The electronic and electrochemical investigations of a Na-adsorbed BC₂N/Blue phosphorene van der Waals heterostructure show that it may operate as a promising anode material for sodium-ion batteries.

We report on theoretical investigations of a methylammonium lead halide perovskite system loaded with iron oxide and aluminum zinc oxide ($\mathrm{ZnO}:\mathrm{Al}/{\mathrm{MAPbI}}_3/{\mathrm{Fe}}_2{\mathrm{O}}_3$) as a potential photocatalyst. When excited with visible light, this heterostructure is demonstrated to achieve a high hydrogen production yield via a z-scheme photocatalysis mechanism. The ${\mathrm{Fe}}_2{\mathrm{O}}_3$: ${\mathrm{MAPbI}}_3$ heterojunction plays the role of an electron donor, favoring the hydrogen evolution reaction (HER), and the $\mathrm{ZnO}:\mathrm{Al}$ compound acts as a shield against ions, preventing the surface degradation of ${\mathrm{MAPbI}}_3$ during the reaction, hence improving the charge transfer in the electrolyte. Moreover, our findings indicate that the $\mathrm{ZnO}:\mathrm{Al}/{\mathrm{MAPbI}}_3$ heterostructure effectively enhances electrons/holes separation and reduces their recombination, which drastically improves the photocatalytic activity. Based on our calculations, our heterostructure yields a high hydrogen production rate, estimated to be $265.05 \mathsf{\mu }\mathrm{mol}/\mathrm{g}$ and $362.99 \mathsf{\mu }\mathrm{mol}/\mathrm{g}$, respectively, for a neutral pH and an acidic pH of 5. These theoretical yield values are very promising and provide interesting inputs for the development of stable halide perovskites known for their superlative photocatalytic properties.

Using density functional theory, a detailed computational study is performed to explore the structural and electronic properties of a black phosphorene monolayer, bilayer, and trilayer under a uniaxial strain along the armchair (b axis) and zigzag (a axis) directions. In the case of a monolayer black phosphorene, it is found that strain along the armchair direction slightly affects the a lattice parameter and the puckering height (Δ). Along the zigzag direction, however, variation of the a lattice parameter is compensated by both the a and b lattice variations while the parameter Δ remains unaffected. In the case of bilayer and trilayer black phosphorene, a similar behavior is observed where the layer-spacing “d” acts as an additional degree of liberty for strain compensation. In terms of electronic properties, strain along the armchair and zigzag directions changes the nature of the Γ point in the bandgap from a direct to an indirect electronic transition as a function of the strain value. In the strain range from −14% to +6%, all black phosphorene structures behave similarly to classical semiconductors. However, the size and strain combined effect significantly affects the Fermi energy position. Around 0% strain, all black phosphorene structures are of p-type, while they switch to an n-type semiconductor in the range of strain values from +2% up to +14%. This p-type to n-type transition may have a major technological impact in fields where mono- and hetero-junctions are considered.