Influence of the Rare Earth (<i>R</i>) Element in Ru‐supported <i>R</i>ScSi Electride‐like Intermetallic Catalysts for Ammonia Synthesis at Low Pressure: Insight into NH<sub>3</sub> Formation Mechanism
Charlotte Croisé, Khaled Alabd, Sophie Tencé, Etienne Gaudin, Antoine Villesuzanne, X. Courtois, Nicolas Bion, Fabien Can
Abstract
Abstract This study investigates the influence of the rare‐earth ( R ) element in Ru/ R ScSi electride‐like intermetallic catalysts for ammonia synthesis under mild conditions (300–450 °C; 1–5 bar). All materials present poor specific surface area and the grain size impacts the ammonia yield. The catalytic performances follow the La to Gd lanthanides series (Ru 1.7 /LaScSi=Ru 1.7 /CeScSi=Ru 1.7 /PrScSi>Ru 1.7 /NdScSi>Ru 1.5 /SmScSi>Ru 1.3 /GdScSi) and appear correlated with the formation of the hydride phase. Ru 1.7 /CeScSi shows remarkable catalytic activity under moderate condition (0.58 mmol NH3 /h/g at 300 °C, 1 bar) associated with its reversible hydrogen storage–release properties. It is evidenced that R ScSi materials assist the N 2 dissociation in agreement with their electride character and that the hydrogen for NH 3 formation mainly comes from gaseous hydrogen and not primarily from the hydride phase. It is suggested that NH X formation could be the rate determining step rather than the N 2 cleavage over these catalysts.