Revealing the intrinsic nature of Ni-, Mn-, and Y-doped CeO 2 catalysts with positive, additive, and negative effects on CO oxidation using operando DRIFTS-MS.

The catalytic activity of a transition metal (host) oxide can be influenced by doping with a second cation (dopant), but the key factors dominating the activity of the doped catalyst are still controversial. Herein, CeO 2 doped with Ni, Mn, and Y catalysts prepared using aerosol pyrolysis were used to demonstrate the positive, negative, and additive effects on CO oxidation as a model reaction. Various characterization results indicated that Ni, Mn, and Y had been successfully doped into the CeO 2 lattice. The catalytic activities of each catalyst for CO conversion were in the order of Ni-CeO 2 > Mn-CeO 2 > CeO 2 > Y-CeO 2 . Operando DRIFTS-MS and various characterization methods were applied to reveal the intrinsic nature of the doping effects. The accumulation rate of the surface bidentate carbonates determined the CO oxidation. A definition to evaluate the doping effect was proposed, which is anticipated to be useful for developing a rational catalyst with a high CO oxidation activity. The CO oxidation reactivities displayed strong correlations with the surface factors obtained from operando DRIFTS-MS analysis and the structure factors from XPS and Raman analyses.