Understanding the contribution of hydroxyl to the energy band of a semiconductor: Bi₂O(OH)₂SO₄vs. Bi₆S₂O₁₅

Abstract

It is still a big challenge to facilely tune the energy bands of a semiconductor. Herein, we have mainly investigated energy bands and photochemical properties of Bi6S2O15 and Bi2O(OH)2SO4, which have very similar layered structures. It is found that the hydroxyls have down shifted the conduction band (CB, 0.21 eV) and valence band (VB, 4.39 eV) of Bi2O(OH)2SO4, compared with those (CB = 0 eV; VB = 3.36 eV) of Bi6S2O15. Moreover, the main oxidative species of Bi6S2O5 and Bi2O(OH)2SO4 are holes (h(+)) and hydroxyl radicals (˙OH) for the degradation of rhodamine B (RhB) dye, respectively. This obvious difference has been mainly attributed to the hydroxyls, which have changed the energy band structure and the band gap. In addition, we have also investigated the morphology-dependent properties of Bi2O(OH)2SO4. Under ultraviolet light irradiation (λ ≤ 420 nm), Bi2O(OH)2SO4 microspheres show an activity 1.3 times and 2.2 times higher than the long flakes and straw sheaves for the degradation of (RhB), respectively. This study provides us a new idea that we can facilely tune the energy band of a semiconductor by introducing or removing hydroxyl or other anions.

Synthesis, Crystal Structures, Spectroscopic Characterization, and Thermal Analyses of the New Bismuth Sulfates NaBi(SO4)2·H2O and ABi(SO4)2 (A = K, Rb, Cs)

“…[34] These Bi-O distances are consistent with those observed in other bismuth ( (Figure 2b). Figure 2c shows that two adjacent chains are connected via oxygen atoms forming a double-layered 2 ϱ [Bi(SO 4 ) 2 ]in the ab plane. For charge compensation, K + cations are located the between 2 ϱ [Bi(SO 4 ) 2 ]anionic layers; the whole structure is shown in Figure 2d along the [001] direction.…”

“…Figure 2c shows that two adjacent chains are connected via oxygen atoms forming a double-layered 2 ϱ [Bi(SO 4 ) 2 ]in the ab plane. For charge compensation, K + cations are located the between 2 ϱ [Bi(SO 4 ) 2 ]anionic layers; the whole structure is shown in Figure 2d along the [001] direction. 4and 1.475(4) Å, respectively, in good agreement with the sum of ionic radii of 1.47 Å.…”

“…Recently, bismuth-based metal sulfates have attracted much attentions due to rich coordination environments of stereoactive lone pair Bi 3+ cations, and their potential attractive properties such as electrochemical property, photocatalytic activity and second-harmonic generation response. [1][2][3] Materials featuring these fundamental properties are used in a large number of applications such as laser frequency conversion, thermal detectors, energy harvesting, and optical communications, etc. [4][5][6][7] A number of bismuth sulfates have already been reported: Bi 2 O 2 SO 4 •H 2 O, [8] [Bi 2 O(OH) 2 ](SO 4 ), [9] Bi 6 S 2 O 15 , [10] KBiCl 2 (SO 4 ), [3,11] A 2 Bi 2 (SO 4 ) 2 Cl 4 (A = NH 4 , K, Rb) [12] and (C 4 H 16 N 3 )[Bi(SO 4 ) 3 (H 2 O)] [13] are one-dimensional chains.…”

“…Recently, bismuth‐based metal sulfates have attracted much attentions due to rich coordination environments of stereo‐active lone pair Bi 3+ cations, and their potential attractive properties such as electrochemical property, photocatalytic activity and second‐harmonic generation response. [ 1–3 ] Materials featuring these fundamental properties are used in a large number of applications such as laser frequency conversion, thermal detectors, energy harvesting, and optical communications, etc. [ 4–7 ]…”

Boosting non-sacrificial H2O2 production on a Bi6S2O15 photocatalyst via creating a crystal surface-dependent internal electric field

“…The Bi 6 S 2 O 15 (BSO) photocatalyst, also developed by our group, exhibits an onset absorption wavelength near 400 nm, indicating that it responds partially to the solar spectrum. 19,20 Previous studies show that both BiPO 4 and BSO exhibit many similarities: high photocatalytic degradation activity due to their oxyacid cations with strong negative charges in the structure. It is worthwhile to evaluate crystal facet-engineered BSO with a wider sunlight absorption as a suitable photocatalyst for H 2 O 2 production.…”