Galvanic Replacement Reaction: A Route to Highly Ordered Bimetallic Nanotubes

Abstract

Hollow bimetallic nanostructures are of great importance for various applications. Understanding the fundamental mechanisms occurring during the synthesis of such nanomaterials by wet chemistry remains very challenging. This Article reports a mechanistic study on the galvanic replacement reaction between planar arrays of silver nanowires grown site-specifically on tall silicon nanogratings and HAuCl 4 in lack of any stabilizing or capping agent, which might complicate and alter the conversion process of silver nanowires into silver−gold nanotubes. The direct contact of the silver nanowires with the substrate is found to modify the reaction as compared to nanowires in suspension. We show that when using diluted HAuCl 4 , AgCl nanoclusters precipitate on the surface during the process resulting in an increased surface roughness of the nanotubes. Overcoming this drawback requires saturating the HAuCl 4 solution with NaCl; this allows distributing the anodic and cathodic sites over the surface of the nano-objects in a homogeneous manner, allowing in turn obtaining nanotubes with a smooth surface. For both protocols (i.e., pure HAuCl 4 or HAuCl 4 saturated with NaCl), the conversion rate was found to increase with the concentration of HAuCl 4 in the solution. We further show that the kinetic of the reaction and the surface roughness of the nanotubes become more important when raising the temperature from 0 to 100 °C. Furthermore, we show that by using the proposed approach, one can synthesize double-walled bimetallic nanotubes.

Controlled synthesis of noble metal nanomaterials: motivation, principles, and opportunities in nanocatalysis

“…Among the different strategies that have been described for the synthesis of supported and controlled catalysts, the galvanic replacement reaction is especially attractive as it allows the formation of uniform, bimetallic and hollow nanomaterials displaying ultrathin walls in a onestep reaction, using water as the solvent, and in short reaction times (Cobley and Xia 2010, Xia et al 2013, El Mel et al 2016. These nanostructures can be easily deposited on the surface of inorganic supports (SiO2, TiO2, Al2O3, etc) by a wet-impregnation approach, leading to the formation of controlled supported nanocatalysts (Jiang 2006.…”

Large-Scale Fabrication of Porous Gold Nanowires via Laser Interference Lithography and Dealloying of Gold–Silver Nano-Alloys

“…Nowadays, tremendous efforts have been dedicated to the development of scalable and efficient fabrication approaches of nanoporous materials since they exhibit exceptional properties, allowing them to be used in a large spectrum of applications including catalysis [ 1 , 2 ], sensors [ 3 , 4 ], and actuators [ 5 , 6 ]. Several methods have been explored to create this kind of nanoscale architectures including templating [ 7 , 8 ], galvanic replacement [ 9 , 10 ], oxidation [ 11 ], and dealloying [ 12 , 13 , 14 ]. The most common technique used to fabricate nanoporous metals is dealloying; it is to remove a less noble metal from an alloy in order to leave behind a highly porous skeleton of the noble metal [ 15 , 16 , 17 ].…”

Ultrathin Wall (1 nm) and Superlong Pt Nanotubes with Enhanced Oxygen Reduction Reaction Performance

“…Hollow metallic nanostructures exhibit open constructions, possessing superior volume capacity, considerable surface‐to‐volume ratio, low density, and tunable optical properties, which seems to transcend their solid counterparts in a number of advanced applications including lithium batteries, catalysis, sensing, biomedical engineering, and many others . Hence, the multitudinous studies of their synthetic strategies based on galvanic replacement, Kirkendall effect, metal alloying then etching, or templating, have been developed to generate a range of hollow metallic architectures containing hollow spheres, cages, rings, and tubes in the past few decades. Among them, hollow Pt nanotubes are of great interest due to their unique anisotropic structure beneficial to popular catalytic reactions, such as hydrogen oxidation reaction (HOR), methanol oxidation reaction (MOR), ethanol oxidation reaction (EOR), and oxygen reduction reaction (ORR) in fuel cell devices .…”