Comparative study of multi-element modification and rhodium promotion of Co3O4-based spinel catalysts for N2O decomposition

The removal of nitrous oxide (N 2 O) from industrial flue gases remains a significant environmental challenge due to the intrinsic kinetic stability of the N 2 O molecule. Among available abatement technologies, the direct catalytic decomposition of N 2 O into harmless N 2 and O 2 (deN 2 O) represents a promising, reagent-free solution. In this study, we systematically screened a series of catalysts obtained from Co 3 O 4 by addition of transition elements, magnesium and aluminum (10 wt%), and analog series with addition of rhodium (Rh; 1 wt%), from which Co-Al-Rh emerged as the most active catalyst formulation. Characterization by H 2 -TPR and XPS indicated improvement in the redox performance and increasing weakening of the Co-O bond upon addition of a second element and of Rh. The addition of Rh resulted also in a significant enhancement in catalytic activity. Complementary kinetic studies revealed a shift in the rate-determining step (RDS) between N-O bond cleavage and O 2 desorption, depending on catalyst composition. These results highlight the critical role of Co-O bond weakening in facilitating oxygen mobility and promoting activity. • Co 3 O 4 -based spinel catalysts were synthesized and doped with Rh by impregnation. • Structural analysis (XRD, Raman, STEM-EDX) confirmed Rh incorporation into the spinel lattice. • Co-Al-Rh catalyst achieved full N 2 O conversion at 250 °C. • Raman, XPS, and H 2 -TPR showed enhanced reducibility and Rh-induced Co–O bond weakening. • N 2 O dissociation was found as RDS for Co 3 O 4 -M, while O 2 desorption was RDS after Rh addition. • A Mars-van Krevelen mechanism involving Rh-Co redox interplay is proposed.