Biogenic Pt/CaCO₃ Nanocomposite as a Robust Catalyst toward Benzene Oxidation

Fabricating the highly dispersive and stable Pt nanoparticles (NPs) on an economical and environmentally friendly support is of great concern in the field of catalysis. Herein, a waste eggshell was used as the support to prepare supported Pt catalysts through a plant-mediated biosynthesis method, in which the Pt precursor was reduced to Pt NPs by employing Cacumen platycladi (CP) leaf extract. The temperature and atmosphere for thermal treatment of such eggshell-supported Pt catalysts were assessed to understand their effects on catalytic performance toward the oxidation of benzene. The optimal Pt/eggshell-Ar (calcined at 400 °C in Ar) demonstrated that the temperature required for 90% benzene conversion (T_90%) was as low as 178 °C (80 000 mL g^-1 h^-1) and could operate steadily for at least 300 h of onstream reaction. The structure of the catalyst after reaction is much the same as that of the unreacted one. Transmission electron microscopy (TEM), thermogravimetry (TG), and X-ray photoelectron spectroscopy (XPS) results showed that Pt NPs were evenly distributed on the eggshell supports, and the calcination conditions had important influences on the residual CP leaf extract, the average Pt NPs size, and the ratio of Pt⁰/Pt²⁺ over the catalysts. Density functional theory (DFT) calculations indicated that the interactions between Pt NPs and porous CaCO₃ could promote benzene activation adsorbed onto the Pt NPs. In addition, biogenic Pt catalysts were proved to overtake the chemically reduced counterparts in the field of catalytic performance; furthermore, both biogenic and chemically reduced Pt NPs supported on the eggshell demonstrated preferable catalytic activity than that of commercial 5Pt/C (com-Pt/C) catalysts. Collectively, immobilizing biogenic noble metal active components on the eggshell-based support could be a promising approach for the preparation of supported noble metal catalysts with excellent catalytic performance toward catalytic oxidation of volatile organic compounds (VOCs).