Engineering Cu⁺/Cu⁰ Interfaces With Lanthanum Doping for Efficient CO₂-to-C₂₊ Conversion

Copper-based catalysts offer promise for CO₂-to-C₂₊ conversion but suffer from instability of Cu⁺ species, which are active sites critical for enabling C-C coupling. In this work, we synthesized Lanthanum (La)-doped Cu_xO (La-Cu_xO) catalysts with varying La/Cu ratios to investigate how the interplay between doping-induced electronic effects and grain boundary (GB)-driven stabilization affects deep CO₂ reduction to C₂₊. Combined density functional theory calculations and in situ spectroscopic characterization reveal that the unique 4f orbital configuration and strong Lewis acidity facilitate charge transfer of La, stabilizing Cu⁺ during CO₂ reduction reaction (CO₂RR), while simultaneously inducing lattice distortion to increase GB density. This modulation preserves Cu⁺/Cu⁰ interfaces while enhancing *CO dimerization kinetics. Furthermore, La doping boosts *CO coverage at GB-rich regions and lowers the C-C coupling barrier. The optimized La-Cu_xO-2 catalyst (La/Cu = 0.224) achieves a 45.2% C₂H₄ Faradaic efficiency (FE) and 75.4% C₂₊ FE at -0.8 V_RHE, with partial current densities of 87.5 and 146.7 mA cm^-2, respectively, surpassing undoped Cu_xO. Remarkably, it retains more than 90% initial activity after 24 h operation, demonstrating exceptional stability. This work provides a rational strategy for stabilizing Cu⁺ and tailoring pathways via rare-earth doping.