Bimetallic Catalysts Have to Demonstrate Better Price to Performance Ratio
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There are many reports on the improved catalytic activities of bimetallic particles. The “second metal” in the system not only helps to significantly increase the catalytic performance compared to monometallic counterparts (e.g. see 78-1685; 78-1688), but also improves the selectivity and stability of the catalyst.
Several methods are available for preparing bimetallic composites, such as impregnation and subsequent reduction of two metal salts, galvanic displacement, and others. However, Electroless Deposition offers advantages in the preparation of bimetallic catalysts through more targeted placement of smaller amounts of the secondary metal. Bimetallic catalysts that have been prepared using Electroless Deposition have more intimate contact between the metals than catalysts prepared using traditional wet methods. Most importantly, the secondary metal species in these new bimetallic compounds is preferentially deposited on specific sites of the primary metal, leaving other active sites available for catalysis.
The Electroless Deposition method involves reducible metals ions (e.g. Au3+, Pt4+) in the solution and “less noble” metals (e.g. Cu0 or Co0) supported on a substrate, which are responsible for the reduction of metallic ions to the metal state. As a result, a noble metal layer is formed on less noble metal particle.
Alternatively, a reducible metal salt (cation or anion) can be deposited on the catalytically active sites of a monometallic primary metal surface through a controlled chemical reaction with a liquid‐phase reducing agent.