Hydrogenation of CO<sub>2</sub> over Cobalt‐Lanthanide Bimetallic Oxide Nanofibers
Ana C. Ferreira, Joana F. Martinho, Joaquim Branco de Oliveira
Abstract
Abstract Cobalt‐lanthanide bimetallic oxide nanofibers (5Co 3 O 4 .3LnCoO 3 , Ln=La, Pr; 4Co 3 O 4 .Ln 2 O 3 , Ln=Sm, Gd, Dy, Yb and 2Co 3 O 4 .CeO 2 ) were prepared by electrospinning technique and for the first time evaluated as catalysts for the hydrogenation of CO 2 . Depending on the lanthanide, the reaction products are different: lighter lanthanides (La, Pr, Sm and Gd) produce mainly CO and are more active to reverse water gas shift (RWGS), whereas the catalysts with Ce, Dy and Yb are more active and selective to methane. Lanthanide intrinsic properties such as ionic radii and basicity strongly correlate with the nanofibers’ catalytic performance: lower lanthanide ionic radii and higher basicity favour the catalysts activity. Moreover, the bimetallic oxide nanofibers catalytic behavior also seems to point to the existence of a synergetic interaction between cobalt and lanthanide. The cobalt‐lanthanide bimetallic oxides present a high deactivation resistance for at least 60 h in the gaseous stream, which is an advantage for any catalytic application. Compared with a commercial catalyst (5 wt.% Rh/Al 2 O 3 ) tested in the same conditions, cobalt‐ytterbium, dysprosium and cerium bimetallic oxide nanofibers present an activity 5 to 13 times higher at 350 °C.