with H₂ and CH₄ fuels. The Ni anode-supported cell with NCM-83 cathode exhibits maximum power density (P_max) of 0.72 W cm⁻² with H₂ fuel at 600 °C. The symmetric cell with NCM-83 electrodes shows high P_max of 0.465 W cm⁻² with H₂ fuel and 0.354 W cm⁻² with CH₄ fuel at 600 °C. And the P_max of the cell with NCM-811 as anode and NCM-83 as cathode is 0.204W cm⁻² with H₂ fuel at 600 °C. The oxygen vacancies in NCM materials are conducive to the rapid oxygen ion conduction of the cathode, and in the anodic reduction atmosphere, the NCM materials will generate Ni/Co active particles in situ, proving the NCM materials can be advanced bifunctional electrode materials for hydrogen oxidation reaction and oxygen reduction reaction at low temperature.     

A simple Ce-doping strategy to enhance stability of hybrid symmetrical electrode for solid oxide fuel cells

Symmetrical solid oxide fuel cell (SSOFC) is a simple and very promising cell for the rest of the most important commercialization process, which has been longing for stable and efficient symmetrical electrodes, from single-phase perovskites to reducible perovskites with in-situ exsolved metal nanoparticles. Herein, we present a new-type hybrid symmetrical electrode consisting of two different perovskite phases for SSOFC, which interact by dynamic compositional change and accordingly improve the electrochemical activity. Furthermore, a simple Ce-doping strategy is successfully developed to solve the redox stability issue of the hybrid symmetrical electrode for SSOFC. Typical Gd_0.65Sr_0.35Co_0.25Fe_0.75O_3-δ (GSCF) consisting of a cubic perovskite phase and an orthorhombic perovskite phase is chosen as a proof-of-concept. Gd_0.65Sr_0.35(Co_0.25Fe_0.75)_0.9Ce_0.1O_3-δ (Ce-GSCF) with an optimized Ce content of only 10% exhibit the enhanced chemical and thermal stability, consisting of a cubic perovskite phase, an orthorhombic perovskite phase and an in-situ exsolved cubic fluorite phase (GDC). More importantly, Ce-GSCF exhibits very high stability in H₂ at 700 °C and a dramatical reduction of averaged thermal expansion coefficient from 19.5 × 10⁻⁶ K⁻¹ to 16.4 × 10⁻⁶ K⁻¹. The single-cell with Ce-GSCF hybrid symmetrical electrode reaches a high maximum power density of 224 mW/cm² at 700 °C, and can work stably for 180 h without any degradation, indicating that the simple Ce-doping strategy is promising to improve stability of hybrid symmetrical electrode for SOFCs.     

Syngas production via partial oxidation of dimethyl ether over Rh/Ce0.75Zr0.25O2 catalyst and its application for SOFC feeding

Dimethyl ether (DME) partial oxidation (PO) was studied over 1 wt% Rh/Ce_0.75Zr_0.25O₂ catalyst at temperatures 300–700 °C, O₂:C molar ratio of 0.25 and GHSV 10000 h⁻¹. The catalyst was active and stable under reaction conditions. Complete conversion of DME was reached at 500 °C, but equilibrium product distribution was observed only at T ≥ 650 °C. High concentration of CH₄ and low contents of CO and H₂ were observed at 500–625 °C 75 cm³ of composite catalyst 0.24 wt% Rh/Ce_0.75Zr_0.25O₂/Al₂O₃/FeCrAl showed excellent catalytic performance in DME PO at O₂:C molar ratio of 0.29 and inlet temperature 840 °C which corresponded to carbon-free region. 100% DME conversion was reached at GHSV of 45,000 h⁻¹. The produced syngas contained (vol. %): 33.4 H₂, 34.8 N₂, 22.7 CO, 3.6 CO₂ and 1.6 CH₄. Composite catalyst demonstrated the specific syngas productivity (based on CO and H₂) in DME PO of 42.8 m³·L_cat⁻¹·h⁻¹ (STP) and the syngas productivity of more than 3 m³·h⁻¹ (STP) that was sufficient for 3 kW_e SOFC feeding. PO of natural gas and liquified petroleum gas can be carried out over the same catalyst with similar productivity, realizing the concept of multifuel hydrogen generation. The syngas composition obtained via DME PO was shown to be sufficient for YSZ-based SOFC feeding.