Current methods for industrial-scale ammonia synthesis rely excessively on fossil fuels, causing severe CO₂ emissions. The electrochemical nitrogen reduction reaction (NRR) is a sustainable and environmentally friendly technology for ammonia synthesis under environmental conditions. Herein, we demonstrate the rational construction of Au₃Cu@Cu nanocages with unique porous core–shell heterostructured walls by a facile two-step synthetic strategy. Due to the hollow cavities, porous core–shell heterostructured walls, and Au₃Cu@Cu two-component composition, the as-constructed Au₃Cu@Cu nanocages exhibit excellent NRR performance in 0.1 M Na₂SO₄ saturated with N₂, achieving a high ammonia yield up to 33.97 μg h⁻¹ mg_cat.⁻¹ and a faradaic efficiency of 21.41% at −0.2 V (vs. the reversible hydrogen electrode). This study will provide insight into the reasonable design and construction of hollow nanostructures with porous heterostructured walls for electrocatalytic applications.