Carbonate Inhibition in Au-Cu/γ-Al2O3 Catalysts for CO Oxidation

Incorporating Cu into gold-based catalysts effectively reduced nanoparticle sintering and free carbonate accumulation, promoting long-term preservation of catalytic surface area over time. This study explores the catalytic activity of monometallic Au and bimetallic AuCu catalysts with varying Au:Cu atomic ratios (1:0.5, 1:1, and 1:1.5) that were synthesized on γ-Al2O3 via sequential deposition–precipitation with urea. The catalysts were pretreated in either air or H2 and evaluated for CO oxidation activity and stability. A comprehensive characterization (EDS, BET, TEM, H2-TPR, O2-TPO, XPS, DRIFTS, and UV–Vis) was used to investigate particle size, metal oxidation states, and redox properties. Among all materials, the AuCu 1:1 catalyst exhibited the highest low-temperature CO conversion (>90% at 0 °C) and improved stability during 24 h tests, reflecting minimal nanoparticle sintering as confirmed by TEM analysis. In situ DRIFTS revealed that the presence of Cu+ and Cu2+ minimizes the accumulation of free carbonates (one of the main deactivation pathways in Au/γ-Al2O3) while promoting the formation of reactive intermediates that facilitate CO2 production. Notably, air pretreatment at moderate temperature proved as effective as H2 pretreatment in activating both monometallic and bimetallic catalysts. These findings highlight the role of Cu as a structural and electronic promoter of gold, offering practical guidelines for designing durable, cost-effective catalysts for low-temperature CO oxidation on non-reducible supports.