Fine-Tuning the Coordination Structure and Identifying Pt₁–O_v–Ce as the Active Site for Selective Hydrogenations over Pt₁/CeO₂ Single-Atom Catalysts

Single-atom catalysts (SACs) have shown exceptional promise in a variety of selective hydrogenations due to their uniform and isolated active sites, yet the intrinsic nature of the active sites and reaction mechanism remain elusive. Herein, by a rapid thermal treatment (RTT) method, we are able to finely tune the coordination structure of Pt₁/CeO₂ SAC and establish a linear correlation between the Pt–O coordination number, electronic structure, and catalytic activity for furfural/3-nitrostyrene hydrogenations. Integrated quasi in situ spectroscopic characterizations and DFT calculations reveal the structural evolution of Pt₁–O_v–Ce active sites and the redox mechanism. RTT at 600 °C results in the formation of Pt₁–O_v–Ce, which allows for the preferential end-on adsorption of ─C═O/–NO₂ groups into O_v and the charge transfer from the Pt₁ single atom to the reactant. On the other hand, hydrogen is dissociated on the Pt single atoms and then reacts with the adsorbed ─C═O/–NO₂ group to accomplish the selective hydrogenation, accompanied by the regeneration of O_v. Moreover, the interfacial Pt₁–O_v–Ce is found to be 2.4–15.7-fold more active than Pt₁–––O_v (peripheral O_v). These findings highlight the dictating role of the coordination structure of SACs and elucidate the cooperative mechanism between Pt single atoms and interfacial oxygen vacancies, thus offering design principles for overcoming the activity-selectivity trade-off in other selective hydrogenations.