Sharp-tip enhanced catalytic CO oxidation by atomically dispersed Pt1/Pt2 on a raised graphene oxide platform

Abstract

Revealing structure–activity relationships of graphene-supported atomically dispersed transition metal catalysts is of key importance in catalysis chemistry and materials science. Here we report a first-principles theoretical study on O₂ activation and CO oxidation catalyzed by atomically dispersed Pt₁/Pt₂ anchored on a raised graphene (Gr) platform. The unique sharp-tip structure of the protuberant graphene platform (carbon-tip) can collect extra polarization electrons on the Pt-tip, promoting electron transfer between the catalyst and adsorbates, and greatly enhancing the chemical activity. Higher carbon-tips on defective graphene oxide with a carbon vacancy (Gr-V) produce more polarization electrons, a more localized electric field, and a larger up-shift of the d-orbital center of the Pt-tip, resulting in better catalytic performance. The carbon-tip enhancement reduces the energy barrier for the CO oxidation on Pt₁O₂/Gr-V from 1.19 eV to 0.56 eV compared with Pt₁ on planar Gr. In addition, CO poisoning is significantly alleviated, with the CO poisoning rate Γ_θ reduced from 2.00 eV to 0.52 eV. Moreover, a linear relationship between the activation barrier and the binding energy of adsorbates is found for various atomically dispersed Pt-tip catalysts on the raised graphene oxide platform. Importantly, the order of catalytic activity is consistent with the carbon-tip enhancement, i.e., Pt₁O₂/Gr-V > Pt₂O₄/Gr-V > Pt₁O₂/Gr > Pt₂O₄/Gr. These findings provide important guidance for rational design of atomically dispersed catalysts.