Support morphology and crystal plane effect of Cu/CeO2 nanomaterial on the physicochemical and catalytic properties for carbonate hydrogenation

Abstract

The present work determined the morphology and crystal plane effects of nanoceria on the activity of Cu/CeO₂ catalysts in the gas/solid-phase hydrogenation of CO₂-derived diethyl carbonate (DEC) to methanol. The effect of the terminating crystalline planes of CeO₂ ({100}, {110}, and {111}) on the behaviour of copper species dispersed over CeO₂ nanocubes, nanorods and nanoparticles was examined in detail using a variety of characterization techniques. HRTEM studies revealed that CeO₂ nanorods were mainly enclosed by {100} and {110} planes, nanoparticles exhibited only {111} surfaces, and nanocubes predominantly displayed {100} planes. Cu/CeO₂ nanorods (Cu/Ce-NR) possessed higher Cu⁺/Cu⁰ ratios and more oxygen vacancies than Cu/CeO₂ nanoparticles (Cu/Ce-NP) and Cu/CeO₂ nanocubes (Cu/Ce-NC), which indicated that there was a stronger interaction between Cu and CeO₂ nanorods. A test of activity in the hydrogenation of DEC showed that Cu/Ce-NR was more active than Cu/Ce-NP and Cu/Ce-NC, which could be attributed to the higher value of S_Cu⁰, surface oxygen mobility and Cu⁺/Cu⁰ ratio. These results confirm that the activity of Cu/CeO₂ catalysts for the hydrogenation of DEC is greatly affected by the shape/crystal planes of CeO₂.