Abstract
<jats:p> Intermetallic catalysts offer a unique platform for the hydrogenation reaction of acetylene, as their well-defined crystal structures and precise stoichiometry enable atomic-level control over active-site composition, geometry, and electronic structure. In ternary intermetallics, the addition of a third element in varying amounts can alter the crystal structure, thereby changing the stable crystal facet(s) and, consequently, the active-site electronic structure, demonstrating an intriguing strategy to boost product selectivity. The site-specific substitution of Sn in NiIn <jats:sub>1-</jats:sub> <jats:italic toggle="yes"> <jats:sub>x</jats:sub> </jats:italic> Sn <jats:italic toggle="yes"> <jats:sub>x</jats:sub> </jats:italic> ( <jats:italic toggle="yes">x</jats:italic> =0.5, 0.8) exhibits two distinct phases belonging to hexagonal ( <jats:italic toggle="yes">x</jats:italic> =0.5) and orthorhombic ( <jats:italic toggle="yes">x</jats:italic> =0.8) crystal systems. Density Functional Theory calculations show that (0001) and (010) facets of hexagonal and orthorhombic phases, respectively, are the most stable. Catalytic performance for the acetylene hydrogenation reaction confirms that the hexagonal NiIn <jats:sub>0.5</jats:sub> Sn <jats:sub>0.5</jats:sub> is more catalytically active and selective towards ethylene than the orthorhombic NiIn <jats:sub>0.2</jats:sub> Sn <jats:sub>0.8</jats:sub> . The Nudged Elastic Band calculations reveal a significant difference in the kinetics of the conversion reactions, making the hexagonal phase more selective than the orthorhombic phase. Thus, this study combines both experimental and theoretical approaches to understand the superior catalytic performance of the hexagonal phase over the orthorhombic phase, which mainly originates from differences in the atomic arrangement of the most stable surface, which significantly influences the reaction kinetics of acetylene hydrogenation. </jats:p>