Metal-Support Interactions on Ag/Co3O4 Nanowire Monolithic Catalysts Promoting Catalytic Soot Combustion

Tuning metal-support interactions (MSIs) is an important strategy in heterogeneous catalysis to realize the desirable metal dispersion and redox ability of metal catalysts. Herein, we use pre-reduced Co3O4 nanowires (Co-NWs) in situ grown on monolithic Ni foam substrates to support Ag catalysts (Ag/Co-NW-R) for soot combustion. The macroporous structure of Ni foam with crossed Co3O4 nanowires remarkably increases the soot-catalyst contact efficiency. Our characterization results demonstrate that Ag species exist as Ag-0 because of the equation Ag+ + Co2+ = Ag-0 + Co3+, and the pre-reduction treatment enhances interactions between Ag and Co3O4. The number of active oxygen species on the Ag-loaded catalysts is approximately twice that on the supports, demonstrating the significant role of Ag sites in generating active oxygen species. Additionally, the strengthened MSI on Ag/Co-NW-R further improves this number by increasing metal dispersion and the intrinsic activity determined by the turnover frequency of these oxygen species for soot oxidation compared with the catalyst without pre-reduction of Co-NW (Ag/Co-NW). In addition to high activity, Ag/Co-NW-R exhibits high catalytic stability and water resistance. The strategy used in this work might be applicable in related catalytic systems.

Automated summary

Tuning metal-support interactions is a crucial strategy in heterogeneous catalysis to achieve desirable performance of metal catalysts. In this study, pre-reduced Co3O4 nanowires supported Ag catalysts were used for efficient soot combustion. The results revealed enhanced interactions between Ag and Co3O4 due to pre-reduction treatment, resulting in increased active oxygen species on the Ag-loaded catalysts. Furthermore, strengthening the metal-support interactions improved metal dispersion and intrinsic activity, leading to higher catalytic performance and stability of the catalyst.