The selectivity consideration on Cu cluster between HER and CO2 reduction

The competition between HER and CO2RR on Cu clusters is studied by using the first-principle density functional theory (DFT) method, and the adsorption energies of the adsorbates concerned in these reactions and the energy barrier at the elementary reaction step are calculated. The obtained results show that HER is well inhibited on Cu20 cluster, since it has very weaker adsorption for H atom, while the relative stronger adsorption for H atom is observed on Cu13, Cu38 clusters and bulk Cu(1 1 1) surface. The subscript means the number of Cu atom. Moreover, the energy barriers in HER on Cu20 is especially higher than that on other Cu clusters and bulk Cu(1 1 1). Simultaneously, in the process of CO2 reduction, Cu20 cluster display a better selectivity for CO2 reduction to HCOOH than that to CO. In a word, Cu20 shows it's superiority in the selectivity in CO2RR with a stronger ability in preventing HER, and the vertex and edge Cu atoms on Cu20 cluster' surface are the potential active sites for CO2 reduction to HCOOH.