Au nanoparticles decorated on activated coke via a facile preparation for efficient catalytic reduction of nitrophenols and azo dyes

Activated coke (AC) exhibits excellent properties with a graphite-like layer crystallite structure and possesses mesopore and macropore structures, which can reduce the influence of internal diffusion on the general rate of adsorption and catalytic process greatly. In this work, AC was served as a support for gold nanoparticles (Au NPs) anchoring to prepare Au/AC catalysts via a facile synthesis using ascorbic acid as a mild reducing agent. The morphology and structure of catalysts were characterized by XRD, TEM, FTIR, and XPS analysis. Our experiment results showed that the abundant functional groups on the surface of AC play a vital role in the immobilization of Au NPs. Au/AC was employed as a highly efficient catalyst with a rate constant of 0.1916 s(-1) for the reduction of 4-nitrophenols by NaBH4. Au/AC was also tested for the catalytic reduction of other nitrophenols (2-nitrophenol and 2,4-dinitrophenol) and azo dyes (congo red, methyl orange and erichrome black T), demonstrating that Au/AC exhibited superior catalytic efficiency compared with other Au NPs catalysts. The catalysts showed good reusability, with conversion of 84% in the reduction of 4-NP in 20 s after six cycles. The Au/AC with high TOF has potential to be a workable and efficient catalyst in industrial applications. Present study not only provides a facile preparation route of catalysts using AC as a promising support, but also sheds light on the understanding of mechanism of the synergistic effect between Au NPs and AC towards the reduction of nitrophenols.