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 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. 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 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 versus reversible hydrogen electrode (RHE) over Cu NCs. The activity/selectivity‐size relations provide a clear understanding of mechanisms in the CO 2 /CORR at the atomic level.