Contents lists available at ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc Full Length Article A comparative investigation of penta-graphene and Pt single atom@penta- graphene in H 2 and O 2 detection: DFT study with assessment of the van der Waals density functionals Razieh Habibpour (Assistant professor) a, ⁎ , Aidin Ahmadi b , Mahdi Faghihnasiri b , Parisa Amani a a Department of Chemical Technologies, Iranian Research Organization for Science and Technology (IROST), Sh. Ehsani Rad St., Enqelab St., Parsa Sq., Ahmadabad Mostoufi Rd., Azadegan Highway, P. O. Box 33535-111, Tehran 3313193685, Iran b Computational Materials Science Laboratory, Nano Research and Training Center, NRTC, Tehran, Iran ARTICLE INFO Keywords: Penta-graphene Pt single atom H 2 O 2 DFT vdW interactions ABSTRACT The gas-adsorption behaviors of O 2 and H 2 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 prop- erties. On the surface of the PG (band gap 2.3 eV), O 2 was strongly physisorbed, which reduced the O 2 /PG band gap to ~0.75 eV and created a p-type semiconductor. The H 2 was very weakly physisorbed without any changes in the band gap. On the semimetal Pt-PG (zero band gap), the H 2 and O 2 were strongly chemisorbed which was dissociative for H 2 .H 2 adsorption opens a band gap of 1.45 eV, making the H 2 /Pt-PG system a semiconductor. But the O 2 /Pt-PG system remains semimetal. The PG can be used for the detection of O 2 but not for H 2 . The presence of the Pt atoms allows the Pt-PG system to detect the H 2 very well. LDA is suggested for investigating H 2 adsorption on both the PG and Pt-PG systems, but the non-local vdWs must be used for the O 2 adsorption study. 1. Introduction Nowadays, the development of new gas sensitive materials with properties such as high single molecule sensitivity, high resistivity, low cost, ease of fabrication, low energy consumption, and miniaturization is of considerable importance [1–8]. Among the nanomaterials that have been used to prepare gas sensors, metal nanoparticles, metal oxides, metal complexes, polymers, and carbon nanotubes can be noted [9–11]. Lately, graphene has been presented as a possible alternative for improving nanostructured gas sensors. It is the frst two-dimensional (2D) material to be discovered that exhibits outstanding physical, chemical, and mechanical properties. In particular, graphene has only a surface and no volume, which maximizes the interaction of adsorbates on the layer [12–14]. However, the physisorption of common gas mo- lecules such as CO 2 , CO, CH 4 ,H 2 O, H 2 ,N 2 , NO 2 , and NO on pristine graphene without a band gap and spin polarization restricts its potential for use in gas sensors [15–18]. Unlike graphene (it is a zero band gap semimetal with only sp 2 hybridization), a new 2D allotrope of carbon, namely penta-graphene (PG), could perform better in the feld of gas sensors; it has a notable intrinsic band gap (quasi-direct in the range of 2.22–4.48 eV) and sp 2 -sp 3 hybridization [19–24]. Chemical gas sensors based on semiconducting graphene-like materials are currently one of the most attractive types of sensor for the detection of molecular gases and pollutants, and noble metals such as platinum are generally the most frequently studied in order to tune selectivity, lower the operation temperature, and improve their response time [25–27]. The high cost and scarcity of noble metals pose a serious challenge for the wide- spread adoption and sustainability of these sensors. Surface phenomena with metal single-atoms refer to adsorption by a surface that contains only isolated single atoms dispersed on a support. This issue was frst introduced in 2011 and has received much attention in recent years in the heterogeneous adsorption feld [28]. A good dispersion of the me- tals at the single-atomic level maximizes their atomic ability, presenting active sites that are more uniform and precise in comparison to the usual nano scale metal surface that involves diferent types of active adsorption sites [29–31]. All transition and noble metals on diferent supports can be used for this purpose. Among them, Pt has been se- lected in this study due to its widespread application: hydrogenation/ https://doi.org/10.1016/j.apsusc.2020.147043 Received 30 December 2019; Received in revised form 11 June 2020; Accepted 19 June 2020 ⁎ Corresponding author at: Department of Chemical Technologies, Iranian Research Organization for Science and Technologies (IROST), Tehran, Iran. E-mail address: Habibpour@irost.ir (R. Habibpour). Applied Surface Science 528 (2020) 147043 Available online 24 June 2020 0169-4332/ © 2020 Elsevier B.V. All rights reserved. T