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Although many benefits are expected by reducing the operating temperature of solid oxide fuel cells ͑SOFCs͒ with alloy interconnectors, it should be of concern that chromium oxyhydroxide vapor generated from an oxide scale (Cr 2 O 3 ), which is formed on the surface of most high temperature oxidation-resistant alloys, degrades the performance of the cathode under polarization. We have investigated a relationship between resistance against the Cr poisoning and compositions of electrode and electrolyte to show the possibility of a mitigating the Cr poisoning without reducing the chromium oxyhydroxide vapor pressure. Sr-doped LaMnO 3 ͑LSM͒ electrode on yttria-stabilized zirconia electrolyte with a current collector made of a Cr-containing alloy showed fast degradation under a polarization, which was due to the precipitation of Cr 2 O 3 at the electrode/electrolyte interface as a result of the reduction of the chromium oxyhydroxide vapor. In the present study, the degradation by the Cr poisoning has been investigated for the LSM electrode on four types of electrolytes. The degree of the degradation was found to depend on the composition of the electrolyte on which the electrode was prepared. This suggests that the electrochemical properties of the electrode/electrolyte interface influence the reduction of the chromium oxyhydroxide vapor. We have found that when La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 and Ce 0.8 Sm 0.2 O 1.9 were used as the electrode and the electrolyte, respectively, the significant Cr poisoning is not caused even in the presence of the chromium oxyhydroxide vapor at the temperature range from 923 to 1173 K.

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The electrochemical oxidation of H2 and CO in a H2‐H2O‐CO‐CO2 system at the interface of a porous Ni‐yttria stabilized zirconia (YSZ) cermet electrode and YSZ electrolyte has been studied using complex‐impedance spectroscopy and direct‐current polarization measurements of 1023 and 1273 K under a constant oxygen partial pressure. The polarization resistance increased when the CO concentration ratio. pCO/false[pH2+pCOfalse] , exceeded 0.2 and 0.5 at 1023 and 1273 K, respectively. The electrochemical oxidation rate of H2 was 1.9–2.3 times and 2.3–3.1 times higher than that of CO at 1023 and 1273 K, respectively, and the water‐gas shift reaction was found to be much faster than the electrode reaction at both temperatures. An equivalent‐circuit analysis of the complex‐impedance spectra suggested that the lower electrochemical oxidation rate of CO (compared to H2 ) was caused mainly by the larger diffusion resistance of CO than H2 on the electrode surface at 1023 K, and by both the larger surface diffusion resistance and charge‐transfer resistance at 1273 K. © 2000 The Electrochemical Society. All rights reserved.

Vasoactive intestinal peptide, a smooth-muscle relaxant neuropeptide with neurotransmitter properties, was relaxed during electrical field stimulation of guinea pig trachea. The amount released correlated with the degree of relaxation, and the release was blocked by tetrodotoxin. Prior incubation of the trachea with antiserum to vasoactive intestinal peptide reduced the relaxation. Thus vasoactive intestinal peptide may mediate the nonadrenergic relaxation of tracheal smooth muscle.

Solid oxide fuel cells (SOFCs) are promising electrochemical devices that enable the highest fuel-to-electricity conversion efficiencies under high operating temperatures. The concept of multi-stage electrochemical oxidation using SOFCs has been proposed and studied over the past several decades for further improving the electrical efficiency. However, the improvement is limited by fuel dilution downstream of the fuel flow. Therefore, evolved technologies are required to achieve considerably higher electrical efficiencies. Here we present an innovative concept for a critically-high fuel-to-electricity conversion efficiency of up to 85% based on the lower heating value (LHV), in which a high-temperature multi-stage electrochemical oxidation is combined with a proton-conducting solid electrolyte. Switching a solid electrolyte material from a conventional oxide-ion conducting material to a proton-conducting material under the high-temperature multi-stage electrochemical oxidation mechanism has proven to be highly advantageous for the electrical efficiency. The DC efficiency of 85% (LHV) corresponds to a net AC efficiency of approximately 76% (LHV), where the net AC efficiency refers to the transmission-end AC efficiency. This evolved concept will yield a considerably higher efficiency with a much smaller generation capacity than the state-of-the-art several tens-of-MW-class most advanced combined cycle (MACC).

Long-term performance testes by CRIEPI (Central Research Institute for Electric Power Industry) on six industrial stacks have revealed an interesting correlation between cathode polarization loss and ohmic loss. To make clear the physicochemical meaning of this correlation, detailed analyses were made on the conductivity degradation of YSZ electrolyte in button cells and then on the ohmic losses in the industrial cells in terms of time constants which are determined from speed of the tetragonal transformation through the Y diffusion from the cubic phase to the tetragonal phase. In some cases, shorter time constants (faster degradations) were detected than those expected from the two-time-constant (with and without NiO reduction effects) model, suggesting that additional ohmic losses after subtracting the contribution from the tetragonal transformation must be caused from other sources such as cathode-degradation inducing effects. Main cathode degradations can be ascribed to sulfur poisoning due to contamination in air in the CRIEPI test site. An important feature was extracted as this cathode degradations became more severe when the gadolinium-doped ceria (GDC) interlayers were fabricated into dense film. Plausible mechanisms for cathode degradations were proposed based on the Sr/Co depletion on surface of lanthanum strontium cobalt ferrite (LSFC) in the active area. Peculiar cathode degradations found in stacks are interpreted in term of changes in surface concentration by reactions with sulfur oxide, electrochemical side reactions for water vapor emission or Sr volatilization, and diffusion of Sr/Co from inside LSCF.