CeO2–MxOy (M = Fe, Co, Ni, and Cu)-Based Oxides for Direct NO Decomposition

Direct decomposition of nitrogen oxides (NOx) into N2 and O2 offers the ideal route to catalytic removal of this air pollutant that contributes to photochemical smog and acid rain. Direct decomposition of NOx is simple and economic, because no reductants are required. Despite their extensive use in automotive exhaust catalytic applications, only a few ceria-based oxides are reported in the literature for direct NO decomposition. In the present study, transition-metal-doped (Fe, Co, Ni, and Cu) ceria-based catalysts were synthesized using a co-precipitation method and examined for direct NO decomposition in the temperature region 400–650 °C. Both CeO2–Co3O4 and CeO2–NiO catalysts exhibit higher activity and N2 selectivity compared to CeO2–Fe2O3 and CeO2–CuO catalysts. Remarkably, Ce–Ni catalysts exhibit 100% selectivity toward N2 at 400 °C and more than 95% selectivity at the remaining temperatures (450, 550, and 650 °C). Structural characterization measurements (X-ray diffraction) indicate that the transi...