Identifying optimal Ru size in NH₃ synthesis can improve reaction activity and maximize the utilization of Ru to reduce catalyst cost. However, previous researches are focused on large Ru particle size (≥2 nm) while that below 2 nm in NH₃ synthesis is unclear. Here we synthesized a series of Rux/BaCeO₃ with different Ru sizes (x = 1.1–3.0 nm) through size-controlled Ru colloid. With the decrease of Ru size, NH₃ synthesis rate over Ru1.1/BaCeO₃ increases to 19.4 mmol g_cat⁻¹h⁻¹ at 400 °C and 1 MPa, which is 5.7 times that of Ru3.0/BaCeO₃ and superior to most of Ru-based catalysts previously reported. It reveals that the reduction of Ru size enhances the generation of Ce³⁺ and oxygen vacancies in BaCeO₃, which can donate electron to Ru centers and promote N₂ dissociation. Moreover, the small Ru size enhances hydrogen spillover from Ru to BaCeO₃ to alleviate hydrogen poisoning, resulting in efficient NH₃ synthesis.

确定NH ₃合成中的最佳Ru 尺寸可以提高反应活性并最大化Ru 的利用率以降低催化剂成本。然而，以前的研究集中在大Ru 粒径（≥2 nm），而NH ₃合成中低于2 nm 的粒径尚不清楚。在这里，我们 通过尺寸控制的 Ru 胶体合成了一系列具有不同 Ru 尺寸 ( x = 1.1–3.0 nm)的 Ru x /BaCeO ₃。随着Ru尺寸的减小，NH ₃合成速率相对于Ru1.1/BaCeO ₃增加到19.4 mmol g _cat ^-1 h ^-1在400 °C 和1 MPa，是Ru3.0/BaCeO _{3 的}5.7倍并且优于之前报道的大多数 Ru 基催化剂。结果表明，Ru尺寸的减小促进了BaCeO ₃中Ce ³⁺和氧空位的产生，可以向Ru中心提供电子并促进N ₂离解。此外，较小的 Ru 尺寸增强了从 Ru 到 BaCeO _{3 的}氢溢出以减轻氢中毒，从而实现高效的 NH ₃合成。