C3H8 oxidation on atomic-scale catalysts: insights into active oxygen species and reaction pathways

Compared to nano-catalysts, atomic-scale dispersed catalysts offer greater potential for elucidating the fundamental nature of catalytic reactions. To investigate the role of ultra-low Ru loading (0.1 wt%) in C3H8 oxidation, single-atom (Ru/CeO2-SA), dual-pair (Ru2/CeO2), and tetra-atomic cluster (Ru4/CeO2) catalysts were employed. Loading Ru on CeO2 suppressed C3H8 adsorption while modulated oxygen activation, thereby influencing the reaction intermediates and engineering the propane oxidation pathways. Notably, Ru/CeO2-SA and Ru4/CeO2 exhibited superior propane oxidation performance compared to Ru2/CeO2 under both hydrated and anhydrous conditions. Ru/CeO2-SA achieved remarkable turnover frequency (TOF) of 43.7 * 10−2 s−1 at 280 °C and 50 % conversion temperature (T50) as low as 267 °C, which surpassed Ru2/CeO2 (TOF = 16.7 *10−2 s−1, T50 = 365 °C) and Ru4/CeO2 (TOF = 33.1*10−2 s−1, T50 = 330 °C), highlighting the critical role of single-atom architecture in enhancing catalytic efficiency. This enhanced performance was attributed to the formation of acrylic acid intermediates, facilitated by the surface lattice oxygen of CeO2 adjacent to Ru. In contrast, the propionic acid generated from chemisorbed oxygen on Ru2/CeO2 demonstrated a weaker promoting effect compared to acrylic acid. Additionally, the rapid oxidation of acetate to formate by lattice oxygen further contributed to the enhanced catalytic activity.