Trace doping of cobalt oxide using lanthanum for effective catalytic oxidation of carbon monoxide

Abstract

To improve the catalytic activity of Co₃O₄ for CO oxidation, we synthesized a series of Co₃O₄ catalysts (x%La-Co₃O₄) with different La doping amounts using the deposition–precipitation method and investigated their catalytic activities and water resistance. The results indicated that the trace doping of La (i.e., 1.0–3.0 atom%) significantly improved the catalytic activity of Co₃O₄ for CO oxidation. The main reason was that the doped La increased the content of Co³⁺ in Co₃O₄, which was the main active Co species for CO oxidation. In addition, doping with La improved the water resistance and catalytic stability of Co₃O₄ under wet conditions. Pure Co₃O₄ was dramatically deactivated within a short period (the CO conversion decreased by 80% in 1 h), while 2%La-Co₃O₄ maintained a CO conversion of over 75% within 15 h. The improved water resistance of 2%La-Co₃O₄ was mainly due to the reduced hydroxyl content on the Co₃O₄ surface, which increased the surface hydrophobicity of Co₃O₄. This work is expected to provide a strategy for the preparation of water-resistant and highly active Co₃O₄ catalysts for CO oxidation.