High-efficiency reduction of p-nitrophenol on green-synthesized gold nanoparticles decorated on ceria nanorods

Abstract

A green synthesis using extract from Citrus maxima peel was developed to fabricate Au–Ce catalysts for the reduction of p-nitrophenol (PNP). Au nanoparticles with a diameter of 6.6 ± 2.5 nm were deposited onto the surface of CeO₂ nanorods with a length of 33.1 ± 15.0 nm and a diameter of 7.1 ± 2.1 nm. The mesoporous and non-porous capillary structures of these materials were observed. The interaction between Au and CeO₂ increased the specific surface area, pore diameter, and pore volume compared with pure CeO₂ (90 m² g⁻¹, 23.8 Å, and 0.110 cm³ g⁻¹ versus 72 m² g⁻¹, 23.0 Å, and 0.089 cm³ g⁻¹). The splitting peaks of the surface oxygen and their shifting at lower temperatures compared with CeO₂ nanorods were found thanks to the Au–CeO₂ interaction, suggesting that their reduction occurred more easily. The synthesized Au–Ce catalysts exhibited excellent activity in the reduction of PNP to p-aminophenol. The 0.2Au–Ce catalyst was the most efficient one for PNP reduction, enabling the conversion of PNP in 30 minutes with a catalyst concentration of 20 mg L⁻¹ and a PNP/NaBH₄ molar ratio of 1/200. Moreover, the 0.2Au–Ce catalyst could be reused for at least five consecutive cycles without considerable loss of its activity.