A functional micro-solid oxide fuel cell with a 10 nm-thick freestanding electrolyte

Abstract

State-of-the-art micro-solid oxide fuel cells (micro-SOFCs) use ion-conducting ceramic electrolytes with thicknesses in the tens to hundreds of nanometers scale, which enabled a drastic decrease in operating temperature without a decrease in cell performance. Here, we present a self-supporting ceramic electrolyte membrane with only 10 nm thickness as a potential platform for the in situ study of nanoionics under fuel cell operating conditions. The challenge lies in the handling of the fragile membrane during the cell fabrication and during the cell operation. The mechanical strength of the ceramic electrolyte membrane was improved by configuring the membrane as a bi-layer structure, where both layers are the same materials with a few nanometers thickness. The bi-layer structure generated the difference in electrolyte microstructures and further reduced the grain sizes of the electrolyte. The cell showed a high open-circuit voltage of 1.05 V and was stable for the entire 14 hours of measurement time, which proved the functionality of the extremely thin electrolyte for micro-SOFCs.