One-Step Synthesis of a High Entropy Oxide-Supported Rhodium Catalyst for Highly Selective CO Production in CO2 Hydrogenation.

Abstract

High entropy oxide (HEO) has shown to be a new type of catalyst support with tunable composition-function properties for many chemical reactions. However, the preparation of a metal nanoparticle catalyst supported on a metal oxide support is time-consuming and takes multiple complicated steps. Herein, we used a one-step glycine-nitrate-based combustion method to synthesize highly dispersed rhodium nanoparticles on a high surface area HEO. This catalyst showed high selectivity to produce CO in CO2 hydrogenation with 80% higher activity compared to rhodium nanoparticle-based catalysts. We also studied the effect of different metal elements in HEO and demonstrated that high CO selectivity was achieved if one of the metals in the metal oxide support favored CO production. We identified that copper and zinc were responsible for the observed high CO selectivity due to their low *CO binding strength. During hydrogenation, a strong metal-support interaction was created through charge transfer and formed an encapsulated structure between rhodium nanoparticles and the HEO support to lower the *CO binding strength, which enabled high CO selectivity in the reaction. By combining different metal oxides into HEO as a catalyst support, high activity and high selectivity can be achieved at the same time in the CO2 hydrogenation reaction.