Copper Template Design for the Synthesis of Bimetallic Copper–Rhodium Nanoshells through Galvanic Replacement

Abstract

metals proving extraordinarily successful, [2] there has recently been a concerted effort to adapt the same synthetic techniques to Rh-based nanostructures. [1a] By establishing control over the size, shape, and faceting of the catalyst and through the synthesis of Rh-based bimetallic architectures, it is proving possible to realize greater catalytic activity and selectivity, and hence, provides a more effective utilization of a finite precious resource.Exerting shape control over Rh nanostructures initially proved to be a formidable challenge due to its exceedingly high surface energy, a characteristic that made it difficult to substantially alter the order of the surface energies of the various facets through the use of capping agents. [1a,3] This synthetic challenge has now, to a large degree, been met through the ingenuity of many researchers who have demonstrated synthetic protocols able to realize well-recognized nanostructure architectures such as Rh nanocubes, [4] nanowires, [5] tetrahedrons, [6] icosahedra, [4b,7] nanoframes, [8] and nanosheets, [6,9] as well as more complex geometries offering convex and/or concave features. [3,6,10] The synthesis of Rh-based bimetallic nanostructures has also shown significant progress, but where the field is at a more nascent stage due to the much larger parameter space associated with binary systems. Bimetallic nanostructures, however, present far greater opportunities from the standpoint of tuning nanostructure properties through alloying or the heterogeneous deposition of one metal on another. [2b] The use of high melting point metals, such as Rh, have the added advantage of enhancing the shape stability of nanostructures at elevated temperatures. [11] With prominent work now appearing for the CuRh, [12] NiRh, [13] PdRh, [8a,11,14] PtRh, [10d,15] and AuRh, [8b,16] systems, it is quite evident that Rhbased bimetallic nanostructures present unique opportunities in catalysis.Galvanic replacement reactions have been widely used to synthesize hollow metal nanostructures and the mechanisms guiding these reactions have been well-documented. [17] Such reactions proceed by exposing a sacrificial metal template to ions of a second metal with a higher electrochemical potential, the result of which is the oxidation and dissolution of the template material as the metal ions are reduced onto its surface. The reaction often leads to bimetallic nanoshells caused by alloying Galvanic replacement reactions are widely used in the synthesis of bimetallic nanoshells. Essential to these syntheses is the design of template materials with electrochemical potentials that are low enough to facilitate the replacement of a wide variety of metals. While Cu is an attractive template from this standpoint, it has only rarely been used due to its propensity for oxidation and the associated difficulties in achieving chemically stable colloids. Here, a synthetic scheme is demonstrated for the design of supported Cu templates and their subsequent replacement with Rh where the detrimenta...

Nickel-Ion-Oriented Fabrication of Spiny PtCu Alloy Octahedral Nanoframes with Enhanced Electrocatalytic Performance

“…In the presence of Ni 2+ , solid Cu octahedral templates with an average edge length about 40 nm were first formed in the initial stage because of the higher reduction rate of Cu 2+ than PtCl 6 2– , which was tuned by glycine (Figure A 1 and CA 1 ). ,, The formation of Cu intermediate was characterized by XRD analysis. Because of the unstable Cu intermediate was easily oxidized under air condition, only the characteristic diffraction peak of CuO (JCPDS: 02–1040) was detected (Figure D). ,, The ICP-MS data (Figure E) also confirmed that Cu was indeed the prominent component of the solid octahedral templates (atomic ratio of Cu 93.5% and Pt 6.5%). As the reaction went on, hollow structures were gradually formed because of the replacement reaction between Cu templates and PtCl 6 2– in the aqueous. ,, Additionally, the coreduction of PtCl 6 2– (H 2 PtCl 6 ) and Cu 2+ (dissolved from solid Cu octahedron) also occurred during the replacement reaction and the resulting Pt and Cu atoms selectively deposited on the apexes whose atoms were more active than other places, leading to the growth of spiny nanothorns (Figure A 2 –A 4 and CA 2 –CA 4 ). , The emerging PtCu alloy characteristic diffraction peaks and the disappearance of CuO characteristic diffraction peak in XRD results also proved the formation of Pt composition in those intermediates during the replacement reaction (Figure D).…”

Plasmonics under Attack: Protecting Copper Nanostructures from Harsh Environments

“…Substrate-based Cu nanostructures have previously been prepared using a number of techniques including the (i) lithographic patterning of polycrystalline films, ,, (ii) dispersal and self-assembly of colloids on surfaces, ,, and (iii) solid-state dewetting of films. ,− Figure shows schematic representations of the three different schemes used to form Cu nanostructures in the current study as well as SEM images of the structures obtained. The first method relies on the solid-state dewetting of an ultrathin sputter-deposited Cu film, a technique in which a heated film breaks up into nanoscale islands that then agglomerate so as to reduce the overall surface energy (Figure a).…”

“…The first method relies on the solid-state dewetting of an ultrathin sputter-deposited Cu film, a technique in which a heated film breaks up into nanoscale islands that then agglomerate so as to reduce the overall surface energy (Figure a). The structures realized are highly crystalline with a truncated nanosphere morphology (Figure b). The second method, which yields highly faceted cuboctahedra, subjects the dewetted structures formed using the first method to a liquid-phase chemical synthesis that promotes facet growth (Figure c). , The structures obtained exhibit crisp faceting characterized by prominent {100} and {111} facets (Figure d).…”

Copper nanoparticles synthesis in hybrid mesoporous thin films: Controlling oxidation state and catalytic performance through pore chemistry

“…[3] , [4] Cu has multiple advantages: it is abundant, it can catalyze a great variety of reactions [5] and it is an inexpensive metal. [6] However, the susceptibility of Cu (0) to oxidation upon exposure to air represents a big challenge for the synthesis of metallic Cu NPs Therefore, literature on Cu NPs is rather limited compared with other metallic NPs. [7] Cu displays multiple oxidation states and usually forms two stable oxides: Cu 2 O and CuO.…”