Platinum nanoparticle-assembled porous biogenic silica 3D hybrid structures with outstanding 4-nitrophenol degradation performance

Abstract Pt/biogenic SiO2 hybrid structures were fabricated by assembling Pt nanoparticles over biogenic porous silica particles from three different sources. Apart from analyzing their morphology, composition and microstructure, the catalytic activity of the nanocomposites have been tested for the degradation of 4-nitrophenol, which is one of the most frequent contaminants in waste water emanation from pharmaceutical and textile industries. The Pt/SiO2 hybrid structures derived from Equisetum myriohaetum (EM) porous silica revealed a complete reduction of 4-NP (to 4-AP) within 90 s at room temperature, and within 20 s at 70 °C. The catalytic activity and apparent kinetic rate constants (kapp, 111 × 10−3 s−1 at 70 °C) of the Pt/SiO2 catalyst were found to be much superior to the corresponding parameters of Ag or Au nanoparticles supported over silica and other common semiconducting supports. The high turnover capacity of the porous silica supported catalyst (7.59 min−1 at 70 °C) could be associated to the presence of ample active sites in densely assembled Pt particles over 3D silica surface, which facilitates the electron transfer process from Pt particles to adsorbed 4-NP molecules. Excellent reusability (only 3% decrease after 8 cycles) of the hybrid catalyst for the purification of 4-NP polluted water in “filtering and catalyzing” device has been demonstrated.