Novel Z-Scheme BiOM_1–xI_x (M = Cl, Br)/β-Bi₂O₃-(001) and BiOI/β-Bi₂O₃-(001) Heterojunction Photocatalysts with O Vacancies: A Study on the Hybrid Density Functional Approach

Abstract

In this paper, the heterostructures between the BiOM (M = Cl, Br, I) (001) and the β-Bi2O3 (001) crystal facet, denoted as BiOM/β-Bi2O3, are reasonably constructed. The hybrid density functional approach investigates their electronic structures, optical absorption, band alignments, and photocatalytic activities. It is found that I-doped BiOM (M = Cl, Br) can make the type I heterostructures BiOM (M = Cl, Br)/β-Bi2O3 change to the direct Z-scheme with increasing I doping concentration. Under a higher I doping concentration, the BiOCl1–x I x /β-Bi2O3 has a stronger reduction potential than the BiOBr1–x I x /β-Bi2O3. Significantly, the BiOI/β-Bi2O3 is the direct Z-scheme heterojunction. Combining the direct Z-scheme heterostructure characters of BiOM1–x I x (M = Cl, Br)/β-Bi2O3 and BiOI/β-Bi2O3 with appropriate band alignments, their electrons and holes can be excited and separated highly effectively. The BiOM1–x I x (M = Cl, Br) or BiOI part has a higher reduction ability, gathers electrons, and works as the reduction catalyst. In contrast, the β-Bi2O3 part has a higher oxidation ability, gathers holes, and works as the oxidation catalyst. Remarkably, the O vacancy in bismuth oxyhalides can further improve the direct Z-scheme alignment structure, accelerate the separation and migration of the photogenerated electron–hole pairs, and also enormously intensify the visible light absorption. The synergistic effect of the direct Z-scheme band alignment character and O vacancy makes the BiOCl28/32I4/32(VO)/β-Bi2O3 and BiOI (VO)/β-Bi2O3 present superior photocatalytic activities. The calculated results can provide insights into the designs and preparations of the visible light response BiOM (M = Cl, Br, I)-based semiconductor photocatalysts.

Exploring the effects of different crystal facet combinations and I-doping in the BiOCl/BiOI heterostructure on photocatalytic properties: a hybrid density functional investigation

“…The BiOX(010) (X = Cl, I) facet has only one stoichiometric surface termination with strong stability, 27 while BiOX(001) facet has three kinds of terminations with different stabilities. 27 Kong et al 28 and Jing et al 29 and our previous investigations 30,31 have demonstrated that the 1Xterminated BiOX(001) (X = Cl, I) surface exhibits much lower surface energy than 2X-terminated BiOX(001) and BiO-terminated BiOX(001) surfaces, and the electronic structure of the 1X-terminated BiOX(001) surface is very similar to that of the bulk. [28][29][30][31] Therefore, it is reasonable to consider the BiOX(010) and 1X-terminated BiOX(001) (X = Cl, I) surfaces to construct the specific crystal facet combination interface models with the (001) and (010) facets of BiOCl and BiOI.…”

“…where E BiOCl/BiOI is the total energy of the BiOCl/BiOI heterostructure, S heter is the cross-sectional area of the hetero-structure, while E BiOCl and E BiOI are the total energies of the isolated BiOCl and BiOI sheets, respectively. 30,[32][33][34][35][36][37] The hybrid functional calculation results for the binding energies of these heterostructures are summarized in Table 38 These results show that the formations of BiOCl(001)/BiOI(001), In order to better analyze the projected band structures of the heterostructures, the band structures, the total density of states (TDOS), and the projected density of states (PDOS) for the individual two-layer 2 × 2 1Cl-terminated (001) surface of BiOCl, the four-layer 1 × 2 (010) surface of BiOCl, the monolayer 2 × 2 1I-terminated (001) surface of BiOI and the twolayer 2 × 2 (010) surface of BiOI were calculated using the hybrid functional. The results are shown in Fig.…”

Evidence of direct Z-scheme triazine-based g-C3N4/BiOI (001) heterostructures: a hybrid density functional investigation

“…Due to the negative binding energy, this heterostructure is thermodynamically stable, which means it can be prepared or grown in a practical way. 70,71 Indeed, the thermostability of the heterojunction g-C 3 N 4 /BiOI (001) is verified via an AIMD simulation at 300 K, shown in Fig. 4(a) and (b).…”

Exploration of Photocatalytic Overall Water Splitting Mechanisms in the Z-Scheme SnS2/β-As Heterostructure

“…At the same time, the powerful redox ability of the heterostructure can be fully utilized. In this study, the Z-scheme heterostructure is qualitatively determined in terms of the built-in electric field, band bending, and electrostatic repulsion, which is a simple and common method at present. − It is worth mentioning that the excited carrier lifetime is a strong evidence for determining Z-scheme heterostructures. It can be calculated by nonadiabatic molecular dynamics simulations combined with first-principles calculations.…”