Accelerated oxygen reduction kinetics in BaCo0.4Fe0.4Zr0.2O3-δ cathode via doping with a trace amount of tungsten for protonic ceramic fuel cells

Abstract

Protonic ceramic fuel cells (PCFCs), which are based on proton conducting electrolytes, are a class of power generation devices that can efficiently operate at the intermediate (500–700 °C), even low (450 °C) temperatures, but their development is hindered by sluggish cathodic kinetics at reduced temperatures. At the PCFC cathode, the absorbed oxygen molecules react with oxygen vacancies, protons and electrons to generate water and release electrical energy. Thus, the PCFC cathode materials require percolation network for proton, oxide-ion, and electron carriers simultaneously. In this work, we developed a triple ionic-electronic conductor BaCo0.4Fe0.4Zr0.15W0.05O3-δ as a new cathode material for the PCFCs using BaZr0.1Ce0.7Y0.1Yb0.1O3-δ as the electrolyte. Anode supported cells were fabricated and the performances were investigated. Compared with the parent oxide, tungsten doping can significantly improve the electrochemical reduction kinetic of oxygen. The BaCo0.4Fe0.4Zr0.15W0.05O3-δ based PCFC obtained the peak power density of 688 mW ⋅ cm−2 at 600 °C, which is 1.29 time higher than that of BaCo0.4Fe0.4Zr0.2O3-δ based PCFC (the peak power density of 534 mW ⋅ cm−2 at 600 °C). Moreover, BaCo0.4Fe0.4Zr0.15W0.05O3-δ has a better thermal expansion matching with the electrolyte material BaZr0.1Ce0.7Y0.1Yb0.1O3-δ.