•Infiltration method was adopted to enhance the electro-catalytic activity.•LSTF0.7 was highly stable in CO and CO2 at 850 °C.•The low Rp and Ea values for LSTF0.7-CeO2 fuel electrode were obtained.•Slow degradation was observed in both SOFC and SOEC modes.In this paper, La0.3Sr0.7Ti0.3Fe0.7O3-δ (LSTF0.7) composite with CeO2 is successfully prepared by infiltration method as a thin porous electrode and examined in detail as a fuel electrode for efficient reversible solid oxide cells (RSOCs) at different ratios of CO/CO2 at the temperatures of 700–850 °C. XRD analysis indicates that the cubic perovskite LSTF0.7 is stable in CO or CO2 at high temperature and compatible with CeO2 and scandia-stabilized zirconia (ScSZ) electrolyte. In electrolysis mode, the current density of 3.56 A cm−2 is obtained from the I–V curve at 2.0 V in 50% CO+ 50% CO2 at the temperature of 850 °C. The polarization resistance (Rp) of the whole cell at 800 °C is 0.28 Ω cm2 when 1.4 V is applied in the same gas composition. The corresponding activation energy of the fuel electrode under open circuit is calculated to be 81.37 kJ mol−1. In fuel cell mode, the maximal power density of 437 mW cm−2 is obtained at 800 °C in 70% CO+ 30% CO2 as well. The reversible operation at 800 °C indicates that a slow degradation phenomenon in both SOFC and SOEC modes is observed, due to the particle agglomeration of the infiltrated fuel electrode.

•LSTF0.7–CeO2 film anode was prepared in order to enhance the electro-catalytic activity.•LSTF0.7 was highly stable in pure H2 and CO and compatible with CeO2 catalyst and ScSZ electrolyte.•Power densities of 825 and 721 mW cm−2 in H2 and CO at 850 °C were achieved.•Rp of LSTF0.7–CeO2 towards H2 and CO oxidation at 850 °C were 0.072 and 0.151 Ω cm2.•Ea values of LSTF0.7–CeO2 anode in H2 and CO were 46.0 and 129.8 kJ mol−1, respectively.Finding cost-effective and efficient anode materials for solid oxide fuel cells (SOFCs) is of prime importance to develop renewable energy technologies. In this paper, La and Fe co-doped SrTiO3 perovskite oxide, La0.3Sr0.7Ti0.3Fe0.7O3−δ (LSTF0.7) composited with CeO2 is prepared as a composite anode by solution infiltration method. The H2 and CO oxidation behavior and the electrochemical performance (electrochemical impedance spectra, I–V and I–P curves) of the scandia-stabilized zirconia (ScSZ) electrolyte supported cells fabricated by tape casting with the LSTF0.7–CeO2 composite anode are subsequently measured at various temperatures (700–850 °C). Electrochemical impedance spectra (EIS) of the prepared cells with the LSTF0.7–CeO2|ScSZ|La0.8Sr0.2MnO3 (LSM)–ScSZ configuration illustrate that the anode polarization resistance distinguished from the whole cell is 0.072 Ω cm2 in H2, whereas 0.151 Ω cm2 in CO at 850 °C. The maximal power densities (MPDs) of the cell at 700, 750, 800 and 850 °C are 217, 462, 612, 815 mW cm−2 in H2 and 145, 349, 508, 721 mW cm−2 in CO, respectively. Moreover, a significant decrease of anode activation energy towards H2 oxidation is clearly demonstrated, indicating a better electrochemical performance in H2 than in CO. These results demonstrate an alternative composite anode with high electrocatalytic activity for SOFC practical applications.

A cermet fuel electrode Cu/Ce0.6Mn0.3Fe0.1O2-δ (Cu/CMF) is proposed for a reversible solid oxide electrochemical cell (SOC) with CO/CO2 as the shuttle. Cu is inert for the carbon deposition and CMF is electrochemically active for CO oxidation and CO2 reduction. The electrode polarization resistances in CO at 700, 750 and 800 °C are 0.328, 0.207 and 0.155 Ω cm2, respectively, presenting high electrochemical activity towards CO oxidation. The maximal power densities can reach up to 303.3, 482.2 and 691.9 mW/cm2 at 700, 750 and 800 °C, respectively. When the reversible SOCs are operated in solid oxide electrolysis cell mode, the polarization resistance of the electrolysis cell for pure CO2 reduction at 800 °C has the minimal value of 0.126 Ω cm2 at 1.8 V. At 2.0 V, the current densities can reach up to 0.584 1.219 and 2.204 A/cm2 at 700, 750 and 800 °C, respectively. The durability of the cell in CO for as long as 200 h indicates the electrode has remarkable stability. And the short-term stability characteristics for CO2 electrolysis at different voltages illustrate that the cell performs well below 2.0 V. The harsh reducing environment at 2.0 V may be detrimental to the Cu/CMF electrode.

The electrolyte supported cells with the La0.3Sr0.7Ti0.3Fe0.7O3-δ (LSTF0.7)-CeO2|ScSZ (scandia-stabilized zirconia)|La0.3Sr0.7Ti0.3Fe0.7O3-δ-CeO2 symmetrical configuration are fabricated by infiltration method and investigated as reversible solid oxide cells (RSOCs) at different CO/CO2 ratios. A well-deposited microstructure is observed in the infiltrated electrode. From the I–V curves, the maximum current density of 1.90 A cm−2 at 2.0 V is obtained for CO: CO2 ratio of 1: 1 for CO2 electrolysis at 850 °C, while the corresponding power density under the same conditions is 357 mW cm−2 in fuel cell mode. Electrochemical impedance spectroscopy (EIS) is conducted for better understanding the electrode catalytic mechanism. The whole symmetrical cell achieves the polarization resistance (Rp) values of 0.284 and 0.203 Ω cm2 at 850 °C under open circuit and at 1.4 V, respectively. Under reversible operation (cyclic voltammetry) at 800 °C, no distinct degradation is found in the cell with the infiltrated LSTF0.7 symmetrical electrodes. The long-term stability at 1.2–2.0 V characterized by potentiostatic measurement indicates that the prepared LSTF0.7-CeO2 composite electrode is comparatively stable at low voltages while a degradation behavior is observed at high voltages. These results illustrate that the LSFT0.7-CeO2 composite is a promising active ceramic electrode for symmetrical RSOCs.

In this paper, a ceramic perovskite anode for solid oxide fuel cells (SOFCs) is prepared by infiltrating La and Fe co-doped strontium titanium, La0.3Sr0.7Ti0.3Fe0.7O3-δ (LSTF0.7) into porous backbone of scandia-stabilized zirconia (ScSZ) and tested in pure H2 at 700–850 °C. LSTF0.7 crystal exhibits high reduction stability and good compatibility with ScSZ electrolyte under reducing atmosphere. In order to improve the electrocatalytic activity, 15 wt% of CeO2 and 7 wt% of Ni are infiltrated into the backbone pores respectively, thus forming LSTF0.7-CeO2 and Ni-CeO2-LSTF0.7 composite anodes. The cell with LSTF0.7 single anode shows a relatively lower maximal power density (MPD) of 401 mW cm−2 in H2 at 800 °C. While the maximal power densities of the cells with LSTF0.7-CeO2 and Ni-CeO2-LSTF0.7 composite anodes are 612 mW cm−2 and 698 mW cm−2 operated at the same conditions, respectively. The three anode polarization resistances (Rp,a) distinguished from the corresponding full cells are 0.176, 0.086 and 0.076 Ω cm2 at 800 °C, respectively. The values of the activation energy (Ea) towards H2 oxidation for the three anodes can be calculated to be 52.2, 46.0, 43.9 kJ mol−1 based on their respective Rp,a. Therefore, the LSTF0.7-based anodes are considered to be promising alternatives for solid oxide fuel cell applications.

•Conventional Ni/YSZ anode was decorated with silver particles by electroless plating.•The electrochemical performance of decorated cells in H2, CH4 and C2H6 are all increased.•The anti-coking ability of the modified anode is greatly improved.•The decorated cell was run 24 h in C2H6 at 0.33 A/cm2 with 1023 K.In this paper, silver (Ag) particles are introduced into the conventional Ni/YSZ anode by utilizing electroless plating method to improve its carbon anti-coking ability in hydrocarbons. The experimental results show that electrochemical performances of the decorated cells in H2, CH4 and C2H6 are all increased as compared to the cell with unmodified Ni/YSZ anode, which are verified by impedance spectrums as well. The durability experiment is carried out for as long as 24 h at the current density of 0.33 A/cm2 where the modified anode is subjected to dry C2H6 indicating the anti-coking ability of the anode is greatly improved. Scanning electron microscope shows that the slight decreasing in the cell terminal voltage can be attributed to the minimized carbon deposition which maybe resulted from the aggregation of silver particles at high temperature. Energy-dispersive X-ray spectroscopy line scanning results after long-term stability operation of the anode suggest that the carbon deposition can be depressed effectively both inside the anode and on the surface of the anode. Therefore, the results show that silver is a promising candidate material for modifying the Ni/YSZ anode with regard to improving electrochemical performance and suppressing the carbon deposition when taking the hydrocarbons as fuels.

•La0.9Ca0.1Fe0.9Nb0.1O3-δ (LCFNb) is prepared by Nb doping in La0.9Ca0.1FeO3-δ.•LCFNb and LCFNb/SDC are stable in both H2 and CO at 850 °C examined by XRD.•A power density of 823 mW cm−2 at 800 °C in H2 is obtained with LCFNb/SDC anode.•LCFNb/SDC gives a desirable anti-coking ability in CO and syngas for 50 h.•LCFNb/SDC shows reasonable sulfur tolerance in 100 ppm H2SH2 for 20 h.A novel La0.9Ca0.1Fe0.9Nb0.1O3-δ (LCFNb) perovskite for solid oxide fuel cells (SOFCs) anode is prepared by means of the citrate-nitrate route and composited with Ce0.8Sm0.2O1.9 (SDC) by impregnation method to form nano-scaled LCFNb/SDC anode catalytic layers. The single cells with LCFNb and LCFNb/SDC impregnated anodes both achieve relatively high power output with maximum power densities (MPDs) reaching up to 610, 823 mW·cm−2 in H2 at 800 °C, respectively, presenting a high potential of LCFNb for use as SOFCs anode. The power outputs of the single cells with LCFNb/SDC composite anode in CO and syngas (COH2 mixture) are almost identical to that in H2 at each testing temperature. This composite anode also presents excellent durability in both H2 and CO for as long as 50 h, showing desirable anti-reduction and carbon deposition resistance abilities. Besides, the cell output is stable in 100 ppm H2SH2 atmospheres for 20 h at a current density of 600 mA·cm−2 with negligible sulfur accumulation on the anode surface. Hence, a novel iron based perovskite LCFNb anode with remarkable cell performance, carbon deposition resistance and sulfur poisoning tolerance for SOFCs is successfully obtained.

•La0.9Ca0.1Fe0.9Nb0.1O3−δ (LCFNb) was used as symmetrical SOFC electrodes.•LCFNb is high stable and activated in reducing and oxidizing atmospheres.•The catalytic activity of LCFNb for H2 oxidation is better than O2 reduction.•Maximum power density of 528 mW cm2 in H2 was obtained at 850 °C.•Short-term stability in H2, CO and syngas for 50 h were achieved.Development of cost-effective and efficient electrochemical catalysts for the fuel cells electrode is of prime importance to emerging renewable energy technologies. Here, we report for the first time the novel La0.9Ca0.1Fe0.9Nb0.1O3−δ (LCFNb) perovskite with good potentiality for the electrode material of the symmetrical solid oxide fuel cells (SSOFC). The Sc0.2Zr0.8O2−δ (SSZ) electrolyte supported symmetrical cells with impregnated LCFNb and LCFNb/SDC (Ce0.8Sm0.2O2−δ) electrodes achieve relatively high power outputs with maximum power densities (MPDs) reaching up to 392 and 528.6 mW cm−2 at 850 °C in dry H2, respectively, indicating the excellent electro-catalytic activity of LCFNb towards both hydrogen oxidation and oxygen reduction. Besides, the MPDs of the symmetrical cells with LCFNb/SDC composite electrodes in CO and syngas (CO: H2 = 1:1) are almost identical to those in H2, implying that LCFNb material has similar catalytic activities to carbon monoxide compared with hydrogen. High durability in both H2, CO and syngas during the short term stability tests for 50 h are also obtained, showing desirable structure stability, and carbon deposition resistance of LCFNb based electrodes. The present results indicate that the LCFNb perovskite with remarkable cell performance is a promising electrode material for symmetrical SOFCs.

•La0.9Ca0.1Fe1-xNbxO3-δ (x = 0, 0.05, 0.1 and 0.2) have been prepared, characterized and tested as anode alternatives.•La0.9Ca0.1FeO3-δ was stabilized in H2 at 800 °C through substitution of Fe by Nb.•Power output can reach up to 467.1 and 375.8 mW/cm2 in H2 and CO at 750 °C, respectively.•La0.9Ca0.1Fe09Nb0.1O3-δ anode demonstrates a stable performance in both H2 and CO.We here report a lanthanum ferrite-based perovskite anode La0.9Ca0.1Fe1-xNbxO3-δ (LCFNbx, x = 0, 0.05, 0.1 and 0.2) for solid oxide fuel cells (SOFCs) with intriguing stability and electrochemical performance. The powders were prepared by citric acid-nitrate method. The LCFNbx/ScSZ ((Sc2O3)0.1(CeO2)0.01(ZrO2)0.89) composite anodes were constructed by infiltrating the corresponding metal nitrate solution into the ScSZ scaffold followed by heat treatment. X-ray diffractometer results indicated that Nb doping in B site can stabilize the material in the reducing atmospheres up to 800 °C. The chemical stability of LCFNb0.1 is attributed to the constrained valence stability of Fe by the Nb introduction in highly charged state. The maximum power densities of the cell with LCFNb0.1/ScSZ composite anode were 467.1 and 375.8 mW/cm2 in H2 and CO at 750 °C, respectively. The area specific resistances of the cell at open circuit voltage were 0.75 and 2.30 Ωcm2, respectively. Scanning electron microscopy results showed that the LCFNb0.1 layer was porous and well adhered to the ScSZ scaffold, which facilitated the electrochemical processes in H2 and CO. The obtained results in this paper indicate that the LCFNb0.1/ScSZ is a promising composite anode for the SOFCs with both high stability and high electrochemical performance in H2 and CO.

•Uniform Ag particles were deposited into Ni/YSZ anode by impregnation.•The layer of Ag particles improved the maximum power density of the SOFC.•The decorated cell had a stable operation for 100 h in dry CH4 at 1023 K.•The carbon deposition was greatly suppressed by the Ag presence.The Ni/YSZ composite anode has been widely explored for solid oxide fuel cells (SOFCs). However, it is susceptible to carbon coking in hydrocarbons because of the high catalytic activity of Ni for carbon formation. In this paper, Ag particles were incorporated into Ni/YSZ anode to suppress the carbon deposition in hydrocarbons. The results showed that the performance of the modified cells was greatly increased as compared to the unmodified ones. The long term stability experiment was conducted for 100 h at 0.30 A/cm2 in dry CH4 at 1023 K indicating the anti-coking ability of the anode was greatly improved. The particle size and morphology of silver particles are the essential factors influencing the cell performance such as the maximum power density and long-term stability. Therefore, silver can be suggested as a promising candidate material for modifying the Ni/YSZ anode with regard to improving electrochemical performance and suppressing the carbon deposition.

The anodic performances of Ni-Y2O3 stabilized ZrO2 (Ni-YSZ) modified by alkaline earth metal oxide BaO were investigated for solid oxide fuel cells operating in H2S-containing hydrogen fuels. The XRF and EDS results indicated that the amount of BaO was about 5%. The cell with BaO/Ni-YSZ anode exhibited almost constant peak power densities when the fuel was switched from wet hydrogen to 50 ppm H2S contaminated wet hydrogen and good stability in wet H2S-contained hydrogen fuels with H2S concentration gradually increased from 5 to 50 ppm. The EDS and XPS results demonstrated that no element S was detectable after sulfur poisoning testing. High water adsorption ability of BaO could be the primary reason for the high sulfur tolerance. The obtained results confirmed the previous conclusion that BaO/Ni interfaces can resist not only deactivation by coking but also sulfur poisoning of a conventional Ni-YSZ anode.Highlights► Sulfur tolerance ability of BaO infiltrated Ni-YSZ anode was investigated. ► Peak power densities were almost constant after 50 ppm H2S was introduced. ► BaO/Ni-YSZ anode showed good stability in 50 ppm H2S contained H2. ► Water adsorption of BaO could be the primary reason for the high sulfur tolerance. ► It could be a cost-effective fabrication approach for sulfur tolerant anode.

Ammonia offers several advantages over hydrogen as an alternative fuel. However, using ammonia as a hydrogen source for fuel cells has not been received enough attention. In present paper, Scandia-stabilized Zirconia (SSZ) thin film electrolyte and Ni-SSZ anode functional layer were developed by tape casting in order to obtain high power output performance in ammonia, the results of a SOFC running on ammonia were described and its performance was compared with that when running on hydrogen. In order to improve the performance of the cell at higher temperatures, the anode was modified by iron through infiltration. A direct comparison of the performance of the modified cell running on either hydrogen or ammonia showed that the cell in ammonia generated slightly higher power densities at 700 and 750 °C. The performance in ammonia, using the anode catalyst, was comparable to that in hydrogen indicating ammonia could be treated as a promising alternative fuel by selecting an appropriate catalyst.Highlights► The cell with SSZ thin film electrolyte was prepared by tape casting method. ► Ni-SSZ anode functional layer was applied for improving the cell performance. ► The as prepared cell showed high performance both in ammonia and in hydrogen. ► The addition of iron accelerated the ammonia decomposition rate. ► The cell with iron-modified anode showed improved cell performance.

A novel composite oxide Ce(Mn,Fe)O2-La(Sr)Fe(Mn)O3 (CFM-LSFM) was synthesized and evaluated as both anode and cathode materials for solid oxide fuel cells. The cell with CFM-LSFM electrodes was fabricated by tape-casting and screen printing technique. The power-generating performance of this cell was comparable to that of the cell with Ni-SSZ anode and LSM-SSZ cathode. During the 120 h long-term test in hydrogen at 800 °C, the performance increased by 8.6% from 256 to 278 mW cm−2. This was attributed to the decrease of polarization resistance and ohmic resistance during the test. The XRD results showed the presence of Fe, MnO and some unknown second phases after heat-treating the electrode materials in H2 which may be beneficial to the anode electrochemical process. The gradual decrease of polarization resistance as increasing the current density possibly resulted from the increasing content of water in the anode.Highlights► The symmetrical cell was fabricated by tape-casting and screen printing method. ► The cell had good performance comparable to the cell with Ni-SSZ anode. ► During the 120 h long-term stability test, the power output increased by 8.6%. ► The second phases may be beneficial to the anode electrochemical oxidation. ► The existence of water possibly facilitated the anode process.

It has been found in our previous study that La0.9Ca0.1Fe0.9Nb0.1O3-δ-Sm0.2Ce0.8O1.9 (LCFNb-SDC) anode shows high catalytic activity and stability for solid oxide fuel cells (SOFCs) under H2 and CO atmospheres. In this study, LCFNb-SDC is further tuned into a promising anode for direct methane SOFCs through surface modification with Ni. The LCFNb, SDC and Ni materials are found to be thermal-mechanically and chemically compatible with each other up to 850 °C. Although LCFNb-SDC anode shows poor catalytic activity for methane oxidation, further modification of such anode with a small amount of Ni particles significantly improves the cell performance in CH4. The maximal power densities of 1031 and 729 mW cm−2 in H2 and CH4 have been achieved for the electrolyte supported SOFC with LCFNb-SDC-Ni|SSZ (Sc0.2Zr0.8O2−δ)|LSM (La0.8Sr0.2MnO3) configuration at 850 °C, respectively. Besides, the same cells also exhibit good stabilities in both H2 (500 h) and CH4 (100 h) with no obvious performance degradation and carbon deposition. Surface tuned LCFNb anode by impregnating SDC and a small amount of Ni is thus highly promising as an anode for direct methane SOFCs to deliver favorable performance with reasonable stability.