Highly efficient multifunctional dually-substituted perovskite catalysts La1−xKxCo1−yCuyO3−δ used for soot combustion, NOx storage and simultaneous NOx-soot removal

A series of K/Cu simultaneously substituted nanometric perovskite catalysts La1−xKxCo1−yCuyO3−δ (x = 0, 0.1; y = 0, 0.05, 0.1, 0.2, 0.3) were synthesized by citric acid complexation, which were employed for soot combustion, NOx storage and simultaneous NOx-soot removal. The physico-chemical properties of the catalysts were characterized by XRD, FT-IR, EXAFS, SEM, H2-TPR, Soot-TPR, TG/DTA, XPS and in situ DRIFTS techniques. When K and Cu are simultaneously introduced into LaCoO3, soot combustion is largely accelerated, decreasing the characteristic temperature (Tm) corresponding to the maximal soot combustion rate at least 80 °C; moreover, NOx reduction by soot is also remarkably facilitated. Among all the catalysts La0.9K0.1Co0.9Cu0.1O3−δ shows the lowest Tm of 360 °C, the highest NOx storage capacity (NSC) of 284 μmol g−1 and the largest NOx reduction percentage of 32%; for soot combustion, it also exhibits the lowest activation energy (80.04 kJ mol−1). The XPS and Soot-TPR results reveal that the catalyst La0.9K0.1Co0.9Cu0.1O3−δ possesses more active and larger amount of surface oxygen species (O2− and O−), more tetravalent cobalt ions and better reducibility than others, which determines its better catalytic performance. Based on in situ DRIFTS and other characterization results, the potential mechanisms for soot combustion, NOx storage and simultaneous NOx-soot removal are proposed.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► La1−xKxCo1−yCuyO3−δ is highly efficient for soot combustion and NOx-soot removal. ► More Co4+ ions and oxygen vacancies are formed in La1−xKxCo1−yCuyO3−δ catalysts. ► Substituted La1−xKxCo1−yCuyO3−δ possesses larger amount of adsorbed oxygen species. ► Dual substitution by K/Cu obviously decreases the soot combustion activation energy. ► Reaction pathways for soot combustion and simultaneous NOx-soot removal are proposed.