Integrating isolated metal sites and sulfur vacancies in supported Ni catalysts for selective catalysis

Abstract

Site-isolated metal catalysts have been found to offer excellent selectivity for catalytic reactions; however, this is generally accompanied by a loss in activity and slow kinetics. Herein, we report an approach which integrates site-isolated Ni atoms with neighboring sulfur vacancies by utilizing the vertex vacancies and confinement effect of sulfur-containing transition metal clusters. Resulting material improves conversion and intrinsic activity for hydrodehalogenation of carbon-halogen bonds without scarifying selectivity owing to cooperative interactions. Through both experimental and computational calculations, a sulfur vacancy results in the increase of the electron density over an isolated Ni active site. The sulfur vacancy lowers the energy barriers of key meta-stable reaction steps (i.e., initial activation, fracture of C-Cl bond), while the isolated Ni species facilitate the dehalogenated product desorption. These work in synergy to give an alternative reaction pathway which yields almost exclusive hydrodehalogenation without altering any other bonds in substrates like dichloroethane.