Promoted three-way catalytic activity of the Co3O4/TiO₂ catalyst by doping of CeO₂ under real engine operating conditions

With the aim to meet ever-increasing strict regulations for three major exhaust gas pollutants, three-way catalytic technology has been effectively applied in automobile industries for purifying automobile exhaust gases. Here we report the efficiency of composite oxide Co₃O₄/TiO₂ with the addition of CeO₂ as a promotor. Modification of Co₃O₄/TiO₂ (15 wt%. Co/TiO₂) based composite catalyst synthesized by incipient wetness impregnation (IWI) method was followed by doping of ceria (CeO₂). The series of catalysts assigned as 15% IWI, 03-CE-IWI, 06-CE-IWI, and 09-CE-IWI having cerium content from 0 to 9 wt%, respectively were prepared. The same relative Co₃O₄/TiO₂ ratio i.e., 15 wt% was sustained in the CeO₂-doped catalysts for clarifying the impact of CeO₂ and its doping quantity for CO and HC oxidation along with NOx reduction. The catalysts were characterized by Scanning Electron microscopy (SEM), X-ray Diffraction (XRD), and Brunauer–Emmett–Teller (BET). The catalysts three-way catalytic converter efficiency was assessed, mounted on a motorcycle engine with an engine capacity of 70 cm³ spark ignition. It was evaluated under steady-state operational conditions. The results revealed the strong impact of doping of CeO₂ on Co₃O₄/TiO₂ composite under real engine operating conditions and the maximum doping, i.e., 09-CE-IWI can considerably enhance the surface area (41.5 m²/g). The improved performance can be credited to a higher dispersion of Co₃O₄/TiO₂ due to CeO₂ doping, possessing a higher surface area as compared to ceria undoped catalysts, and there exists a catalytic synergistic effect of Co₃O₄ and CeO₂. The 09-CE-IWI revealed the best catalytic activity for all three constituents i.e., CO and unburned HC at 6000 rpm and NOx specifically at 2000 rpm. Maximum three-way catalytic conversion efficiencies achieved in the case of CO, HC, and NOx are 92%, 83%, and 90%, respectively.