The Thermodynamic Stability, Electronic and Photocatalytic Properties of the ZnWO₄(100) Surface as Predicted by Screened Hybrid Density Functional Theory

Abstract

Zinc tungstate (ZnWO 4 ) is an outstanding photocatalyst for water splitting and organic contaminant degradation under visible light irradiation. Surface termination stabilities are significant for understanding the photochemical oxidation and reactions on the ZnWO 4 surface. Based on density functional theory, we calculated the thermodynamic stability of possible surface terminations for ZnWO 4 (100). The surface stability phase diagrams show that the Zn 2 O 4 -Zn 8 W 6 O 28 , W 2 O 4 -Zn 8 W 10 O 36 , and Zn 2 -Zn 8 W 6 O 24 terminations of ZnWO 4 (100) can be stabilized under certain thermodynamic equilibrium conditions. The electronic structures for these three possible stability surface terminations are calculated based on the Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional to give dependable theoretical band gap values. It is found that the surface states of W 2 O 4 -Zn 8 W 10 O 36 termination are in the band gap, which shows a delocalized performance. The calculated absorption coefficients of W 2 O 4 -Zn 8 W 10 O 36 termination show stronger absorption than bulk ZnWO 4 in the visible-light region. The band edge calculation shows that the valence band maximum and conduction band minimum of the W 2 O 4 -Zn 8 W 10 O 36 termination can fulfill the hydrogen evolution reaction and oxygen evolution reaction requirements at the same time. Furthermore, work functions are extraordinarily distinct for various surface terminations. This result suggests that the ZnWO 4 -based direct Z-scheme heterostructure can be controlled by obtaining the thermodynamically preferred surface termination under suitable conditions. Our results can predict ZnWO 4 (100) surface structures and properties under the entire range of accessible environmental conditions.

The surface reconstruction induced enhancement of the oxygen evolution reaction on α-SnWO4 (010) based on a density functional theory study

“…This is due to the fact that the (010) facets of the a-SnWO 4 crystal have demonstrated notable photocatalytic water splitting ability in experiments. 15 Similar to previous findings [40][41][42] as well as our previous studies, 34,43,44 symmetrical layers terminated on both sides are used to cancel the macroscopic dipole moment perpendicular to the polar (010) surface of SnWO 4 (Fig. 1).…”

“…This behaviour has also been observed in the previous reports. 33,43,44,56 Specifically, this occupied surface state primarily consists of the hybridized O 2p and W 5d states (Fig. 7(b)).…”

First principles calculation of the ZnV2O6(001) surface terminations: the thermodynamic stability and electronic structure study

“…1. To describe the different O-excess and V-excess surface terminations in detail, we combined the surface nomenclature presented in previous studies 3,26,28 and labeled the surface terminations as A-I for convenience. The slabs were labeled according to the cut positions of the atomic stack, as shown in Fig.…”

Z-Scheme Photocatalytic Degradation of Potassium Butyl Xanthate by a 2D/2D Heterojunction of Bi2WO6 Using MoS2 as a Co-Catalyst

“…This ex- The identification of the exact band-edge position is also important for investigating the electron and hole migration pathways and the corresponding free-radical generation. The band-edge positions were calculated using the standard procedure presented in the literature [29]. Additionally, the valence band (VB) and conduction band (CB) potentials are measured using the empirical formulae: E VB = χ − E e + (0.5) E g ; E CB = E VB − E g .…”