Charge-Separated Pd δ- -Cu δ+ Atom Pairs Promote CO 2 Reduction to C 2 .

Positively charged Cu sites have been confirmed to significantly promote the production of multicarbon (C) products from an electrochemical CO reduction reaction (CORR). However, the positively charged Cu has difficulty in existing under a strong negative bias. In this work, we design a Pd-CuN catalyst containing charge-separated Pd-Cu atom pair that can stabilize the Cu sites. In situ characterizations and density functional theory reveal that the first reported negatively charged Pd sites exhibited a superior CO binding capacity together with the adjacent Cu sites, synergistically promoting the CO dimerization process to produce C products. As a result, we achieve a 14-fold increase in the C product Faradaic efficiency (FE) on Pd-CuN, from 5.6% to 78.2%. This work provides a new strategy for synthesizing negative valence atom-pair catalysts and an atomic-level modulation approach of unstable Cu sites in the CORR.