Alkali treatment modulated borate anions in layered double hydroxides as precursors of highly efficient Au-based catalysts for water-gas shift reaction

Abstract

Layered double hydroxides (LDHs) as an adjustable layered materials were considered as good candidates for the supports of water-gas Shift (WGS) catalysts. However, there is rare report about the exfoliation preparation and WGS application of LDHs containing BO33− as intercalated anions. Herein, we reported a mild alkali treatment modulation of the intercalated borate anions in LDHs for improving the WGS catalytic performance of Au-based catalysts. Compared with inactive Au supported LDHs without alkali treatment, the moderate alkali treatment consumes intercalated BO33− anions in LDHs, arousing the WGS activities of Au-based catalysts. Among the different alkali treatment concentration, Au-LDHs-1M treated with 1 M NaOH present the highest WGS activity and excellent stability with a reduction of only 10 % for 60 h. The moderate alkali treatment promotes the exfoliation of LDHs into nanosheets covered Co3O4 small nanoparticles, which facilitated the high dispersion of Au species and also easily converted into active Fe3O4 and metallic Co phases. While Au-LDHs-5M presents such large Au particles that it exhibits low activity, and Au-LDHs-0M is inactive due to the formation of B2O and Fe23B6 poison phases for the WGS reaction.