Electrochemical promotion of bulk lattice-oxygen extraction for direct methane conversion to syngas in SOFCs with Ni-YSZ anodes

A phenomenon of electrochemical promotion of lattice-oxygen extraction from the bulk phase of YSZ is observed during direct methane oxidation to generate syngas at 800 °C in solid oxide fuel cells (SOFCs) with Ni-YSZ (yttria-stabilized zirconia) anodes. Markedly higher amount of oxygen than that equivalent to the measured current is extracted for anodic oxidation. This promotion effect increases as the potential (voltage) increases. A phenomenon of “fuel-free current” is observed to be a consequence of this effect. The electrochemically promoted extraction of bulk lattice oxygen is influenced by both the operating condition and the reaction type. Both rate enhancement ratios of CO and CO2 formations are linearly related to the measured current density but inversely linearly related to the voltage. As the current density increases, both methane conversion and CO selectivity increase. Electrochemical promotion of bulk lattice-oxygen extraction enhances the syngas generation.