SOFC Anode Research Articles

Thermodynamics assessment and dynamic simulation of a low-carbon syngas-fueled SOFC system using a green hydrogen blend

Green hydrogen is currently eye-catching in terms of its production, storage and delivery to facilitate energy transition. In the present research, it is tried to demonstrate the capability of green hydrogen in blending with syngas (produced by biomass gasification) to feed an SOFC system in order to supply electrical power and heating for an existing educational building. Dynamic simulation has been performed in TRNSYS Software to calculate the hydrogen production annually at different scenarios. Effects of hydrogen concentration in the fuel mixture on the performance of the proposed CHP system are assessed. Results indicated that utilizing a reasonable roof area can offer approximately 10,000 kg H2 and 70,000 kg H2 per year in cases of grid-zero connected and grid 85% connected, respectively. It is revealed that increasing the hydrogen share in fuel mixture from 5% to 30% increases noticeably the hydrogen gas percentage at the SOFC anode inlet and outlet while it has a reverse effect on the H2O amount. In addition, the studied increment in hydrogen share could increase 18% of the net output power from the system. Finally, related to the CO2 emission from the system, it is found that 58% reduction could be achieved by increasing the hydrogen share in the fuel blended.

Electrochemical Study of La0.31Sr0.58Ti0.97Ni0.03O3-δ Thin Film and Pt-10Sc1CeSZ Electrodes

In this work thin film SOFC anode MIEC La0.31Sr0.58Ti0.97Ni0.03O3-δ (LSTN) electrodes with embedded 200 nm thick Pt current collectrors (CC-s) and electrodes without CC-s deposited on 10Sc1CeSZ electrolyte were studied in 650 °C in 98.5% H2 and 1.5 % H2O at ambient pressure. Additionally Pt-10Sc1CeSZ electrodes were characterized to determine CC-s own electrochemical activity. It was found that the embedded Pt was the most active part of an LSTN electrode with Pt CC despite the common presumption that covering Pt current collector with dense MIEC layer makes it inactive. Diffusion of H2 through both LSTN and Pt layers and reaction on the Pt-10Sc1CeSZ interface is proposed. Formation of bubbles under embedded Pt in hydrogen atmosphere was seen and is explained with formation of trapped H2O.

Investigation of Surface Oxide Layer Structure to Improve Durability of Stainless Steels Under Humidified Hydrogen

Durability of low cost stainless steels, selected from the materials widely used in other applications, was investigated under humidified hydrogen of SOFC anode condition. JIS SUS430J1L exhibited higher resistance for water oxidation. The feature came mainly from the thin Cr-rich oxide layer covering the alloy uniformly with little defects or segregations. Under humidified H2 at 700oC, Mn migrated outward and the morphology changed. Durability of the alloy seems to depend on the inner side of the surface oxide layer. Although the Cr-rich oxide layer blocked outward diffusion of metal ions, the layer could not block inward diffusion of oxygen ion completely. Improvement of the durability is possible by controlling the thickness of the surface oxide layer by the pre-heat-treatment.

Modeling and prediction of structural/thermophysical properties of sintered NiO/YSZ anode for SOFC by molecular dynamics method

Anode is an important multi-functional porous cermet applied in solid oxide fuel cell. It is significant but challenging to understand co-sintering mechanism of electron-conducted NiO materials and ion-conducted (Y2O3)0.08(ZrO2)0.84 (YSZ) materials, as well as effect on the sintered structures at pore/particle scale. In the current study, an all-atom model coupled molecular dynamics simulation method is developed to capture the co-sintered NiO/YSZ porous cermet structures, as well as to evaluate effect of sintering parameters on the structural/ thermophysical properties. It is found that the initial stage of the sintering process is the major step where both the structural and thermophysical parameters change greatly. It is also captured that the effective particle stress is highly correlated with the microstructural parameters, while a high stress is mainly concentrated in the sintered necks, particle junctions and lattice boundaries. Various thermal properties are also evaluated for identifying influence of the sintering conditions. The findings obtained from this study may provide a guideline for investigating and optimizing the practical sintering parameters of the porous cermet electrodes, as well as a bottom-up approach for evaluating overall structural/thermophysical properties often applied at SOFC cell and stack studies.

Preparation of SOFC Anodes at Lower Temperature with Boosted Electrochemical Performance

Preparation of SOFC Anodes at Lower Temperature with Boosted Electrochemical Performance

Use of hydrogen produced by the air conversion of motor diesel fuel in an electrochemical generator

At present, the production of electric energy consumer remote from agro-based centralized networks is done using diesel-generator technology with limited service life of the engine and the extremely low efficiency in the use of expensive fuel. In this paper, is considered an innovative technology of combined production of electricity and heat using a preliminary conversion of diesel fuel in the synthesis gas and then serving it at high temperature electrochemical generator. Synthetic gas to operate the generator air conversion is made of an electrochemical engine diesel fuels in catalytic reactor-burner. On the basis of heat balances of the torch, battery power and boiler are calculated: battery electric efficiency SOFC, chemical efficiency burner, SOFC anode temperature, EMF Planar element, the proportion of hydrogen, oxidized anode SOFC, unit cost of diesel fuel for the production of electricity and thermal energy. Specific consumption of diesel fuel for the production of electrical energy 114 g/kWh (162 g. w. t./kWh), and thermal 31.7 kg/Gj (45.1 kg/GJ, w. t. 189 kg standard fuel/Gcal).

The conversion of naphthalene on SOFC anodes and its impact on the cell performance

The operation of a SOFC with biomass-derived syngas would provide convincing solutions for combined heat and power production from renewable sources. In principle, the tar components in the wood gas can be reformed on Ni-based SOFC anodes, hence, giving access to additional hydrogen as fuel. The investigation of the kinetic-limited conversion process on anodes and its effect on the electrochemical processes of the SOFC is yet still insufficient. This paper presents the experimental study of the conversion of naphthalene on a single planar electrolyte-supported cell with varying temperature and naphthalene concentration. Thereby the impact of the incomplete conversion of naphthalene on open circuit voltage, methane conversion and cell performance is investigated. A 1-D kinetic model reveals the correlation between the slow naphthalene reforming and the open circuit voltage. The adsorption of naphthalene on the Ni catalyst not only impedes the reforming of methane, but also slows down the kinetics of electrochemical reaction. However, the produced hydrogen from steam reforming reaction is still beneficial in terms of preventing Ni re-oxidation under higher fuel utilization in H2 gas mixture.

Improved cell performance and sulphur tolerance using A-site substituted Sr2Fe1.4Ni0.1Mo0.5O6–δ anodes for solid-oxide fuel cells

AbstractSolid-oxide fuel cells (SOFCs) offer great promise for producing electricity using a wide variety of fuels such as natural gas, coal gas and gasified carbonaceous solids; however, conventional nickel-based anodes face great challenges due to contaminants in readily available fuels, especially sulphur-containing compounds. Thus, the development of new anode materials that can suppress sulphur poisoning is crucial to the realization of fuel-flexible and cost-effective SOFCs. In this work, La0.1Sr1.9Fe1.4Ni0.1Mo0.5O6–δ (LSFNM) and Pr0.1Sr1.9Fe1.4Ni0.1Mo0.5O6–δ (PSFNM) materials have been synthesized using a sol-gel method in air and investigated as anode materials for SOFCs. Metallic nanoparticle-decorated ceramic anodes were obtained by the reduction of LSFNM and PSFNM in H2 at 850°C, forming a Ruddlesden–Popper oxide with exsolved FeNi3 bimetallic nanoparticles. The electrochemical performance of the Sr2Fe1.4Ni0.1Mo0.5O6–δ ceramic anode was greatly enhanced by La doping of A-sites, resulting in a 44% decrease in the polarization resistance in reducing atmosphere. The maximum power densities of Sr- and Mg-doped LaGaO3 (LSGM) (300 μm) electrolyte-supported single cells with LSFNM as the anode reached 1.371 W cm −2 in H2 and 1.306 W cm–2 in 50 ppm H2S–H2 at 850°C. Meanwhile, PSFNM showed improved sulphur tolerance, which could be fully recovered after six cycles from H2 to 50 ppm H2S–H2 operation. This study indicates that LSFNM and PSFNM are promising high-performance anodes for SOFCs.

Integration of wind turbine with biomass-fueled SOFC to provide hydrogen-rich fuel: Economic and CO2 emission reduction assessment

Addressing the energy crisis and global warming issues would entail urgent development of efficient and environmentally-benign power generation systems to mitigate the future clean energy policies. The biomass-driven SOFC systems are considered in this regard as pioneer technologies to supply clean power, particularly for decentralized applications. However, enough biomass availability and supply is a main challenge to run these systems. In current research to reduce biomass consumption, the biomass-driven SOFC is hybridized with wind turbines to produce pure hydrogen via a PEM electrolyzer. Produced hydrogen is added to the anode of SOFC to enrich the hydrogen content of the synthesis gas fuel. Feasibility assessment of proposed hybrid SOFC/wind turbine structure is examined considering first and second laws. Then, comprehensive economic and environmental appraisals are considered to inspect trade-offs between increased costs (associated with wind turbine and electrolyzer) and increased power as well as decreased CO2 emission. Finally to determine the optimal conditions for proposed system operation, triple-objective optimization via genetic algorithm is implemented. Obtained results have revealed exergy efficiency enhancement by 7.3% and CO2 emission reduction by 13.0 %, via incorporation of wind turbine. These technical and environmental performance enhancements are achieved at the expense of around 6.4 % increase in unit electricity cost, due to the increment of capital expenditures associated with the wind turbine and water electrolyzer. From parametric analysis, it is found that, the proposed framework yields lower electricity price and CO2 emission under higher cell temperatures and lower fuel utilization factors.

A rational design of highly active and coke-resistant anode for methanol-fueled solid oxide fuel cells with Sn doped Ni-Ce0.8Sm0.2O2−δ

A crucial challenge in the commercialization of Ni-based materials as the anode of solid oxide fuel cell is the fast voltage drop due to carbon deposition and structural degradation during cell operation. Herein, Sn-doped Ce0.8Sm0.2O2−δ (SDC) supported Sn-Ni alloy anode is rationally designed and prepared, via a simple and convenient dual-modification strategy. The substitution of Sn of Ce in the oxide phase enhances the mobility of lattice oxygen in SDC. Meanwhile, Sn exsolves partially from the oxide phase and forms Ni3Sn and Ni3Sn2 intermetallic compounds with Ni after reduction. The composite anode thus formed achieves unprecedent activity in the electrochemical oxidation of H2 and CH3OH. The maximum power densities of a cell supported by 500 μm-thick Ce0.8Sm0.2O2−δ-carbonate electrolyte layer with the Ni-Ce0.7Sn0.1Sm0.2O2−δ (Ni-SSn10DC) anode reach 1.99 and 2.11 W cm−2 at 700 °C, respectively for using H2 and methanol as fuels. The doping of Sn also remarkably enhances the coking resistance of the anode. This work opens a path on the design of high-performance SOFC anode.

A Solid Oxide Fuel Cell Runs on Hydrocarbon Fuels with Exceptional Durability and Power Output

AbstractSolid oxide fuel cells (SOFCs) that can operate on hydrocarbon fuels offer an efficient and cost‐effective solution for electricity generation. However, broader commercialization of SOFCs is hindered by inadequate performance and limited durability due to the sluggish hydrocarbon reforming/oxidation kinetics and coking on the SOFC anode. Here it has been reported that these findings in design, synthesis, and characterization of a novel anode catalyst Ba(Zr0.8Y0.2)0.9(Ni0.5Ru0.5)0.1O3‐δ (BZYNR) that overcomes the problems, enabling direct utilization of nearly dry hydrocarbon fuels (e.g., methane, ethanol, and iso‐octane with only 3 vol% H2O) with exceptional power output for over 1000 h on both button cells and tubular cells. The outstanding performance of BZYNR is attributed to the high activity of hydrocarbon reforming and the accelerated water‐mediated carbon cleaning process on Ni‐based SOFC anode.

Development of highly efficient and durable large-area solid oxide fuel cell by a direct-ink-writing three-dimensional printer

The commercialization of efficient and durable solid oxide fuel cells is hugely hindered due to the expensive and complex fabrication process. In this regard, the additive manufacturing technique, i.e., three-dimensional printing (3-D printing), has gained tremendous attention because of its ability to fabricate tunable functional ceramic layers with cost-effectiveness and mass customization. Therefore, in this work, the anode (NiO-ScSZ) and cathode (LSM) of the large-area SOFC (5 × 5 cm2) are printed using a direct-ink-writing (DIW) printer. The anode-functional and electrolyte layers are coated by spray and spin coating. The viscosity of the optimized anode and cathode inks are 5.85 Pa s and 0.97 Pa s, respectively. The electrochemical impedance and the performance of 3D-SOFC are investigated by supplying hydrogen and air. The maximum power density of the cell is 368 mW cm−2 at 800 °C. However, by inserting a hybrid scandia stabilized zirconia layer by spraying followed by magnetron sputtering onto the AFL, the electrochemical performance of the cell is significantly (21%) enhanced; the peak power density is 442 mW cm−2, and the corresponding polarization resistance is 0.267 Ω cm2 at 800 °C. Furthermore, the long-term cell test under galvanostatic mode (j = 0.5 A cm−2) at 700 °C for 100 h and thermal cycling between 400 and 700 °C concludes that the 3D-SOFC exhibits exceptional stability with a voltage loss of 0.845% h−1 and thermomechanical durability.

A-Site Doping Effect on the Performance of Sr2Fe1.4 Ni0.1Mo0.5O6-Δ Anodes for SOFCs

A site doped Sr2Fe1.4 Ni0.1Mo0.5O6- δ (SFNM), i.e., La0.1Sr1.9Fe1.4Ni0.1Mo0.5O6-δ (LSFNM) and Pr0.1Sr1.9Fe1.4Ni0.1Mo0.5O6-δ (PSFNM) materials have been synthesized by sol-gel method in air and investigated as anode catalysts for intermediate temperature solid oxide fuel cells. Metallic nanoparticle-decorated ceramic anodes were prepared by in situ reduction of the LSFNM and PSFNM in H2 at 850 °C, forming Ruddlesden−Popper structure and FeNi3 bimetallic alloy nanoparticle catalyst. The electrochemical performance of the doped SFNM ceramic anode is greatly enhanced by A site La or Pr doping due to the ~50% decrease of the polarization resistance. The maximum power densities of the LSGM (320μm) electrolyte supported single cells with LSFNM and PSFNM as the anode reached 1.142 and 1.084 W cm− 2 in wet H2 at 850 °C, respectively. LSFNM and PSFNM are promising high-performance anodes for solid oxide fuel cells.Acknowledgements: Financial support from the U.S. National Science Foundation (DMR–1832809) is greatly appreciated.

Impact of Different Supports on the Performance of Ir Oxide Based Catalysts Synthesized Using Incipient Wetness Method

Development of an active and durable catalyst for oxygen evolution reaction (OER) is a pivotal part of designing an efficient PEM water electrolyser. Iridium is one of the best available catalysts because of its corrosion resistance and activity [1]. Use of Ir is however, limited by its scarcity, limited durability and high cost. Its deposition on a support is a popular way to improve the available surface area, activity and stability [2]. For applications in acidic water electrolysis, supports with the highest chemical resistance and conductivity are preferred. While different methods have been studied to impregnate a support with catalyst nanoparticles, such as Adams’s fusion method and polyol method, their scalability remains questionable due to intensive resource requirements. In this work, Ir oxide based supported catalysts have been synthesized using the incipient wetness method (IWM), one of the most commonly used method of catalyst synthesis in the industry due to its ease of scalability, limited resource requirement and the opportunity to explore the effect of strong metal support interactions. This method however has not been discussed in literature. In this study, Ir oxide (IrOx) (Ir loading on support = 20 wt. percent) was dispersed on commercial supports (ZrO2, Nb2O5, Ta2O5, ATO) using H2IrCl6.xH2O precursor (99.9% trace metal basis, Sigma Aldrich). The catalysts were calcined at 400oC for 2 h in a muffle furnace to produce Ir oxide based catalysts.Electrochemical measurements were carried out on a standard rotating-disk electrode (RDE) system (PINE Research MSR Rotator), and a three-electrode electrochemical cell in 1.0 M sulfuric acid electrolyte (H2SO4 optima grade, Fisher Scientific). The performance of the aforementioned supported Ir oxide catalyst was compared among themselves, and to benchmark commercial catalysts (Umicore Ir Black and IrOx TKK) using metrics such as mass normalized activity (A/g-1 Ir), ECSA normalized activity (mA/cm2 Ir ECSA), Tafel slope (mV/dec) and charge transfer resistance (Rct) measured during the electrochemical test. It was observed that the activity of IrOx/ZrO2 (415 A/gIr, 5.2 mA/cm2 Ir ECSA) was the best among all the 4 impregnated catalysts, and was in fact, more than an order of magnitude greater than that of IrOx/ATO (30 A/gIr, 0.3 mA/cm2 Ir ECSA) at a potential of 1.53 VRHE. A significant drop in the Tafel slope measured in the potential range of 1.45-1.55 VRHE was observed upon changing the support from ATO (80 mV/dec) to ZrO2 (60 mV/dec) hinting towards a change in the reaction mechanism. IrOx/ATO was used as a baseline due to prevalent recognition of ATO as an excellent support for OER catalysts in the literature.Upon comparison with commercial benchmark catalysts it was observed that the Ir ECSA normalized activity of IrOx/Nb2O5, IrOx/Ta2O5, IrOx/ZrO2 surpasses both Umicore Ir black ( 2.23 mA/cm2 Ir ECSA) and IrOx TKK (1.23 mA/cm2 Ir ECSA) with IrOx/ZrO2 providing the highest activity. While Yttria-stabilized zirconia (YSZ) has been a popular choice as an electrolyte and anode for high temperature SOFC due to its non-reducing nature, high thermal stability and mechanical strength, and acceptable oxygen ion conductivity [3], its application in PEM water electrolysis as catalyst support has not been discussed. In this work, we focus on finding the causes for superior performance of ZrO2 as a support for Ir oxide based OER reaction in acidic conditions through the lens of electrocatalysis.

Characteristics of (Sr0.92Y0.08)0.85Ti1-XNixO3-

Perovskite with A-site deficiency(A1-xBO3) is promising candidate due to introduction of oxygen vacancy for ionic conductivity and nano-sized exsolution of B component with metal phase for catalytic activity. In this study, Ni-doped Sr0.92Y0.08TiO3 perovskite has been investigated to improve the catalytic activity for CO2 dry internal reforming of methane in solid oxide fuel cells. (Sr0.92Y0.08)0.85Ti1-xNixO3- \U0001d6ff (x=0.05, 0.10, 0.15, 0.20) perovskite with A-site deficiency is prepared by pechini method and compared to stoichiometric Sr0.92Y0.08Ti1-xNixO3- \U0001d6ff (SYTN15) perovskite. The physical and physicochemical characteristics of the synthesized powders are analyzed by GC, XRD, BET, TEM, XPS, and TPO. (Sr0.92Y0.08)0.85Ti0.85Ni0.15O3- \U0001d6ff (SYTN(+)15) shows the highest methane conversion with 93% and carbon dioxide conversion with 86%. In addition, the SYTN(+)15 results to the lowest decreasing rate of the methane conversion with 1.86% drop for 50h. The SYTN(+)15 shows better catalytic performance by 10% for dry reforming of methane (DRM) comparing to the SYTN15. The cell performances of the SYTN(+)15 and the SYTN15 are 60.05mW/cm2 and 28.50mW/cm2, respectively. Consequently, A-site deficiency catalyst, SYTN(+)15 exhibits excellent catalytic activity for DRM and sufficient electrochemical property for SOFC anode materials.

A study on mass transfer modelling in SOFC anode: Comparison of diffusion mass transfer models for estimation of diffusion overpotential

A study on mass transfer modelling in SOFC anode: Comparison of diffusion mass transfer models for estimation of diffusion overpotential

Layer-by-Layer Formation of the NiO/CGO Composite Anode for SOFC by 3D Inkjet Printing Combined with Laser Treatment

Layer-by-Layer Formation of the NiO/CGO Composite Anode for SOFC by 3D Inkjet Printing Combined with Laser Treatment

Efficient conversion of low-concentration coal mine methane by solid oxide fuel cell with in-situ formed nanocomposite catalyst

Solid oxide fuel cell is promising to efficiently convert the low-concentration coal mine methane (methane concentration c(CH4) <30%) from pollutant to clean energy. However, the low internal reforming performance and the coking at anode become the big challenges of SOFC using LC-CMM. Therefore, the Mo-doped NiTiO3 catalyst layer is fabricated over SOFC anode in this work. The catalyst can be in-situ reduced to nanoscale Ni and Mo-doped TiO2-δ composite catalyst with plentiful oxygen vacancies, thus adsorbing oxygen species to enhance CH4 internal reforming and remove carbon. It is demonstrated that the catalyst-modified SOFC using LC-CMM exhibits the much better electrochemical performance, anti-carbon effect and discharging stability than the un-modified SOFC. The modified SOFC also shows the good electrochemical and internal reforming performances under different LC-CMM with various methane concentration c(CH4) and oxygen concentration c(O2). The distribution of relaxation time (DRT) indicates that the catalyst can remove carbon and facilitates the adsorption, dissociation and transport of surface species through the enhanced oxygen-species mediated surface reactions. Besides, a 2D multi-physics coupling model is built to study the reforming-enhancing and anti-carbon mechanisms of the catalyst layer.

Locating the rate-limiting step of hydrogen conversion on Sr2Fe1.5Mo0.5O6 (0 0 1) surface: Implications for efficient SOFC anode design

Density functional theory (DFT) based first-principles calculations have been employed to explore the hydrogen conversion mechanism on Sr2Fe1.5Mo0.5O6 (SFM) surface. Results show that hydrogen molecule exhibits weak physical adsorption behavior while hydrogen atom strongly chemisorbed on SFM (001) surface. Hydrogen molecule preferably dissociates at surface (Fe)-Fe-(Fe) site with an activation barrier of 0.69 eV. Hydrogen oxidation on SFM (001) surface is favorable both in kinetics and thermodynamics, and the resultant H2O molecule desorption only needs to overcome energy barrier of 0.22–0.24 eV. Oxygen atom diffusion from bulk to surface prefers to follow the path from subsurface (Fe)-O-(Fe) site to outer-surface (Fe)-VO-(Mo) vacancy site, which needs to overcome an energy barrier of 0.49 eV. The rate-limiting step of hydrogen conversion on the SFM surface is determined to be hydrogen dissociation at temperature below 775 °C while it switches to hydrogen adsorption at temperature above 775 °C. The theoretical findings in current study are expected to offer fundamental basis for designing efficient perovskite-based SOFC anodes.

Investigating the Influence of Ni, ZrO2, and Y2O3 from SOFC Anodes on Siloxane Deposition

Siloxanes, as a type of impurity in biogas, can poison the Ni-YSZ anode of SOFCs. However, the influence of individual components of the anode, such as Ni, ZrO2, and Y2O3, on the siloxane deposition process has not been investigated extensively. In this study, Ni, ZrO2, and Y2O3 pellets were exposed to H2 + N2 + H2O + D4 (octamethylcyclotetrasiloxane, 2.5 ppmv) and H2 + N2 + D4 (2.5 ppmv siloxane) gas mixtures at 750 °C to investigate their affinity and tolerance for siloxane degradation. Surface morphology analysis and electrochemical analysis including electrochemical impedance spectroscopy (EIS), related distribution of relaxation times (DRT) analysis and equivalent circuit modeling with complex nonlinear least square (CNLS) fitting were conducted. A microstructure parameter—tortuosity factor to porosity ratio calculated by diffusion polarization resistance was utilized for siloxane deposition evaluation. After comparing pellets surface morphology changes before and after experiments and change following the contamination, Ni is considered as a major factor in siloxane deposition reactions in Ni-YSZ anode.