The newly-assisted catalytic mechanism of surface hydroxyl species performed as the promoter in syngas-to-C2 species on the Cu-based bimetallic catalysts

Abstract

In the conversion process of syngas-to-C2 species, the OH species are inevitably produced accompanying the production of key intermediates CHx (x = 1–3), traditionally, the function of surface OH species is generally accepted as the hydrogenating reactive species. This work for the first time proposed and confirmed the assisted catalytic mechanism of surface OH species that performed as the promoter for syngas-to-C2 species on Cu-based catalysts. DFT and microkinetic modeling results reveal that the produced OH species accompanying the intermediates CHx production on the MCu (M = Co, Fe, Rh) catalysts can stably exist to form OH/MCu catalysts, on which the presence of surface OH species as the promoter not only presented better activity and selectivity toward CHx (x = 1–3) compared to MCu catalysts, but also significantly suppressed CH3OH production, providing enough CHx sources to favor the production of C2 hydrocarbons and oxygenates. Correspondingly, the electronic properties analysis revealed the essential relationship between the electronic feature of OH/MCu catalysts and catalytic performance, attributing to the unique electronic micro−environment of the catalysts under the interaction of surface OH species. This new mechanism is called as OH-assisted catalytic mechanism, which may be applied in the reaction systems related to the generation of OH species.