Size‐dependent activity and selectivity of atomic‐level Cu nanoclusters during CO/CO2 electroreduction

As a favourite descriptor, the size effect of Cu-based catalysts has been regularly utilized for activity and selectivity regulation toward CO 2 /CO electroreduction reactions (CO 2 /CORR). However, little progress has been made in regulating the size of Cu nanoclusters at the atomic level. Here, 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 a creative acetylenic-bond-directed site-trapping approach. Electrocatalytic measurements show a significant size effect in both the activity and selectivity toward CO 2 /CORR. Increasing the size of Cu nanoclusters will improve catalytic activity and selectivity toward C 2+ productions in CORR. A high C 2+ conversion rate of 312 mA cm -2 with the Faradaic efficiency of 91.2% are achieved at -1.0 V vs. reversible hydrogen electrode (RHE) over Cu NCs. The presented activity/selectivity-size relations provide a clear understanding of mechanisms in the CO 2 /CORR at the atomic level .