Electrochemical Oxidation of CO/H₂ Mixtures on Ni and Ceria Pattern Anodes

Abstract

Electrochemical oxidation of dry CO/H 2 mixtures on symmetrical Ni and ceria pattern anodes on YSZ electrolyte has been examined between 700-850 o C. Dry environment was used to exclude the possible side reactions like water-gas-shift (WGS) in the case of CO and CO/H 2 mixtures. Electrochemical impedance spectroscopy (EIS) showed 2.5 times higher polarization resistance for pure CO as compared to that of pure H 2 for Ni anodes and 5 times higher in case of ceria anodes. With the addition of small quantities of H 2 in CO, the polarization resistance dropped drastically. For all considered mixtures, the size of impedance arc was closer to that of pure H 2 as compared to that of pure CO. The activation energies obtained by equivalent circuit model (ECM) fitting of impedance spectra were similar to that of pure H 2 clearly indicating that H 2 is preferentially oxidized.

Monolithic Carbon Spherogels as Freestanding Electrodes for Supercapacitors

“…At higher frequencies, a semicircle followed by a diffusion-controlled region is observed for all three samples. The semicircle commonly observed in freestanding electrode systems indicates the presence of an electrolyte layer between the current collectors and the carbon material inducing a charge transfer resistance at the collector/carbon interface. , The diffusion-controlled region (depicted by ovals on the Nyquist plot in Figure b) is characterized by a transition from a resistive (phase angle ∼ 0°) to a capacitive behavior (phase angle ∼ −90°) as the frequency of the excitation signal increases (inset of Figure a). The relaxation time for each sample can be extracted from the Bode plot (Figure c) by looking at the maximum imaginary capacitance on the frequency range tested.…”

Opportunities and Challenges in Using SOFCs in Waste to Energy Systems

“…Pattern anodes are usually chosen for studying electrochemistry due to their advantages of easily quantifiable TPB length and the simplified 2D structure. The 2D structure of patterns eliminate the structural and even the gas phase effects which exist in the cermet anodes and can help in understanding the effect of fuel contaminants on the electrochemical reactions kinetics [27,28,29,30,31]. Experiments are then carried out porous symmetric cells and complete cells with anode and cathode to study these effects further [32,33].…”