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

The structural and electronic properties of Pt13 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 Pt13 nanoparticles, ensuring their stability on defective graphene surfaces and suggesting their enhanced catalytic activity toward the interaction with O2. Strong hybridization of the Pt13 nanoparticle with the sp2 dangling bonds of neighboring carbon atoms near the monovacancy site leads to the strong binding of the Pt13 nanoparticle on defective graphene (−7.45 eV in adsorption energy). Upon both adsorption of the Pt13 nanoparticle on defective graphene and O2 on Pt13–defective graphene, strong charge depletion of the Pt atom at the interfaces of Pt–C and Pt–O2 is observed. Pt13 nanoparticles are able to donate charge to both defective graphene and O2. The Pt13–defective graphene complex shows an O2 adsorption energy of −2.30 eV, which is weaker than the O2 adsorption energy of −3.92 eV on a free Pt13 nanoparticle. Considering the strong stability of the Pt nanoparticles and relatively weaker O2 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 O2 binding strength that may allow for enhanced catalyst turnover.