Ag Dendrite-Based Au/Ag Bimetallic Nanostructures with Strongly Enhanced Catalytic Activity

Abstract

Dendritic Ag/Au bimetallic nanostructures have been synthesized via a galvanic replacement reaction (GRR) of Ag dendrites in a chlorauric acid (HAuCl4) solution. After short periods of time, one obtains structures with protruding flakes; these will mature into very porous structures with little Ag left over. The morphological, compositional, and crystal structural changes involved with reaction time t were analyzed by using scanning and transmission electron microscopy (SEM and TEM, respectively), energy-dispersive X-ray spectrometry (EDX), and X-ray diffraction. High-resolution TEM combined with EDX and selected area electron diffraction confirmed the replacement of Ag with Au. A proposed formation mechanism of the original Ag dendrites developing pores while growing Au flakes cover this underlying structure at longer reaction times is confirmed by exploiting surface-enhanced Raman scattering (SERS). Catalytic reduction of 4-nitrophenol (4-NP) by sodium borohydride (NaBH4) is strongly enhanced, implying promising applications in catalysis.

Insight into the fabrication and perspective of dendritic Ag nanostructures

“…Dendritic Ag NPs have hierarchical branches and leaves as shown in Figure 1. It stands out among other nanostructures due to its large surface area and its unique interfacial structure towards adding substrate or metals, which bring its amazing application in surface-enhanced Raman scattering (SERS) [19,20], surface-enhanced fluorescence [21], super-hydrophobic [22][23][24], antibacterial [25,26], chemical sensors [27,28] and catalysis [29][30][31].…”

In Situ Synthesis of Bimetallic Hybrid Nanocatalysts on a Paper-Structured Matrix for Catalytic Applications

“…In recent years, there has been a growing interest in bimetallic hybrid NPs, since their chemical and physical properties are different from those for both the bulk metals and their monometallic NP counterparts [15][16][17][18][19][20]. Toshima et al have reported that core-shell bimetallic NPs exhibit a higher catalytic activity than the monometallic counterparts because the catalytic activity of the shell atoms can be electronically influenced by the core atoms [21][22][23][24][25].…”

Reduction of 4‐Nitrophenol as a Model Reaction for Nanocatalysis

“…Th e catalytic activity of Pd and Pd-M alloy NPs decreased in the order Pd > Pd-Cu ≈ Pd-Ni > Pd-Ag ≈ Pd-Au > Pd-Pt. Th is result is extraordinary since most of the bimetallic catalysts had an enhanced catalytic activity as compared to the monometallic catalysts reported so far [8,67,102,126].…”

“…Instead, the enhanced rate of the nanowires is due to the abundance of grain boundaries. [3,[8][9][10]126] Zeng et al [9] presented the occasional case of synthesis using the titration of Ag nanocubes with chloroauric acid (HAuCl 4 ) in an aqueous solution under refl ux to produce three diff erent types of Au-based hollow nanostructures. Th ese were nanocages (the most porous morphology with the thinnest walls), nanoboxes and partially hollow nanoboxes.…”

“…Replacing the outer Au shell with a thin Pd shell further increases the catalytic activity (orange) simply because Pd is more catalytically active than Au [82]. Huang et al synthesized Au-Ag [126] and Pd-Ag [8] bimetallic dendrites using Ag dendrite-based galvanic replacement (Figure 13.22). Th ey obtained diff erent morphologies, compositions, and crystal structures by varying the reaction times.…”