Understanding support effects at the molecular level is vital for improving the design of the platinum-group metal (PGM) three-way catalyst (TWC). As a first step, we performed density functional theory (DFT) calculations for tetrahedral M₄ clusters (M = Pt, Pd, or Rh) supported on CeO₂(111) and ZrO₂(111) and examined their activity toward NO adsorption and reduction. We found that the M₄ clusters are positively charged on ceria but close to neutral on zirconia. The site preference of NO adsorption is not affected much by changing ceria for zirconia. NO tends to gain slightly more negative charge from M₄/ZrO₂ than from M₄/CeO₂. The reaction of CO with adsorbed NO does not exhibit strong support dependence. In contrast, NO dissociation at the metal/oxide interface exhibits strong support dependence, with the transition state (TS) lowered by 0.7–1.1 eV by changing ceria for zirconia. This lowering occurs because Zr in ZrO₂, carrying more positive charge than Ce in CeO₂, interacts more strongly with the O end of NO to promote dissociation. The calculated TS energy for NO dissociation (as well as the dissociative adsorption energy) is strongly correlated with the NO-reduction activity obtained in our comparative TWC experiments. Thus, the ability of a catalyst to bind N and O, with the help of the oxide support, is key for the NO-reduction activity of PGM catalysts.

在分子水平上了解支持作用对于改进铂族金属（PGM）三效催化剂（TWC）的设计至关重要。第一步，我们对CeO ₂（111）和ZrO ₂（111）上负载的四面体M ₄簇（M = Pt，Pd或Rh）进行了密度泛函理论（DFT）计算，并检查了它们对NO吸附和吸附的活性。减少。我们发现M ₄簇在二氧化铈上带正电，而在氧化锆上接近中性。氧化铈改变氧化铈对NO吸附的位置偏好影响不大。NO倾向于从M ₄ / ZrO ₂获得的负电荷比从M ₄ / CeO ₂获得的负电荷略多。CO与吸附的NO的反应不表现出强烈的载体依赖性。相反，在金属/氧化物界面的NO分解表现出强烈的支持依赖性，通过改变氧化锆的二氧化铈，过渡态（TS）降低了0.7–1.1 eV。发生这种降低的原因是，ZrO _2中的Zr比CeO _2中的Ce带更多的正电荷，与NO的O端相互作用更强，从而促进了离解。计算出的用于NO离解的TS能量（以及离解吸附能）与在我们的比较TWC实验中获得的NO还原活性密切相关。因此，借助于氧化物载体，催化剂结合N和O的能力是PGM催化剂的NO还原活性的关键。