Structurally ordered intermetallic nanocrystals (NCs) and single-atom catalysts (SACs) are two emerging catalytic motifs for sustainable chemical production and energy conversion. However, both have synthetic limitations which can lead to the aggregation of NCs or metal atoms. Single-atom alloys (SAAs), which contain isolated metal atoms in a host metal, can overcome the aggregation concern because of the thermodynamic stabilization of single atoms on host metal surfaces. Here we report a direct solution-phase synthesis of Cu/CuAu core/shell NCs with tunable SAA layers. This synthesis can be extended to other Cu/CuM (M = Pt, Pd) systems, in which M atoms are isolated in the copper host. Using this method, the density of SAAs on a copper surface can be controlled, resulting in both low and high densities of single atoms. Alloying gold into the copper matrix introduced ligand effects that optimized the chemisorption of *NO₃ and *N. As a result, the densely packed Cu/CuAu material demonstrated a high selectivity toward NH₃ from the electrocatalytic nitrate reduction reaction with an 85.5% Faradaic efficiency while maintaining a high yield rate of 8.47 mol h⁻¹ g⁻¹. This work advances the design of atomically precise catalytic sites by creating core/shell NCs with SAA atomic layers, opening an avenue for broad catalytic applications.

结构有序的金属间化合物纳米晶体 (NCs) 和单原子催化剂 (SACs) 是可持续化学生产和能源转换的两种新兴催化基序。然而，两者都有可能导致 NC 或金属原子聚集的合成限制。单原子合金 (SAA) 在主体金属中包含孤立的金属原子，由于单个原子在主体金属表面的热力学稳定性，可以克服聚集问题。在这里，我们报告了具有可调 SAA 层的 Cu/CuAu 核/壳 NC 的直接溶液相合成。这种合成可以扩展到其他 Cu/CuM (M = Pt, Pd) 系统，其中 M 原子在铜主体中被隔离。使用这种方法，可以控制铜表面上 SAA 的密度，从而产生低密度和高密度的单个原子。₃和 *N。结果，致密堆积的 Cu/CuAu 材料表现出对来自电催化硝酸盐还原反应的 NH _{3的高选择性，法拉第效率为 85.5%，同时保持 8.47 mol h} ^-1  g ^-1的高产率。这项工作通过创建具有 SAA 原子层的核/壳 NCs 推进了原子精确催化位点的设计，为广泛的催化应用开辟了道路。