Influence of pretreatment conditions and support type on CO oxidation activity of Au–Ni catalysts: Insights from operando DRIFTS

In this report, operando DRIFTS–MS analyses were applied to determine the influence of thermal pretreatment on the oxidation states and catalytic performance of Au–Ni catalysts supported on TiO 2 or γ-Al 2 O 3 during the catalytic CO oxidation reaction over a temperature range of –100 °C to 200 °C, monitoring the real-time evolution of surface-adsorbed intermediates. Operando DRIFTS–MS, XPS, TPR, and STEM–HAADF revealed that support material critically influences catalyst behavior: TiO 2 -supported catalysts exhibit enhanced CO conversion compared to those on Al 2 O 3 . Notably, pre-reduced catalysts on TiO 2 showed an important synergistic effect, primarily through the formation of reactive Au δ- species resulting from the partial reduction of Au 0 sites. In contrast, pre-oxidized catalysts maintained a higher fraction of oxidized Au species, correlating with moderate activity. Operando DRIFTS–MS data showed that the incorporation of Ni into the bimetallic nanoparticles prevents the formation of adsorbed bicarbonate species or promotes their conversion into more reactive carbonate and carboxylate species, coinciding with the formation of Au δ- sites and leading to increased CO 2 production. Al 2 O 3 -supported catalysts exhibit persistent spectator intermediates, such as formate species, which likely block active sites and slow CO 2 production. These insights underscore the significant roles of metal–support interactions, thermal pretreatment conditions, and bimetallic synergistic effects in catalyst design, providing a rational basis for developing more effective Au–Ni catalysts for low-temperature CO oxidation. • Ni modifies the electronic environment of Au, enhancing its catalytic activity. • Au-Ni synergistic effect is pronounced on TiO 2 but limited on Al 2 O 3 support. • Pre-reduced AuNi red /TiO 2 shows high CO conversion at 0 °C via Au δ⁻ species. • Transformation of bicarbonate intermediates into more reactive species via Au δ⁻ . • Al 2 O 3 catalysts show persistent formate spectators blocking sites.