A-site of Co-doped Pt-LaMnO3 catalyst enhances NO oxidation activity

• Transition metal Co is chosen to substitute La sites of LaMnO 3 . • Co can not only replace La at A sites but also create the new phase of CoMn 2 O 4 . • CoMn 2 O 4 -LaMnO 3 interface interaction induced more oxygen vacancies as active sites for O 2 . • The appearance of Co 3+ offers new sites for NO adsorption and activation. • Simultaneous increase of oxygen vacancies and Co 3+ enhances NO oxidation activity. Perovskite oxides are always applied in the reaction of NO oxidation to NO 2 for diesel exhaust after-treatment systems. Elemental substitution is commonly used to modify the perovskites to enhance their redox properties. In this work, a series of Pt-La 1−x Co x MnO 3 was prepared with different contents of Co replacing La in LaMnO 3 . Pt-La 0.8 Co 0.2 MnO 3 exhibited outstanding NO oxidation activity at the fresh state (NO Conversion = 52.7 %) and at the aged state (NO Conversion = 44.7 %). XRD and TEM results verified partial Co doping into the lattice to replace La, while the other Co existed in the form of CoMn 2 O 4 phases. XPS, Raman, and EPR results showed that electron transformation occurring on the Co-O-Mn structure from the interface between LaMnO 3 and CoMn 2 O 4 led to more Mn 3+ , the Mn-O bonds were weakened, and oxygen vacancies increased to facilitate O 2 activation. Besides, NO-TPD and in situ DRIFTS confirmed that Co 3+ also served as NO adsorption and activation sites with the decline of Mn 4+ . The cooperative effort of increasing oxygen vacancies for O 2 and Co 3+ for NO adsorption and activation enhances the NO oxidation activity.