Green synthesis of Pt–Au dendrimer-like nanoparticles supported on polydopamine-functionalized graphene and their high performance toward 4- nitrophenol reduction

[Display omitted] •A green route is demonstrated to synthesize PtAu dendrimer-like alloys on PDA/RGO.•The hybrid shows enhanced catalytic activity and stability for reduction of 4-NP.•The effects of support material and chemical composition are studied.•Pt3Au1-PDA/RGO exhibits superior efficiency for water purification. A facile, environmentally friendly route is demonstrated for the synthesis of Pt–Au dendrimer-like nanoparticles on the surface of polydopamine (PDA)-wrapped reduced graphene oxide (RGO), in which Pt–Au alloy nanoparticles are synthesized by the reduction of H2PtCl6 and HAuCl4 with ascorbic acid. The effects of support material and chemical composition on the catalytic activity for the reduction of 4-nitrophenol (4-NP) are investigated in detail. Pt nanoparticles supported on PDA/RGO (Pt-PDA/RGO) exhibit significantly higher catalytic activity as compared to those exhibited by Pt nanoparticles deposited on pristine graphene sheets (Pt-RGO) and commercial Pt/C catalyst. Furthermore, the chemical composition seriously affects the catalytic ability of the catalysts. With Pt-to-Au molar ratios of 3/1 and 1/1, significantly enhanced catalytic activities are observed, outperforming the support decorated with each single constituent. The high activity of Pt-Au-PDA/RGO can be explained by electronic effect involving in two types of electron transfers: (1) from the PDA coating to both Au and Pt atoms; (2) from Au to Pt atoms. Moreover, the Pt3Au1-PDA/RGO composite keeps a stable conversion efficiency of around 100% over six successive reduction reaction cycles. Through an experimental device of “filtering and catalyzing,” the Pt3Au1- PDA/RGO sample exhibits superior efficiency for the purification of water containing 4-NP. Within 8s, the water becomes colorless.