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Symmetrical solid oxide fuel cell (SOFC) adopting the same material at both electrodes is potentially capable of promoting thermomechanical compatibility between near components and lowering stack costs. In this paper, MnCr 2 O 4 –Gd 0.1 Ce 0.9 O 2-δ (MCO-GDC) composite electrodes prepared by co-infiltration method for symmetrical electrolyte supported and anode supported solid oxide fuel cells are evaluated at a temperature range of 650–800 °C in wet (3% H 2 O) hydrogen and air atmospheres. Without any alkaline earth elements and cobalt, the co-infiltrated MCO-GDC composite electrode shows excellent activity for oxygen reduction reaction but mediocre activity for hydrogen oxidation reaction. With MCO-GDC as the cathode, the Ni-YSZ (Y 2 O 3 stabilized ZrO 2) anode supported asymmetrical cell demonstrates a peak power density of 665 mW cm−2 at 800 °C. The above results suggest MCO-GDC is a promising candidate cathode material for solid oxide fuel cells. • MnCr 2 O 4 is chemically stable at typical dual atmospheres of SOFC. • Co-infiltration promotes the performance of MnCr 2 O 4 -GDC composite electrode. • MnCr 2 O 4 -GDC exhibits reasonable activity as cathode. • Anode supported cell achieves a peak power density of 665 mW cm−2 at 800 °C. [ABSTRACT FROM AUTHOR]

Dense bismuth oxides stabilized with lanthanide dopants (δ-Bi 2 O 3 ) are always used as interlayer for thin layer GDC (gadolinia-doped ceria) or YSZ (yttria-stabilized zirconia) electrolyte solid oxide fuel cell to improve the cell performance. Dense ESB (Bi 1.6 Er 0.4 O 3 ) layer preparation needs special equipment or well synthesized nano-sized powders, which is not friendly for large scale and commercial application. In this paper, anode support unsintered cathode cell with porous ESB interlayer is prepared through simple screen print and its electrochemical performance is tested. No matter sintered or not, porous ESB interlayer lowers both the polarization resistance and ohmic resistance, and enhances cell performance, especially for the ohmic resistance of unsintered cells. The cell with ESB porous interlayer and SSC (Sm 0.5 Sr 0.5 CoO 3-δ )-ESB unsintered cathode achieves a peak power density of 1.329 W cm −2 at 700 °C, which is 1.61 times higher than that of the cell without ESB interlayer and 0.93 times higher than that of the sintered cell. However, the durability of porous ESB interlayer enhanced cells is not ideal and it should be improved in further works. [ABSTRACT FROM AUTHOR]

In LaNbO 4 , Sm, Gd and Yb were investigated as substitutes to enhance its ion conductivity, for its application in solid oxide fuel cell. La 0.9 M 0.1 NbO 4 (M = Sm, Gd, Yb) was prepared via a solid–state reaction route and single phase was attained by calcining the constituent oxides at 1200 °C for 5 h. The total conductivity of LaNbO 4 was increased by partly replaced La with Sm, Gd and Yb, due to the muti-valences of the substitutions. The highest conductivity (1.76 × 10 −4 S cm −1 ) was achieved for La 0.9 Sm 0.1 NbO 4 at 800 °C in wet air, more than one order higher compared to that of LaNbO 4 . The introduction of Sm, Gd or Yb also slightly increased the ion transport number of LaNbO 4 , indicating that the increase of the total conductivity was mainly contributed by the enhanced ion conductivity, which was beneficial for its application as a pure ion conductor. [ABSTRACT FROM AUTHOR]

LaNb 1− x Mo x O x with x = 0, 0.10, 0.15, 0.20 and 0.30 were prepared by a step-firing procedure to avoid Mo volatilization, and investigated by X-ray diffraction, thermal expansion and electrical measurements. Doping LaNbO 4 with Mo tended to stabilize the high temperature tetragonal phase to room temperature, at which single tetragonal phase was achieved only in LaNb 0.8 Mo 0.2 O 4 . The total conductivity of LaNb 0.8 Mo 0.2 O 4 was 2.65 × 10 −2 and 8.11 × 10 −2 S cm −1 at 900 °C in air and 5 vol.% H 2 –N 2 , respectively. At temperatures between 500 and 900 °C, the ion transport number of LaNb 0.8 Mo 0.2 O 4 was above 0.95 in the oxidizing atmosphere and below 0.51 in the reducing atmosphere. The high conductivity and mixed conduction in the reducing atmosphere were related to the valence change of some Mo ions from +6 to + δ (≤4). The reduced LaNb 0.8 Mo 0.2 O 4 transformed from the tetragonal to the monoclinic structure, and the tetragonal structure was restored by subsequent oxidation in air. [ABSTRACT FROM AUTHOR]

A solid oxide cell (SOC) integrating solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) usually utilizes two different materials as the anode and cathode prepared by the costly multi-elements co-doping process. In this work, LaCo 0.6 Ni 0.4 O 3−δ (LCN) is employed as the contact material and the electrode for the symmetrical SOC and exhibits good catalytic activities towards the four typical reactions, i.e., oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), oxygen evolution reaction (OER), and CO 2 reduction reaction (CO 2 RR). The LCN-GDC electrode has the low activation energies of 1.18 and 0.55 eV as the cathode and anode of SOFC, respectively. High peak power densities (PPDs) of 1.896 and 0.562 W cm−2 are obtained at 800 °C for the Ni-YSZ (8 mol.% Y 2 O 3 stabilized ZrO 2) anode-supported and YSZ (200 μm)-supported symmetrical SOFCs, respectively. An electrolysis current density (ECD) of 2.316 A cm−2 is obtained at 800 °C and 2.0 V and a robust operation for over 120 h with a degradation rate of about 0.5 mV h−1 is achieved with LCN as the current collector in air side at 750 °C for the symmetrical SOECs. Such a multi-functional material shows attractive competitiveness and successfully achieves fivefold applications in SOCs. The protocol described herein affords a new vision towards material development basing on the consideration of enhancing the chemical compatibility and lowering the cost of the whole SOC but not just one electrode. We report the successful fivefold applications of the multi-functional LaCo 0.6 Ni 0.4 O 3-δ in solid oxide cells for the multipurpose scenarios basing on the perceptively and integrally consideration of enhancing the chemical compatibility and lowering the fabrication cost of the whole integrated solid oxide device but not just one electrode. Image 1 • LCN is employed as electrodes to enhance the compatibility and lower the cost of the whole SOC but not just one component. • The fivefold applications of LCN benefit from its high conductivity and phase diversity against atmospheres. • LCN-GDC has small activation energies of 1.18 and 0.55 eV as the cathode and anode of SOFC, respectively. • PPDs of 1.896 and 0.562 W cm−2 are obtained at 800 °C for the anode-supported and symmetrical SOFCs, respectively. • An ECD of 2.316 A cm-2 at 800 °C and 2.0 V and good stability of over 120 h are obtained for the symmetrical SOECs. [ABSTRACT FROM AUTHOR]

New approach to activating carbon active sites to facilitate the electroconversion of CO 2 through N-vacancy engineering is proposed and confirmed by the density functional theory calculations and experimental results. N-vacancy engineered graphitic C 3 N 4 (g-C 3 N 4) is identified as an efficient electrocatalyst to boost CH 4 formation owing to the three-coordinating to two-coordinating transition of the carbon atoms that surround N vacancies. The defected g-C 3 N 4 (DCN) exhibits a 44% faradaic efficiency with a CH 4 partial current density of 14.8 mA/cm2 at −1.27 V RHE in 0.5 M KHCO 3 electrolyte, exceeding all the reported carbon-based materials and even being comparative to Cu-based electrocatalysts. Creation of more unsaturated carbon atoms enables the harmonic energy overlap near band gap edge between DCN and *CO, accounting for an improved strength of *CO on DCN, a lower energy barrier and an enhanced CO 2 RR to form CH 4. This strategy holds the promise for tuning atomic configuration to enhance activity of catalyst. We report the new strategy to tune the elelctronic structure of N-vacancy engineered g-C 3 N 4 and harmonize activation and adsorption energies between the key intermediate adsorbate (*CO) and catalysts for the electrocatalytic CO 2 reduction to deep reduction product CH 4 with high selectivity and partial current density. Image 1 • N 2V -vacancy engineered g-C 3 N 4 is adapted as the electrocatalyst for CO 2 RR to form CH 4 for the first time. • DFT calculation identifies N 2V- vacancy engineered g-C 3 N 4 identified as an efficient electrocatalyst for CO 2 RR to CH 4. • Newly formed PDOS overlap intensifies the interaction between *CO and g-C 3 N 4 and facilitates *CO activation. • N 2V -vacancy engineered g-C 3 N 4 delivers a maximum FE CH4 (44%) and partial current density of −14.8 mA/cm2 at −1.27 VRHE. • Enhanced adsorption of key intermediates on g-C 3 N 4 and lowered activation energy of RDS improve the activity of g-C 3 N 4. [ABSTRACT FROM AUTHOR]

This study analyzed the influence of channel resistance, inlet flow rate, manifold depth and other related parameters on the gas distribution uniformity and pressure drop in an external 20-cell solid oxide fuel cell stack by computational fluid dynamics (CFD) technique. It provides a basis for determining the physical and geometric parameters of the stack. Furthermore, the flared inlet tube structure shows the effect of controlling the initial velocity of gas inflow and buffering; the flared outlet tube structure has the benefit of reducing the local pressure loss and the pressure drop. Combined with the perforated sheet structure, the gas in the inlet manifold is redistributed to improve the uniformity of gas flow. Compared with the basic model, the pressure drop of perforated sheet stack was reduced by 17.6% from 349.5 Pa to 288.5 Pa, and the gas flow uniformity index of that was reduced from 4.06% to 0.22%. • The physical and geometric parameters of a 20-cell SOFC stack are studied. • The diameter of inlet and outlet flared tubes are optimized. • A perforated sheet is designed to improve the flow uniformity and pressure drop. [ABSTRACT FROM AUTHOR]

The effect of addition of molybdenum in Fe Cr Mn based alloy on the chromium deposition and poisoning of LSM cathodes is investigated at 800 °C by electrochemical impedance spectroscopy and microstructure analysis. The Fe Cr Mn Mo ferrite stainless steel metallic interconnect shows much less Cr deposition and poisoning on the LSM cathodes as compared with the Fe Cr Mn alloy. The addition of Mo into the alloy suppressed Cr evaporation from interconnects, decreased the degradation of cathode performance caused by Cr. According to SEM results, MoO 3 and MnMoO 4 is observed at the depositional area. The segregated MnO from LSM cathode can act as a nuclei agent, and react with vaporized Mo to form Mo-contained oxide particles, which will not inhibit the oxygen reduction reactions in the three phase boundary (TPB). As a result, suitable addition of Mo into the interconnect alloy can effectively alleviate the Cr poisoning of the LSM cathode. [ABSTRACT FROM AUTHOR]

To increase corrosion resistance of gadolinium-doped cerium oxide (GDC) electrolytes for direct carbon solid oxide fuel cells with liquid Sb anodes, GDC-based electrolytes with Fe 2 O 3 addition of 1 (GDCF-1), 2 (GDCF-2) and 3 (GDCF-3) mol.% have been prepared and evaluated chemically and electrochemically in contact with liquid Sb and Sb 2 O 3 at 750 °C for 100 h. The results show that Fe 2 O 3 addition significantly increases the resistance of the electrolytes to the chemical corrosion by liquid Sb, and GDCF-2 demonstrates the highest resistance with a corrosion affected thickness of about 60 μm, which is smaller than 1/8 of that of GDC. What's more, the affected thickness is only about 4 μm for GDCF-2 in contact with liquid Sb 2 O 3. Under a current density of 100 mA cm−2 with liquid Sb as anode, the cell voltage almost increases linearly and cell ohmic resistance decreases in the 100 h's operation. The performance promotion is resulted from the reduction of GDCF-2 thickness caused by liquid Sb/Sb 2 O 3 corrosion, but the total thickness reduction is about 200 μm, which is only 2/5 of that of GDC. • Fe 2 O 3 addition enhances GDC's resistance to hot corrosion by liquid Sb and Sb 2 O 3. • GDC with 2 mol.% Fe 2 O 3 demonstrates highest resistance to liquid Sb corrosion. • GDC with 2 mol.% Fe 2 O 3 shows a corrosion rate smaller than 1/8 of that of GDC. • Cell ohmic impedance is proved to be a feasible indicator of corrosion degree. [ABSTRACT FROM AUTHOR]

A newly developed interconnect alloy for solid oxide fuel cells, containing Fe, Cr, Mn and Mo as well as other minor elements and designated as FeCM, is investigated on its poisoning effect on (La 0.8 Sr 0.2 ) 0.95 MnO 3−δ (LSM) cathode by electrochemical impedance spectroscopy and microstructure observation. Compared with commercial SUS430 stainless steel, which is usually used as a essential interconnect in the SOFCs stacks, the FeCM alloy as the interconnect reduces the ohmic of the cell (R Ω ) and polarization resistance of the cathode (R P ) and increases the electrochemical performance of the cathode. At 850 °C the R Ω remains almost unchanged at a level slightly above 2.0 Ω cm 2 and the R P decreases from 5.76 to 1.68 Ω cm 2 within 20 h, while the cathode potential at 200 mA min −1 is virtually stabilized at below 1.0 V and the overpotential is decreased from 0.43 to 0.16 V. Based on the evidence of a narrower oxide deposition zone on the electrolyte surface near the cathode and a deposition-free cathode/electrolyte interface, this improvement is attributed to the reduced degree of volatilization of oxide scale formed on the surface of the FeCM alloy. [ABSTRACT FROM AUTHOR]

The solid oxide electrolysis cell (SOEC) has attracted increased attention in recent years due to its capability to reduce CO 2 emissions in a highly efficient and environmentally sustainable fashion. Previous work in our group has fabricated an A-site Ce doped La 0.7 Sr 0.3 Cr 0.5 Fe 0.5 O 3-δ (LSCrF) with gadolinium doped ceria (GDC) as the cathode material in SOEC by the conventional method. This composite cathode presents a satisfying electrochemical performance and good stability due to the presence of excessive oxygen vacancies and strong CO 2 adsorption ability. However, its electrochemical catalytic activity is still limited by the catalyst specific area. Hence, the optimization of electrode microstructure is considered as a promising way to further improve the SOEC performance by increasing the active reaction area. In this study, highly active (La 0.65 Sr 0.3 Ce 0.05) 0.9 (Cr 0.5 Fe 0.5) 0.85 Ni 0.15 O 3-δ (Ni-LSCeCrF)/GDC nanostructured cathode was successfully fabricated by incorporating infiltration and in situ exsolution processes. The optimized microstructure contains fine and uniformly distributed perovskite particles on GDC backbone with nano-socketed Ni-Fe alloy nanoparticles. The Ni-LSCeCrF/GDC cathode shows significantly improved electrochemical performance, CO production rate, and Faraday efficiency for CO 2 reduction reaction. Furthermore, the density functional theory calculations show that Ni doping could reduce the segregation energy of Fe, revealing a new strategy of multiple elements doping to form active alloy by in situ exsolution. Image 1 [ABSTRACT FROM AUTHOR]