High‐Entropy Rare Earth Oxides Anchoring Tunable Cu ^δ+ Nanochimneys for Self‐Tandem C‐C Coupling Catalysis

Copper (Cu)-based materials are promising for carbon-carbon bond (C─C) coupling catalysis, but they are limited to poor structural stability, high activation energy, and low selectivity toward C₂₊ products. Here a customized synthetic protocol is defined for the fabrication of 2D ultrathin high-entropy rare earth (RE) oxides (HE-REOs) with rich lattice distortions and oxygen vacancies, which act as robust supports for anchoring Cu^δ+ serial domains with tunable oxidation states. The rationally integrated HE-REOs-Cu^δ+ heterostructures feature largely exposed synergistic multi-site driving rapid *CO spillover, and multiple stabilized Cu^δ+ chimneys promoting cascade *CO coupling, together with intrinsic electron activation channels enabling RE 4f electron delocalization to lower the energy barrier. The optimal CeZrZnAgPbO-Cu^0.44+ self-tandem catalysts achieve a high Faradaic efficiency (FE) of 51.7% for C₂₊ gaseous products at a low potential of -0.9 V versus (vs) reversible hydrogen electrode (RHE) in H-type cell. The study proposes an "all-in-one" design principle for advanced RE-based catalysts through integrating advantageous individuals in a predictable manner.