Beyond single-atom catalysts: Exploration of Cu dimer and trimer for CO2 reduction to methane

We extend the single-atom catalysts (SACs) concept to metal-dimer and trimer catalysts anchored on graphene and explore their characteristic performance in catalyzing CO2RR into methane using first-principles calculations. In designing the catalyst, we first identify highly energetically stable Cu dimer and trimer atomic configurations in graphene host and then compute the Gibbs free energy changes in the reaction pathway from carbon dioxide to methane. Remarkably, compared to Cu SAC, the limiting potential is 0.60 V for the Cu-trimer and 1.22 V for Cu-dimer, which is lower than 1.82 V for SAC. The Cu dimer is suggested to be the optimal choice because it demonstrates reasonably high activity to CO2RR and high selectivity against HER than SAC. The methodology study suggested that the adsorption term plays the key role in the whole CO2RR process. The present work points out a new strategy for designing high-performance catalysts beyond single atoms for CO2RR. [Display omitted] •We extend the SACs concept to metal-dimer and trimer catalysts and explore their characteristic performance in catalyzing CO2RR into methane.•Compared to Cu SAC, the limiting potential is 0.60 V for the Cu-trimer and 1.22 V for Cu-dimer, which is lower than 1.82 V for SAC.•The Cu dimer is suggested to be the optimal choice because it demonstrates reasonably high activity to CO2RR and high selectivity against HER than SAC.