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Large-scale solid oxide fuel cell (SOFC) systems create operational challenges owing to their size and scale. An SOFC dynamic digital twin model can help users understand the system status and determine the operating action. In this study, a dynamic digital twin of a 25 kW SOFC plant was presented as a simulator to help operators safely and stably determine the operating conditions for a real commercial SOFC plant. In the scale-up process, the data from the 1 kW SOFC pilot plant were used to analyze the reliability and electrode parameters and develop a digital twin model that matches actual conditions at the plant. The scale-up digital twin model is applied to a 25 kW SOFC system, in which the SOFC is connected with upstream reformers, downstream burners, and multiple heat exchangers. The 25 kW SOFC digital twin model was validated by steady-state data and applied to on-site operation prediction with very high accuracy. The digital twin was used as an operating reference in the field, and the results showed that it could effectively help operators determine operation strategies using simulations to safely and stably execute the process.

this study presented a competitive electrochemical mechanism of the hydrogen and carbon monoxide to describe the real electrochemical reactions in SOFC. The SOFC models employed the competitive electrochemical mechanism was validated with a variety of fuels as the feedstocks, such as methane, mixing gas of H2 and CO, blast furnace gas (BFG), and coke oven gas (COG), via pilot-scale SOFC modules of 1 kW and 50 kW. The models were implemented on Aspen Custom Modeler platform to simulate steady-state results. Further, the SOFC of the 50 kW pilot simulation considering the whole pilot process including pre-reformers, heat exchangers, and fuel recycling. The results showed the SOFC employed the competitive electrochemical mechanism has the better performances of the power generation and voltage predictions regardless of the what fuel used in SOFC of the 1 kW scale, compared to the SOFC only employed hydrogen electrochemical mechanism. The mean voltage error of the SOFC with the competitive electrochemical mechanism using various fuels was 1.52%. the minimum error was 0.73% using COG as the feedstock. The validation of the SOFC model of the 50 kW scale showed that only a 5% error with the experiment in steady-state and 6.91% error in transition.

Yttria-stabilized zirconia (YSZ) is the most commonly used electrolyte material for solid oxide fuel cells. The use of relatively inexpensive metal components would require a trade-off in the lowering of the operating temperature below 800 °C. However, the reduced temperature results in an increased resistivity of YSZ. This can be overcome by reducing the electrolyte thickness using thin film techniques. In this study, the preparation of a thin film of YSZ via the sputter deposition technique was reported. YSZ electrolyte films were deposited on anode substrates at 650/750 °C. The gas permeability test indicated a gas-tight electrolyte with a gas leak rate − 7 lcm − 2 s − 1 . The measured open circuit voltage was 1.1 V, while the maximum power density was 515 mW cm − 2 .

The various composite cathode layers on the solid oxide fuel cells (SOFCs) with a dense electrolyte of yttria-stabilized zirconia (YSZ) are investigated in this study. The ceramic powders of La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF), Ba0.5Sr0.5Co0.2Fe0.8O3−δ (BSCF), La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM), and Gd0.2Ce0.8O3−δ (GDC) are prepared by the glycine-nitrate combustion process. The different formations of composite cathode layers are coated onto the NiO–YSZ/YSZ half-cells via a screen printing method. Scanning electron microscopy (SEM) micrographs show that all of the samples can be well adherent to the YSZ electrolyte. From the energy dispersive X-ray (EDX) result, the undesired compound of SrZrO3 is formed between the YSZ electrolyte and the composite cathode layers with LSCF and BSCF at the sintering temperature of 1000 °C. According to the results of the electrochemical test and electrochemical impedance spectroscopy (EIS), the composite cathode layer with YSZ–La0.8Sr0.2MnO3−δ (LSM) interlayer exhibits the best electrochemical performance. The maximum power density can achieve the value above 400 mW/cm2 for the samples with YSZ–LSM interlayer.

An electrochemical-catalytic cell (ECC) was constructed with Ni–YSZ as the anode, YSZ as the electrolyte, and La0.8Sr0.2MnO3 (LSM) or La0.6Sr0.4Co0.8Cu0.2O3 (LSCC) as the cathode materials. The ECC is simplified from solid oxide fuel cell by deleting the current collecting parts and does not consume any reductant. Very high concentration of NOx can be treated in the ECC. Higher oxygen concentration results in higher NO conversion. In the high NOx concentration range, higher NOx concentration also results in higher NO conversion. This higher NO conversion is associated with larger rate of oxygen desorption induced by higher oxygen mobility during direct NO decomposition. The beneficial effect of temperature is to increase the oxygen mobility.

This work is aimed at understanding the reaction mechanism of propane internal reforming in the solid oxide fuel cell (SOFC). This mechanism is important for the design and operation of SOFC internal processing of hydrocarbons. An anode-supported SOFC unit with Ni–YSZ anode operating at 800 °C was tested with direct feeding of 5% propane. CO 2 reforming of propane was carried out in a reactor with Ni–YSZ catalyst to simulate internal propane processing in SOFC. The performance of this direct propane SOFC is stable. The C specie formed over the anode functional layer of SOFC can be completely removed. The major gas products of SOFC are H 2 , CO, CH 4 , C 2 H 4 and CO 2 . Pseudo-steady-state internal processing of propane in the anode catalytic layer of SOFC is associated with a CO 2 /C 3 H 8 molar ratio of about 1.26 and basically CO 2 reforming of propane. CO 2 dissociation to produce the O species to oxidize the C species from dehydrogenation and dissociation of propane and its fragments should be the major reaction during CO 2 reforming of propane.

The Sm 0.5 Sr 0.5 CoO 3− δ (SSC) with perovskite structure is synthesized by the glycine nitrate process (GNP). The phase evolution of SSC powder with different calcination temperatures is investigated by X-ray diffraction and thermogravimetric analyses. The XRD results show that the single perovskite phase of the SSC is completely formed above 1100 °C. The anode-supported single cell is constructed with a porous Ni–yttria-stabilized zirconia (YSZ) anode substrate, an airtight YSZ electrolyte, a Sm 0.2 Ce 0.8 O 2− δ (SDC) barrier layer, and a screen-printed SSC–SDC composite cathode. The SEM results show that the dense YSZ electrolyte layer exhibits the good interfacial contact with both the Ni–YSZ and the SDC barrier layer. The porous SSC–SDC cathode shows an excellent adhesion with the SDC barrier layer. For the performance test, the maximum power densities are 464, 351 and 243 mW cm −2 at 800, 750 and 700 °C, respectively. According to the results of the electrochemical impedance spectroscopy (EIS), the charge-transfer resistances of the electrodes are 0.49 and 1.24 Ω cm 2 , and the non charge-transfer resistances are 0.48 and 0.51 Ω cm 2 at 800 and 700 °C, respectively. The cathode material of SSC is compatible with the YSZ electrolyte via a delicate scheme employed in the fabrication process of unit cell.

The anode-supported single cell was constructed with porous Ni–Yittria-stabilized zirconia (YSZ) as the anode substrate, an airtight YSZ as the electrolyte, and a screen-printed La 0.8 Sr 0.2 MnO 3−δ (LSM)–Gadolinia-doped ceria (GDC)/LSM double-layer cathode. The SEM results show that the YSZ thin film is highly integrated, fully dense with a thickness of 13 μm, and exhibits excellent compatibility between cathode and electrolyte layers. The effects of feed rates of the reactants, temperature, and contact pressure between the current collector and the unit cell were systematically investigated. The results are based on the assumption that the anode contribution to the polarization resistance is negligible. Our analysis showed that the electrochemical reaction is limited by mass transfer control when the airflow rate is decreased to 500 ml min −1 . The maximum power density is 204.6 mW cm −2 at 800 °C with H 2 and air at flow rates of 800 and 2000 ml min −1 , respectively. According to the AC-impedance data, the resistances of charge transfer at the electrode/electrolyte interface are 3.79 and 1.90 Ω cm 2 . The resistances of oxygen-reduction processes are 3.63 and 1.01 Ω cm 2 at 700 and 800 °C, respectively. The results from the sensitivity analysis of the variation of contact pressure between current collectors and membrane electrode assembly (MEA) show that the influence is enhanced at the regions of the high current density.

Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3− δ (BSCF) and gadolinia-doped ceria (GDC) were synthesized via a glycine-nitrate process (GNP). A cubic perovskite of BSCF was observed by X-ray diffraction (XRD) at a calcination temperature above 950 °C. An anode-supported solid-oxide fuel cell was constructed from the porous NiO + YSZ as the anode substrate, the yittria-stabilized zirconia (YSZ) as the electrolyte, and the porous BSCF-GDC layer as the cathode with a GDC barrier layer. For the performance test, the maximum power density was 191.3 mW cm −2 at a temperature of 750 °C with H 2 fuel and air at flow rates of 335 and 670 sccm, respectively. According to the AC-impedance data, the charge-transfer resistances of the electrodes were 0.10 and 1.59 Ω cm 2 , and the oxygen-reduction and oxygen-ion diffusion resistances were 0.69 and 0.98 Ω cm 2 at 750 and 600 °C, respectively. SEM microstructural characterization indicated that the fuel cell as fabricated exhibited good compatibility between cathode and electrolyte layers.

The solid oxide fuel cell (SOFC) was constructed with NiO/YSZ (yttria stabilized zirconia) as anode supported substrate, with YSZ electrolyte, and La 0.8 Sr 0.2 MnO 3 (LSM) cathode. Here, we show a novel phenomenon of that original Ni grains of micron-scale size in anode of SOFC can be segregated to form nano grains by electrochemical reaction at 800 °C. This breeding function can enhance cell performance obviously. The mechanism for the breeding of nano-scale Ni grain involves two reactions of: 1. NiO + H 2 → Ni + H 2 O ; 2. Ni + O 2 - → NiO + 2 e - , and a non-fuel current can be generated by Reaction 2, which implies that Ni acts as not only a catalyst but also a reactant.

A temperature-programmed methane reaction with self de-coking and a fixed-temperature methane reaction were performed over gadolinia-doped ceria (GDC)-supported Ni catalysts. Experimental results reveal that, at below 810 °C, CO 2 formation rate is higher than that of CO, where below 700 °C, the latter is practically zero. The O species that is needed to form CO and CO 2 during and after CH 4 decomposition are supplied mainly from the bulk lattice of GDC. A drop in the supply rate of the O species from the GDC bulk lattice reduces the rates of CO and CO 2 formation; the CO formation rate decreases much more than the CO 2 formation rate. The CO and CO 2 formation rates can be controlled by both the mobility and the concentration of the bulk lattice oxygen. The concentration of the bulk lattice oxygen influences the self de-coking capability. Low temperature, low concentration of methane gas, or a short methane supply time can result in the formation of only CO 2 during self de-coking.

Temperature-programmed reaction of methane and temperature-programmed reduction were performed over gadolinia-doped ceria (GDC). It was found that CO2 formation can occur at very much lower temperature than CO formation. The surface lattice oxygen acts as the active site for CH4 adsorption. This active site has a dynamic characteristic due to the mobility of the lattice oxygen. The rates of CO and CO2 formations can be controlled by the supply rate of the lattice oxygen from the GDC bulk; this supply rate depends on the mobility and the concentration of the bulk lattice oxygen. CO2 formation is associated with the existing surface lattice oxygen while CO formation depends on the oxygen species coming from the bulk lattice during methane reaction.

Temperature-programmed self de-coking tests were carried out to study the factors in forming CO and CO2 over Ni-gadolinia-doped ceria (GDC), Fe-GDC, and Ni-Fe-GDC cermet catalysts with relation to direct methane SOFCs. It was found that the bulk lattice oxygen plays a very important role in forming CO and CO2. CO formation is generally associated with O species coming from the bulk lattice oxygen while CO2 formation generally is associated with the surface OH species. With Ni:GDC = 3:5 in weight, a very large amount of CO is formed with relatively negligible CO2 formation. With 1 wt% Ni, preferential CO2 formation can be realized below 700 °C. The activity of CH4 decomposition over Fe is much lower than that over Ni, but CO2 formation is favored over Fe. A large promotion of the CO2 formation activity appears with the addition of 0.1 wt% Fe into 1 wt% Ni and a synergistic effect is demonstrated. In general, CO2 formation is favored below 700 °C while CO formation favored above 800 °C. However, with Fe addition, CO2 formation can be favored over Ni-GDC at 1000 °C due to the high-temperature redox property of the Fe species. Thus, for preferential CO2 formation, highly dispersive Ni distribution with Fe addition is recommended for the anode cermet of intemediate-temperature SOFCs.

The anode-supported solid oxide fuel cells (SOFCs) with an yttria-stabilized zirconia (YSZ) electrolyte have been successfully prepared by the sequential steps of fabricating technique including tape casting, spin coating, and screen-printing. Two types of the SOFCs are manufactured and their cell performances are characterized via the detail analysis of the electrochemical impedance spectroscopy (EIS). The maximum power densities are 411 and 289 mW/cm 2 for the high and low performance cells at 800°C, respectively. According to the EIS analysis, the electrochemical performance of the poor cell is dominated by the anodic non-charge-transfer resistance, which is mainly resulted by the gas diffusion polarization due to the low porosity of the anode. The high performance cell is controlled by the simultaneous contributions of the ohmic resistance (R O ), the anodic polarization (R AP ), and the cathodic polarization (R CP ) at the operation temperature of 800°C. However, the R CP will dominate the performance of the cell as the temperature is lowered down to 700°C.