Phonon Spectrum Simulations Research Articles

Highly efficient photocatalytic performance of Z-scheme BTe/HfS2 heterostructure for H2O splitting

Constructing van der Waals (vdW) heterostructures is one of the effective strategies for developing highly efficient photocatalysts. In this study, we have designed a novel BTe/HfS2 heterostructure and systematically investigated its electronic properties and photocatalytic performance using first-principles calculations. The dynamic stability and thermodynamic stability of the heterostructure are verified through phonon spectrum simulations and ab initio molecular dynamics (AIMD) simulations, respectively, enhancing the likelihood of experimental synthesis. The bandgap of the BTe/HfS2 heterostructure is 0.12 eV, and the band edge positions satisfy the overall water splitting requirements for photocatalysts. The charge density difference, work function, Bader charge, and band alignment all confirm that the BTe/HfS2 heterostructure is a typical direct Z-scheme heterostructure, effectively facilitating the separation of photogenerated charge carriers and exhibiting strong redox capability. The solar-to-hydrogen (STH) efficiency of the BTe/HfS2 heterostructure reaches as high as 17.32 %. Moreover, the heterostructure exhibits strong light absorption capability, reaching a magnitude of 105. The carrier mobility of the BTe/HfS2 heterostructure surpasses that of two individual monolayer materials, with the hole mobility in the x-direction reaching an impressive 28357.15 cm2s-1V-1. Simultaneously, the Gibbs free energy indicates that the BTe/HfS2 heterostructure can undergo the hydrogen evolution reaction (HER) with only 0.19 eV of external potential at pH = 0. Moreover, at pH = 7, it can spontaneously convert H2O into O2. Therefore, the newly designed BTe/HfS2 heterostructure offers a new direction for practical applications of photocatalysts.

Discovery of a new quantum spin Hall phase in bilayer plumbene

Two-dimensional (2D) large-gap quantum spin Hall (QSH) insulator are imperative for achieving dissipationless transport devices. The bottleneck preventing applications from QSH phase, however, is lack of feasible 2D films experimentally. By using first-principles calculations, here we propose a new 2D topological phase in the bilayer plumbene. Its geometric stability is confirmed by phonon spectrum simulation and ab initio molecular dynamics simulation. We find that it can turn into a nontrivial QSH phase under tensile strain and its nontrivial gap is highly tunable by external strains. The origin behind QSH effect can be identified by s–px,y band inversion, topological invariant Z2, and helical edge states within the bulk gap. Also, a heterostructure composed of bilayer plumbene deposited on semiconducting MoS2 substrate remains topologically nontrivial properties with a sizable gap. These findings provide a promising platform to design a large-gap QSH insulator in Pb film, which show potential applications in spintronics devices.