A Comprehensive Mechanistic Study for Dry Reforming of Methane over CeO₂-Supported TM₄ clusters (TM = Ru, Pt, Co, Ni)

In this work, the mechanism of dry reforming of methane (DRM) over a series of CeO₂ (111)-supported transition metal (TM) clusters, TM₄/CeO₂(111) (TM = Ru, Pt, Co, Ni), was investigated by using density functional theory (DFT) and microkinetic modeling. According to the results of DFT calculations, Ru₄/CeO₂(111) and Co₄/CeO₂(111) exhibit strong oxygen adsorption capabilities due to the oxophilic properties of Ru and Co metals, which facilitate CO₂ activation more effectively than other metals. Ru₄/CeO₂(111) demonstrates the highest efficiency for both CH₄ and CO₂ activation. Pt₄/CeO₂(111) has great anticoking ability because the C* coupling has a higher energy barrier. Microkinetic simulations indicate that the turnover frequency (TOF) rate follows the trend: Ru₄/CeO₂(111) > Pt₄/ CeO₂(111) > Co₄/CeO₂ (111) > Ni₄/ CeO₂(111). Ru/CeO₂ exhibits the highest activity and selectivity. Pt/CeO₂ has the best ability for anticoking due to the high energy barrier of C* coupling. Co/CeO₂ is prone to deactivation from oxygen poisoning, attributed to its strong oxophilic properties and weak CH₄ activation ability, Ni/CeO₂ shows the poorest activity and stability, as it is easily deactivated by coke formation and has the lowest selectivity. The analysis of key steps indicates that there are different rate-controlled steps for various metals due to inherent differences in their properties. We anticipate that our results will offer a strategy for designing DRM catalysts by selecting the appropriate metal catalysts.