Gas Diffusion Resistance Research Articles

Optimization of La0.6Sr0.4CoO3-Δ (LSC) Cathode Layer for the High Electrochemical Performance

It is important to optimize the microstructure of the cathode layer to improve the electrocatalytic activity of the solid oxide fuel cells (SOFCs). In this study, the most recent LSC cathodes with various thicknesses in the temperature range of 650-750 oC were considered. This was achieved experimentally with symmetric cells with different cathode layer thicknesses of 6 – 55 µm. Prior to that, optimization of the sintering temperature and minimization of the cathode contact resistance were carried out. The cathode thickness was confirmed by electron microscopy (SEM), and electrochemical impedance spectroscopy was performed to measure the polarization resistance. In addition, the effect of thickness on the oxygen reduction reaction process was also considered. The polarization resistance decreases until the thickness of the cathode increases to 30 μm, and starts to increase at a thickness beyond that. In addition, the main contribution of charge transfer resistance at the electrolyte/cathode interface and the remarkable effect of gas diffusion resistance with cathode thickness were also highlighted.

Enhancement of Desulfurization Capacity with Cu-Based Macro-Porous Sorbents for Hydrogen Production by Gasification of Petroleum Cokes

Macro-porous alumina was used as a support for a pellet-type Cu-based desulfurization sorbent in the gas purification process for producing blue hydrogen by the gasification of petroleum coke. The effects of the macro-porous alumina on the pellet-type sorbents in reducing the gas diffusion resistance into the pores were investigated. The results showed that the macro-porous alumina enhances the diffusion resistance, resulting in an improved sulfur capacity of CuO absorbents. Such effects were more significant on the pellet type CuO absorbents than the powder type. In addition, CO production was observed experimentally during the desulfurization reaction of carbonyl sulfide (COS) at low temperatures (~473 K). Density functional theory calculations were also performed to understand the kinetics of desulfurization and CO production. The simulation results predicted that the kinetics of desulfurization is strongly affected by the local surface environment. The CO generated from C–O bond breaking from COS had a lower adsorption energy than the CO2 formation. These results suggest that the Cu-based desulfurization sorbent has potential catalytic activity for producing CO from COS dissociation.

Deconvolution of Gas Diffusion Polarization in Ni/Gadolinium-Doped Ceria Fuel Electrodes

Electrochemical impedance spectroscopy and the subsequent impedance data analysis by the distribution of relaxation times (DRT) represent a powerful method to unfold electrochemical processes in solid oxide cells. This approach has been successfully demonstrated for electrolyte [1, 2] as well as anode-supported [3] solid oxide cells exhibiting a nickel / yttria-stabilized zirconia (Ni/YSZ) fuel electrode. Applying this methodology, all physicochemical loss processes occurring in the cells could be identified by their relaxation frequencies and subsequently quantified by means of CNLS-fitting.However, in the case of cells exhibiting a Ni/Gadolinium-doped ceria (Ni/CGO) fuel electrode, an unambiguous process assignment in the DRT has not been feasible up to now, since the charge transfer and gas diffusion overlap in the spectrum [4, 5]. The latter is caused by the oxygen non-stoichiometry of CGO, which results in a large chemical capacity, shifting the relaxation frequency of the charge transfer process towards lower relaxation frequencies. The resulting overlap of charge transfer and gas diffusion process in the spectrum impedes a direct deconvolution of these two processes [6].Facing this challenge, we here present a solution of isolating and quantifying the gas diffusion process at the fuel electrode with the help of ternary fuel mixtures exhibiting different gas diffusion coefficients. The gas diffusion coefficients of hydrogen and steam were altered by changing the inert gas component between nitrogen and helium respectively. As the two gas mixtures exhibit identical reactant and reaction product concentrations, the charge transfer polarization is not affected. The differences in polarization resistance R pol, which become visible in figure 1, are solely caused by the differences in gas diffusion polarization [2].In this contribution the detailed procedure to quantify the gas diffusion polarization and an effective gas transport parameter predicting the gas diffusion resistance for arbitrary fuel mixtures are introduced. Furthermore, the applicability of this approach for the parameterization of a zero-dimensional cell model [3] for a solid oxide cell with Ni/CGO fuel electrode will be presented.

Enhanced Gas Diffusion in Reversible Solid Oxide Cell Fabricated by Phase-Inversion Tape Casting

Electrochemical characteristics of a hydrogen-electrode-supported solid oxide cell (SOC) fabricated by phase-inversion tape casting are experimentally evaluated in both fuel cell (FC) and electrolysis cell (EC) operations. Particular focus is on the effect of the microchannels formed in the hydrogen electrode on the gas diffusion performance in the electrode. Current-voltage and impedance characteristics are measured and compared with those obtained from an SOC fabricated by conventional tape casting technique. The activation resistance is found to be almost identical between the tested cells because both cells are fabricated with a spin-coated functional layer in the hydrogen electrode. On the other hand, the concentration resistance is significantly decreased in the cell fabricated by the phase-inversion tape casting because the microchannels in the hydrogen electrode enhances the gas diffusion performance. This is more remarkable when the cells are operated in diluted fuel composition and with higher current densities. The asymmetric behavior is observed in the current-voltage characteristics of the cells, meaning that the overpotentials in the FC and EC modes are not the same at the same FC and EC currents. The overpotential is found to be always larger in EC mode, however, the extent of asymmetry is reduced in the cell fabricated by the phase-inversion tape casting. This is mainly because the microchannels in the hydrogen electrode reduces the gas diffusion resistance associated with the steam transport in EC mode. Microstructure of the fabricated cells is also analyzed in micro- and nano-scale to quantify the structure of the microchannels formed in the hydrogen-electrode. The microchannels are initiated below the immersed surface during the phase-inversion process, and then grow towards the bottom of the layer. The average diameter of the microchannels increases, whereas its number density decreases. Also, the total porosity in the phase-inversion electrode is found to be almost the same as that in the conventional cell.

A microporous polymer TFC membrane with 2-D MOF nanosheets gutter layer for efficient H2 separation

The polymeric gutter layers of current thin film composite membranes (TFCMs) suffer from high gas diffusion resistance and fast performance deterioration. We designed a TFC membrane consisting of an ultrathin 2-D MOF nanosheets gutter layer and an ultrathin selective microporous polymer top layer via interfacial polymerization for H2 separation. The 2-D MOF nanosheets gutter layer was shown to be thin and highly permeable with extremely low resistance for gas transport, thereby maximizing the gas permeance of the resulting composite membranes. The resulting TFCMs exhibited outstanding H2 permeance (8.2 × 10−7 mol m−2 s−1 Pa−1) with an ideal H2/CO2 selectivity of 12.3–12.6. In addition, the TFCMs showed excellent long-term stability due to the rigidity and integrity of the 2-D MOF nanosheets. This study is expected to provide a new approach to design high performance TFCMs for H2 separation.

(Invited) Highly Durable and Active Electrocatalysts Using SnO2 Supports for Polymer Electrolyte Fuel Cells

Toward the widespread use of polymer electrolyte fuel cells (PEFCs) in electric vehicles, highly durable and active catalysts are required. Pt catalysts loaded on high surface area carbon blacks are promising candidate catalysts with high oxygen reduction reaction (ORR) activity [1]. In the future, the improvement of the catalyst durability is also desired for PEFCs for heavy use applications. Alternative candidate catalysts with high activity and high durability, during both startup/shutdown and load cycling, are Pt catalysts supported on non-carbon ceramic supports [2,3]. Our group confirmed that Pt catalysts supported on SnO2 (Pt/M-SnO2, M = Nb, Ta) without carbon additive were superior in ORR activity and durability (startup/shutdown, load cycling) to those of commercial Pt catalysts, e.g., supported on either graphitized carbon black (Pt/GCB, TEC10EA30E, TKK) or carbon black (Pt/CB, TEC10E30E, TKK), by evaluation of membrane-electrode assemblies [4-8]. The non-carbon support of SnO2 nanoparticles has a unique carbon-like microstructure consisting of a fused-aggregate network structure, which enhances the electronically conducting pathways via the aggregated microstructure and gas diffusion pathways via the open pores in the microstructure. In addition, the interface control between Pt and SnO2 support also affects the decrease of both the overpotential for the ORR and the resistance of the cathode catalyst layer (CL). We have also proposed ways to design the three-phase boundary within the CL to diminish the gas diffusion resistance (Fig. 2). The cell performance using the Pt/SnO2 cathode CL at operating temperatures from 80oC to 120oC is quite promising for the development of high power density with simultaneous high durability. Acknowledgments This work was partially supported by funds for the “Superlative, Stable, and Scalable Performance Fuel Cell” (SPer-FC) project and the “Advanced Research Program for Energy and Environmental Technologies” from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, and JSPS KAKENHI Grant Number (B24350093, B17H03410) from the Ministry of Education, Culture, Sports, Science and Technology. References N. Ramaswamy, W. Gu, J.M. Ziegelbauer, S. Kumaraguru, J. Electrochem. Soc., 167, 064515 (2020).A. Masao, S. Noda, F. Takasaki, K. Ito, K. Sasaki, Electrochem. Solid-State Lett., 12, B119 (2009).E. Fabbri, A. Rabis, R. Kötz, T.J. Schmidt, Phys. Chem. Chem. Phys., 16, 13672 (2014).K. Kakinuma, M. Uchida, T. Kamino, H. Uchida, M. Watanabe, Electrochim. Acta, 56, 2881 (2011).Y. Senoo, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, M. Watanabe, RSC Adv., 6, 321800 (2014).Y. Chino, K. Taniguchi, Y. Senoo, K. Kakinuma, M. Watanabe, M. Uchida, J. Electrochem. Soc., 162, F736 (2015).K. Kakinuma, R. Kobayashi, A. Iiyama, M. Uchida, J. Electrochem. Soc., 165, J3083 (2018).K. Kakinuma, K. Suda, R. Kobayashi, T. Tano, C. Arata, I. Amemiya, S. Watanabe, M. Matsumoto, H. Imai,Iiyama, M. Uchida, ACS Appl. Mater. Interfaces 11, 34957 (2019). Figure 1

Bimodal-porous hollow MgO sphere embedded mixed matrix membranes for CO2 capture

We reported the use of high-performance, CO2-accelerated mixed matrix membranes (MMMs) consisting of sub-micron porous magnesium oxide (MgO) fillers and an amphiphilic polymer matrix. Bimodal-porous, hollow MgO (bh-MgO) spheres were synthesized through a one-step spray pyrolysis and precipitation method. The synthesized bh-MgO spheres were introduced into poly(vinyl chloride)-graft-poly(oxyethylene methacrylate) (PVC-g-POEM), forming MMMs for CO2/N2 separation. The amphiphilic property of PVC-g-POEM ensured an intimate contact between the bh-MgO filler and polymer matrix with the encapsulation of bh-MgO spheres. The bimodal porous and hollow structure of bh-MgO decreased the gas diffusion resistance in the membranes. Moreover, specific interactions between the surfaces of the bh-MgO and CO2 molecules enhanced the CO2 solubility and accelerate the CO2 molecules more than the N2 molecules. The dual-functional bh-MgO sphere enhanced the CO2 permeability through physical and chemical mechanisms, simultaneously. The best gas separation performance was obtained in the MMM with 10 wt% bh-MgO fillers, which demonstrated a CO2 permeability of 179.2 Barrer and 42.6 of CO2/N2 selectivity.

Multiscale model for steam enhancement effect on the carbonation of CaO particle

A multiscale model including scales at the surface, grain, and particle was developed to understand the steam enhancement mechanism on the carbonation of CaO particle. The interaction of H2O with CaO occurring at the surface scale exhibited an enhancement effect on the product layer diffusion at the grain scale, while the grain growth due to the product layer diffusion at the grain scale exhibited an important effect on the pore structure and intraparticle gas diffusion at the particle scale. The developed multiscale model was validated with the experimental data, and the effect of steam addition on carbonation performance was discussed. The effect of steam on CaO carbonation at higher temperatures (600 ~ 700 °C) was much less significant than that at lower temperatures (400 ~ 500 °C), due to the pore plugging phenomenon. In addition, the controlling step of the carbonation in the presence of steam was analyzed. Calculated results show that the external gas diffusion resistance is small enough during the reaction process. The controlling step of the carbonation at 400 °C is the chemical reaction step, while the controlling step of the carbonation at 700 °C is the intraparticle gas diffusion step.

Nickel–Ceramic Electrodes with High Nickel Content for Solid Electrolyte Electrochemical Devices

Composite powders (66 wt % NiO + 34 wt % Zr0.84Y0.16O1.92 were obtained according to the solution combustion synthesis technique by crystallization of nickel oxide particles on the surface of Zr0.84Y0.16O1.92particles. The samples pressed from powders after sintering and reduction in moist hydrogen had high electrical conductivity, more than 16 × 103 S cm–1 at room temperature. Impedance spectroscopic studies have shown that in a humid atmosphere of Ni – Zr0.84Y0.16O1.92, electrodes formed on the surface of a dense Zr0.84Y0.16O1.92 electrolyte have low electrochemical activity. The impregnation of the electrodes with a solution of cerium nitrate followed by thermolysis made it possible to increase the electrochemical activity of the electrode by two to three orders of magnitude. An analysis of the electrochemical impedance spectra through the calculation of the distribution function of the relaxation time showed that the rate of hydrogen oxidation at the electrodes is limited by surface–adsorption processes. After impregnation, the gas diffusion resistance significantly limits the electrode reaction rate.

Sonochemical synthesis of novel decorated graphene nanosheets with amine functional Cu-terephthalate MOF for hydrogen adsorption: Effect of ultrasound and graphene content

A novel graphene oxide nanosheet (GO) decorated with functional Cu-terephthalate (Cu-BDC-NH2) metal-organic framework (MOF) designed for hydrogen adsorption and storage. The composite framework was produced under low-frequency high-power ultrasound (20 kHz) waves to improve reaction time and yield. The obtained green powder was then characterized by SEM, XRD, FTIR, BET, and TGA analysis. Box-Behnken Design (BBD) was applied to optimize the reaction condition and GO content. Compared to pure MOF, our results revealed that the coupled effects of sonochemical synthesis and GO content improved both the production yield and hydrogen adsorption capacity of the composite framework. Also, it was observed that ultrasound waves improve the solvent exchange process for framework activation. Besides, the incorporation of GO enhances the chemical and thermal stability of the Cu-BDC-NH2 framework. The ultrasound wave and GO content increased the hydrogen adsorption capacity by improving the BET surface area, more active sites population and decreasing gas diffusion resistance by creating more defects.

Kinetic studies on bituminous coal char gasification using CO2 and H2O mixtures

ABSTRACTThe isothermal gasification kinetics of bituminous coal char was investigated within 1173–1373 K range. Also, the impacts of gasification temperature, gas composition, and gasification time on gasification process were analyzed. As the results of experiments suggest, there is a significant rise for the carbon conversion degree of bituminous coal char when gasification temperature and gasification time increase, but also when ratios of CO2/H2O decrease. Kinetic studies were also carried out. It is concluded that the gasification of bituminous coal char is controlled by internal chemical reaction in the early stage and diffusion in the later stage. Moreover, we studied the activation energy of various gas atmosphere and stages of gasification. Finally, our research shows that that reaction rate constant rises when the ratio of CO2/H2O rises. It is proposed that the diffusion-control step is significantly shortened with the decrease of CO2/H2O ratio. As SEM results suggest, bituminous coal char gasified in H2O atmosphere has numerous inner pores (0–10 μm). Therefore, in the process of gasification, the inner bore provides a gas channel, which reduces the gas diffusion resistance and thus shortens the diffusion control step. These results can serve as a reference to the industrialized application of the technology of coal gasification-direct reduction iron.

Novel SOFC Anodes Using Pyrochlore-Type Mixed Conducting Materials

In this study, four pyrochlore oxides such as (Gd0.9Ca0.1)2Ti2O7-δ, Gd2(Ti0.8Ru0.2)2O7-δ, (Sm0.9Ca0.1)2Ti2O7-δ, and (Y0.9Ca0.1)2Ti2O7-δ were investigated as new mixed ionic and electronic conductors for SOFC anodes. Cermets of nickel and the pyrochlores were fabricated as an anode, and current-voltage (I-V) characteristics were evaluated using yttria-stabilized zirconia and lanthanum manganite as an electrolyte and cathode, respectively. It was found that ohmic resistance and polarization resistance for the anodic reaction over some of the Ni-pyrochlore cermet anodes were smaller than those of Ni-YSZ, whereas the polarization resistance stemming from gas diffusion in the anode was significantly large over the pyrochlore anodes, leading to inferior I-V characteristics to Ni-YSZ. To improve the anode structure for better gas diffusion, pyrochlore oxides were prepared by solid-state synthesis method. The anode using these pyrochlore oxides exhibited smaller gas diffusion resistance and comparable I-V characteristics with Ni-YSZ anode.

Essential microstructure of cathode functional layers of solid oxide electrolysis cells for CO2 electrolysis

This study has demonstrated the importance of cathode functional layer of solid oxide electrolysis cells for CO2 electrolysis via comparing with that of solid oxide fuel cells and varying microstructure. Reducing inactive CO2 over cathodes dominates CO2 electrolysis performance in solid oxide electrolysis cells while H2 oxidation over Ni-based anodes has less effect on solid oxide fuel cells performance. Two supporting cathodes with different functional layer microstructure are compared. The cathode with dendritic pore structure shows higher performance than that with microchannel structure in terms of gas diffusion and polarization resistance owing to the faster gas diffusion pathway. The dendritic pore structure also prevents particle sintering during densifying electrolyte film. Therefore, the microstructure of cathode functional layer plays an essential role in CO2 electrolysis.

Gasification Kinetics of Bituminous Coal Char in the Mixture of CO2, H2O, CO, and H2

The gasification kinetics of bituminous coal char was investigated in a mixture of CO2, H2O, CO, H2, and N2 under isothermal conditions. In addition, the impacts of gasification temperature, gasification time, and gas composition on the gasification process were analyzed. As the experimental results suggest, there is a significant increase of the carbon conversion degree of bituminous coal char not just when gasification temperature and time increase, but also when H2 and CO concentration decreases. The kinetics of bituminous coal char in the gasification process was successfully modeled as a shrinking unreacted core. It is concluded that the gasification of bituminous coal char is controlled by an internal chemical reaction in the early stage and diffusion in the later stage. The activation energies of bituminous coal char gasification for different stages were studied. Moreover, it is proposed for the first time, to our knowledge, that the diffusion-control step is significantly shortened with the decrease of the CO2/H2O ratio. As scanning-electron-microscopy results suggest, bituminous coal char gasified in CO2/H2O = 1/3 atmosphere has numerous inner pores (0–5 m). Therefore, in the process of gasification, the inner pores provide a gas channel that reduces the gas diffusion resistance and thus shortens the diffusion-control step. These results can serve as a reference for industrialized application of the technology of coal gasification direct reduced iron.

Experimental and Modeling Study on the Effect of Shale Composition and Pressure on Methane Diffusivity

In this study, we present a comprehensive experimental and modeling study on six shale samples to investigate the effect of shale composition and pressure on methane diffusivity. By correlating shale composition, pressure, and methane diffusivity, it was found that both macro- and micropore diffusivity decreased with increasing pressure, while total organic carbon content had little effect on macropore diffusivity and negatively affected micropore diffusivity. This phenomenon may be a result of nonporous organic matter (OM) in transitional shale acting as solid material instead of porous media, occupying micropore volume, prolonging gas diffusion length, and increasing diffusion resistance. Clay minerals with connected microstructures positively affect micropore diffusivity while negatively affecting macropore diffusivity, which may be a result of the filling of macropores with clay particles, blocking gas diffusion pathways, and increasing gas diffusion resistance. Brittle minerals have a positive effect...

High performance anode with dendritic porous structure for low temperature solid oxide fuel cells

A dendritic porous supported microstructure simultaneously creates small pore size and broad gas diffusion pathways in a solid oxide fuel cell anode membrane. This microstructure also achieves pore sizes that reduce with increasing depth within the membrane without increasing the structure tortuosity. Such a microstructure supplies high triple phase boundary density, fast gas diffusion and low polarization resistance. Here we characterise the performance of a porous anode with such a dendritic microstructure. The solid oxide fuel cell with this high performance anode achieved 0.92 W cm−2 power density at 600 °C.

Robust Freeze-Cast Bilayer Dual-Phase Oxygen Transport Membrane Targeting Chemical Reactor Application

A bilayer Zr0.84Y0.16O1.92-La0.8Sr0.2Cr0.5Fe0.5O3-δ (YSZ-LSCrF) dual-phase membrane with a hierarchical structure is successfully prepared for membrane reactor application by the freeze-drying tape-casting method. The oxygen permeation flux of the membrane is extremely enhanced from 0.001 32 to 0.0165 mol m–2 s–1 at 950 °C under an air/CO gradient, which is attributed to the effectively decreased gas diffusion resistance in the support as well as the significantly lowered oxygen ion diffusion resistance in the functional layer. The superior oxygen permeability and stability enable the bilayer YSZ-LSCrF oxygen transport membrane to be a suitable candidate for membrane reactor applications.

Development of a technical approach to modify the internal surface of biomedical tubes and other elongated small lumen macrodevices with parylene coating

A multitude of differently composed biomedical polymers has been researched for many years for their distinctive ease of production and wide range of applications. New technologies and new material characteristics have always evolved accordingly. The lumina of biomedical polymer tubes such as catheters, intravenous tubes, and biomedical microfluidic channels do not necessarily show the required biocompatibility and desired functionality. In such cases, the products are provided with additional inner liner or coatings to achieve the desired specific properties. Specific adjustments, for example, low friction coefficient, low gas diffusion resistance, wear resistance, and hydrophobicity, are key properties which are in focus for the improvement of biomedical surfaces. In this pilot study, a technical method was developed to deposit parylene-AF4 on the inner surface of silicone tubes with aspect ratios exceeding 78:1. Uncoated and parylene-AF4-coated silicone tubes were investigated in respect to the aforementioned physical properties. Compared to the uncoated tubes, the parylene-coated tubes showed superior quality with respect to friction coefficient, gas diffusivity as well as wear resistance. It could be demonstrated that the new technical approach is suitable to parylene-coat the inner surfaces of tubes with high aspect ratios thereby achieving conformal coatings.

Mixed-matrix membranes containing nanocage-like hollow ZIF-8 polyhedral nanocrystals in graft copolymers for carbon dioxide/methane separation

Abstract Nanocage-like, hollow ZIF-8 (H-ZIF) polyhedral nanocrystals were synthesized via the use of seed crystals, epitaxial ZIF-8 growth, and excavation of ZIF-67 sacrificial templates. The highly porous and hollow structure of the H-ZIF polyhedral nanocrystals was confirmed by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction (XRD), and Brunauer-Emmett-Teller analysis. The H-ZIF nanocrystals were distributed in an amphiphilic poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) graft copolymer matrix to form mixed-matrix membranes (MMMs) for CO2/CH4 separation. The microphase-separated nature of the structure of the PVC-g-POEM was induced by the solubility difference between the hydrophobic PVC backbone and the hydrophilic POEM side chains. Specific interactions between the micro-structured PVC-g-POEM polymer matrix and the imidazole moiety of the H-ZIF enhanced the interfacial contact and improved the dispersion of the H-ZIF within the MMM; this was confirmed by XRD, FE-SEM, and differential scanning calorimetry. The hollow structure of the H-ZIF reduced the gas diffusion resistance of the MMM, resulting in increased gas permeability. Moreover, the molecular sieving properties and CO2-philic amine groups in the imidazole linkers of the H-ZIF led to high CO2 separation performance. The PVC-g-POEM/H-ZIF MMM exhibited an approximately fivefold increase in CO2 permeability, with a value of 210.6 barrer, compared to 43.5 barrer for a pristine PVC-g-POEM membrane with a CO2/CH4 selectivity of 14.3, which is close to upper bound reported by Robeson in 2008.

Electrochemical characteristics and carbon tolerance of solid oxide fuel cells with direct internal dry reforming of methane

Direct internal dry reforming is a promising way for solid oxide fuel cells (SOFCs) to directly use hydrocarbon fuels, since biogas already contains carbon dioxide and methane, which are both greenhouse gas contributing to global warming. In this paper, detailed experimental investigation and thermodynamic calculation were carried out to investigate the influence of CO2 addition on fuel cell’s electrochemical characteristics and stability using CO2 to CH4 ratio ranging from 0 to 3. The maximum power densities were obtained at CO2 to CH4 ratios of 1.5 and 1.7 for fuel gas mixture with and without N2 carrier gas, respectively. These two values are very close to thermodynamic calculation results about non-carbon limit. An analysis of distribution of relaxation time (DRT) for SOFC operated under dry reforming gas mixtures was first proposed in this study. The results show that the addition of CO2 can significantly reduce both the anode activation polarization and the fuel gas diffusion resistance at low CO2 to CH4 ratio, while the influence became weaker at higher CO2 to CH4 ratio. An additional peak, with a larger relaxation time of 10−1 ∼ 101 s, was observed with dry reforming gas mixtures. This process, related to dry reforming reaction and water-gas shift reaction, was also influenced by the addition of CO2. Besides, we observed an improvement of fuel cell performance by adding appropriate N2 carrier gas to fuel gas, which may provide a new way to enhance the performance and durability of biogas-fueled SOFC.