Abstract: The present invention provides a gold-copper alloy nanostructure which can be used as a catalyst for electrochemical CO2 reduction reaction and a method for synthesizing the same. The provided gold-copper alloy nanostructure has a heterophase composed of a hexagonal close-packed phase and a face-centered cubic phase. This gold-copper nanostructure shows an atomic ratio of 99 to 1 for gold to copper. The present invention adopts delicately structural modulation of nanomaterials based on the phase engineering of nanomaterials strategy and offers a promising way for the design and preparation of novel catalysts, especially those with unconventional phase, for enhancing their performances in various catalytic applications.