A New Method for the Preparation of Nanostructured Metal Clusters

Abstract

Nanostructured metal clusters and colloids are of interest as catalysts for organic and inorganic reactions. as electrocatalysts in fuel cells. and as components for materials with special electronic, optical, or magnetic properties."' They are usually prepared by chemical reduction of metal salts. In order to prevent undesired agglomeration with formation of either large metal particles in the micrometer range or metal powders, stabilizers such as special ligmds,r31 polymers,[41 or tetraalkylaminonium salts[" generally need to be used. Nevertheless, high yields, simple isolation and purification. and control of the cluster size is only seldom possible.[61 Recently we described an electrochemical process by which metal foils are anodically dissolved, and the metal salts formed as intermediates are cathodically reduced with quantitative formation of metal clusters stabilized by tetraalkylammonium salts.'7. Besides the simple isolation and the high purity of the clusters, another advantage is the control of particle size (1 -10 nm) by adjusting the current density, that is, the overpotential. Tetraalkylammonium salts serve simultaneously as supporting electrolyte and stabilizer for the cluster. Though this method can be employed for relatively easily oxidizable metals (for example, Pd, Ni, Cu, Au, etc.),['. ' I for anodically less readily soluble metals like Pt, Rh. Ru, and M o it functions poorly or not at all. This is unfortunate, because precisely these metals are of interest as potential catalysts.We now report a solution to this problem based on the use of metal salts."] Initially a mixture of PtClz and (NRJBr in acetonitrile/THF (1 :3) was electrolyzed in a simple electrolysis cell["] consisting of a Pt anode and a Pt cathode. Unfortunately. only a small amount of Pt-containing material was formed, which was difficult to isolate. Because the oxidation process at the anode (for example, Br-+ Br') possibly caused problems, in a renewed attempt we used PtClz as the metal source and (NRJOAc as the supporting electrolyte and stabilizer. in the hope that the Kolbe electrolysis would ensure the chemical "disposal" at the anode (Scheme 1).

Palladium(0) Nanoparticles on Glass‐Polymer Composite Materials as Recyclable Catalysts: A Comparison Study on their Use in Batch and Continuous Flow Processes

“…Usually, catalytically active nanoparticles are prepared from a metal salt, a reducing agent, and a stabilizer and are supported on an oxide, [2] charcoal, [3] a zeolite [4] or a polymer. [5] Physical methods for preparation, such as the electrochemical route developed by Reetz, [6] are also numerous. [7,8] Currently, several diverse protocols for preparing nanoparticles are being pursued such as impregnation, [9] co-precipitation, [9,10] deposition/pre-cipitation, [11] sol-gel, [9,12] gas-phase organometallic deposition, [13] sonochemical, [14] micro-emulsion, [15] laser ablation, [16] electrochemical, [17] and cross-linking modalities.…”

Well-Dispersed Bimetallic Nanoparticles

“…Pd/Pt, Ni/Pd, Fe/Co and Fe/Ni bimetallic nanoparticles have been prepared by this method [124,125]. This preparative method has many advan-tages such as low cost, high yield, simple control of the metal content, and the possibility of continuous operation.…”

Electrochemical deposition of gold on indium zirconate (InZrOx with In/Zr atomic ratio 1.0) for high temperature automobile exhaust gas sensors

“…The mixture was subsequently degassed for several minutes before the electrolysis. The sacrificial Au anode electrolysis was later executed in the potentiostatic mode with the potential difference of 1.5 V between the working and reference electrodes [24,25]. The procedure was stopped after the accumulation of 100 C total charge.…”