High-resolution electron microscopy characterization of partially crystallized Fe78Si12B10 alloy as a catalyst

As a catalyst, partially crystallized Fe₇₈Si₁₂B₁₀ alloy shows a three times higher activity than totally crystallized Fe₇₈Si₁₂B₁₀ in the hydrogenation of CO. High-resolution electron microscopy (HREM) reveals that the catalyst contains a great number of minute (less than 10 nm), highly dispersed -Fe particles which act as the major active component. Many tiny B and Si oxide clusters also exist in the amorphous matrix. After being rinsed by a NaOH solution, the catalyst exhibits a decreasing selectivity to methane due to the dissolution or aggregation of B and Si species. After reaction, the sizes of the active particles increase and an overlayer of B or Si species is found over the surface of some -Fe particles. This coverage is thought to be the primary origin of the deactivation of the catalyst.