Electrochemical nitrogen reduction reaction (ENRR) is a mild and environmentally friendly process that can be potentially complementary to the traditional Haber-Bosch process. Development of high-performance ENRR catalysts and understanding of the activity origin of the catalyst are essential for the practical application of ENRR process. Herein, we report the size-dependent ENRR activity of monodisperse Au nanoparticles (NPs) sized ranging from 4 nm to 10 nm. 8 nm Au NPs is found to be an excellent ENRR catalyst with an ammonia production rate and Faradic efficiency of 17.49 μg h⁻¹ mg⁻¹_Au and 5.79%, respectively. The high ENRR performance of 8 nm Au NP is rationalized with DFT studies, which indicate that an optimal proportion of the surface step sites is key to suppressing hydrogen evolution reaction and improving the catalytic activity towards ENRR. The study herein may provide guidelines for tailoring the ENRR catalysis on nanostructured metal catalysts.

电化学氮还原反应（ENRR）是一种温和且环保的工艺，可以与传统的Haber-Bosch工艺互补。高性能ENRR催化剂的开发和催化剂活性来源的理解对于ENRR工艺的实际应用至关重要。在本文中，我们报告了大小从4 nm到10 nm的单分散Au纳米颗粒（NPs）的尺寸依赖性ENRR活性。发现8 nm Au NPs是一种出色的ENRR催化剂，其氨的产生速率和法拉第效率为17.49μgh ^-1 mg ^-1 _Au和5.79％。通过DFT研究合理化了8 nm Au NP的高ENRR性能，这表明表面台阶部位的最佳比例是抑制氢释放反应和提高对ENRR的催化活性的关键。本文的研究可为定制纳米结构金属催化剂上的ENRR催化提供指导。