Co3O4-Impregnated NiO-YSZ: An Efficient Catalyst for Direct Methane Electrooxidation.

Co3O4-impregnated NiO-YSZ (yttria-stabilized zirconia) is a possible electrocatalyst for direct methane electrooxidation with both high catalytic activity and the ability to mitigate coking. The physical and electrochemical properties of Co3O4-impregnated NiO-YSZ anodes are investigated and benchmarked against NiO-YSZ and CeO2-impregnated NiO-YSZ anodes. The following methane electrooxidation activity trend: Co3O4-impregnated NiO-YSZ > CeO2-impregnated NiO-YSZ > NiO-YSZ with io (exchange current density) values of 88, 83, and 2 mA cm-2, respectively, is obtained in the high overpotential region. The high activity of Co3O4-impregnated NiO-YSZ is attributed to the changes in the electronic structure and microstructure with the incorporation of nickel into the lattice of Co3O4 as observed using X-ray photoelectron spectroscopy, temperature-programmed reduction, high-resolution transmission electron microscopy, and field emission scanning electron microscopy. Co3O4-impregnated NiO-YSZ also demonstrated the least coking during operation, confirming its utility as a methane electrooxidation catalyst.