Size-Dependent Activity and Selectivity of Atomic-Level Copper Nanoclusters during CO/CO₂ Electroreduction

As a favorite descriptor, the size effect of Cu-based catalysts has been regularly utilized for activity and selectivity regulation toward CO₂ /CO electroreduction reactions (CO₂ /CORR). However, little progress has been made in regulating the size of Cu nanoclusters at the atomic level. Herein, the size-gradient Cu catalysts from single atoms (SAs) to subnanometric clusters (SCs, 0.5-1 nm) to nanoclusters (NCs, 1-1.5 nm) on graphdiyne matrix are readily prepared via an acetylenic-bond-directed site-trapping approach. Electrocatalytic measurements show a significant size effect in both the activity and selectivity toward CO₂ /CORR. Increasing the size of Cu nanoclusters will improve catalytic activity and selectivity toward C₂₊ productions in CORR. A high C₂₊ conversion rate of 312 mA cm^-2 with the Faradaic efficiency of 91.2 % are achieved at -1.0 V versus reversible hydrogen electrode (RHE) over Cu NCs. The activity/selectivity-size relations provide a clear understanding of mechanisms in the CO₂ /CORR at the atomic level.