Facile and fast synthesis of a reduced graphene oxide/carbon nanotube/iron/silver hybrid and its enhanced performance in catalytic reduction of 4-nitrophenol

A facile, eco-friendly approach is proposed for fast preparation of a partially reduced graphene oxide/carbon nanotube/iron/silver hybrid (rGO/CNT/Fe/Ag) under ambient conditions. The partial reduction and exfoliation of GO, the ultrafast growth of CNT on the rGO surface, and the formation of AgNPs occurred simultaneously within 10-30 s using a domestic microwave oven. The morphology and structure of the rGO/CNT/Fe/Ag hybrid are discussed in detail, and a possible formation mechanism is proposed. The obtained rGO/CNT/Fe/Ag hybrid exhibited high catalytic activity for reduction of 4-nitrophenol (4-NP) by NaBH4 with a kinetic rate constant of 14.66 x 10(-3) s(-1), a normalized rate constant of 1884.31 s(-1 )x g(-1) and a turnover frequency of 33.6h(-1) due to the synergistic effect of all consisting components in the hybrid. With a high surface area, GO serves as a good substrate for immobilization of more AgNPs, whereas rGO/CNT with a high electrical conductivity promoted the electron transfer in the reduction of 4-NP. AgNPs were the catalytic active sites for the reduction of 4-NP, whereas the presence of FeNPs and Fe3C facilitate for recovering and recycling the catalyst easily. Moreover, the rGO/CNT/Fe/Ag hybrid maintained high catalytic activity and stability after five cycles and easy reusability by an external magnet.