Mechanism of Catalytic CO 2 Hydrogenation to Methane and Methanol Using a Bimetallic Cu 3 Pd Cluster at a Zirconia Support.

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 CO 2 methanation reaction on the oxidized bimetallic Cu 3 Pd tetramer (Cu 3 PdO 2 ) supported on a zirconia model support represented by Zr 12 O 24 based on the energy profile obtained from density functional theory calculations on the reaction of CO 2 and H 2 . In order to determine the role of the Pd atom, the performance of Cu 3 PdO 2 with monometallic Cu 4 O 2 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 Cu 4 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.