Controllable Synthesis Of Noble Metal Nanocomposites And Their Application In Catalytic Reduction Of 4-Nitrophenol

Removal of organic pollutant from industrial waste has received great attention in the view of environmental.Among them,4-nitrophenol(4-NP)and nitroaromatic compounds are highly toxic and difficult to degrade in nature,so the treatment of wastewater containing nitroaromatic compounds is a worldwide technical problem.As a reduction product of 4-NP,4-aminophenol(4-AP)has low toxicity and easy degradation.It is also a synthetic intermediate of analgesics and antipyretics.Hence,the hydrogenation of 4-NP is of great commercial value,not only can solve the environmental problem but also can turn trash to treasure.Recently,noble metals(e.g.,Pd,Pt,Ag,and Au)have received significant attention for their remarkable catalytic properties.Meanwhile,scientists from all over the world also developed a series of catalysts with enhanced catalytic activity for 4-NP reduction.Therefore,we proposed some novel strategies to construct shape-controlled noble-based catalysts for improving their catalytic performances.In this paper,we synthesized and characterized three different noble metal nanomaterials by a simple one-pot aqueous method using poly(ethyleneimine)(PEI),5-azacytosine and linagliptin as the structure-directors and stabilizing agents.Besides,the prepared three nanocatalysts were explored for the catalytic reduction of 4-NP to 4-AP.Specific contents are follows:(1)One-pot synthesis of highly branched Pt@Ag core-shell nanoparticles as a recyclable catalyst with dramatically boosting the catalytic performance for 4-nitrophenol reductionHerein,highly branched Pt@Ag core-shell nanoparticles(Pt@Ag NPs)were fabricated by a facile one-pot wet-chemical approach,where poly(ethyleneimine)(PEI)served as structure-directing and capping agents.Their structure,morphology and composition were mainly characterized by a set of techniques.And their growth mechanism was discussed in some detail.The prepared catalyst exhibited remarkable enhancement in catalytic activity of 4-NP reduction as a proof-of-concept application,surpassing commercial Pt black and home-made Ag NPs catalysts.Also,the as-obtained catalyst showed superior stability without sacrificing the catalytic activity.These observations endow the catalyst possibility for practical applications in nitrophenols environmental remediation.(2)Controlled fabrication of well-dispersed Ag Pd nanoclusters supported on reduced graphene oxide with highly enhanced catalytic properties towards 4-nitrophenol reductionA simple one-pot coreduction method was developed for preparing well-dispersed Ag Pd alloyed nanoclusters uniform Ly dispersed on reduced graphene oxide(Ag Pd NCs/r GO)at room temperature by utilizing 5-azacytosine as the capping agent.The nanocomposites were characterized by a set of physical characterizations.The formation mechanism and catalytic mechanism were discussed in some details.Moreover,the prepared Ag Pd NCs/r GO exhibited dramatically increased catalytic properties towards the reduction of 4-NP in the presence of Na BH4 when compared to commercial Pd/C(20 wt%).(3)Solvothermal synthesis of N-doped graphene supported Pt Co nanodendrites with highly catalytic activity for 4-nitrophenol reductionA simple solvothermal method was developed to prepare N-doped reduced graphene oxide supported homogeneous Pt Co nanodendrites(Pt Co NDs/N-r GO),where ethylene glycol(EG)served as the reducing agent and the solvent,and linagliptin as the structure-directing and stabilizing agent for Pt Co NDs and dopant for r GO,respectively.Controlled researches showed that the dosage of linagliptin and the ratios of the two metal precursors were important in the current synthesis.The Pt Co NDs/N-r GO nanocomposite exhibited higher catalytic activity towards the reduction of 4-NP in contrast with the referenced Pt1Co3 NCs/N-r GO,Pt3Co1 NCs/N-r GO and commercial Pt/C catalysts.More importantly,the constructed catalyst exhibited the superior stability without sacrificing the catalytic activity,showing great prospect for the reduction of 4-NP in practice.