Enhancement of Alkyne Semi-Hydrogenation Selectivity by Electronic Modification of Platinum

We demonstrate that atomically thin Pt shells deposited on transition metal carbide or nitride cores induce up to a 4-fold enhancement in C2H4 selectivity during the partial hydrogenation of acetylene compared with commercial carbon-supported Pt (Pt-comm) nanoparticles. While Pt typically catalyzes the complete hydrogenation of alkynes to alkanes, a catalyst comprising a nominal one monolayer (ML) Pt shell on titanium tungsten nitride cores (Pt/TiWN) is capable of net C2H4 generation under industrial front-end reaction conditions featuring a large excess of C2H4 and H-2. Microcalorimetry measurements are consistent with a change in the Pt electronic structure that decreases C2H4 binding strength, thus increasing partial hydrogenation selectivity. Density functional theory (DFT) calculations and X-ray absorption near edge structure (XANES) both indicate broadening of the Pt d-band and concomitant down-shifting of the d-band center. The ability to control shell coverage and core composition opens up extensive opportunities to modulate the electronic and catalytic properties of noble metal-based catalysts.