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This work investigates the reaction characteristics of the anode and cathode by overpotential analyses in 100 cm2 class planar anode-supported SOFCs. The reactant gas addition (RA) technique was applied to analyse the overpotential, which uses the reactant gas flow rate and partial pressure as parameters due to their variation upon adding a reactant species to an electrode. The anodic overpotential was determined to be made up of mass transfer-induced overpotentials of H 2 and H 2 O species. The H 2 O species account for the majority of the anodic overpotential at the measured current range i.e., 0–150 mA cm−2. Thus, the anodic reaction is under an extreme H 2 O-induced mass-transfer resistance compared with H 2. The RA method showed that the cathodic overpotential was mainly due to a deficiency of O 2 species in the mass transfer through the gas phase rather than the solid phase. Furthermore, both cathodic and anodic overpotentials depended on gas flow rate and utilisation, indicating a significant gas-phase mass transfer effect. • Anode is the gas phase mass transfer controlling processes of H 2 and H 2 O. • Overpotential due to the water deficiency is dominant at the anode. • Cathode is the mass transfer controlling process of O 2 species at the gas phase than the solid phase. • Reactant gas addition method reveals overpotential of each reactant gas species. [ABSTRACT FROM AUTHOR]

Nd 1− x BaCo 2 O 6−δ (N 1− x BCO) is evaluated as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The effects of Nd-deficiency on the crystal structure, thermal expansion behavior, electrical conductivity and electrochemical performance are studied. N 1− x BCO oxides crystallize in the orthorhombic symmetry with Pmmm space group. A good chemical compatibility between N 1− x BCO and CGO electrolyte is found at 1100 °C in air. Introducing Nd-deficiency promotes the formation of oxygen vacancy, and significantly improves the electrochemical performance of N 1− x BCO cathodes. The lowest area specific resistance (ASR) value of 0.043 Ω cm 2 is obtained on the N 0.96 BCO cathode at 700 °C in air. The rate limiting step for electrochemical oxygen reduction reaction (ORR) is charge transfer process at the interface. The power output of the electrolyte supported cell Ni-CGO/CGO/N 0.96 BCO reaches 0.6 W cm −2 at 700 °C. [ABSTRACT FROM AUTHOR]

Different amount of metal silver particles are infiltrated into porous Sm1.8Ce0.2CuO4 (SCC) scaffold to form SCC–Ag composite cathodes. The chemical stability, microstructure evolution and electrochemical performance of the composite cathode are investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and AC impedance spectroscopy respectively. The composite cathode exhibits enhanced chemical stability. The metal Ag remains un-reacted with SCC and Ce0.9Gd0.1O1.95 (CGO) at 800 °C for 72 h. The polarization resistance of the composite cathode decreases with the addition of metal Ag. The optimum cathode SCC-Ag05 exhibits the lowest area specific resistance (ASR, 0.43 Ω cm2) at 700 °C in air. Investigation shows that metal Ag accelerates the charge transfer process in the composite cathode, and the rate limiting step for electrochemical oxygen reduction reaction (ORR) changes to oxygen dissociation and diffusion process. [ABSTRACT FROM AUTHOR]

Nd 1.93 Sr 0.07 CuO 4 nanofibers are prepared by electrospinning technique followed by a simple thermal treatment. The morphology and phase evolution of as-obtained fibers are characterized by TG-DTA, XRD, FT-IR and SEM, respectively. Typical ceramic fiber diameter is 100–200 nm, with length exceeding tens of microns. Rapid heating the nanofiber cathode at 1000 °C for 15 min results in homogeneous porous microstructure and good contact with the CGO electrolyte. EIS analysis of the nanofiber electrode gives a polarization resistance of 0.26 Ω cm 2 at 700 °C in air, two times smaller than that from the powder cathode with the same composition. The excellent electrochemical performance can be attributed to the well constructed microstructure of the fiber cathode, which can promote surface oxygen diffusion or adsorption processes on the cathode. [ABSTRACT FROM AUTHOR]

Abstract: Nd1.93Sr0.07CuO4 nanofibers are prepared by electrospinning technique followed by a simple thermal treatment. The morphology and phase evolution of as-obtained fibers are characterized by TG-DTA, XRD, FT-IR and SEM, respectively. Typical ceramic fiber diameter is 100–200 nm, with length exceeding tens of microns. Rapid heating the nanofiber cathode at 1000 °C for 15 min results in homogeneous porous microstructure and good contact with the CGO electrolyte. EIS analysis of the nanofiber electrode gives a polarization resistance of 0.26 Ω cm2 at 700 °C in air, two times smaller than that from the powder cathode with the same composition. The excellent electrochemical performance can be attributed to the well constructed microstructure of the fiber cathode, which can promote surface oxygen diffusion or adsorption processes on the cathode. [Copyright &y& Elsevier]

Abstract: We are developing a new hydrogen production process, named a hybrid thermo-chemical process, which is based on synthesis and decomposition, and electrolysis with a solid electrolyte at . In order to improve the energy efficiency, it is necessary to reduce electrolysis resistance. For refining the rate determining process of electrolysis, we performed electrolysis with YSZ solid electrolyte, and it was found that YSZ solid electrolyte resistance was small enough to be regarded as unimportant, and that electrolysis resistance was almost due to the electrode reaction, which meant the rate determining process was involved in the electrode reaction. In order to analyze this experiment, we created an analytical model. With this model , we concluded that the rate determining process was the adsorption and dissociation reaction near the three phase boundary at and the surface diffusion on the electrode at , and it was important to encourage the adsorption and dissociation reaction near the three phase boundary in order to improve electrolysis in low temperature or high pressure range. [Copyright &y& Elsevier]