Rational synthesis of bimetallic catalysts using electroless deposition methods

This review focuses on the concepts of electroless deposition (ED) methods for preparation of true bimetallic catalysts where both metals are co-existent in the same particle in a relatively-controlled manner of preparation; individual monometallic particles are non-existent. The compositions of the bimetallic particles can be varied in a systematic manner by changing the amount and rate of second metal deposited on the base metal. For controlled, sub-monolayer coverages of the shell metal, bimetallic surfaces are formed to give possibilities of ensemble, electronic, and bi-functional effects to occur. Higher coverages of the second metal result in formation of core-shell bimetallic particles that give more efficient use of the shell metal component and electronic epitaxial effects at the core-shell interface. Adjustment of ED parameters make it possible to conduct ED over a very wide combination of metals and metal salts. Continuous ED has also been studied with adding components continuously from metering pumps or syringes throughout the experiment. Continuous ED can be extended to co-deposition of two metal salts to give ultimate control of formation of uniform, bimetallic shells that provide the possibility of surface alloys with unique properties and stability. Equally important, the versatility and simplicity of ED make it readily straightforward for scale-up and amenable for commercial applications.