Trends in Adsorption Energies of the Oxygenated Species on Single Platinum Atom Embedded in Carbon Nanotubes
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Herein we study the effect of strain on the catalytic activity of different Pt-doped single wall metallic carbon nanotubes (SWCNT) towards the oxygen reduction reaction (ORR). We consider the possibility of the Pt-doped at single vacancy inside the SWCNT to investigate the effect of confinement on the reaction mechanism. Density functional theory calculations indicate that for the SWCNTs with tube diameters below 7 Å, the strain energy varies significantly influencing the adsorption energies of the key intermediates of the ORR reaction. For the SWCNTs with tube diameters above 7 Å, on the other hand, both the calculated strain and the adsorption energies are almost constant. We furthermore find that the adsorption energies are strongly affected by confinement effects as shown for Pt-doped systems that are located inside the SWCNT. We show that the Pt-doped at single vacancy of the SWCNT strongly binds the oxygenated species under ORR potentials and therefore the active species is covered by oxo- or hydroxo group. Because the presence of Pt atoms doped at the single and double vacancies of the SWCNT is equivalently probable we also studied the Pt-doped at double vacancy. We find that the most active motif is the Pt-doped at double vacancy of SWCNT with 0.24V overpotenital.
KeywordsOxygen reduction reaction Single wall carbon nanotube (SWCNT) Pt-doped at single and dobule vacancy
We gratefully acknowledge support from the U.S. Department of Energy, Office of Sciences, Office of Basic Energy Sciences, to the SUNCAT Center for Interface Science and Catalysis. S.S acknowledges support from the Global Climate Energy Project (GCEP) at Stanford University (Fund No. 52454). The calculations were financially supported by Henan University of Science and Technology (No. 2013ZCX018) and National Natural Science Foundation of China (Nos. U1404212 and 11404098).
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