Synthesis and characterisation of a ceria-based cobalt-zinc anode nanocomposite for low-temperature solid oxide fuel cells (LT-SOFCs)

Abstract

One important factor limiting the development of solid oxide fuel cell is its high operational temperature (700–750 °C), significantly hindering its commercialization. Here, for the first time, it is reported that nanocrystalline Co1-x-Znx-Gd0.1Ce0.9O1.95 (x = 0.50, and 0.65) anode powders can provide a practical solution toward Ni-free low temperature SOFCs (LT-SOFCs; 450–550 °C) by illustrating strikingly high redox capabilities at temperatures below 400 °C. An anode-electrolyte bilayer with tailored electrical conductivity is fabricated by co-sintering a Gd0.1Ce0.9O1.95 disc (as support) and the synthesized Co1-x-Znx-Gd0.1Ce0.9O1.95 anode powder. During co-sintering, the tunable internal Zn supply from the anode composite to the electrolyte support significantly decreases the densification temperature of the GDC electrolyte support (down to 1100–1200 °C), while promoting the cell efficiency (∼ 7%) by drastically reducing the electron conductivity through the GDC electrolyte layer (open circuit voltage ∼ 0.91 V at 650 °C). The electrolyte layer shows excellent compatibility with the anode electrode, leading to possible long term thermal cyclability to room temperature. Fuel cell characterizations over a broad range of operating conditions estimate activation energies of 0.49, 0.48, and 0.63 eV for the three identified anodic processes. Zinc can increase the cell power-density by about five times compared to Co-based anode composites.