Immobilization of Nanogold on Reduced Graphene Oxide and the Catalytic Reduction of 4-Nitrophenol

In this work, reduced graphene oxide/carboxymethyl chitosan/nanogold (rGO/CMC/AuNPs) composites were synthesized using carboxymethyl chitosan (CMC) as the reducing and stabilising agent. The structures of the rGO/CMC/AuNPs composites were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM-EDS), high-resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FT-IR). The catalytic reduction of 4-nitrophenol (4-NP) by the complexes was investigated when NaBH₄ was used as the hydrogen donor. The results showed that rGO with a C/O ratio of 3.97 was obtained by using CMC with a substitution degree of 0.665 as the reducing agent. rGO/CMC/AuNPs composites showed that spherical or quasi-spherical AuNPs were uniformly distributed on the surface of rGO. rGO/CMC/AuNPs composites showed high catalytic activity for the catalytic reduction reaction of 4-NP. The average particle size of AuNPs in rGO/CMC/AuNPs composites, which prepared by CMC with a substitution degree of 0.456, was (54.7±13.3) nm. And when it was used as catalyst, the conversion of 4-NP could reach 98.1% at 30 ℃ for 30 min, the reaction rate constant could be up to 0.152 0 min^-1, and the activation energy of the reaction E_a was 31.2 kJ·mol^-1.