Cu-CHA materials are efficient catalysts for NH₃–SCR of NO_x in oxygen excess. A crucial step in the reaction is oxygen (O₂) activation, which still is not well understood. Density functional theory calculations in combination with ab initio thermodynamics and molecular dynamics are here used to study O₂ dissociation on $\text{Cu}{({\text{NH}}_3)}_2^{+}$ species, which are present under NH₃–SCR conditions. Direct dissociation of O₂ is found to be facile over a pair of $\text{Cu}{({\text{NH}}_3)}_2^{+}$ complexes whereas dissociation on a single $\text{Cu}{({\text{NH}}_3)}_2^{+}$ species is unlikely due to a high activation energy. The presence of NO promotes oxygen dissociation on both single and pairs of $\text{Cu}{({\text{NH}}_3)}_2^{+}$ complexes. Nitrites and nitrates are easily formed as O₂ dissociates, and NO adsorption over nitrates leads to facile formation of NO₂. The results stress the importance of ligand-stabilized Cu species in Cu-CHA catalysts for NH₃–SCR.

Cu-CHA材料是过量氧气中NO _x的NH ₃ -SCR的有效催化剂。反应中的关键步骤是氧（O ₂）活化，目前尚不清楚。结合从头算热力学和分子动力学的密度泛函理论计算，用于研究O _2的解离。$\text{铜}{（{\text{NH}}_3）}_{\mathrm{2个}}^{+}$在NH ₃ -SCR条件下存在的物种。发现O _2的直接解离在一对$\text{铜}{（{\text{NH}}_3）}_{\mathrm{2个}}^{+}$ 复杂而单个解离 $\text{铜}{（{\text{NH}}_3）}_{\mathrm{2个}}^{+}$高活化能是不可能的。NO的存在会促进单个和一对氧的离解$\text{铜}{（{\text{NH}}_3）}_{\mathrm{2个}}^{+}$复合体。O ₂离解时，容易形成亚硝酸盐和硝酸盐，而硝酸盐上的NO吸附导致NO _2的形成容易。结果强调了NH ₃ -SCR在Cu-CHA催化剂中配体稳定的Cu物种的重要性。