Identification of Active Sites in Pt–Co Bimetallic Catalysts for CO Oxidation

Abstract

Identifying the active sites of catalysts under working conditions is crucial for precise understanding of reaction mechanisms and rational design of catalysts. However, the nature of active sites of bimetallic catalysts for CO oxidation is still a subject of debate. Herein, we employ in situ X-ray absorption and infrared spectroscopy to monitor the realistic structures of active centers in a bimetallic Pt−Co/Al 2 O 3 catalyst during CO oxidation. This catalyst brings 100% CO conversion at room temperature and 30-fold higher turnover frequency than monometallic Pt/Al 2 O 3 catalysts. The in situ studies reveal that under the CO oxidation condition, a fraction of Co atoms are segregated from the PtCo alloy into the surface CoO species that decorates the remaining PtCo nanoparticles through direct Pt−O−Co interfacial bonds. The bond-valence analysis unravels one dangling Co−O coordination per Co 2+ in the surface CoO, which acts as the active sites for O 2 activation. The synergy between the CoO species and the PtCo alloy brings the superior catalytic activity. We also show that the directly connected Pt−O−Co interface is more beneficial to the catalytic performance than the unconnected Pt−CoO interface and provides a promising strategy toward the design of advanced catalysts for the redox reaction.

Synergistic interface between metal Cu nanoparticles and CoO for highly efficient hydrogen production from ammonia borane

“…The peaks in the spectra at around 780.7 and 796.6 eV, associated with the satellite peaks at 785.5 and 802.5 eV, are characteristic features of the Co 2p 3/2 and 2p 1/2 of CoO, respectively. 18,39,40 Moreover, the binding energy of Co 2p 3/2 in Cu 0.5 –(CoO) 0.5 /TiO 2 (780.7 eV) is 0.2 eV higher than that (780.5 eV) of CoO/TiO 2 . The opposite trend in the Cu 2p 3/2 and Co 2p 3/2 binding energies is due to the transfer of electrons from CoO to Cu, indicating that the Cu–CoO heterostructure of Cu 0.5 –(CoO) 0.5 /TiO 2 exhibits strong electronic interactions and interfacial synergism.…”

Optimizing the synergy between alloy and alloy–oxide interface for CO oxidation in bimetallic catalysts

“…Details of the synthetic route for a series of Pt–Co/Al 2 O 3 bimetallic catalysts have been elucidated in our previous work. 43 In brief, a series of Pt–Co/Al 2 O 3 catalysts was synthesized by loading colloidal Pt nanoparticles on the Co 2+ impregnated Al 2 O 3 . In a typical synthesis, colloidal Pt nanoparticles were obtained according to the reported method.…”

“…39 Both the modification of the electronic structure and the shift of the d-band center would alter the adsorption and desorption behaviors of reactants, intermediates, and/or products on the catalytic sites. [40][41][42][43] Hence, in such a composite catalyst with an abundance of the alloy-oxide interface, the synergetic effect between the alloy and the oxide may dramatically affect the catalytic performance. However, to the best of our knowledge, oxide-decorated alloy catalysts are still rarely reported.…”

“…Synthesis of Pt 1 Co x /Al 2 O 3 catalysts. Details of the synthetic route for a series of Pt-Co/Al 2 O 3 bimetallic catalysts have been elucidated in our previous work 43. In brief, a series of Pt-Co/Al 2 O 3 catalysts was synthesized by loading colloidal Pt nanoparticles on the Co 2+ impregnated Al 2 O 3 .…”

Metal–support interactions for heterogeneous catalysis: mechanisms, characterization techniques and applications

“…WMSIs can be constructed by changing the morphology and structure of the carrier to improve the heterogeneous catalytic performance. For example, Sun et al successfully synthesized Pt/ Ti 4 O 7 - (5,10,20) with different loadings (Pt and Ti 4 O 7 were 0.05, 0.1, and 0.2, respectively) using an improved polyol technique. 208 The uniformly distributed Pt NPs showed different morphologies, with Pt/Ti 4 O 7 -5 being rod-like and Pt/Ti 4 O 7 -10 and Pt/Ti 4 O 7 -20 being approximately spherical.…”