Enhanced catalytic reduction of 4-nitrophenol using magnetic Ni-Ag bimetal supported on reduced graphene oxide

Designing a catalyst with high activity and good recyclability for the reduction of 4-nitrophenol (4-NP) is a challenge of great significance. Herein, we report a one-step synthesis of highly effective and magnetically recyclable Ni-Ag bimetal supported on reduced graphene oxide (Ni-Ag/rGO), carried out via the co-reduction of Ag⁺, Ni²⁺, and graphene oxide (GO) using hydrazine hydrate as a reducing agent. The morphologies and structures of the prepared Ni-Ag/rGO composites were investigated using XRD, SEM, and TEM. The catalytic performance of the obtained Ni-Ag/rGO catalysts with different contents of rGO (0, 0.1, 0.5, and 1 wt%) was also studied. The results showed that the Ni-Ag/rGO catalyst with 0.5 wt% rGO exhibited higher catalytic activity, with a reaction rate constant of 0.8585 min^-1, which is 3.4 times that of the catalyst without GO. The enhanced catalytic activity of the Ni-Ag/rGO catalyst with 0.5 wt% rGO can be attributed to the improved dispersity of Ni-Ag bimetallic nanoparticles (NPs) and accelerated electron transfer between the catalyst and rGO. It is noteworthy that the Ni-Ag/rGO catalyst shows superior magnetic recyclability and stability, with maintenance of more than 90% of its catalytic activity after 10 cycles of catalysis experiments, suggesting that the Ni-Ag/rGO catalyst is a resource-saving, highly effective catalyst for reducing 4-NP.