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Photocatalytic water-splitting for hydrogen generation is a promising way to solve the energy crisis, yet the design of efficient photocatalysts is still a challenge. By utilization of first principles calculations, we predict the photocatalytic properties of monolayer boron phosphide (BP) based BP/XY2 (X = Mo, W; Y = S, Se) composites of different rotated configurations. Our results suggest that the BP/XY2 composites can be stably formed, and the narrowed bandgaps ensure these composites are suitable for absorbing visible light. The bandgaps and band edge positions are slightly affected by the rotation angles. The BP/MoS2, BP/MoSe2, and BP/WSe2 are type II heterostructures. Furthermore, the transferred charge from BP to XY2 layers leads to the formation of electric fields, which efficiently separate the photoinduced carriers. The band alignments of BP/MoS2, BP/MoS2, BP/MoSe2, and BP/WSe2 satisfy the requirements of overall water-splitting within the pH scope of 3.6-7.9, 6.8-7.9, 4.0-8.0, and 8.7-8.8. This work will provide valuable insight for designing efficient water-splitting photocatalysts.

Hybrid density functional has been adopted to theoretically investigate the structural, electronic, and optical properties of AlN/MoSe2, AlN/WS2, and AlN/WSe2 heterostructures with the consideration of effects of strains and pH so as to explore their potential visible light photocatalytic activities for water splitting. AlN/MoSe2, AlN/WS2, and AlN/WSe2 heterostructures with proper strains are energetically favorable due to the good lattice mismatch and the interface adhesion energies between the constituent monolayers. The charge accumulation/depletion around the interfaces of these heterostructures are beneficial for the generation and separation of photogenerated carriers, which is also favorable for improving the photocatalytic activities. Through adjusting the strains and the pH of the electrolyte, the AlN/MoSe2, AlN/WS2, and AlN/WSe2 heterostructures could own suitable bandgaps for absorbing visible light and appropriate band edge positions with respect to water redox levels for the spontaneous generation of hydrogen and oxygen. The band edge positions of AlN/MoSe2, AlN/WS2, and AlN/WSe2 heterostructures are thermodynamically feasible for over water splitting when the pHs of the electrolyte are respectively around 13, in the range of 4.5–8.1, and greater than 10.7. These findings pave a way to design the efficient AlN-based heterostructures for visible light photocatalytic water splitting.

We analyze the influences of interstitial atoms on the generalized stacking fault energy (GSFE), strength, and ductility of Ni by first-principles calculations. Surface energies and GSFE curves are calculated for the 〈11〉 (111) and 〈10〉 (111) systems. Because of the anisotropy of the single crystal, the addition of interstitials tends to promote the strength of Ni by slipping along the 〈10〉 direction while facilitating plastic deformation by slipping along the 〈11〉 direction. There is a different impact on the mechanical behavior of Ni when the interstitials are located in the slip plane. The evaluation of the Rice criterion reveals that the addition of the interstitials H and O increases the brittleness in Ni and promotes the probability of cleavage fracture, while the addition of S and N tends to increase the ductility. Besides, P, H, and S have a negligible effect on the deformation tendency in Ni, while the tendency of partial dislocation is more prominent with the addition of N and O. The addition of interstitial atoms tends to increase the high-energy barrier γmax, thereby the second partial resulting from the dislocation tends to reside and move on to the next layer.

Effects of Cr, Mo, and Nb on the ferritic stainless steel Σ(210) grain boundary and intragranularity are investigated using the first-principles principle. Different positions of solute atoms are considered. Structural stability is lowered by Cr doping and enhanced by Mo and Nb doping. A ranking on the effect of solute atoms enhancing the cohesive strength of the grain boundary, from the strongest to the weakest is Cr, Mo, and Nb. Cr clearly prefers to locate in the intragranular region of Fe rather than in the grain boundary, while Mo and Nb tend to segregate to the grain boundary. Solute Mo and Nb atoms possess a strong driving force for segregation to the grain boundary from the intragranular region, which increases the grain boundary embrittlement. For Mo- and Nb-doped systems, a remarkable quantity of electrons accumulate in the region close to Mo (Nb). Therefore, the bond strength may increase. With Cr, Mo, and Nb additions, an anti-parallel island is formed around the center of the grain boundary.

The possibility of using organic materials (NPB) as two-dimensional (2D) photonic band gap (PBG) crystals was investigated. Different aspects of the absolute PBG formation for 2D photonic crystals consisting of air pores drilled into NPB films were examined. The formation of PBG was shown and confirmed by a calculation of the transfer matrix method. It was found that the NPB hexagonal network structure could be a good candidate for absolute inhibition of reflection in the visible frequency region for the given orientation.