Simultaneous Site Adsorption Shift and Efficient CO Oxidation Induced by V and Co in Pt Catalyst
2017
Ahmad, Rafia | Singh, Abhishek K.
A complete solution for CO poisoning of Pt catalysts requires a design that entirely prevents CO adsorption on Pt atoms. Here, we explore the CO adsorption sites and oxidation capability of 3d transition metal doped small magic clusters of Pt₄. Among Pt₃M, only the Pt₃V free-standing cluster entirely eliminates the prospect of Pt poisoning by inverting the adsorption site of CO to V atom. The V d-band center lies closer to the Fermi level than that of Pt atoms, resulting in a larger number of empty d-antibonding states, thereby making V comparatively more reactive toward CO. The inversion of the CO adsorption site is also observed for larger PtₙVₘ clusters and becomes possible for PtₙCoₘ clusters for sizes larger than m + n = 12 atoms. Formation and removal of CO₂ via the Langmuir–Hinshelwood mechanism occurs with low reaction barriers, exhibiting a high catalytic activity for the Ptₙ(V/Co)ₘ clusters. A maximum catalytic efficiency is attained for Pt₄₁V₁₄, which at room temperature gives a CO₂ turnover frequency comparable to the conventional catalysts. The oxidation of CO becomes more favorable by the Mars van Krevelan mechanism for the cluster supported on vacancy prone Li-doped MgO(100). Our results present a rationale design of Pt poisoning free fuel cells and automobile exhaust catalysts, which can be entirely protected from CO poisoning and maintain long-term high catalytic efficiency.
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