Carburization induced phase transition of Ni3In to Ni3InC0.5 intermetallic carbide for acetylene semihydrogenation

Abstract

In this work, we develop a carburization strategy to transform hexagonal Ni₃In into face-centered cubic Ni₃InC_0.5 intermetallic carbide, leveraging partially isolated Ni sites for improved acetylene semihydrogenation. The catalyst synthesized via carburization of Ni₃In intermetallic compound derived from Ni/In/Mg/Al layered double hydroxides in a C₂H₂/H₂ atmosphere is evidenced to show Ni₃InC_0.5 intermetallic carbide phase through detailed characterizations, including high-resolution transmission electron microscopy and X-ray absorption spectroscopy. Catalytic tests reveal that the Ni₃InC_0.5 catalyst achieves 92.0% ethylene selectivity at full acetylene conversion, outperforming the Ni and Ni₃In catalysts. Both experimental and theoretical evidence demonstrate that interstitial carbon atoms in Ni₃InC_0.5 synergize with neighboring In atoms to modify the electronic structure of surface Ni sites via significant hybridization between Ni 3d, In 5p, and C 2p orbitals. These unique features enable higher kinetic favorability of ethylene desorption over its further hydrogenation on the Ni₃InC_0.5 catalyst and thus contribute to the enhanced semihydrogenation.