Abstract
An 8 nm-thick gadolinium-doped ceria (GDC) layer was inserted as a cathodic interlayer between the nanoscale proton-conducting yttrium-doped barium zirconate (BZY) electrolyte and the porous platinum cathode of a micro-solid oxide fuel cell (μ-SOFC), which has effectively improved the cathode reaction kinetics and rendered high cell power density. The addition of the GDC interlayer significantly reduced the cathodic activation loss and increased the peak power density of the μ-SOFC by 33% at 400 °C. The peak power density reached 445 mW/cm2 at 425 °C, which is the highest among the reported μ-SOFCs using proton-conducting electrolytes. The impressive performance was attributed to the mixed protonic and oxygen ionic conducting properties of the nano-granular GDC, and also to the high densities of grain boundaries and lattice defects in GDC interlayer that favored the oxygen incorporation and transportation during the oxygen reduction reaction (ORR) and the water evolution reaction at cathode.
Highlights
IntroductionA triple-conducting cathode provides more reaction sites for both the oxygen reduction reaction (ORR) and water evolution reaction to take place that is believed to effectively decrease the cathode polarization resistance, and the reported cell performances using such cathode material are impressive[13]
The improved cathode kinetics by the gadolinium-doped ceria (GDC) interlayer can be identified from the corresponding Bode plot of each EIS curve (Fig. 6c)
Two rate limiting steps were observed for both cells with and without GDC interlayer: the proton migration from the electrolyte to the triple phase boundary (TPB), which corresponds to the HF resistance, and the oxygen dissociative adsorption and diffusion, which is related to the MF resistance[16]
Summary
A triple-conducting cathode provides more reaction sites for both the ORR and water evolution reaction to take place that is believed to effectively decrease the cathode polarization resistance, and the reported cell performances using such cathode material are impressive[13]. To apply such concept to μ-H-SOFCs, adding an interlayer between the cathode and electrolyte, or the so-called bi-layered electrolyte, can be an effective method. The electrochemical impedance and fuel cell performance of the fabricated μ-H-SOFCs with and without the GDC interlayer were characterized to understand the effect of such cathode interlayer on the cathode kinetics behavior
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