Two-dimensional (2D) materials have shown extraordinary performances as photocatalysts compared to their bulk counterparts. Simulations have made a great contribution to the deep understanding and design of novel 2D photocatalysts. Ab initio simulations based on density functional theory (DFT) not only show efficiency and reliability in new structure searching, but also can provide a reliable, efficient, and economic way for screening the photocatalytic property space. In this review, we summarize the recent developments in the field of water splitting using 2D materials from a theoretical perspective. We address that DFT-based simulations can fast screen the potential spaces of photocatalytic properties with the accuracy comparable to experiments, by investigating the effects of various physical/chemical perturbations. This, at last, will lead to the enhanced photocatalytic activities of 2D materials, and promote the development of photocatalysis.

•A comprehensive study on the electronic structure and lattice dynamic stability of single-layer TMDs.•The TA mode softening along Γ–K direction becomes more evident from S to Se and to Te in the single-layer TMDs of Mo & W.•The single layers of Nb dichalcogenides are found instable with P-6m2 symmetry but stable with P-3m1 symmetry.•The infrared and Raman frequencies of the stable structures are presented.In the quest for advanced semi-conductors, we have expanded our knowledge on a series of single-layer TMDs by calculating the electronic structure and lattice dynamic stability based on the first-principles density functional theory. The single layers of Mo and W dichalcogenides are found to be stable with P-6m2 symmetry. The reduction of dimension opens up and increases the bandgap. The charge transfer is found to decrease from sulfide to selenide and to telluride due to the decrease of electronegativity of chalcogen, which also induces the reduction of bandgap. The TA mode softening is found along Γ–K direction and becomes more significant from sulfide to selenide and to telluride in the single-layer TMDs of Mo and W, which corresponds to the vibration of transition metal cations along y-axis. The single layers of Nb dichalcogenides are found to be instable with P-6m2 symmetry but stable with P-3m1 symmetry. It is also speculated that the interactions of cations mediated by electron–phonon coupling are accountable for the dynamic instability of the single-layer TMDs of Nb with P-6m2 symmetry. The unstable P-6m2 single-layer Nb dichalcogenides can transform to the stable P-3m1 structure during the exfoliation from the bulk, via the displacement of two anion layers of the sandwich structure.

The structural, dynamical, and electronic properties of compressed SrC2 were systematically investigated up to 200 GPa by using ab initio method. Three new phases are obtained by means of evolutionary algorithm. The confirmed most stable structure has C2/c symmetry at zero pressure, which transforms into an orthorhombic Cmcm phase at 4.5 GPa, followed by another orthorhombic Immm phase, which is stabilized at wide pressure range of 21.5–123.5 GPa, and then transformed into MgB2-type phase (space group, P6/mmm). Although SrC2 has similar structural transformation to that of compressed CaC2, SrC2 holds small electron–phonon coupling, which leads to its low superconducting critical temperature (only 1.8 K).

Phosphorene has attracted intense interest due to its unexpected high carrier mobility and distinguished anisotropic optoelectronic and electronic properties. In this work, we unraveled strain engineered phosphorene as a photocatalyst in the application of water splitting hydrogen production based on density functional theory calculations. Lattice dynamic calculations demonstrated the stability for such kind of artificial materials under different strains. The phosphorene lattice is unstable under compression strains and could be crashed, whereas phosphorene lattice shows very good stability under tensile strains. Further guarantee of the stability of phosphorene in liquid water is studied by ab initio molecular dynamics simulations. Tunable band gap from 1.54 eV at ambient condition to 1.82 eV under tensile strains for phosphorene is evaluated using parameter-free hybrid functional calculations. Appropriate band gaps and band edge alignments at certain pH demonstrate the potential application of phosphorene as a sufficiently efficient photocatalyst for visible light water splitting. We found that the strained phosphorene exhibits significantly improved photocatalytic properties under visible-light irradiation by calculating optical absorption spectra. Negative splitting energy of absorbed H2O indicates the water splitting on phosphorene is energy favorable both without and with strains.

Two-dimensional (2D) materials have shown extraordinary performances as photocatalysts compared to their bulk counterparts. Simulations have made a great contribution to the deep understanding and design of novel 2D photocatalysts. Ab initio simulations based on density functional theory (DFT) not only show efficiency and reliability in new structure searching, but also can provide a reliable, efficient, and economic way for screening the photocatalytic property space. In this review, we summarize the recent developments in the field of water splitting using 2D materials from a theoretical perspective. We address that DFT-based simulations can fast screen the potential spaces of photocatalytic properties with the accuracy comparable to experiments, by investigating the effects of various physical/chemical perturbations. This, at last, will lead to the enhanced photocatalytic activities of 2D materials, and promote the development of photocatalysis.