Recent advances in the catalytic properties of metastable materials

New catalysts and electrocatalysts which are amorphous alloys themselves or prepared from amorphous and other metastable alloys are reviewed in this paper. The most important characteristic of metastable materials including amorphous and nanocrystalline alloys from the chemical point of view is the homogeneous single phase nature consisting of a variety of elements, whose concentrations sometimes exceed the solubility limits at equilibrium. For the enhancement of the activity various treatments are carried out before catalytic reaction, such as oxidation-reduction and selective dissolution of alloy constituents. For example, after immersion in HF, amorphous Cu-Zr alloys show higher activity than amorphous Cu-Ti alloys for dehydrogenation of 2-propanol and hydration of acrylonitrile. This is due to dissolution of smaller amounts of titanium from Cu-Ti alloys than dissolution of zirconium from Cu-Zr alloys in HF, since the corrosion resistance of titanium in HF is higher than zirconium. The catalysts prepared from some amorphous nickel alloys are most effective for methanation of CO2 at atmospheric pressure. Amorphous nickel-refractory metal alloys are the best cathode materials for electrolytic hydrogen evolution. The catalyst for CO2 methanation and the electrode for electrolytic hydrogen evolution are used for building a CO2 recycling plant to avoid global warming and to supply abundant energy. (C) 1997 Elsevier Science S.A.