Hybrid Density Functional Theory Study on Structural and Optoelectronic Properties of ZnSe_1–xTe_x for the Photocatalytic Applications

Abstract

In this work, hybrid density functional theory has been used to investigate the structural and optoelectronic properties of wurtzite ZnSe1–x Te x solid solutions. The calculated bandgap values are 2.82, 2.60, 2.48, 2.38, and 2.15 eV for the ZnSe, ZnSe0.75Te0.25, ZnSe0.50Te0.50, ZnSe0.25Te0.75, and ZnTe, respectively, which are in agreement with the experimental results. The valence band maximum of ZnSe1–x Te x solid solutions is mainly comprised of Se-4p, Te-5p, Zn-3p, and Zn-3d states. Moreover, a red shift (toward longer wavelength) is observed in the absorption edges of the ZnSe1–x Te x solid solutions, which enables them to effectively utilize visible light for the photocatalytic applications. The Te doping into ZnSe can increase the n-type conductivity of the obtained solid solutions. Effective mass of photogenerated charge carriers at all Te concentrations is less than 1.5m 0, implying the high mobility of charge carriers in the ZnSe1–x Te x solid solutions. The charge separation can be improved at the 25% and 50% doping of Te. Moreover, the positions of valence and conduction band edges of ZnSe1–x Te x ternary alloys straddle the potentials of both CO2 reduction and water oxidation, implying that these solid solutions are promising for the photocatalytic reduction of CO2 and oxidation of water. In addition, the water and CO2 molecules are strongly adsorbed on the surface of solid solutions.

Unconventional Anisotropy in Excitonic Properties and Carrier Mobility in Iodine-Based XTeI (X = Ga, In) Monolayers for Visible-Light Photocatalytic Water Splitting

“…For InTeI, the electron and hole mobilities along the x - and y -directions are comparable to that of MoS 2 (200 cm 2 V –1 s –1 ), , whereas for GaTeI, it is higher than that of MoS 2 along the x -direction. Moreover, the deviation of the relative ratio of holes and electrons, d = m h * / m e * , from unity is the measure of the rate of carrier recombination. − The magnitude of d along different directions is shown in Table . They range from ∼1.3 to ∼2.0, which is a significant deviation from 1.…”

Understanding the Influence of C-Doping on CO2 Photoreduction at SnS2 Nanosheets: A First-Principles Study

“…As a semiconductor catalyst for photocatalytic CO 2 reduction, it must have a suitable band edge position matching the potential of CO 2 /hydrocarbons and H 2 O/O 2 because the band edge positions determine the redox ability of photogenerated electrons and holes. Referring to the normal hydrogen electrode (NHE), the CBM and VBM of all catalytic substrates are calculated by the work function method − where E g is the band gap, E VB and E CB are the VB and CB potentials versus NHE (pH = 7), respectively, and ϕ is the work function.…”

Lead-Free Halide Perovskite Cs2AgBiBr6/Bismuthene Composites for Improved CH4 Production in Photocatalytic CO2 Reduction

“…The CO 2 conversion to CH 4 is not a straightforward process, as there are thermodynamic and kinetic limitations to the reaction. An efficient semiconductor photocatalyst for this kind of reaction should have a conduction band edge with a lower potential than that of the target reduction reaction, the ability to absorb a wide energy range of solar irradiation, high mobility, and efficient separation of the photogenerated charges …”