Controllable Synthesis Micro/Nanostructures Based On Au, Ag And Their Catalytic Performances

Recently, with the development of investigation in the field of noble metal, catalysts based on Au, Ag, Pt, Pd, have attracted broad interests bacause of their unique catalytic performances, and they are widely extended to various fields.1. Synthesis and investigation of graphene oxide-induced dendritic gold nanostructuresNoble metal nanocrystals (NMNCs) of a unique morphology yet a well–defined uniform facet have attracted broad interests, wherein those with a highly branched architecture have gained particular attention. Most of the currently existing highly branched NMNCs, however, are enclosed by mixed facets. We now report that Au nanodendrites could be facilely fabricated by mixing an aqueous solution of KAuCl4, an aqueous dispersion of graphene oxide, and ethanol under ambient conditions. Interestingly, unilike the conventional highly branched NMNCs, our Au nanodendrites are predominately enriched with a uniform facet of {111}. In comparison to the spherical Au nanostructures exposed with mixed facets, our nanodendrites of a uniform facet display superior catalytic performances not only towards the catalytic reduction of4–nitrophenol but also towards the electrocatalytic oxidation of methanol. Our investigation represents the first example that Au nanostructures simultaneously featured with a highly branched architecture and a uniform crystal facet could be formulated. Our Au nanodendrites provide a fundamental yet new scientific forum to disclose the correlation between the surface atomic arrangement and the catalytic performances of highly branched NMNCs.2. Synthesis of graphene oxide-induced gold nanosheeets and their phased catalytic performancesIn the presence of graphene oxide, gold nanosheets could be simplely synthesized by mixing an aqueous solution of KAuCl4and ethanol under ambient conditions. Interestingly, the gold nanosheets display a two stage catalytic performance towards the catalytic reduction of4–nitrophenol. We suggest that the formation of reduced graphene oxide could further improve catalytic properties. Graphene oxide plays a crucial role in the synthesis and catalytic processes:the interactions between oxygen functionalities and Au3+cations would lead to a localized enrichment of Au3+cations around these oxy–functional groups; in the catalytic process, the formation of reduced graphene oxide futher improved catalytic performances.3. Silver Iodide Microstructures of a Uniform Tower Like Shape: Morphology Purification via a Chemical Dissolution, Simultaneously Boosted Catalytic Durability and Enhanced Catalytic PerformancesThe fabrication of micro/nanostructures of a uniform yet well defined morphology has attracted broad interests from a variety of fields of advanced functional materials, especially catalysts. Most of the conventional methods generally suffer from harsh synthesis conditions, requirement of bulky apparatus, or incapability of scalable production, etc. To meet these formidable challenges, it is strongly desired to develop a facile, cost effective, scalable method to fulfill a morphology purification. By a precipitation reaction between AgNO3and KI, we report that irregular AgI structures, or their mixture with tower like AgI architectures could be fabricated. Compared to the former, the mixed structures exhibit enhanced catalytic reactivity towards the photodegradation of methyl orange pollutant. Its catalytic durability, which is one of the most crucial criterions that required by superior catalysts, however, is poor. We further show that the irregular structures could be facilely removed from the mixture via a KI assisted chemical dissolution, producing AgI of a uniform tower like morphology. Excitingly, after such simple morphology purification, our tower like AgI displays not only a boosted catalytic durability but also an enhanced catalytic reactivity. Our chemical dissolution based morphology purification protocol might be extended to other systems, wherein high quality advanced functional materials of desired properties might be developed.