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.

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The theoretical prediction, electronic properties, and thermal transport properties of novel monolayer TlPt 2 Se 3 are investigated using the first-principles calculations and semi-classical Boltzmann transport theory. The calculated phonon band structure and exfoliation energy confirm that monolayer TlPt 2 Se 3 is a stable material and can be exfoliated from its bulk counterpart. The exfoliation energy of the monolayer turns out to be 37 meV Å −2 , comparable with the exfoliation energy of monolayer PdSe 2 . The HSE06 indirect bandgap of monolayer (bulk) TlPt 2 Se 3 amounts to 1.18 eV (0.63 eV). The relaxation time is calculated considering three types of scattering mechanisms. The monolayer outperforms the bulk counterpart in the Seebeck coefficient and power factor for both p-type and n-type dopings. Monolayer TlPt 2 Se 3 shows a high p-type Seebeck coefficient of 211 µV K −1 compared to the n-type Seebeck coefficient of 103 µV K −1 at maximum considered temperature (600 K) and a carrier concentration (10 20 cm −3 ). The calculated lattice thermal conductivity of monolayer TlPt 2 Se 3 is 1.92 W m −1 K −1 at 600 K which is lower than the monolayer PtSe 2 and MoSe 2 . The p-type figure of merit of 0.64 (at 600 K) affirms that the monolayer TlPt 2 Se 3 is an excellent thermoelectric material.

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