Beyond Monometallic Limits: PdFe Alloy Nanoparticles Achieve Methanation-Free Carbon Dioxide Hydrogenation to Carbon Monoxide

The formation of bimetallic alloys enables simultaneous tuning of geometric and electronic structures, offering an avenue to control adsorption and reaction pathways on catalytic surfaces. In this study, we elucidate how Pd−Fe alloy nanoparticles achieve such modulation at the atomic level. Colloidal synthesis ensures homogeneous atomic mixing, allowing the disentanglement of ensemble and ligand effects in CO adsorption and hydrogenation. Herein, we demonstrate that PdFe alloy nanoparticles effectively suppress the sequential hydrogenation of CO to CH4, enabling CO production with near-unity selectivity, an outcome unattainable with monometallic catalysts. Comparative analysis with PdCo alloys reveals that the role of Fe lies in its ability to downshift the Pd d-band center and geometrically isolate Pd sites, leading to weakened CO binding and inhibited C−O bond hydrogenation. These findings highlight the cooperative geometric and electronic effects underlying alloy formation and establish Pd−Fe as a model system for understanding selective adsorption control in catalytic alloys.