Researchers from Huazhong University of Science and Technology and Eindhoven University of Technology recently reported a new class of gold–perovskite catalysts that enable efficient and selective oxidation of ethanol to acetaldehyde under aerobic conditions.
The study focused on Au nanoparticles supported on Cu‑doped LaMnO₃ perovskites (Au/LaMn₁₋ₓCuₓO₃), where the optimized composition, Au/LaMn₀.₇₅Cu₀.₂₅O₃, achieved an acetaldehyde yield of 95% at 225 °C with a space‑time yield of 715 g AC gAu⁻¹ h⁻¹. The catalyst exhibited stable performance over extended reaction periods, outperforming previously reported Au/MgCuCr₂O₄ systems under comparable conditions.
Mechanistic and computational analyses revealed a cooperative effect between Au, Mn, and Cu species within the perovskite structure. Density functional theory and microkinetic simulations showed that moderate Cu incorporation generates adjacent Cu⁺ and Mn²⁺ sites near Au nanoparticles, which collectively promote ethanol activation and facilitate key reaction steps.
The ethanol oxidation pathway involves two sequential hydrogen abstraction processes: O–H bond cleavage by lattice oxygen in the perovskite and α‑C–H bond cleavage on the Au surface. The formation and reoxidation of surface oxygen vacancies proceed through molecular O₂ adsorption and peroxide (O₂²⁻) intermediates.
The rate‑determining step was identified as water formation during the reoxidation phase, with moderate Cu doping lowering the energy barrier through weaker Cu–O interactions relative to Mn–O. Excessive Cu incorporation, however, led to the formation of metallic or Cu²⁺‑rich domains, compromising the integrity of the active Cu⁺–OV–Mn²⁺ ensembles and suppressing overall activity.
These results elucidate the atomic‑level mechanism governing Au–Mn–Cu synergy in perovskite‑based catalysts and highlight compositional tuning as a viable strategy for enhancing the stability and efficiency of noble‑metal–supported perovskite oxides in selective oxidation reactions.
