Effect of Alkali Metal Addition to a Ru/CeO₂ Catalyst Prepared by NaBH₄ Reduction on the Catalytic Performance for H₂ Production via NH₃ Decomposition

Abstract

The Ru/CeO 2 (JRC-CEO-3) catalyst prepared by NaBH 4 reduction showed a high activity for NH 3 decomposition compared with the other catalysts prepared in this work; however, this catalyst gradually lost its activity due to the accumulation of adsorbed species produced during the reaction. Cs signi cantly improved the catalytic performance of the Ru/CeO 2 catalyst, and the optimum Cs/Ru molar ratio was 0.4 because excess Cs species gradually covered the exposed Ru metal active sites. Cs-Ru/CeO 2 -0.4 catalyzed the NH 3 decomposition reaction without H 2 pretreatment because the catalyst was activated by NH 3 or H 2 produced by NH 3 decomposition. Moreover, Cs not only increased the N-H bond dissociation rate but also decreased the e ect of the H 2 partial pressure on the catalytic performance. Consequently, the Cs-Ru/CeO 2 -0.4 catalyst exhibited a high, stable activity (NH 3 conversion: 92% at 623 K and 60% at 573 K) with a gas hourly space velocity of 2000 mL-NH 3 g-cat 1 h 1 .