Two-Dimensional Sc2CCl2/XSe2(X=Mo, Pt) van der Waals Heterojunctions: Promising Photocatalytic Hydrogen Evolution Materials.

In the field of photocatalysis, new heterojunction materials are increasingly explored to achieve efficient energy conversion and environmental catalysis under visible light and sunlight. This paper presents a study on two newly constructed two-dimensional van der Waals heterojunctions, Sc2CCl2/MoSe2 and Sc2CCl2/PtSe2, using density-functional theory. The study includes a systematic investigation of their geometrical structure, electronic properties, and optical properties. The results indicate that both heterojunctions are thermodynamically, kinetically, and mechanically stable. Additionally, Bader charge analysis reveals that both heterojunctions exhibit typical type II band properties. However, the band gap of the Sc2CCl2/MoSe2 heterojunction is only 1.18 eV, which is insufficient to completely cross the reduction and oxidation (REDOX) potential of 1.23 eV, whereas the band gap of Sc2CCl2/PtSe2 heterojunction is 1.49 eV, which is theoretically capable for water decomposition. The subsequent calculation of the Sc2CCl2/PtSe2 heterojunction demonstrate excellent hole carrier mobility and high efficiency light absorption in the visible light range, facilitating the separation of photogenerated electrons and holes. More importantly, Sc2CCl2/PtSe2 vdW type II heterojunction can achieve full water decomposition from pH 1 to pH 4, and its thermodynamic feasibility is confirmed by Gibbs free energy results. The aim of this study is to develop materials and analyses that will result in optoelectronic devices that are more efficient, stable, and sustainable.

A bicomponent synergistic MoxW1-xS2/aluminum nitride vdW heterojunction for enhanced photocatalytic hydrogen evolution: a first principles study.

The coupling of two-dimensional van der Waals heterojunctions is an effective way to achieve photocatalytic hydrogen production. This paper designs the MoxW1-xS2/AlN (x = 0, 0.25, 0.5, 0.75, 1) van der Waals heterojunction as a possible photocatalytic material. By using first-principles calculations, the effects of different Mo/W ratios on the band gap and photocatalytic hydrogen production performance of heterojunctions were investigated. The results show that the heterojunction is a direct Z-scheme photocatalyst and can achieve overall water splitting. By calculating the absorption spectrum, it is found that the heterojunction has a wider visible light absorption range when the bimetal is added, and there is still a strong absorption peak at 615 nm. With the increase of the Mo atom ratio, the absorption spectrum is red-shifted. The Gibbs free energy of the two-component Mo0.5W0.5S2/AlN heterojunction is only -0.028 eV. Our work provides a new perspective for the modification of 2D transition metal dichalcogenide photocatalytic heterojunctions.

Boosting the photocatalytic hydrogen evolution performance of monolayer C2N coupled with MoSi2N4: density-functional theory calculations.

Very recently, an important two-dimensional material, MoSi2N4, was successfully synthesized. However, pure MoSi2N4 has some inherent shortcomings when used in photocatalytic water splitting to produce hydrogen, especially a low separation rate of photogenerated electron-hole pairs and a poor visible light response. Interestingly, we find that the MoSi2N4 can be used as a good modification material, and it can be coupled with C2N to form an efficient heterojunction photocatalyst. Here, using density functional theory, a type-II heterojunction, C2N/MoSi2N4, is designed and systematically studied. Based on AIMD simulations and phonon dispersion verification, C2N/MoSi2N4 shows sufficient thermodynamic stability. As well as its perfect interface electronic properties, its large interlayer charge transfer and good visible light response lay the foundation for its excellent photocatalytic performance. In addition, the oxidation and reduction potentials of the C2N/MoSi2N4 heterojunction not only can meet the requirements of water splitting well but can also maintain a delicate balance between oxidation and reduction reactions. More importantly, the |ΔGH*| value of the C2N/MoSi2N4 heterojunction is very close to zero, indicating great application potential in the field of photocatalytic water splitting. In brief, our research paves the way for the design of future MoSi2N4-based efficient heterojunction photocatalysts.

Role of Temperature in the Growth of Silver Nanoparticles Through a Synergetic Reduction Approach.

This study presents the role of reaction temperature in the formation and growth of silver nanoparticles through a synergetic reduction approach using two or three reducing agents simultaneously. By this approach, the shape-/size-controlled silver nanoparticles (plates and spheres) can be generated under mild conditions. It was found that the reaction temperature could play a key role in particle growth and shape/size control, especially for silver nanoplates. These nanoplates could exhibit an intensive surface plasmon resonance in the wavelength range of 700-1,400 nm in the UV-vis spectrum depending upon their shapes and sizes, which make them useful for optical applications, such as optical probes, ionic sensing, and biochemical sensors. A detailed analysis conducted in this study clearly shows that the reaction temperature can greatly influence reaction rate, and hence the particle characteristics. The findings would be useful for optimization of experimental parameters for shape-controlled synthesis of other metallic nanoparticles (e.g., Au, Cu, Pt, and Pd) with desirable functional properties.