A comparative investigation of penta-graphene and Pt single atom@penta-graphene in H2 and O2 detection: DFT study with assessment of the van der Waals density functionals

Abstract

The gas-adsorption behaviors of O2 and H2 on penta-graphene (PG) and Pt single atom@penta-graphene (Pt-PG) were investigated using density functional theory calculations. To illustrate the importance of the van der Waals (vdW) interactions, in addition to popular local density approximation (LDA) and semilocal Perdew-Burke-Ernzerhof generalized gradient approximation (GGA-PBEsol) functionals, two non-local (vdW-DF2 and rev-vdW-DF2) functionals were investigated through the correlation between energetic, structural, and electronic properties. On the surface of the PG (band gap 2.3 eV), O2 was strongly physisorbed, which reduced the O2/PG band gap to ~0.75 eV and created a p-type semiconductor. The H2 was very weakly physisorbed without any changes in the band gap. On the semimetal Pt-PG (zero band gap), the H2 and O2 were strongly chemisorbed which was dissociative for H2. H2 adsorption opens a band gap of 1.45 eV, making the H2/Pt-PG system a semiconductor. But the O2/Pt-PG system remains semimetal. The PG can be used for the detection of O2 but not for H2. The presence of the Pt atoms allows the Pt-PG system to detect the H2 very well. LDA is suggested for investigating H2 adsorption on both the PG and Pt-PG systems, but the non-local vdWs must be used for the O2 adsorption study.