Precise design and synthesis of Pd/InO_x@CoO_x core-shell nanofibers for the highly efficient catalytic combustion of toluene

In this work, Pd/InO_x@CoO_x core-shell nanofibers, CoO_x@Pd/InO_x core-shell nanofibers and Pd/InO_x/CoO_x nanofibers with different morphologies have been successfully synthesized for the catalytic combustion of toluene. Among them, the Pd/InO_x@CoO_x core-shell sample is novel and composed of Pd/InO_x nanotube cores, CoO_x nanocubes and CoO_x nanoparticle shells derived from ZIF-67. On the contrary, the CoO_x@Pd/InO_x core-shell catalyst is assembled by CoO_x nanocube cores and Pd/InO_x nanotube shells. Finally, the Pd/InO_x/CoO_x nanofibers as references are synthesized by a method similar to the synthesis of the CoO_x@Pd/InO_x core-shell sample. Interestingly, the Pd/InO_x@CoO_x core-shell sample displayed the best activity for toluene oxidation with T₉₀ = 253 °C, good thermal stability and good cyclic stability during three runs. Through some characterizations, it was verified that the Pd/InO_x@CoO_x core-shell sample exhibited the best performance for toluene oxidation reactions due to a larger specific surface area, higher reducibility, more abundant structural defects and oxygen vacancies, higher proportion of Pd⁰ and Co³⁺ species and higher lattice oxygen species than others. Simultaneously, the Pd/InO_x@CoO_x core-shell sample exhibited good thermal stability and cyclic stability, which might be due to the layer of the CoO_x shell to protect the stability of the Pd nanoparticle core.