Aspera Susan Meñez, Arevalo Ryan Lacdao, Chantaramolee Bhume, Nakanishi Hiroshi, Kasai Hideaki
National Institute of Technology, Akashi College, 679-3 Nishioka, Uozumi, Akashi, Hyogo 674-8501, Japan.
Phys Chem Chem Phys. 2021 Mar 28;23(12):7153-7163. doi: 10.1039/d0cp06453j. Epub 2021 Mar 18.
NO dissociation is an important reaction step in the NO reduction reaction, particularly in the three-way catalyst conversion system for automotive gas exhaust purification. In this study, we used first-principles calculations based on density functional theory to analyze the interaction and dissociation of NO on the PdRuIr ternary alloy. The electronic properties of the atomic combination of the PdRuIr ternary alloy create an effective catalyst that is active for NO dissociation and relatively stable against the formation of volatile RuO through a weakened O adsorption. This study also shows that for an alloyed system, the strength of NO adsorption may not necessarily predict the dissociation activity. This tendency is observed in the PdRuIr ternary alloy where Ru top is the active site for NO adsorption albeit not an effective site for dissociation. It is presumed that NO dissociation is mediated by its molecular diffusion to active sites for dissociation, which are usually high Ru- and/or Ir-coordinated hollow or bridge sites. These active sites allow high charge transfer from the surface to NO, which fills the NO anti-bonding state and facilitates dissociation. This therefore assumes that the strength of NO molecular adsorption is not a descriptor for NO dissociation on metal alloys but rather the ability of the surface to transfer charge to NO and homogeneity of the strength of adsorption. Furthermore, O adsorption on the ternary alloy, particularly near the Ru sites, is relatively weaker as compared to the pure Ru surface. This weakened O adsorption is attributed to charge re-distribution through alloying, particularly charge transfer from the Ru atom to the Ir and Pd atoms.
NO解离是NO还原反应中的一个重要反应步骤，尤其在用于汽车尾气净化的三元催化剂转化系统中。在本研究中，我们基于密度泛函理论使用第一性原理计算来分析NO在PdRuIr三元合金上的相互作用和解离。PdRuIr三元合金原子组合的电子性质产生了一种有效的催化剂，该催化剂对NO解离具有活性，并且通过减弱的O吸附对挥发性RuO的形成相对稳定。本研究还表明，对于合金体系，NO吸附强度不一定能预测解离活性。在PdRuIr三元合金中观察到这种趋势，其中Ru顶是NO吸附的活性位点，尽管不是有效的解离位点。据推测，NO解离是通过其分子扩散到解离活性位点来介导的，这些活性位点通常是高Ru和/或Ir配位的空心或桥位点。这些活性位点允许从表面到NO的高电荷转移，这填充了NO反键态并促进了解离。因此，这假定NO分子吸附强度不是金属合金上NO解离的描述符，而是表面向NO转移电荷的能力和吸附强度的均匀性。此外，与纯Ru表面相比，三元合金上的O吸附，特别是在Ru位点附近，相对较弱。这种减弱的O吸附归因于通过合金化的电荷重新分布，特别是从Ru原子到Ir和Pd原子的电荷转移。
