Reversible characterization of power generation and steam electrolysis for protonic ceramic cells with bi-layer electrolyte of BaZr0.8Yb0.2O3-δ and BaZr0.1Ce0.7Y0.1Yb0.1O3-δ

Abstract

This work presents the reversible operation between fuel cell and steam electrolysis modes in a protonic ceramic cell (PCC) with a bi-layer electrolyte structure composed of BaZr0.8Yb0.2O3-δ and BaZr0.1Ce0.7Y0.1Yb0.1O3-δ. PCC using the bi-layer electrolyte demonstrated a slightly less leakage current and an improved performance than other samples using only BaZr0.8Yb0.2O3-δ electrolyte. In the fuel cell mode, the cell exhibited the maximum power density of 0.61 W cm−2 at 600 °C. Meanwhile, in steam electrolysis mode at 600 °C, the cell showed a current density of 0.94 A cm−2 and a Faraday efficiency 46% when operating in thermoneutral voltage. However, when evaluated in steam electrolysis mode at 600 °C with a current density of 0.6 A cm−2 for 250 h, it was confirmed that the air electrode had deteriorated, causing a decrease in Faraday efficiency from 46% to 25% after 250 h of operation, indicating a degradation in the efficacy of leak current mitigation during extended operating conditions. After 250 h operating a distribution of relaxation times analysis revealed a characteristic peak at low frequencies that could be associated with variation in the ionic transference number of the electrolyte after long-term operation.