Abstract

Abstract Copper (Cu) nanomaterials are a unique kind of electrocatalysts for high‐value multi‐carbon production in carbon dioxide reduction reaction (CO 2 RR), which holds enormous potential in attaining carbon neutrality. However, phase engineering of Cu nanomaterials remains challenging, especially for the construction of unconventional phase Cu‐based asymmetric heteronanostructures. Here the site‐selective growth of Cu on unusual phase gold (Au) nanorods, obtaining three kinds of heterophase fcc‐2H‐fcc Au–Cu heteronanostructures is reported. Significantly, the resultant fcc‐2H‐fcc Au–Cu Janus nanostructures (JNSs) break the symmetric growth mode of Cu on Au. In electrocatalytic CO 2 RR, the fcc‐2H‐fcc Au–Cu JNSs exhibit excellent performance in both H‐type and flow cells, with Faradaic efficiencies of 55.5% and 84.3% for ethylene and multi‐carbon products, respectively. In situ characterizations and theoretical calculations reveal the co‐exposure of 2H‐Au and 2H‐Cu domains in Au–Cu JNSs diversifies the CO* adsorption configurations and promotes the CO* spillover and subsequent C–C coupling toward ethylene generation with reduced energy barriers.