The single-layer MoS₂ is a highly sought-after semiconductor material in the field of photoelectric performance due to its exceptional electron mobility and narrow bandgap. However, its photocatalytic efficiency is hindered by the rapid recombination rate of internal photogenerated electron–hole pairs. Currently, the construction of heterojunctions has been demonstrated to effectively mitigate the recombination rate of photogenerated electron–hole pairs. Therefore, this paper employs the first principles method to calculate and analyze the four heterojunctions formed by MoS₂/WSe₂, MoS₂/MoSe₂, MoS₂/AlN, and MoS₂/ZnO. The study demonstrates that the four heterojunctions exhibit structural stability. The construction of heterojunctions, as compared to a monolayer MoS₂, leads to a reduction in the band gap, thereby lowering the electron transition barrier and enhancing the light absorption capacity of the materials. The four systems exhibit II-type heterojunction. Therefore, the construction of heterojunctions can effectively enhance the optical properties of these systems. By forming heterojunctions MoS₂/WSe₂ and MoS₂/MoSe₂, the absorption coefficient in the visible light region is significantly increased, resulting in a greater ability to respond to light compared to that of MoS₂/ZnO and MoS₂/AlN. Consequently, MoS₂-based heterojunctions incorporating chalcogenide components WSe₂ and MoSe₂, respectively, exhibit superior catalytic activity compared to MoS₂ heterojunctions incorporating non-chalcogenide components ZnO and AlN, respectively. The absorption spectrum analysis reveals that MoS₂/MoSe₂ exhibits the highest light responsivity among all investigated systems, indicating its superior photoelectric performance.

The energy band structure, density of states, and optical properties of monolayers of MoS₂ doped with alkaline earth metals (Be/Mg/Ca/Sr/Ba) are systematically studied based on first principles. The results indicate that all the doped systems have a great potential to be formed and structurally stable. In comparison to monolayer MoS₂, doping alkaline earth metals results in lattice distortions in the doped system. Therefore, the recombination of photogenerated hole–electron pairs is suppressed effectively. Simultaneously, the introduction of dopants reduces the band gap of the systems while creating impurity levels. Hence, the likelihood of electron transfer from the valence to the conduction band is enhanced, which means a reduction in the energy required for such a transfer. Moreover, doping monolayer MoS₂ with alkaline earth metals increases the static dielectric constant and enhances its polarizability. Notably, the Sr–MoS₂ system exhibits the highest value of static permittivity, demonstrating the strongest polarization capability. The doped systems exhibit a red-shifted absorption spectrum in the low-energy region. Consequently, the Be/Mg/Ca–MoS₂ systems demonstrate superior visible absorption properties and a favorable band gap, indicating their potential as photo-catalysts for water splitting.

Heterojunction GaN/MoSe₂ has recently piqued the interest of researchers due to its exceptional electronic and optical properties. Despite this, the higher rate of photogenerated carrier recombination limits their technical application. Implementing a promising approach to the formation of the 2D heterostructure with vacancies may improve photocatalytic activity. By first-principles, the stability, electronic structure, and optical properties of monolayer GaN and MoSe₂, GaN/MoSe₂ (GN/MS), GaN/MoSe₂ with a Ga vacancy (V_Ga-GN/MS), GaN/MoSe₂ with an N vacancy (V_N-GN/MS), and GaN/MoSe₂ with vacancies of Ga and N (V_{[email protected]}-GN/MS) are systematically computed. Compared with monolayer GaN, MoSe₂, and GaN/MoSe₂, the results show that vacancies do not destroy the stability of heterojunctions and cause a decrease in their bandgaps and a redshift of the absorption spectra. Type-II band alignment is observed through Perdew–Burke–Ernzerhof calculations in all heterostructures. V_Ga-GN/MS and V_{[email protected]}-GN/MS are p-type semiconductors, while V_N-GN/MS is an n-type semiconductor. Based on the analysis of Mulliken occupancy, work function, and optical properties, we speculate that vacancies of Ga and N cause GN/MS to be energetically favorable for water splitting.

The reasonable design of low-cost, high-activity single-atom catalysts (SACs) is crucial for achieving highly efficient electrochemical CO₂RR. In this study, we systematically explore, using density functional theory (DFT), the performance of transition metal (TM = Mn, Fe, Co, Ni, Cu, Zn)-doped defect-type hexagonal boron nitride (h-BN) SACs TM@B₋₁N (B vacancy) and TM@BN₋₁ (N vacancy) in both CO₂RR and the hydrogen evolution reaction (HER). Integrated crystal orbital Hamiltonian population (ICOHP) analysis reveals that these catalysts weaken the sp orbital hybridization of CO₂, which promotes the formation of radical-state intermediates and significantly reduces the energy barrier for the hydrogenation reaction. Therefore, these theoretical calculations indicate that the Mn, Fe, Co@B₋₁N, and Co@BN₋₁ systems demonstrate excellent CO₂ chemical adsorption properties. In the CO₂RR pathway, Mn@B₋₁N exhibits the lowest limiting potential (U_L = −0.524 V), and its higher d-band center (−0.334 eV), which aligns optimally with the adsorbate orbitals, highlights its excellent catalytic activity. Notably, Co@BN₋₁ exhibits the highest activity in HER, while U_L is −0.217 V. Furthermore, comparative analysis reveals that Mn@B₋₁N shows 16.4 times higher selectivity for CO₂RR than for HER. This study provides a theoretical framework for designing bifunctional SACs with selective reaction pathways. Mn@B₋₁N shows considerable potential for selective CO₂ conversion, while Co@BN₋₁ demonstrates promising prospects for efficient hydrogen production.

作为一种稳定性好、抗辐射能力强、原材料丰富的宽禁带半导体，ZnO在光催化的研究领域中成为热点材料，但是其仅能吸收可见光中的紫光，因此如何扩大ZnO对可见光的响应范围是一个值得研究的问题.掺杂改性是解决这个问题的常用方法.基于以上考量，本文应用第一性原理计算方法研究了N与Pr掺杂对ZnO的电子结构和光学性质的影响.研究结果表明：共掺体系比单掺体系更容易形成，且共掺体系的稳定性随Pr浓度的增加先增强后变弱；同一体系的最短Zn–O键与最长Zn–O键的布居数比例随杂质浓度的增大先增大后减小，说明杂质的掺入对体系的晶格畸变有很大的影响，有利于光生空穴-电子对的分离，从而提高材料的光催化活性.N 2p态与Pr 4f态发生杂化对晶体的完整性产生了破坏，在杂质原子周围形成晶场，造成能级劈裂，带隙减小；介电函数虚部的主峰位均向低能区域移动，吸收光谱中各掺杂体系发生红移，各共掺体系随着杂质原子Pr浓度的增加，在可见光区的响应范围依次扩大，吸收能力也依次增加，说明N与Pr的共掺杂对提高ZnO的光催化性是有利的.

We investigate the charge separation mechanisms in ZnO–MX ₂ (M = Mo, W; X = S, Se) heterojunctions. Distinct type-I/type-II characteristics and dielectric polarization variations are observed, where ZnO–WS ₂ exhibit enhanced charge separation and dual OER/HER activity.