Insight into the Improvement Effect of Nitrogen Dopant in Ag/Co3O4 Nanocubes for Soot Oxidation: Experimental and Theoretical Studies

Different doping amounts of N-doped Ag/Co 3 O 4 nanocubes were synthesized for the first time for catalytic soot oxidation. The N-doped sample exhibited remarkably improved catalytic activity, of which the maximum decrease in temperature for 90% soot conversion was almost 40 ℃. Characterization results analyzed by TEM, XPS, EPR, H 2 -TPR, O 2 -TPD, etc. revealed that the incorporation of N atoms can alter the electronic structure, leading to the generation of more oxygen vacancies and enhancement of lattice oxygen mobility. Meanwhile, larger surface area, rugged morphology and promoted reducibility also contribute to the performance improvement. DFT calculations on the differential charge density, Gibbs free energy, etc. were performed to investigate the intrinsic reasons on an atomic level. Due to the relatively higher electronegativity, N dopant could be an electron-appealing center to promote efficient electron transfer, resulting in the redistribution of charge density and formation of conductive Co–N bonds. This variation in electronic structure favors lowering the formation energy of oxygen vacancies and facilitating the activation of the lattice oxygen originated from the highly hybridized Co–O bonds, which ultimately reduces the activation barriers for reactants/intermediates and accelerates the reaction kinetics. This study evidenced that N doping could be an effective strategy to promote catalytic soot oxidation. • Different N-doped Ag/Co 3 O 4 nanocubes were synthesized for catalytic soot oxidation. • Improved catalytic activity with a decrease in T 90 of almost 40 °C was achieved. • N doping can generate more oxygen vacancies and enhance lattice oxygen mobility. • N dopant can be an electron-appealing center to promote efficient electron transfer. • Activation of lattice oxygen from the highly hybridized Co–O bonds was facilitated.