Interfacial sites in platinum−hydroxide−cobalt hybrid nanostructures for promoting CO oxidation activity

Abstract

Metal–oxide/hydroxide hybrid nanostructures provide an excellent platform to study the interfacial effects on tailoring the catalysis of metal catalysts. Herein, a hybrid nanostructure of Pt@Co(OH)₂ supported on SiO₂ was synthesized by incipient wetness impregnation of Co(OH)₂ with the aid of H₂O₂ and successive urea-assisted deposition−precipitation of platinum nanoparticles. The Fenton-like reaction between Co₂⁺ and H₂O₂ during the impregnation process facilitates the formation of active interfacial sites. This hybrid nanostructure exhibits much higher catalytic activity towards CO oxidation than Pt/SiO₂ nanoparticles with a similar Pt loading and particle size. In situ diffuse reflectance infrared Fourier transform spectroscopy was used to track the CO adsorption processes and to identify the reaction intermediates during CO oxidation. It shows that the OH species at the Pt–OH–Co interfacial sites could readily react with CO adsorbed on neighboring Pt to yield CO₂ by forming *COOH intermediates and oxygen vacancies. Under the CO + O₂ oxidation conditions, O₂ molecules are activated by the oxygen vacancy and react with the CO molecules adsorbed on Pt to generate CO₂, via forming the highly active *OOH intermediates as observed by DRIFTS.