Molybdenum disulfide (MoS 2 )h as been widely studied as ap otential earth-abundant electrocatalyst for the hydrogen-evolution reaction (HER). Defect engineering and heteroelemental doping are effective methods to enhance the catalytic activity in the HER, so exploring an efficient route to simultaneously achieve in-plane vacancy engineering and elemental doping of MoS 2 is necessary.I nt his study,Z inc, al ow-cost and moderately active metal, has been used to realizethis strategy by generation of sulfur vacancies and zinc doping on MoS 2 in one step.D ensity functional theory calculations reveal that the zinc atoms not only lower the formation energy of Svacancies,but also help to decrease DG H of S-vacancy sites near the Zn atoms.A ta no ptimal zincreduced MoS 2 (Zn@MoS 2 )example,the activated basal planes contribute to the HER activity with an overpotential of À194 mV at 10 mA cm À2 and al ow Tafel slope of 78 mV/dec.

Using first-principles calculations within density functional theory, we study Friedel oscillations (FOs) in the electron density at different metal surfaces and their influence on the lattice relaxation and stability of ultrathin metal films. We show that the FOs at the Pb(111) surface decay as 1/x with the distance x from the surface, different from the conventional 1/x(2) power law at other metal surfaces. The underlying physical reason for this striking difference is tied to the strong nesting of the two different Fermi sheets along the Pb(111) direction. The interference of the strong FOs emanating from the two surfaces of a Pb(111) film, in turn, not only results in superoscillatory interlayer relaxations around the center of the film, but also determines its stability in the quantum regime. As a simple and generic picture, the present findings also explain why quantum size effects are exceptionally robust in Pb(111) films.

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Pressure has been demonstrated to be an effective parameter to alter the atomic and electronic structures of materials. By using the first-principles calculations based on density functional theory (DFT), we systematically investigated the changes in the atomic and electronic structures of the cubic MAPbI(3) phase under pressures. It is found that the band gap of the compressed cubic MAPbI(3) structure exhibits a remarkable redshift to 1.114/1.380 eV in DFT/HSE-SOC calculation under a mild pressure of 2.772 GPa, and subsequently shows a widening at higher pressures until similar to 20 GPa. As the pressure further increases, the band gap closes at similar to 80 GPa. Detailed structural and electronic characteristic analyses indicate that the band gap of the cubic MAPbI(3) structure is determined by two competing effects: the lattice contraction decreases its band gap while the PbI6 octahedral filling increases it. Given that, pressure can be a powerful tool to help understanding the optoelectronic properties of perovskite materials. AbstractPressure has been demonstrated to be an effective parameter to alter the atomic and electronic structures of materials. By using the first-principles calculations based on density functional theory (DFT), we systematically investigated the changes in the atomic and electronic structures of the cubic MAPbI3 phase under pressures. It is found that the band gap of the compressed cubic MAPbI3 structure exhibits a remarkable redshift to 1.114/1.380 eV in DFT/HSE-SOC calculation under a mild pressure of 2.772 GPa, and subsequently shows a widening at higher pressures until ∼20 GPa. As the pressure further increases, the band gap closes at ∼80 GPa. Detailed structural and electronic characteristic analyses indicate that the band gap of the cubic MAPbI3 structure is determined by two competing effects: the lattice contraction decreases its band gap while the PbI6 octahedral tilting increases it. Given that, pressure can be a powerful tool to help understanding the optoelectronic properties of perovskite materials.

The C2N/α-Te vdW heterojunction possessed a unique type-II band alignment, tunable band gap, improved optical absorption strength, and broad spectrum width (ultraviolet to near-infrared).