Shape-controlled and undercoordinated site-abundant Ru nanocrystals for low-temperature and additive-free benzene semi-hydrogenation

Abstract

Shape manipulation of Ru nanocrystals (NCs) may afford the prominent enhancement in the catalytic performances and a well-defined catalytic model for mechanistic investigation in benzene semi-hydrogenation (BSH) by remolding the surface-atom arrangements. Herein, the Ru NCs with tailored shapes including irregular assemblies (IASs), nanospheres (NSPs), ultrathin triangle nanoplates (TNPs), and ultrathin irregular nanoplates (INPs) were fabricated, which were recognized to determine both the types and numbers of active sites. Ru IASs exposed few undercoordinated (unc) sites including atomic edges, vertexes, and defects as well as few coordinately saturated (csa) sites such as atomic terraces, while Ru NSPs primarily exposed csa sites, and Ru TNPs and Ru INPs exposed dominant and increased unc sites. Such difference contributed to a decreased order of turnover frequency (TOF) of benzene in Ru IASs > Ru INPs > Ru TNPs > Ru NSPs but an increased sequence of cyclohexene selectivity in Ru IASs < Ru NSPs < Ru TNPs < Ru INPs via manipulating the coordination configuration of benzene and so the net formation rate of cyclohexene. The initial selectivity toward cyclohexene (S0) attained to 90.6% on Ru INPs exposed most unc sites under green conditions, evidencing its high catalytic efficiency in BSH.