Abstract:

The structural and electronic properties of Pt₄ nanoparticles adsorbed on monolayer graphitic carbon nitride (Pt₄/g-C₃N₄), as well as the adsorption behavior of oxygen molecules on the Pt₄/g-C₃N₄ surface have been investigated through first-principles density-functional theory (DFT) calculations with the generalized gradient approximation (GGA). The interaction of the oxygen molecules with the bare g-C₃N₄ and the Pt₄ clusters was also calculated for comparison. Our calculations show that Pt nanoparticles prefer to bond with four edge N atoms on heptazine phase g-C₃N₄ (HGCN) surfaces, forming two hexagonal rings. For s-triazine phase g-C₃N₄ (TGCN) surfaces, Pt nanoparticles prefer to sit atop the single vacancy site, forming three bonds with the nearest nitrogen atoms. Stronger hybridization of the Pt nanoparticles with the sp2 dangling bonds of neighboring nitrogen atoms leads to the Pt₄ clusters strongly binding on both types of g-C₃N₄ surface. In addition, the results from Mulliken charge population analyses suggest that there are electrons flowing from the Pt clusters to g-C₃N₄. According to the comparative analyses of the O₂ adsorbed on the Pt₄/HGCN, Pt₄/TGCN, and pure g-C₃N₄ systems, the presence of metal clusters promotes greater electron transfer to oxygen molecules and elongates the O―O bond. Meanwhile, its greater adsorbate-substrate distortion and large adsorption energy render the Pt₄/HGCN system slightly superior to the Pt₄/TGCN system in catalytic performance. The results validate that being supported on g-C₃N₄ may be a good way to modify the electronic structure of materials and their surface properties improve their catalytic performance.

Key words: Graphitic carbon nitride, Pt cluster, Oxygen molecule, Adsorption, Photocatalyst, Density functional theory