Mechanism of Catalytic CO2 Hydrogenation to Methane and Methanol Using a Bimetallic Cu3Pd Cluster at a Zirconia Support.

Abstract

For very small nanocluster-based catalysts, the exploration of the influence of the particle size, composition, and support offers precisely variable parameters in a wide material search space to control catalysts' performance. We present the mechanism of the CO2 methanation reaction on the oxidized bimetallic Cu3Pd tetramer (Cu3PdO2) supported on a zirconia model support represented by Zr12O24 based on the energy profile obtained from density functional theory calculations on the reaction of CO2 and H2. In order to determine the role of the Pd atom, the performance of Cu3PdO2 with monometallic Cu4O2 at the same support has been compared. Parallel to methane formation, the alternative path of methanol formation at this catalyst has also been investigated. The results show that the exchange of a single atom in Cu4 with a single Pd atom improves catalyst/s performance via lowering the barriers associated with hydrogen dissociation steps that occur on the Pd atom. The above-mentioned results suggest that the doping strategy at the level of single atoms can offer a precise control knob for designing new catalysts with desired performance.