Distinctive morphology effects of porous-spherical/yolk-shell/hollow Pd-nitrogen-doped-carbon spheres catalyst for catalytic reduction of 4-nitrophenol.

Pd-nitrogen-doped-carbon nanocatalysts (Pd-C/N) with different morphologies, such as porous spheres, yolk-shell and hollow structures, had been synthesized and compared. The yolk-shell Pd-nitrogen-doped-carbon nanocatalysts (YS-Pd-C/N) and hollow Pd-nitrogen-doped-carbon nanocatalysts (H-Pd-C/N) were prepared through different etch time using SiO2 spheres as hard-templates. The as-prepared catalysts were characterized thoroughly by TEM, BET, XRD, FT-IR, and XPS. Importantly, the catalysts have moderate BET specific surface area in the range from 200 to 300m2g-1 and pore volume between 0.2 and 0.3cm3g-1. The reduction of 4-nitrophenol is chosen as a model reaction to research the morphology effects of these prepared Pd-C/N catalysts with the same chemical compositions. Interestingly, H-Pd-C/N exhibited the best catalytic performance, which could be attributed to its high nitrogen content, the uniform distribution of abundant active sites, as well as the synergistic effect of graphitic C/N shell and Pd species for the catalytic reaction. Especially, the unique hollow morphology and porous shell of H-Pd-C/N made it to be a nanoreactor, which was beneficial to improve the catalytic activities. In addition, H-Pd-C/N nanocatalysts exhibited favorable stability in the recycling reactions.