DFT-Based Study on Oxygen Adsorption on Defective Graphene-Supported Pt Nanoparticles

The structural and electronic properties of Pt-13 nanoparticles adsorbed on monovacancy defective graphene have been determined to understand oxygen adsorption on Pt nanoparticles based upon density functional theory predictions using the generalized gradient approximation. We demonstrate that a monovacancy site of graphene serves a key role as an anchoring point for Pt-13 nanoparticles, ensuring their stability on defective graphene surfaces and suggesting their enhanced catalytic activity toward the interaction with O-2. Strong hybridization of the Pt-13 nanoparticle with the sp(2) dangling bonds of neighboring carbon atoms near the monovacancy site leads to the strong binding of the Pt 13 nanoparticle on defective graphene (-7.45 eV in adsorption energy). Upon both adsorption of the Pt-13 nanoparticle on defective graphene and O-2 on Pt-13-defective graphene, strong charge depletion of the Pt atom at the interfaces of Pt-C and Pt-O-2 is observed. Pt-13 nanoparticles are able to donate charge to both defective graphene and O-2. The Pt-13-defective graphene complex shows an O-2 adsorption energy of -2.30 eV, which is weaker than the O-2 adsorption energy of -3.92 eV on a free Pt-13 nanoparticle. Considering the strong stability of the Pt nanoparticles and relatively weaker O-2 adsorption energy due to the defective graphene support, we expect that the defective graphene support may increase the catalytic activity of Pt nanoparticles compared to flat Pt metal surfaces, not only by preventing sintering of Pt nanoparticles due to the strong anchoring nature of the graphene defect sites but also by providing a balance in the O-2 binding strength that may allow for enhanced catalyst turnover.