Regulating potassium state to enable the high performance of Co3O4 for catalytic oxidation

Enhancement in oxidation performance of Co3O4-based catalysts can be achieved by regulating K, and the promotion effects were strongly depended on the amount and existing state of K. Only the surface Co substituted by optimum amount of K (CoK2 with K/Co mole ratio of 1.56 × 10-2), unexpectedly high activities could be achieved. The specific activity of CoK2 were 20 and 2.7 times higher than that of Co3O4 for CO oxidation and CH4 combustion. However, the excess K in the form of carbonate or nitrate deactivated the active sites, so the performance against K amount behaved as a volcano curve. Based upon the electronic and structural modification of K, the electron density of Co and O simultaneously decreased which weakened CO adsorption strength and improved the CH bond activation. Since efficiency in various pollutants removal, CoK2 could be considered as a promising candidate for noble metal catalysts.