Porous electrodes that conduct electrons, protons, and oxygen ions with dramatically expanded catalytic active sites can replace conventional electrodes with sluggish kinetics in protonic ceramic electrochemical cells. In this work, a strategy is utilized to promote triple conduction by facilitating proton conduction in praseodymium cobaltite perovskite through engineering non‐equivalent B‐site Ni/Co occupancy. Surface infrared spectroscopy is used to study the dehydration behavior, which proves the existence of protons in the perovskite lattice. The proton mobility and proton stability are investigated by hydrogen/deuterium (H/D) isotope exchange and temperature‐programmed desorption. It is observed that the increased nickel replacement on the B‐site has a positive impact on proton defect stability, catalytic activity, and electrochemical performance. This doping strategy is demonstrated to be a promising pathway to increase catalytic activity toward the oxygen reduction and water splitting reactions. The chosen PrNi0.7Co0.3O3−δ oxygen electrode demonstrates excellent full‐cell performance with high electrolysis current density of −1.48 A cm−2 at 1.3 V and a peak fuel‐cell power density of 0.95 W cm−2 at 600 °C and also enables lower‐temperature operations down to 350 °C, and superior long‐term durability.

a b s t r a c tThe effects of electrical contact configuration for La 2 CuO 4 sensing electrodes for a planar-based potentiometric gas sensor were studied in order to further quantify the effects of processing on sensor performance. Five configurations of La 2 CuO 4 were used for the sensing electrode. The La 2 CuO 4 sensing electrode was screen printed opposite a Pt counter electrode on a tape cast YSZ electrolyte. Three sensors were prepared for each configuration to test repeatability. Each sensor was tested at temperatures from 400 to 700• C at various concentrations of NO 2 , NO, and CO in an environment of 3% O 2 with a balance of N 2 . Results show that these sensors exhibit suitable sensitivity to all the gases tested. More importantly, it was shown that the sensitivity, selectivity/cross-sensitivity, and repeatability of these sensors are dependent on the sensing electrode configuration.

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The performance of solid-state ionic devices is often dependent on chemisorption and surface reactions. Due to the nature of these processes, they can be influenced with electric fields. The primary focus of this work was to explore the use of externally-generated (i.e., not directly biased) electric fields to modify the behavior and performance of solid-state gas sensors. This electric-field effect was displayed using a planar gas sensor, which consisted of sensing electrodes exposed to the same environment. The effect was further investigated using an air-reference sample to simultaneously monitor changes in the electrical properties of a semiconducting oxide/electrolyte couple and changes in gas composition coming off the electrode as a result of the electric field. In order to gauge effects to the semiconducting oxide alone, temperature programmed desorption (TPD) experiments were conducted. Changes in catalytic conversion, shifts in adsorption energies, and modifications to the sensor signals are discussed. IntroductionUnder normal conditions adsorbates and the atoms of a surface have individual local electric fields (1,2). The way in which these fields interact with each other can influence reaction mechanisms, and ultimately the performance, in solid-state ionic devices. This means that the performance of a device may be modified if the properties of these fields can be changed. Therefore, the primary focus of this work was to explore the use of an externally-generated electric field to modify the performance of solid-state ionic devices. Particular attention was given to the effect of an electric field on potentiometric gas sensors. Such gas sensors have shown great promise as robust, inexpensive devices for the detection of multiple gas species in combustion exhausts and in medical applications. The sensing mechanisms are summarized in the Differential Electrode Equilibria theory (3-6), which includes contributions from electrochemical reactions (mixed potential), heterogeneous catalysis, and band-bending when at least one semiconducting electrode is used. Recent results from a multifunctional sensor array have brought such devices very close to reaching commercial success (3).Several configurations were used to investigate the electric-field effect. Initially experiments involved a planar gas sensor with all sensing electrodes in the same gas environment. The next sample was air-reference based, where changes in the potential of the sensing electrode to varying analyte concentration were measured in conjunction with gas analysis of the effluent coming off this electrode. A third configuration investigated took the form of a capacitor-type chip made from the sensing electrode material (i.e., without solid electrolyte). This sample was used in temperature programmed desorption

This work involves the development of small, easily manufactured, potentiometric gas sensor arrays for continuous monitoring of pollutant (NO x , CO, HCs) concentrations. These low-power devices consist of coplanar sensing electrodes operating in the same gas environment without the need for an air-reference. The selectivity of a sensing electrode-pair is temperature dependent and may be enhanced with the use of integrated heating elements. General trends of baseline shift and sensitivity with changes in individual electrode temperatures are discussed. The results demonstrate that a gas sensor array with thermally modified sensing electrodes yields a device capable of selectively determining the concentrations of combustion byproducts. IntroductionSolid-state potentiometric gas sensors based on semiconducting metal-oxides show much promise as NO x detectors for emissions control in combustion exhausts (1). They are sensitive to ppm levels of NO x , CO, and HCs and have fast response times (1,2). However, the selectivity of these sensors is currently inadequate for commercial application (3). In fact, this is the major limitation of most solid-state gas sensors (4).One approach for improving selectivity is the use of an array with multiple sensing electrodes, each with a different selectivity. An initial calibration sequence yields a set of linear algorithms to correlate sensor responses to changes in the concentration of various gas species. The array can then be used to find the ppm levels of each species of interest. This approach was demonstrated using multiple resistance-based sensors in the same enclosure to quantitatively determine the concentrations of CO, NO, NO 2 , and O 3 in ambient air (5,6). Ideally, each sensing electrode-pair in a gas sensor array is selective toward only a single species present in the gas environment. In this case, the pattern recognition necessary to determine the gas concentrations of individual species is less complex.A well-suited material for NO x detection in combustion exhausts is La 2 CuO 4 (LCO), a p-type semiconducting metal-oxide. As with most sensing electrode materials, the sensitivity of LCO to NO and NO 2 varies with temperature. This means that thermal modification of individual electrodes in an array may result in improved selectivity. Past results demonstrate that this can be achieved with a device capable of controlling the local temperature of each sensing electrode (7). This first-generation gas sensor array allowed the individual detection of both NO and NO 2 in a single device. In this work, a second-generation device has been developed to further probe the capabilities of

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SOFCs with GDC electrolytes present challenges for stack modeling due to the variation in conductivity and chemical activity of GDC as a function of effective oxygen partial pressure P O2, which varies significantly down the channel in SOFC anodes with increasing fuel utilization. This paper presents a 3-D model for an intermediate-temperature SOFCs with GDC electrolytes, Ni/GDC anodes, and LSCF/GDC cathodes. The model uses fitted kinetics to capture, internal reforming and water-gas-shift in the anode as well as variations in open circuit voltage and activation overpotentials as a function of flow composition and temperature along the length of the channel. The model is validated against button cell data. The results show that for 600 and 650°C inlets, super-equilibrium concentrations of CH4 remain after 5 cm of channel. For the same fuel stoichiometry and cell voltage, humid H2 provides over 30% more power than reformate with more than 5% CH4.