Cyanogel Coordination Polymers as Precursors to Transition Metal Alloys and Intermetallics − from Traditional Heating to Microwave Processing

Cyanogel coordination polymers are amorphous Prussian blue analogues formed in a hydrogel state by the reaction of a chlorometalate with a cyanometalate in aqueous solution. At elevated temperatures, cyanogels thermally autoreduce to form transition-metal alloys. This work demonstrates the general nature of this type of sol−gel processing chemistry to prepare binary and ternary transition-metal alloys (Pd/Co, Pt/Co, Ru/Co, Ir/Co, Pd/Ni, Pt/Ni, Pt/Ru, Pd/Fe, Pd/Fe/Co) and intermetallics (Pt3Fe, Pt3Co, PtCo). Tuning of the composition of the gels and alloys by a variety of methods is demonstrated. The thermal autoreduction can be induced either by convective heating or by microwave irradiation, as microwave dielectric heating of cyanogels leads to a sufficient temperature increase in the sample to cause the reduction of the metal centers.