Palladium (Pd) has been widely regarded as a high-performance catalyst for various oxidative reactions, however, the actual structure of active site remains controversial due to structural evolution under operation conditions. Herein, we prepared a series of bismuth (Bi)-doped silica-supported Pd catalysts and found a hydrogen-controlled structural reconstruction mechanism of palladium-bismuth oxide cluster to single atom alloy to efficiently catalyze low-temperature CO oxidation. The formation of Pd_xBi_yO_z clusters with unique Pd−O−Bi coordination structure could enhance the sinter-resistance ability of Pd species. This structural evolution of active site is clearly uncovered by in-situ XAFS results, in which metallic Bi−Pd shell gradually generates as the increase of reduction temperature without any metallic Bi−Bi bond. More importantly, PdBi₁ single atom alloy exhibits a good CO oxidation activity with a CO₂ production rate of 413 μmol_CO2·g_Pd⁻¹·s⁻¹ at 100 °C and excellent catalytic stability. Density function calculation (DFT) results indicate that there are geometric and electronic effects between Bi and Pd atoms, which favor total linear-CO adsorption, activate CO and O₂ molecules, and reduce the barrier for the formation of OO-CO intermediates in PdBi₁ single atom alloy.

钯（Pd）被广泛认为是各种氧化反应的高性能催化剂，然而，由于操作条件下的结构演变，活性位点的实际结构仍然存在争议。在此，我们制备了一系列铋 (Bi) 掺杂二氧化硅负载的 Pd 催化剂，并发现了钯 - 氧化铋簇到单原子合金的氢控制结构重构机制，可有效催化低温 CO 氧化。_{Pd x} Bi _y O _z的形成具有独特Pd-O-Bi配位结构的团簇可以增强Pd物种的抗烧结能力。原位 XAFS 结果清楚地揭示了活性位点的这种结构演变，其中金属 Bi-Pd 壳随着还原温度的升高逐渐生成，没有任何金属 Bi-Bi 键。更重要的是，PdBi ₁单原子合金表现出良好的CO氧化活性，在100 °C时CO ₂生成率为413 μmol _CO2 ·g _Pd ^-1 ·s ^-1和优异的催化稳定性。密度函数计算（DFT）结果表明Bi和Pd原子之间存在几何和电子效应，有利于总线性CO吸附，激活CO和O _{2分子, 并降低 PdBi 1}单原子合金中 OO-CO 中间体形成的势垒。