Unlocking the Potential of Metal Complexes in Supported Catalysts: Enhancing Activity and Stability for the Water–Gas Shift Reaction

The reaction environment plays a pivotal role in shaping the structure and composition of supported metal catalysts, leading to diverse active configurations, including nanoparticles, clusters, and single atoms, which may be covered by reactants and intermediates. In water–gas shift (WGS) reactions, accurately identifying active species remains elusive owing to the difficulties in characterizing small clusters or single-atom species under reaction conditions. In this study, comprehensive ab initio thermodynamic calculations combined with first-principles microkinetic simulations were employed to investigate the formation and activity of various Pt catalysts supported on CeO₂, including single-atoms, clusters, and extended surfaces under WGS conditions. Our results reveal that single-nucleus Pt₁(CO)₁(OH)₁ complexes exhibit superior stability and catalytic activity compared with multinucleus Pt complexes, extended Pt surfaces, supported bare Pt atoms and clusters, acting as the active species for the WGS reaction. The redox mechanism emerged as the most favorable pathway, with H₂ formation identified as the rate-determining step. We found that oxygen vacancies promote metal complex formation. Importantly, the ubiquitous formation of single-atom complexes is prevailed in supported late-transition metal catalysts for WGS reactions. The valuable insights revealed on the formation of single-atom complex as the active species under operational conditions could apply to other catalytic reactions.