Colossal figure of merit and compelling HER catalytic activity of holey graphyne

Abstract

Herein, we have conducted a comprehensive study to uncover the thermal transport properties and hydrogen evolution reaction catalytic activity of recently synthesized holey graphyne. Our findings disclose that holey graphyne has a direct bandgap of 1.00 eV using the HSE06 exchange–correlation functional. The absence of imaginary phonon frequencies in the phonon dispersion ensures its dynamic stability. The formation energy of holey graphyne turns out to be − 8.46 eV/atom, comparable to graphene (− 9.22 eV/atom) and h-BN (− 8.80 eV/atom). At 300 K, the Seebeck coefficient is as high as 700 μV/K at a carrier concentration of 1 × 1010 cm-2. The predicted room temperature lattice thermal conductivity (κl) of 29.3 W/mK is substantially lower than graphene (3000 W/mK) and fourfold smaller than C3N (128 W/mK). At around 335 nm thickness, the room temperature κl suppresses by 25%. The calculated p-type figure of merit (ZT) reaches a maximum of 1.50 at 300 K, higher than that of holey graphene (ZT = 1.13), γ-graphyne (ZT = 0.48), and pristine graphene (ZT = 0.55 × 10–3). It further scales up to 3.36 at 600 K. Such colossal ZT values make holey graphyne an appealing p-type thermoelectric material. Besides that, holey graphyne is a potential HER catalyst with a low overpotential of 0.20 eV, which further reduces to 0.03 eV at 2% compressive strain.

Electronic, Thermal and Mechanical Properties of Carbon and Boron Nitride Holey Graphyne Monolayers

“…In order to investigate the electronic properties of the C-and BN-HGY monolayers, we carried out the electronic band structure calculations using PBE/GGA and HSE06 functionals, which are illustrated in Figure 2. The C-HGY monolayer is found to be a direct gap semiconductor with band gaps of 1.00 (0.50) eV, according to the HSE06(PBE) functional occurring at point K. The predicted electronic band gaps of the C-HGY monolayer match excellently with a recent theoretical report [38]. In contrast with the native C-HGY lattice, the BN-HGY monolayer is found to be an indirect gap insulator with a large band gaps of 5.58 (4.20) eV, according to the HSE06(PBE) methods.…”

“…These novel lattices are made of periodically benzene rings linked by triple C≡C bonds, exhibiting patterns of six-vertex and elongated eight-vertex rings. The predicted lattice constant of the C-HGY matches excellently with recent reports [25,38]. To examine the nature of the interactions in C-and BN-HGY lattices, electron localization function (ELF) [39] with an isosurface value of 0.75 is also shown in Figure 1.…”

Topological electronic states in holey graphyne

“…By employing DFT calculations, we obtain the stable realspace structure of HGY with a lattice constant of a 0 = 10.85 Å (see bonding information in supplementary note S1) and the band structure as depicted in figures 1(a) and (b), respectively, in good agreement with the results in previous works [47,54]. The structure in figure 1(a) can be regarded as a network of hexagons (benzene rings) and octagons, and there are two types of carbon sites, one belongs to the hexagon (shared with the octagon) and the other only belongs to the octagon.…”

Graphsene as a novel porous two-dimensional carbon material for enhanced oxygen reduction electrocatalysis

“…In a significant advancement, the recent synthesis of holey-graphyne has marked a pivotal development. This functional porous material, with an electronic band gap energy of 1.1 eV, not only exhibits a high thermoelectric figure of merit (ZT = 1.5) at room temperature but also demonstrates enhanced hydrogen evolution reaction (HER) performance 25 , 26 .…”