Ammonia Decomposition Catalyzed by Co Nanoparticles Encapsulated in Rare Earth Oxide.

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We fabricated Co-based catalysts by the low-temperature thermal decomposition of R-Co intermetallics (R = Y, La, or Ce) to reduce the temperature of ammonia cracking for hydrogen production. The catalysts synthesized are nanocomposites of Co/ROx with a metal-rich composition. In the Co13/LaO1.5 catalyst derived from LaCo13, Co nanoparticles of 10-30 nm size are enclosed by the LaO1.5 matrix. The nanocomposite exhibited superior catalytic activity (91% at 500 °C), which was attributed to dual advantages; the low workfunction of the supporter, O-deficient LaO1.5-x nanoparticles, promotes electron donation to the Co catalyst in the interface, which leads to enhanced N-H bond dissociation. Moreover, such a composite structure is effective in suppressing the grain growth of Co nanoparticles because the LaO1.5 layer works as a diffusion barrier against Co. The thermal decomposition of intermetallics is a new route for the facile synthesis of catalysts having an electronically active support.