Galvanic hydrogen pumping performance of copper electrodes fabricated by electroless plating on a BaZr0.9-xCexY0.1O3-δ proton-conducting ceramic membrane

Abstract

Fuel electrodes on proton-conducting ceramics, such as BaZr0.9-xCexY0.1O3-δ (BZCY), must be stable at high temperatures in reducing and hydrocarbon-containing gases. This work investigated thin Cu-based electrodes (~1 μm) deposited by electroless plating on tubular substrates composed of a dense BZCY film (~25 μm) on a porous Ni-BZCY support. Ru, Pd, and Cu were studied as activation catalysts and the performance of those electrodes (Ru/Cu, Pd/Cu, and Cu/Cu) was evaluated during the galvanic hydrogen pumping at 700 °C in reducing and hydrocarbon-containing feeds. The hydrogen flux was measured with a stoichiometric titration experiment and the highest flux (3.1 NmL·cm−2·min−1) was obtained with Ru/Cu at 400 mA·cm−2. The metric to compare the electrodes was the power required to pump 1 NmL H2·min−1 at 40 mA·cm−2. Those numbers for Ru/Cu, Pd/Cu, and Cu/Cu electrodes in a 10% H2 in Ar feed were 34, 22, and 268 mW/(NmL H2·min−1). Due to the order of magnitude higher power requirement for the pure Cu electrode, only the Ru/Cu and Pd/Cu electrodes were investigated further and their performance was found to deteriorate in the presence of a predominantly methane-feed. The post mortem microstructural analysis showed that the Ru/Cu and Pd/Cu electrodes did reorganize significantly under bias and coke formation was only observed on the BZCY membrane.