Ab initio random structure searching and catalytic properties of copper-based nanocluster with Earth-abundant metals for the electrocatalytic CO2-to-CO conversion

Understanding the effect of nano-structuring and metal doping on the properties of copper-based clusters is crucial to developing effective catalysts for the electrochemical conversion of CO2 to value-added chemicals. We present a computational approach based on density functional and random structure searching to investigate the structures of mono- and bi-bimetallic nanoclusters, the acti-vation of CO2 on the catalyst, and the mechanism of CO2 dissociation. We have applied this approach to predict the structure and catalytic properties of Cun (n = 1–55) and (Cu-M)m (M = Fe, Sn, Zn with 1 ≤ m ≤ 27) nanoclusters. We also considered the CO2 acti-vation and conversion on the low index Cu and Cu-M (100) surfaces and high-symmetry (icosahedral) and core-shell Cu-M clusters. We found low-symmetry pure copper clusters with an amorphous character to be the most stable and have higher catalytic activity than the copper surface and high-symmetry icosahedral nanoclusters. In both pure copper and bimetallic systems, the physiosorbed state of CO2 is the most stable and energy is required to activate the molecule. Stabilization of the chemisorbed state occurs in sys-tems such as Cu-Fe where there is a delocalization of orbitals around the Fermi level, causing the large charge transfer from the cata-lyst to CO2. We have also conducted calculations of the free energy profiles of the CO2-to-CO conversion and the competitive hy-drogen evolution reaction (HER). The CO2 reduction reaction is dominant over HER on the Cu randomly generated cluster due to the lower potential limiting step. Among other considered bimetallic, the core@shell models also display good catalytic activity and selectivity towards the CO2 reduction reaction. This work identifies insightful structure-property relationships for CO2 activation, highlighting the influence of size and composition on the CO2 activation and intermediate stability in designing catalytic cupper-based mono- and bi-metallic clusters for the CO2 reduction reaction.