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

Abstract

Hydrogenation of CO₂ to ethanol is an efficient process for the utilization of CO₂ along with the production of value-added chemicals. However, CO₂ hydrogenation to ethanol is a complicated reaction, requiring the catalyst to activate CO₂ 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 TiO₂ with different crystal phase compositions (anatase, rutile, and P25), which were applied for the selective CO₂ hydrogenation to ethanol. The RhFeO_x/P25 catalyst presented a high dispersion of Rh nanoparticles on the P25 support with abundant Rh⁰–Rh^δ+–O_V–Ti³⁺ (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 H₂/D₂ exchange and C₂H₄ pulse hydrogenation experiments demonstrated that the Rh⁰–Rh^δ+–O_v–Ti³⁺ interfacial sites played a crucial role in the conversion of CO₂ to ethanol. The surface Rh⁰ sites facilitated the CO₂ activation and hydrogenation, while the Rh⁰–Rh^δ+–O_v–Ti³⁺ 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 CO₂ hydrogenation.