Composition Optimization of Triple Conducting PrNixCo1-XO3-δ Oxygen Electrodes for Protonic Ceramic Electrochemical Cells

Abstract

Using protonic ceramic electrochemical cells (PCECs) to produce hydrogen is a promising approach to achieve the renewable energy storage, and development of critical materials is the key step to facilitate fast hydrogen production rate. Particularly, the sluggish electrode kinetic at reduced temperatures (400~600 °C) and chemical stability under realistic high steam concentration raises concern. We have recently reported a triple conducting oxide of PrNi0.5Co0.5O3-δ perovskite as an oxygen electrode in PCECs, which exhibits superior electrochemical performance in both fuel cell and electrolysis modes, and potential increased stability due to the absence of alkaline elements such as Ba and Sr in the composition. In this work, the continuous composition optimization of PrNixCo1-xO3-δ (x=0.1, 0.3, 0.5, 0.7, and 0.9) oxides is carried out to find the dependence of Ni/Co ratio on the catalytic activity towards oxygen reduction and water splitting reactions. The isotope water temperature-programmed desorption and thermogravimetric analysis is used to study the water uptake capability for understanding the proton concentration variation as function of doping level. The Fourier-transform infrared spectroscopy (FTIR) is also utilized to observe relative intensity change of the hydroxyl band on electrode surface to further explain the possible species evolution in the relevant reaction modes. This work provides a representative approach on composition optimization for oxygen electrode candidate down selection.