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

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 CeO 2 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 CeO 2 increased the specific surface area, pore diameter, and pore volume compared with pure CeO 2 (90 m 2 g -1 , 23.8 Å, and 0.110 cm 3 g -1 versus 72 m 2 g -1 , 23.0 Å, and 0.089 cm 3 g -1 ). The splitting peaks of the surface oxygen and their shifting at lower temperatures compared with CeO 2 nanorods were found thanks to the Au-CeO 2 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/NaBH 4 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.