Effects of extrinsic defects originating from the interfacial reaction of CeO2-x-nickel silicate on catalytic performance in methane dry reforming

Abstract

Dry reforming of methane is a promising process to convert two greenhouse gases into syngas. Calcinated nickel silicate nanotubes (C-NSNT) as well as CeO2-x interface-confined and nickel silicate nanotubes (NSNT)-derived Ni catalysts, which are marked as λCeO2-x-NSNT (λ = 0.5, 1, 1.5 and 2.25), is prepared and evaluated in dry reforming of methane. Compared with C-NSNT, the λCeO2-x-NSNT samples exhibit improved catalytic performance in dry reforming of methane, which is closely related to Ni-CeSiO2-x interface along with extrinsic defects from the interfacial reaction between CeO2 and NSNT during the reduction process. Extrinsic defects can generate oxygen vacancies that can be accompanied by Ce3+ species. The enhancement of catalytic activity is ascribed to confined effects of extrinsic defects at contact interface of Ni-CeSiO2-x and electronic effects of CeO2-x. Furthermore, Ni-CeSiO2-x interface with rich extrinsic defects can promote the adsorption and activation of CO2 as electron donor on reduced λCeO2-x-NSNT catalysts, which is fast dissociated into CO* and O*. Meanwhile, oxygen vacancies can transfer adsorbed O* species to Ni active sites to promote the carbon gasification reaction, which is responsible for the enhancement of catalytic stability in methane dry reforming for λCeO2-x-NSNT catalysts. 1.5CeO2-x-NSNT sample with more extrinsic defects has particular higher catalytic stability due to the improvement of anti-coking.