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Author: search.filters.author.Kotmool, K.

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    Revealing the binding mechanism of redox intermediates in sodium–sulfur batteries by two-dimensional Janus monolayers
    (2023-11-30)
    Kaewmaraya, T.
    ;
    Thatsami, N.
    ;
    Tangpakonsab, P.
    ;
    Klinkla, R.
    ;
    Kotmool, K.
    Ultrahigh theoretical energy density and naturally abundant electrode materials (i.e., sodium and sulfur) have rendered room-temperature sodium-sulfur batteries (Na-SBs) to be the emerging alternative for the large-scale applications. Nevertheless, rapid capacity decay caused by the shuttle effect, poor electrical conductivity of sulfur, and sluggish electrochemistry pose major obstacles to achieving commercial viability. Herein, we have proposed a new functionality of Janus-type transition metal dichalcogenides (TMDs) as cathode hosting materials to resolve the mentioned hindrances. Based on density functional theory (DFT), this work reports the interfacial interactions of sodium polysulfides (Na<inf>2</inf>S<inf>n</inf>) and a series of Janus MSX (M = Mo, W and X = Se, Te), electronic properties, and the crucial parameters of the electrochemical reaction. Among MSX, we find that MoSTe binds with Na<inf>2</inf>S<inf>n</inf> via chemical Na–S bonds causing the strongest binding energies (−1.18 to −2.48 eV) which are greater than do the electrolytes (−0.20 to −0.98 eV), thus effectively alleviating the shuttle effect. This immense binding is attributed to the magnified polar nature of MoSTe which intensifies the Na<inf>2</inf>S<inf>n</inf>–MoSTe interaction. Moreover, the charge accumulation in MoSTe as donated by Na<inf>2</inf>S<inf>n</inf> maximizes the electronic conductivity of MoSTe to improve the charge transport during the redox process. Importantly, this material facilitates the overall reversible electrochemical reactions by lowering the energy barriers of conversions among the redox intermediates in the sulfur reduction reaction (SRR), the decomposition barrier of final discharge product Na<inf>2</inf>S, and diffusion barrier of Na<sup>+</sup> ions. Hence, Janus MoSTe offers the manifold benefits for boosting the efficiency of Na-SBs.
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    Ultrahigh hydrogen storage using metal-decorated defected biphenylene
    (2023-08-30)
    Kaewmaraya, T.
    ;
    Thatsami, N.
    ;
    Tangpakonsab, P.
    ;
    Kinkla, R.
    ;
    Kotmool, K.
    Hydrogen (H<inf>2</inf>) energy has emerged as a principal contender for renewable green energy applications because of the ultra-high energy density and natural abundance. The implementation of this prospective technology necessitates the ultra-high capacity of H<inf>2</inf> storage mediums. This work reports the exceptional H<inf>2</inf> storage capacities of two-dimensional (2D) carbon allotrope biphenylene (BPL) functionalized by Li, Na, K, and Ca. The combined theoretical approaches including the density functional theory (DFT), ab-initio molecular dynamics (AIMD), maximally localized Wannier functions (MLWFs), and thermodynamic analysis were employed to elucidate the storage efficiencies at operationally practical conditions. The findings reveal that pristine BPL decorated by the selected metals are all inefficient for H<inf>2</inf> storage because of the sensitive crystal instability caused by the energetic aggregation of the metallic dopants. On the other hand, point-defected BPL resolves this issue because it adequately magnifies the binding energies with all the decorated metals via the highly ionic bonds. Crucially, these binding energies exceed the cohesive counterparts of the parental metal bulks, consequently stabilizing the crystal integrity. Intriguingly, the Li- and Na-decorated divacancy BPL retain the ultimate H<inf>2</inf> storage capacities of 6.76 wt% and 6.66 wt% at the practical temperature and pressure, respectively, surpassing the goal value of 5.50 wt% to be achieved by 2025. Hence, metal-functionalized BPL are conclusively the promising carbon materials for the H<inf>2</inf> storage functionality.
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    Hydrogen-induced phase stability and phonon mediated-superconductivity in two-dimensional van der Waals Ti2C MXene monolayer
    (2022-12-09)
    Tsuppayakorn-Aek, P.
    ;
    Bovornratanaraks, T.
    ;
    Ahuja, R.
    ;
    Luo, W.
    ;
    Kotmool, K.
    Herein, we report the phase stability of the hydrogenated Ti<inf>2</inf>C MXene monolayer using an evolutionary algorithm based on density functional theory. We predict the existence of hexagonal Ti<inf>2</inf>CH, Ti<inf>2</inf>CH<inf>2</inf>, and Ti<inf>2</inf>CH<inf>4</inf>. The dynamic and energetic stabilities of the predicted structures are verified through phonon dispersion and formation energy, respectively. The electron-phonon coupling is carefully investigated by employing isotropic Eliashberg theory. The T<inf>c</inf> values are 0.2 K, 2.3 K, and 9.0 K for Ti<inf>2</inf>CH, Ti<inf>2</inf>CH<inf>2</inf>, and Ti<inf>2</inf>CH<inf>4</inf>, respectively. The translation and libration adopted by stretch and bent vibrations contribute to the increasing T<inf>c</inf> of Ti<inf>2</inf>CH<inf>4</inf>. The high-frequency hydrogen modes contribute to the critical temperature increase. Briefly, this work not only highlights the effect of H-content on the increments of T<inf>c</inf> for Ti<inf>2</inf>CH<inf>x</inf>, but also demonstrates the first theoretical evidence of the existence of H-rich MXene in the example of Ti<inf>2</inf>CH<inf>4</inf>. Therefore, it potentially provides a guideline for developing hydrogenated 2D superconductive applications.
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    High-Pressure Structural Transformation Pathway and Electronic Properties of AgGaTe2: Ab Initio Evolutionary Structural Searching
    (2022-01-01)
    Kotmool, K.
    ;
    Tsuppayakorn-Aek, P.
    ;
    Luo, W.
    ;
    Ahuja, R.
    ;
    Bovornratanaraks, T.
    We have used systematic ab initio evolutionary structural searching to uncover the high-pressure transformation pathway of a promising thermoelectric material, AgGaTe2. The global structures of the ternary Ag-Ga-Te system have been predicted up to 100 GPa. The known chalcopyrite phase at ambient pressure is validated by the searching method. The B3-like structure with the space group (s.g.) of P4¯ m2 exhibits a metastable one at a low-pressure range. The first structural phase transition is calculated at about 4 GPa, processing the I4¯ 2d phase to a B1-like phase (s.g. Pmma). Other predicted structures, Pmn21 and Pm phases, are potentially coexisting phases up to 30 GPa because of the slightly different enthalpy. This finding reasonably explains the ambiguous results in the previous experiments. The high-pressure phase beyond 30 GPa is proposed to be a short-range alloy of bcc-Te and B2-AgGa rather than a cation-disordered B2-like phase. The band gap of the I4¯ 2d phase is increased with increasing pressure, while the metastable P4¯ m2 phase is a narrow band gap semiconductor. The electron-phonon coupling of the metallic phases of ternary IB-IIIA-VIA2 compounds is derived for the first time in AgGaTe2. They exhibit superconductors with a maximum Tc of 2.4 K in the Pmma phase at 6 GPa. The findings of this work not only provide a clear explanation of the high-pressure transformation pathway of AgGaTe2 but also suggest promising electronic properties guiding further applications, especially in a thermometric device, of this material under high pressure.