Graphene based catalyst supports for high temperature PEM fuel cell application

In this study, the effect of graphene nanoplatelet (GNP) and graphene oxide (GO) based carbon supports on polybenzimidazole (PBI) based high temperature proton exchange membrane fuel cells (HT-PEMFCs) performances were investigated. Pt/GNP and Pt/GO catalysts were synthesized by microwave assisted chemical reduction support. X-ray diffraction (XRD), Thermogravimetric analysis (TGA), Brauner, Emmet and Teller (BET) analysis and high resolution transmission electron microscopy (HRTEM) were used to investigate the microstructure and morphology of the as-prepared catalysts. The electrochemical surface area (ESA) was studied by cyclic voltammetry (CV). The results showed deposition of smaller Pt nanoparticles with uniform distribution and higher ECSA for Pt/GNP compared to Pt/GO. The Pt/GNP and Pt/GO catalysts were tested in 25 cm² active area single HT-PEMFC with H₂/air at 160 °C without humidification. Performance evaluation in HT-PEMFC shows current densities of 0.28, 0.17 and 0.22 A/cm² for the Pt/GNP, Pt/C and Pt/GO catalysts based MEAs at 160 °C, respectively. The maximum power density was obtained for MEA prepared by Pt/GNP catalyst with H₂/Air dry reactant gases as 0.34, 0.40 and 0.46 W/cm² at 160 °C, 175 °C and 190 °C, respectively. Graphene based catalyst supports exhibits an enhanced HT-PEMFC performance in both low and high current density regions. The results indicate the graphene catalyst support could be utilized as the catalyst support for HT-PEMFC application.     

Syngas production through CH4-assisted co-electrolysis of H2O and CO2 in La0.8Sr0.2Cr0.5Fe0.5O3-δ-Zr0.84Y0.16O2-δ electrode-supported solid oxide electrolysis cells

High temperature co-electrolysis of H₂O/CO₂ allows for clean production of syngas using renewable energy, and the novel fuel-assisted electrolysis can effectively reduce consumption of electricity. Here, we report on symmetric cells YSZ-LSCrF | YSZ | YSZ-LSCrF, impregnated with Ni-SDC catalysts, for CH₄-assisted co-electrolysis of H₂O/CO₂. The required voltages to achieve an electrolysis current density of ?400 mA·cm^?2 at 850 °C are 1.0 V for the conventional co-electrolysis and 0.3 V for the CH₄-assisted co-electrolysis, indicative of a 70% reduction in the electricity consumption. For an inlet of H₂O/CO₂ (50/50 vol), syngas with a H₂:CO ratio of ≈2 can be always produced from the cathode under different current densities. In contrast, the anode effluent strongly depends upon the electrolysis current density and the operating temperature, with syngas favorably produced under moderate current densities at higher temperatures. It is demonstrated that syngas with a H₂:CO ratio of ≈2 can be produced from the anode at a formation rate of 6.5·mL min^?1·cm^?2 when operated at 850 °C with an electrolysis current density of ?450 mA·cm^?2.     

High CO tolerance of new SiO2 doped phosphoric acid/polybenzimidazole polymer electrolyte membrane fuel cells at high temperatures of 200–250 °C

The high CO tolerance or resistance is critical for the practical application of proton exchange membrane fuel cells (PEMFCs) coupled with on board reformers for transportation applications due to the presence of high level of CO in the reformats. Increasing the operating temperature is most effective to enhance the CO tolerance of PEMFCs and therefore is of high technological significance. Here, we report a new PEMFC based on SiO₂ nanoparticles doped phosphoric acid/polybenzimidazole (PA/PBI/SiO₂) composite membranes for operation at temperatures higher than 200 °C. The phosphoric acid within the polymer matrix is stabilized by PA/phosphosilicate nanoclusters formed via prior polarization treatment of the membrane cells at 250 °C at a cell voltage of 0.6 V for 24 h, achieving a high proton conductivity and excellent stability at temperatures beyond that of conventional PA/PBI membranes. The proton conductivity of PA/PBI/SiO₂ composite membranes is in the range of 0.029–0.041 S cm^?1 and is stable at 250 °C. The PA/PBI/SiO₂ composite membrane cell displays an exceptional CO tolerance with a negligible loss in performance at CO contents as high as 11.7% at 240 °C. The cell delivers a peak power density of 283 mW cm^?2 and is stable at 240 °C for 100 h under a cell voltage of 0.6 V in 6.3% CO-contained H₂ fuel under anhydrous conditions.     

Investigating different break-in procedures for reformed methanol high temperature proton exchange membrane fuel cells

The present work focuses on reducing the complexities involved in the mass production of HT-PEM fuel cell systems integrated with a methanol reformer. Different break-in procedures are investigated on a single HT-PEMFC. The work is divided into two parts, the first in which different break-in times are tested in order to reduce the usual break-in time of around 100 h, and the second one, where simulated reformed fuel is tested during and after break-in to understand the impact on degradation over time.In this study, two set of tests are carried out with different break-in times, the normal break-in (100 h), intermediate break-in (30 and 50 h) and no break-in (0 h). After break-in, all the cells were subjected to a load cycling profile between 0.2 and 0.6 A cm^?2 with 5 min at each current density. The test was then carried out to compare the cell performance over time when the break-in is carried out with simulated reformed gas having a composition of 64.7% H₂, 21.3% CO₂, 12% H₂O and 2% CH₃OH. The break-in time for this test was 100 h. The cells are operated at 0.2 A cm^?2 during break-in and thereafter at 0.6 A cm^?2 under normal operation. The cell performance and impedance change over time is analyzed. The different resistances are deduced using equivalent circuit models and analyzed to understand the changes occurring in the MEA during break-in and how they affect the durability of an HT-PEMFC. The degradation rate for the different operating strategy is calculated from the voltage trajectory over time. The comparison of degradation and break-in time suggests that the normal break-in induces a uniform ohmic resistance changes in the cell over time, while the fast cycling leads to non-uniform changes in resistances. However, the performance and degradation are not significantly affected over $\approx$750 h test. The test with simulated reformed fuel indicates that the break-in with pure H₂ is important for longer durability when operation thereafter is with reformed fuel. The cell with reformed fuel break-in degrades much faster compared to the cell with H₂ break-in.     

Composite membrane by incorporating sulfonated graphene oxide in polybenzimidazole for high temperature proton exchange membrane fuel cells

The objective of this work is to examine the polybenzimidazole (PBI)/sulfonated graphene oxide (sGO) membranes as alternative materials for high-temperature proton exchange membrane fuel cell (HT-PEMFC). PBI/sGO composite membranes were characterized by TGA, FTIR, SEM analysis, acid doping&acid leaching tests, mechanical analysis, and proton conductivity measurements. The proton conductivity of composite membranes was considerably enhanced by the existence of sGO filler. The enhancement of these properties is related to the increased content of –SO₃H groups in the PBI/sGO composite membrane, increasing the channel availability required for the proton transport. The PBI/sGO membranes were tested in a single HT-PEMFC to evaluate high-temperature fuel cell performance. Amongst the PBI/sGO composite membranes, the membrane containing 5 wt. % GO (PBI/sGO-2) showed the highest HT-PEMFC performance. The maximum power density of 364 mW/cm² was yielded by PBI/sGO-2 membrane when operating the cell at 160 °C under non humidified conditions. In comparison, a maximum power density of 235 mW/cm² was determined by the PBI membrane under the same operating conditions. To investigate the HT-PEMFC stability, long-term stability tests were performed in comparison with the PBI membrane. After a long-term performance test for 200 h, the HT-PEMFC performance loss was obtained as 9% and 13% for PBI/sGO-2 and PBI membranes, respectively. The improved HT-PEMFC performance of PBI/sGO composite membranes suggests that PBI/sGO composites are feasible candidates for HT-PEMFC applications.     

Ni-samaria-doped ceria (Ni-SDC) anode-supported solid oxide fuel cell (SOFC) operating with CO

The performance of nickel-samaria-doped ceria (Ni-SDC) anode-supported cell with CO-CO₂ feed was evaluated. The aim of this work is to examine carbon formation on the Ni-SDC anode when feeding with CO under conditions when carbon deposition is thermodynamically favoured. Electrochemical tests were conducted at intermediate temperatures (550–700 °C) using 20 and 40% CO concentrations. Cell operating with 40% CO at 600–700 °C provided maximum power densities of 239–270 mW cm^?2, 1.5 times smaller than that achieved with humidified H₂. Much lower maximum power densities were attained with 20% CO (50–88 mW cm^?2). Some degradation was observed during the 6 h galvanostatic operation at 0.1 A cm^?2 with 40% CO fuel at 550 °C which is believed due to the accumulation of carbon at the anode. The degradation in cell potential occurred at a rate of 4.5 mV h^?1, but it did not lead to cell collapse. EDX mapping at the cross-section of the anode revealed that carbon formed in the Ni-SDC cell was primarily deposited in the anode section close to the fuel entry point. Carbon was not detected at the electrolyte-anode interface and the middle of the anode, allowing the cell to continue operation with CO fuel without a catastrophic failure.     

Synergetic integration of a methanol steam reforming cell with a high temperature polymer electrolyte fuel cell

In this work an integrated unit, combining a methanol steam-reforming cell (MSR-C) and a high temperature polymer electrolyte membrane fuel cell (HT-PEMFC) was operated at the same temperature (453 K, 463 K and 473 K) allowing thermal integration and increasing the system efficiency of the combined system. A novel bipolar plate made of aluminium gold plated was built, featuring the fuel cell anode flow field in one side and the reformer flow field on the other. The combined unit (MSR-C/HT-PEMFC) was assembled using Celtec^® P2200N MEAs and commercial reforming catalyst CuO/ZnO/Al₂O₃ (BASF RP60). The water/methanol vaporisation originates oscillations in the vapour flowrate; reducing these oscillations increase the methanol conversion from 93% to 96%. The MSR-C/HT-PEMFC showed a remarkable high performance at 453 K. The integrated unit was operated during ca. 700 h at constant at 0.2 A cm^?2, fed alternately with hydrogen and reformate at 453 K and 463 K. Despite the high operating temperature, the HT-PEMFC showed a good stability, with an electric potential difference decreasing rate at 453 K of ca. 100 μV h^?1. Electrochemical impedance spectroscopy (EIS) analysis revealed an overall increase of the ohmic resistances and charge transfer resistances of the electrodes; this fact was assigned to phosphoric acid losses from the electrodes and membrane and catalyst particle size growth.     

A comparative study of electrodes in the direct synthesis of CH4 from CO2 and H2O in molten salts

Since the Industrial Revolution, the heavy reliance on the limited fossil energy has emitted huge number of CO₂ into the air and led to a severely global warming. We propose a new green technology to moderate greenhouse gas CO₂ emission and transform it into low-carbon renewable energy in this paper. Through this manner, electricity is transformed into chemical energy. CO₂ and H₂O is directly simultaneous electrolysis under constant 0.25 A with 30 cm² nickel anode and 30 cm² iron cathode in a 600 °C alkali carbonate with LiOH electrolyte in mole ratio of n_H:n_C = 0.15:1, achieving the storage of electricity to chemical energy. This electrolysis provides a gaseous product comprising 45.9% methane, 53.1% H₂, 0.92% CO and trace amounts of longer (than methane) hydrocarbons. Simultaneously, the current efficiency is still ～51% for 60 min.     

Biogas steam reformer for hydrogen production: Evaluation of the reformer prototype and catalysts

This work aims to investigate a biogas steam reforming prototype performance for hydrogen production by mass spectrometry and gas chromatography analyses of catalysts and products of the reform. It was found that 7.4% Ni/NiAl₂O₄/γ-Al₂O₃ with aluminate layer and 3.1% Ru/γ-Al₂O₃ were effective as catalysts, given that they showed high CH₄ conversion, CO and H₂ selectivity, resistance to carbon deposition, and low activity loss. The effect of CH₄:CO₂ ratio revealed that both catalysts have the same behavior. An increase in CO₂ concentration resulted in a decrease in H₂/CO ratio from 2.9 to 2.4 for the Ni catalyst at 850 °C, and from 3 to 2.4 for the Ru catalyst at 700 °C. In conclusion, optimal performance has been achieved in a CH₄:CO₂ ratio of 1.5:1. H₂ yield was 60% for both catalysts at their respective operating temperature. Prototype dimensions and catalysts preparation and characterization are also presented.     

Micro-cogeneration application of a high-temperature PEM fuel cell stack operated with polybenzimidazole based membranes

High temperature Proton Exchange Membrane Fuel Cells (HT-PEMFC) have attracted the attention of researchers in recent years due to their advantages such as working with reformed gases, easy heat management and compatibility with micro-cogeneration systems. In this study, it is aimed to designed, manufactured and tested of the HT-PEMFC stack based on Polybenzimidazole/Graphene Oxide (PBI/GO) composite membranes. The micro-cogeneration application of the PBI/GO composite membrane based stack was investigated using a reformat gas mixture containing Hydrogen/Carbon Dioxide/Carbon Monoxide (H₂/CO₂/CO). The prepared HT-PEMFC stack comprises 12 cells with 150 cm² active cell area. Thermo-oil based liquid cooling was used in the HT-PEMFC stack and cooling plates were used to prevent coolant leakage between the cells. As a result of HT-PEMFC performance studies, maximum 546 W and 468 W power were obtained from PBI/GO and PBI membranes based HT-PEMFC stacks respectively. The results demonstrate that introducing GO into the PBI membranes enhances the performance of HT-PEMFC technology and demonstrated the potential of the HT-PEMFC stack for use in micro-cogeneration applications. It is also underlined that the developed PBI/GO composite membranes have the potential as an alternative to commercially available PBI membranes in the future.     

Validation of an externally oil-cooled 1 kWel HT-PEMFC stack operating at various experimental conditions

The performance of 1 kW_el 48-cell HT-PEMFC at various experimental conditions is presented, particularly at several CO concentrations (up to 1.0%). Polarization curves measured at various anode (1.0–2.5) and cathode (1.6–4.0) stoichiometries; stack operating temperatures (120–160 °C) and gas pressures (up to 0.5 bar_g) are reported and analysed. The minimum gas stoichiometries of 1.25 and 2.0 were determined for the anode and cathode, respectively. The highest stack power density of 225 mW cm⁻² was measured at 160 °C and 0.4 A cm⁻². Operation at CO concentrations up to 1% was achieved, although a loss of performance of about 4% was observed for low CO concentrations. The operating temperature enhanced fuel cell performance and tolerance to CO, even when supplied with higher CO concentration in the anode feed gas.     

LaCoO3-δ-coated Ba0.5Sr0.5Co0.8Fe0.2O3-δ: A promising cathode material with remarkable performance and CO2 resistance for intermediate temperature solid oxide fuel cells

LaCoO_3-δ (LC)-coated Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ (BSCF) cathode is fabricated by the solution impregnation method and promoted electrochemical performance is obtained. After being coated by LC shell, the polarization resistance can be as low as 0.197 Ω cm² and the peak power density is 0.243 W cm^?2 at the operating temperature of 600 °C. The excellent CO₂ resistance of LC-coated BSCF cathode is verified by the CO₂-poisoning test. Even in the operating atmosphere with high CO₂ concentration, the polarization resistance change of LC-coated BSCF cathode is much smaller than that of the blank BSCF cathode. By long-term test of single cells, the remarkable electrochemical performance stability of LC-coated BSCF cathode is shown. The promoted electrochemical performance, excellent CO₂ resistance and remarkable long-term stability make LC-coated BSCF cathode promising for intermediate temperature solid oxide fuel cells.     

Elevated temperature pressure swing adsorption process for reactive separation of CO/CO2 in H2-rich gas

Purification of CO and CO₂ to the ppm level in H₂-rich gas without losing H₂ is one of the technical difficulties for fuel cell power systems. In this work, a two-column seven-step elevated temperature pressure swing system with high purification performance was proposed. The concept of reactive separation by adding water gas shift catalysts into the columns filled with elevated temperature CO₂ adsorbents was adopted. The H₂ recovery ratio and H₂ purity were greatly improved by the introduction of steam rinse and steam purge, which could be realized due to the increasing operating temperature (200–450 °C). An optimized operating region to both achieve high efficiency and low energy consumption was proposed. The optimized case with 0.09 purge-to-feed ratio and 0.15 rinse-to-feed ratio could achieve 99.6% H₂ recovery ratio and 99.9991% H₂ purity at a stable state for a feed gas containing 1% CO, 1% CO₂, 10% H₂O, and 88% H_2. No performance degradation was observed for at least 1000 cycles. The proposed (ET-PSA) system possessed self-purification ability while the columns were penetrated by CO₂. It is however suggested that periodical heat regeneration should be adopted to accelerate performance recovery during long-term operation.     

Demonstrating feasibility of a high temperature polymer electrolyte membrane fuel cell operation with natural gas reformate composition

Experimental data on the performance of a single cell PBI-based HT-PEMFC operated with a fuel composition similar to natural gas reformate and oxygen enriched cathode air are presented. A test studying the effect of CO₂, H₂O and CO in the fuel on fuel cell performance revealed that the presence of CO₂ mainly worsens mass transport, H₂O improves proton conduction and CO influences reaction kinetics as well as causing mass transport limitations. A small increase of the O₂ concentration in the oxidant provided a boost on performance. Electrical efficiency of the fuel cell was improved from 36.6% with H₂/air operation up to 38.2% with synthetic reformate gas/30% O₂ enriched air. Three 1000 h long-term tests at constant load conditions were performed. The first test showed a degradation rate of ?21.4 μV/h and was operated with H₂/30% O₂. The second test was performed with the same kind of MEA but different fuel composition (54% H₂, 15% CO₂ and 31% H₂O) and exhibited a reduction of the degradation rate to ?5.5 μV/h. The main reason for this lifetime improvement is H₂O because its transport from anode to cathode may sweep along PA that soaks catalyst active sites and limits HOR. Moreover, water in rich H₂ reformate streams also relieves formation of CO from CO₂ via RWGS. The third test was performed with a different kind of MEA (extra PTFE content in GDE) but the same fuel composition than the second one. A higher degradation rate of ?22.2 μV/h was observed but it was mainly caused by unprotected shut-downs during operation. Two preliminary long-term tests were also performed with a fuel composition similar to natural gas reformate (54% H₂, 14% CO₂, 1% CO and 31% H₂O). These latest tests revealed that the fuel cell should be operated at higher temperatures to diminish CO catalyst coverage, and that anode purge with dry gases avoids water condensation in gas pipes. In addition, CO poisoning on anode catalyst is time dependent and operation at high current densities enhances CO catalyst coverage.     

Improved performance of molten carbonate fuel cells with (Li/Na)2CO3 electrolytes by using BYS coated cathode at low operating temperatures

In order to improve the stack life time of MCFCs, it is necessary to reduce the operating temperature of MCFCs below 600 °C, because reduced operating temperature minimizes electrolyte loss due to evaporation and corrosion. However, at the low operating temperature below 600 °C, the cell performance of MCFCs with (Li/Na)₂CO₃ electrolyte is too low to operate the fuel cell stack and system. In this study, we have performed wettability control of the liquid molten carbonate electrolyte by coating NiO cathodes with poor wetting property of the mixed ionic and electronic conductor (MIEC) such as BYS (Bi_1.5Y_0.3Sm_0.3O_3-δ). From experiments with symmetrical cells, each polarization component with various temperatures and gas conditions were studied. To investigate effects of the BYS coated cathode on the performance of MCFCs, a 100 cm² single cell of MCFCs was employed. The performance of a 100 cm² single cell with BYS coated cathode was better than that with conventional cathode by a factor of 1.84, because BYS coated cathode reduces activation polarization and mass transfer resistance greatly.     

Effect of CaCO3 addition on the electrochemical generation of syngas from CO2/H2O in molten salts

A novel green method was presented for the simultaneous synthesis of syngas, a mixture of CO and H₂, via the co-electrolysis of CO₂/H₂O using an established eutectic-salt electrolyte. Optimum electrolysis was carried out at 2.2 V using a two-electrode system composed of a coiled Fe cathode and a coiled Ni anode in eutectic Li_1.07Na_0.75Ca_0.045CO₃/0.15LiOH. The molar ratio of H₂/CO was finely tuned from 1.96 to 7.97 by controlling the amount of CaCO₃. The optimized current efficiency, ～92%, was acquired by 14.28 wt% CaCO₃ addition. Moreover, the relatively low operating temperature of 600 °C was beneficial for practical applications compared to previously reported temperatures in excess of 800 °C, providing a feasible basis for syngas production via electrochemical synthesis. In this manner, CO₂/H₂O was synergistically converted into valuable chemicals, allowing the CO₂ to be utilized efficiently for the conversion and storage of electricity to chemical energy.     

Performance assessment of thermochemical CO2/H2O splitting in moving bed and fluidized bed reactors

In this paper, we present the assessment of moving bed reactors and fluidized bed reactors operating in different fluidizing regimes for solar thermochemical redox cycles (STRC) for syngas production. The reduction reactor with a moving bed (MB_RED) while the oxidation reactor (OXI) is either a moving bed reactor (MB_OXI) or bubbling bed (BB_OXI) yields higher performance. It was observed that only water splitting is suitable at 1400 °C and 10⁻³ bar reduction conditions. The higher reduction temperature and pressure improved the efficiency of the CO₂/H₂O splitting unit. The requirement of the H₂/CO ratio drives the gas feed (CO₂/H₂O) into OXI. To achieve an H₂/CO ratio of 1, MB_OXI and BB_OXI require an equimolar mixture of CO₂ and H₂O at 1600 °C. However, to achieve a similar H₂/CO ratio at a lower temperature of 1500 °C, the gas feed of the CO₂/H₂O ratio required is 3. A similar H₂/CO ratio is achieved for OXI operating in a turbulent and fast fluidizing, but the selectivity is lower due to lower reaction rates. OXI as a transport bed is least suited based on solid conversion (X_OXI), H₂/CO, or efficiency. The results are useful in designing the redox reactors for syngas.     

Investigation of the effect of graphitized carbon nanotube catalyst support for high temperature PEM fuel cells

In this study, it is aimed to investigate the graphitization effect on the performance of the multi walled carbon nanotube catalyst support for high temperature proton exchange membrane fuel cell (HT-PEMFC) application. Microwave synthesis method was selected to load Pt nanoparticles on both CNT materials. Prepared catalyst was analyzed thermal analysis (TGA), Transmission Electron Microscopy (TEM) and corrosion tests. TEM analysis proved that a distribution of Pt nanoparticles with a size range of 2.8–3.1 nm was loaded on the Pt/CNT and Pt/GCNT catalysts. Gas diffusion electrodes (GDE) were manufactured by an ultrasonic spray method with synthesized catalyst. Polybenzimidazole (PBI) membrane based Membrane Electrode Assembly (MEA) was prepared for observe the performance of the prepared catalysts. The synthesized catalysts were also tested in a HT-PEMFC environment with a 5 cm² active area at 160 °C without humidification. This study demonstrates the feasibility of using the microwave synthesis method as a fast and effective method for preparing high performance Pt/CNT and Pt/GCNT catalyst for HT-PEMFC. The HT-PEMFC performance evaluation shows current densities of 0.36 A/cm²0.30 A/cm² and 0.20 A/cm² for the MEAs prepared with Pt/GCNT, Pt/CNT and Pt/C catalysts @ 0.6 V operating voltage, respectively. AST (Accelerated Stress Test) analyzes of MEAs prepared with Pt/GCNT and Pt/CNT catalysts were also performed and compared with Pt/C catalyst. According to current density @ 0.6 V after 10,000 potential cycles, Pt/GCNT, Pt/CNT and Pt/C catalysts can retain 61%, 67% and 60% of their performance, respectively.     

Performance of a poly(2,5-benzimidazole) membrane based high temperature PEM fuel cell in the presence of carbon monoxide

The performance of a poly(2,5-benzimidazole) (ABPBI) membrane based high temperature PEM fuel cell in presence of carbon monoxide, at various temperatures is reported here. The ABPBI was synthesized by polymerization of 3,4-diaminobenzoic acid in a polymerization medium containing methanesulfonic acid (CH₃SO₃H) and phosphorous pentoxide (P₂O₅). The ABPBI membranes were characterized by fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). A maximum conductivity of 0.026 S cm⁻¹ at 180 °C was obtained for the membrane doped with 1.2 molecules of phosphoric acid (H₃PO₄) per polymer repeat unit. Fuel cell performance was evaluated using dry hydrogen/oxygen gases and was comparable with that reported in the literature. Performance of a single cell at different temperatures was studied with 0.48 and 1.0 vol.% of CO in the hydrogen fuel. The studies lead to the conclusion that CO poisoning is not a serious problem above 170 °C. Performance of the fuel cell operating at 210 °C is not at all affected by 1.0 vol.% of CO in the hydrogen feed.     

Catalytic activity of infiltrated La0.3Sr0.7Ti0.3Fe0.7O3−δ–CeO2 as a composite SOFC anode material for H2 and CO oxidation

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, La_0.3Sr_0.7Ti_0.3Fe_0.7O_3?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|La_0.8Sr_0.2MnO₃ (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.