Accessing Basic Sites on Modified CoFe2O4 Nanoparticles: Addressing the Selective Oxidation of Benzyl Alcohol and Unraveling the Au:Pd Ratio Effects by XPS
Laíse N. S. Pereira, Marco A. S. Garcia, Jennifer Rozendo, Pedro Vidinha, Alfredo Duarte, Carla V. R. de Moura, Edmilson M. de Moura
AuPd nanoparticles have gained substantial attention due to their application in selective oxidation of alcohols. However, due to the radical nature of the oxidation of benzyl alcohol, under specific conditions, even without a catalyst, the reaction occurs and affects the selectivity of the system. Therefore, we aimed to develop a catalyst that enables the control of the oxidation leading to higher reaction selectivity. To accomplish this, we have prepared a catalytic support comprised of CoFe2O4 nanoparticles impregnated with Sr(OH)2 that presented a significant control of the reaction selectivity without any metal or external base addition. After the impregnation of AuPd nanoparticles in a specific ratio, the reaction reached a selectivity of > 99% for benzaldehyde, in 3.5 h, with a recycle regime of five runs without loss of activity and selectivity. Our results show that the judicious choice of the ratio of the metals prevents the necessity of manipulating the reaction conditions to improve the performance of the system. Additionally, studies under N2 and O2 environments, with or without water, confirmed the role of the O2 in the system. Holding all this information, we propose a possible mechanism for the prepared system.