Novel Ag2S nanoparticles on reduced graphene oxide sheets as a super-efficient catalyst for the reduction of 4-nitrophenol

Here, Ag₂S nanoparticles on reduced graphene oxide (Ag₂S NPs/RGO) nanocomposites with relatively good distribution are synthesized for the first time by conversing Ag NPs/RGO to Ag₂S NPs/RGO via a facile hydrothermal sulfurization method. As an noval catalyst for the reduction of 4-nitrophenol (4-NP), it only takes 5 min for Ag₂S NPs/RGO to reduce 98% of 4-NP, and the rate constant of the composites is almost 13 times higher than that of Ag NPs/RGO composites. The high catalytic activity of Ag₂S NPs/RGO can be attributed to the following three reasons:(1) Like metal complex catalysts, the Ag₂S NPs is also rich with metal center Ag(δ⁺), with pendant base S(δ^-) close to it, and thus the Ag and basic S function as the electron-acceptor and proton-acceptor centers, respectively, which facilitates the catalyst reaction; (2) RGO features the high adsorption ability toward 4-NP which provides a high concentration of 4-NP near the Ag₂S NPs; and (3) electron transfer from RGO to Ag₂S NPs, facilitating the uptake of electrons by 4-NP molecules.