(265f) Control of Surface Reactivity Towards Unsaturated C-C Bonds and H over Ni-Based Intermetallic Compounds in Semi-Hydrogenation of Acetylene

Olefin production and functionalization are critical for many building block chemicals in industry, however, these reactions suffer from selectivity issues due to lack of control of activation towards unsaturated C–C bonds over noble metals. Intermetallic compounds composed of transition metals and semimetals or post-transition metals have been shown to exhibit elevated selectivity in olefins and aromatics production and other reactions that require specific degree control of C=C activation and functionalization. The vast number of element combinations available for intermetallic compound production necessitates down-selecting to isolate catalytically useful compositional spaces. Therefore, it is critical to investigate how to control surface reactivity towards unsaturated C-C bonds and H by selecting constituent elements and manipulating bulk and surface composition. In this study, we investigated the semi-hydrogenation of acetylene over isoelectronic IMCs composed of nickel and the boron group elements at a bulk stoichiometry of 1:1 via DFT calculation.

It was found that orbital overlap between IMC constituent elements tracks well with the nature of their bulk bonding and surface reactivity towards C and H, which also translated to catalytic activity preference for each material. Results suggested that changes of surface chemistry of IMCs is related with the nature of electronic structure, which transforms from moderately hybridized (NiB) to highly hybridized (NiAl and NiGa) and back to moderately hybridized (NiIn and NiTl) as a function of the Ni-p-element orbital overlap. Changes in IMC bulk bonding also produce a full spectrum of surface chemical traits that would be characterized as electronic and ensemble-like depending on the contribution of the surface p-elements to the observed surface chemistry. New BEP correlations are also evident over the Ni+B-group IMCs that exhibit strong electronic effects and pronounced p-element contributions to the surface chemistry. The trends isolated appear to be universal and mark a subspace within intermetallic compounds that is promising for other reactions such as dehydrogenation, selective hydrogenation of unsaturated aldehyde, and reforming.