Enhancing CO Oxidation Rate via Electronic Tuning of CO Binding on Bimetallic Nanoparticle Catalysts

Catalytic CO oxidation on supported metal catalysts, such as platinum, is often promoted by adding a secondary metal, yet the relative importance of interfacial synergy at metal-metal and metal-oxide interfaces over geometric/electronic effects depends on specific systems and can be difficult to disentangle. Existing studies frequently observe electronic promotion alongside interfacial synergy but rarely elucidate how modified CO adsorption translates to a reaction rate change. Here, we use bimetallic Pt-Co catalysts as model systems to disentangle interfacial and electronic contributions. Reaction results show that Pt-Co/Al2O3 catalysts exhibit significantly higher CO oxidation rates than Pt/Al2O3, a 46-fold increase in turnover frequency on Pt3Co1/Al2O3, with less negative reaction order with respect to CO (-0.14 vs -0.57) but comparable order to O2 (0.72 vs 0.80). The kinetic advantage is supported by in situ CO-DRIFTS, revealing weakened CO adsorption on Pt upon Co incorporation. Despite lacking high-density redox sites, the CO oxidation rates on Pt-Co/Al2O3 catalysts are comparable to those on Pt/CeO2, a catalyst known to promote interfacial oxygen exchange. This promotion effect is mirrored in Pt-Ni and Pt-Cu systems, and CO-DRIFTS results confirm a general trend linking weakened CO binding to enhanced rates. Together, these results establish a direct link between reduced CO binding strength and enhanced CO oxidation rates, demonstrating that the rate promotion arises from electronic modification-induced reduced CO coverage rather than from metal oxide interface sites. This work illustrates that the design of a bimetallic catalyst based on electronic structure modifications complements the conventional focus on interfacial active sites.