Electrochemical CO 2 reduction to value-added chemical feedstocks is of considerable interest for renewable energy storage and renewable source generation while mitigating CO 2 emissions from human activity. Copper represents an effective catalyst in reducing CO 2 to hydrocarbons or oxygenates, but it is often plagued by a low product selectivity and limited long-term stability. Here we report that copper nanowires with rich surface steps exhibit a remarkably high Faradaic efficiency for C 2 H 4 that can be maintained for over 200 hours. Computational studies reveal that these steps are thermodynamically favoured compared with Cu(100) surface under the operating conditions and the stepped surface favours C 2 products by suppressing the C 1 pathway and hydrogen production.