Construction of Active Rh–TiO_x Interfacial Sites on RhFeO_x/P25 for Highly Efficient Hydrogenation of CO₂ to Ethanol

Abstract

Hydrogenation of CO 2 to ethanol is an efficient process for the utilization of CO 2 along with the production of valueadded chemicals. However, CO 2 hydrogenation to ethanol is a complicated reaction, requiring the catalyst to activate CO 2 efficiently and accurately regulate the C−C coupling to achieve a high ethanol selectivity simultaneously. Herein, we report the synthesis of RhFeO x catalysts supported on TiO 2 with different crystal phase compositions (anatase, rutile, and P25), which were applied for the selective CO 2 hydrogenation to ethanol. The RhFeO x /P25 catalyst presented a high dispersion of Rh nanoparticles on the P25 support with abundant Rh 0 −Rh δ+ −O V −Ti 3+ (O V : oxygen vacancy) interfacial sites over the anatase/rutile junction. The optimized RhFeO x /P25 catalyst exhibited a high ethanol space−time yield of 18.7 mmol g cat −1 h −1 and a high Rh turnover frequency of 544.8 h −1 with 90.5% ethanol selectivity. An in-depth investigation via various ex situ and in situ characterizations as well as H 2 /D 2 exchange and C 2 H 4 pulse hydrogenation experiments demonstrated that the Rh 0 −Rh δ+ −O v −Ti 3+ interfacial sites played a crucial role in the conversion of CO 2 to ethanol. The surface Rh 0 sites facilitated the CO 2 activation and hydrogenation, while the Rh 0 −Rh δ+ −O v −Ti 3+ interfacial sites boosted the C−C coupling to produce ethanol. The high-performance RhFeO x /P25 catalyst also provides an attractive route for highly efficient ethanol synthesis via CO 2 hydrogenation. KEYWORDS: selective hydrogenation of CO 2 , ethanol, Rh 0 −Rh δ+ −O v −Ti 3+ interfacial sites, C−C coupling, anatase/rutile junction