First-Principles Study on the Electronic Structure and Optical Properties of BiOIO₃ Doped with As, Se, and Te

Abstract

This study calculates the electronic structure and optical properties of intrinsic BiOIO₃ and X-BiOIO₃ (X = As, Se, or Te) using PBE (Perdew–Burke–Ernzerhof) and MBJ (Modified Becke–Johnson) functionals based on density functional theory, with MBJ showing better correlation with experimental values. The X-BiOIO₃ systems exhibit relative stability under MBJ potential and show crystal lattice distortion compared to intrinsic BiOIO₃, creating localized potential differences that enhance polarization and adjust the bandgap. Doping reduces the bandwidth and increases energy level density, promoting electron transitions. Consequently, based on the computational results presented in this paper, it can be inferred that both BiOIO₃ and X-BiOIO₃ facilitate water hydrolysis and oxygen generation due to their favorable energy band positions. Notably, Se-BiOIO₃ exhibits the highest visible light absorption capacity, which may enhance photocatalytic efficiency by strengthening the built-in electric field and promoting charge carrier generation.

1. Introduction

Under specific lighting conditions, TiO₂ exhibits photocatalytic properties that enable water splitting for the production of clean and sustainable hydrogen energy, thereby driving traditional photocatalysis research in the scientific community [1]. Subsequent studies have revealed that conventional photocatalysts, such as TiO₂, ZnO, and SiO₂, possess the capability to not only facilitate water decomposition but also effectively degrade various pollutants [2]. However, the pronounced recombination rate of photo-generated electron–hole pairs in conventional photocatalytic materials significantly hampers their practical implementation in industrial production [3]. In recent years, the quest for novel photocatalytic materials [4] has emerged as a prominent trend in scientific research, garnering significant attention from numerous scholars.

As early as 2004, Grosso et al. [5] proposed the concept of utilizing ferroelectrics in the realm of photocatalysis, subsequently leading to the identification of several ferroelectric materials exhibiting exceptional photocatalytic activity [6,7]. Bismuth-based material BiOIO₃, as a representative ferroelectric catalyst, achieved removal efficiencies of 100%, 85.2%, and 65.2% for methyl orange, rhodamine B, and methylene blue, respectively, after 16 min of ultraviolet light exposure. Compared to commercial TiO₂ and other bismuth oxides, BiOIO₃ nanosheets exhibited significantly enhanced photocatalytic activity, with the apparent reaction rate constant for methyl orange being 10.26 times higher than that of TiO₂ [8]. The exceptional photocatalytic ability of BiOIO₃ can be attributed to its unique layered structure [9], comprising nested [Bi₂O₂]²⁺ and [IO₃]⁻ units. Notably, the latter exhibits a triangular pyramidal configuration, as illustrated in Figure 1. Due to the asymmetric distribution of its atoms, the separation of positive and negative charge centers gives rise to a dipole moment in the [IO₃]⁻ triangular pyramidal system, with a flow of negative charge to positive charge. The polarization directions of [IO₃]⁻ groups are systematically aligned along the C-axis, resulting in a pronounced macroscopic polarization effect [9] in the BiOIO₃, as well as the establishment of an inherent electric field due to spontaneous polarization. The intrinsic electric field [10] plays a pivotal role in facilitating rapid carrier migration and suppressing electron–hole recombination, thereby significantly enhancing the photocatalytic efficiency of BiOIO₃ [11,12,13]. As a result of these unique properties, BiOIO₃ holds great potential for broad applications in the field of photocatalysis.

Although the presence of an internal electric field in BiOIO₃ enhances its photocatalytic performance [11], its larger band gap width of 3.3 eV hinders further improvement in its photocatalytic ability [14]. Existing research has demonstrated that doping modification could enhance the photocatalytic performance of BiOIO₃. In their experimental studies, Huang et al. [15] employed BiOIO₃ and N-BiOIO₃ as photocatalysts for the degradation of various pollutants including Rhodamine B, bisphenol A, and tetracycline. Their findings revealed that N-BiOIO₃ demonstrated superior photocatalytic degradation efficiency compared to intrinsic BiOIO₃. Liu et al. [16] incorporated sulfur atoms into the oxygen sites of BiOIO₃, resulting in a downward shift of the conduction band edge and a reduction in the bandgap. Huang et al. [17] accomplished a visible-light photocatalytic performance in the layered bismuth-based photocatalyst BiOIO₃ through iodine ion doping. In contrast to pure BiOIO₃, the photoresponse range of iodine-doped BiOIO₃ was significantly expanded from ultraviolet light to visible light, while attaining a tunable bandgap. The aforementioned modifications result in a reduction in the energy required for electron transition and facilitate the process, thereby significantly enhancing its photocatalytic efficacy. The enhancement achieved through non-metal doping demonstrates the remarkable potential of this modification strategy to improve the photocatalytic performance of BiOIO₃. In order to evaluate the photocatalytic performance of BiOIO₃ substitutional doped non-metallic elements, this study employs first principles to calculate the electronic structure and optical properties of BiOIO₃-doped X. The rationale for selecting As, Se, and Te as doping elements lies in their classification within similar groups (Group VA and Group VIA) of the periodic table. These elements exhibit analogous chemical and physical properties, enabling them to form substitutional or interstitial dopants within the same host material matrix. Consequently, this facilitates the effective modification of the material’s electronic properties. The incorporation of arsenic, selenium, and tellurium can modulate the energy band structure of materials, particularly semiconductors, thereby enhancing light absorption capabilities and improving the separation efficiency of photo-generated carriers, which ultimately boosts photocatalytic activity. Additionally, the introduction of As, Se, and Te atoms significantly alters the carrier concentration of the material, thereby influencing its charge transport properties and reactivity. The obtained calculation results will offer theoretical guidance for the synthesis of BiOIO₃ catalysts that are modified using the doping method.

2. Materials and Methods

In this study, the crystal structure of BiOIO₃ is orthorhombic, exhibiting a space group of Pca2₁ (No. 29) [11]. This non-centrosymmetric arrangement (NCS) consists of interleaved [Bi₂O₂]²⁺ and [IO₃]⁻ units. The model of doped BiOIO₃, as depicted in Figure 2, demonstrates the utilization of one X atom being substituted for one I atom. Hence, the doping concentration of X-BiOIO₃ is precisely 6.25%. The replaced position of atom I must be excluded outside the boundaries in order to mitigate boundary effects. Moreover, within the unit cell, any position of atom I is symmetrical and satisfies the requirements of symmetry. Hence, the replacement position of atom I can be chosen arbitrarily within the unit cell without impacting the final calculation results. In this study, we ultimately selected the coordinate position of replaced atom I as (0.748, 0.366, 0.335). The electronic configurations of the elements discussed in this article are as follows, Bi: 6s² 6p³; I: 5s² 5p⁵; O: 2s² 2p⁴; As: 4s² 4p³; Se: 4s² 4p⁴; Te: 5s² 5p⁴.

The calculations are predominantly performed using the Vienna Ab-initio Simulation Package (VASP 6) [18], specifically employing the generalized gradient approximation (GGA) within density functional theory (DFT) and utilizing the MBJ semi-local exchange-correlation potential [19] for material characterization. The cut-off energy for the BiOIO₃ was set at 550 eV. The K-point grid was determined according to Monkhorst’s scheme [20], employing a 4 × 4 × 4 configuration. The convergence criterion for internal stress was established to be no greater than 0.02 GPa, while the energy convergence threshold was defined as being within 2 × 10⁻⁶ eV/atom. Additionally, the self-consistency iteration convergence accuracy was specified to be 2 × 10⁻⁶ eV/atom, and the MBJ parameter c value was determined to be 1.34. Due to the discrepancy between results obtained from calculations using monoclinic cells and actual conditions, an expanded cell model was employed to optimize computational resources while ensuring accuracy. Ultimately, a 2 × 2 × 1 BiOIO₃ supercell model was selected.

3. Results and Discussion

3.1. Geometric Optimization Results

To improve the precision of the computational results, this study conducts geometric optimization on the systems, with the outcomes presented in

Table 1. The lattice constant and volume of each model.

Model	a/nm	b/nm	c/nm	V/nm3
BiOIO3 (Experiment) [21]	0.5658	1.1039	0.5748	/
BiOIO3 (This work)	0.5712	1.1263	0.5788	1.4898
As-BiOIO3	0.5698	1.1311	0.5779	1.4899
Se-BiOIO3	0.5706	1.1237	0.5780	1.4826
Te-BiOIO3	0.5695	1.1272	0.5775	1.4830

. After optimization, it is observed that the lattice constant ratio (c/a) for intrinsic BiOIO₃ is 1.013, exhibiting a negligible deviation of only 0.2% from the experimental value of 1.0159. This observation suggests that the computational parameters employed in this study exhibit reliability and generate precise outcomes. The volume of each doped system changes, indicating that these systems experience lattice distortion relative to the calculated values of intrinsic BiOIO₃. Considering the inherent non-centrosymmetric (NCS) nature of BiOIO₃, it naturally induces a polarization effect. The doping further enhances this phenomenon, facilitating the generation of localized potential differences within the systems and augmenting the migration rate of photo-generated electron–hole pairs.

3.2. Structural Stability of BiOIO₃ and X-BiOIO₃

To conduct a detailed investigation of the stability of the four systems, the formation energy and binding energy are calculated for each system. The binding energy [22] and formation energy [23] serve to characterize the stability of the system and the ease of doping, respectively. A lower formation energy indicates a greater ease of doping, while a lower binding energy correlates with the enhanced stability of the system. Additionally, the doping formation energy (E_f) [24] and binding energy (E_b) [25] for different systems are determined using Equations (1) and (2).

$$E_f=E_{XBIO}-E_{BIO}-m{\mu }_x+n{\mu }_I$$

(1)

$$E_b=1/N(E_{tot}-E_{BIO})$$

(2)

In the equation, E_tot is the total energy of all the atoms of the system in their free state. E_XBIO represents the total energy of the system after doping. E_BIO denotes the total energy of the BiOIO₃. μ_x and μ_I denote the chemical formulas of the dopant atom X and the host atom I, respectively. m and n denote the quantities of dopant atoms and substituted atoms, respectively (in this study, m = n = 1). N denotes the total number of atoms present in the system. All the calculated results are listed in

Table 2. The total energy, binding energy, and formation energy of each model before and after doping.

Model	E/eV	Eb/eV	Ef/eV
BiOIO3	−477.2118	/	/
As-BiOIO3	−479.9295	−0.3186	−4.9405
Se-BiOIO3	−479.3817	−0.3183	−2.1449
Te-BiOIO3	−479.9295	−0.3185	−2.6956

E represents the total energy of BiOIO₃ and the X-BiOIO₃ systems.

. The binding energy and formation energy of all doped systems exhibit negative values, implying that the formation of these systems is straightforward. The As-doped BiOIO₃ demonstrates optimal stability and facile formation, as evidenced by its significantly lower binding energy and formation energy compared to the other systems observed.

3.3. Electronic Structure of BiOIO₃ and X-BiOIO₃

To further investigate the variations in electronic structure among different systems, this study computes the energy band and electron state density for each system. The high symmetry points in the Brillouin region of the BiOIO₃ cells are denoted by Γ (0, 0, 0), M (0.5, 0, 0), K (0.5, 0.5, 0), Z (0, 0.5, 0), and Γ (0, 0, 0), as shown in Figure 3. The line with zero energy is designated as the Fermi level. The density of states for intrinsic BiOIO₃ is presented in Figure 3a,b, calculated using the PBE functional [26] and MBJ functional, respectively. The results indicate that the bandgap value obtained from the PBE calculation is 2.043 eV, which deviates by approximately 38% from the experimental value (3.3 eV) [14]. This underestimation occurs because when solving the Cohen–Shen equation, PBE does not consider the excited states of the system, thereby leading to the underestimation of the band gap. To solve this problem, the kinetic energy density term is added to the MBJ function on the basis of GGA-PBE in order to improve the accuracy of energy and band structure calculations. Therefore, the MBJ potential achieves a significantly higher accuracy in energy and band structure calculations [27]. To enhance the accuracy of the bandgap, we employ the MBJ functional to perform a recalculation of the band structure of materials. The recalculated result of 3.308 eV exhibits a deviation of approximately 0.24% from the experimental value, thereby substantiating its reliability. Consequently, we will employ the MBJ functional approach for subsequent sections to conduct further investigations into the electronic structure.

The band structure of non-metallic doped materials is depicted in Figure 4. From the figure, it can be observed that the bandgap values of As-BiOIO₃, Se-BiOIO₃, and Te-BiOIO₃ are calculated as 2.590 eV, 3.171 eV, and 2.867 eV, respectively. These values are found to be smaller than the intrinsic bandgap of BiOIO₃ by 21.7%, 4.1%, and 13.3%, respectively, facilitating an easier transition of valence band electrons to the conduction band. Consequently, this enhances the probability of electron transition and further modulates the optical performance of the systems. Among them, As-BiOIO₃ exhibits the smallest bandgap, accompanied by an impurity level at 2.072 eV that facilitates electron transitions and enhances the probability of such transitions. Accordingly, doping leads to a denser energy band structure, thereby promoting electron migration.

To further investigate the impact of doping on the electronic structure of the system, we present herein the total and partial density of states prior to and subsequent to doping, as visually depicted in Figure 5. Figure 5a presents the electron density of states for the intrinsic BiOIO₃. The valence band maximum (VBM) primarily originates from the 2p orbitals of oxygen and the 6s orbitals of Bi, while the conduction band minimum (CBM) predominantly comprises the 5p orbitals of I, along with the 6p orbitals of Bi and the 2p orbitals of O. Figure 5b presents the electron density of states for the As-doped BiOIO₃. The VBM primarily originates from the O-2p, Bi-6s, I-5p, and I-5s orbitals, with a minor contribution from the As-4p orbital. In contrast, the CBM is predominantly composed of the I-5p, O-2s, Bi-6p, and O-2p orbitals, as well as including contributions from the As-4s and As-4p orbitals. Furthermore, the introduction of an impurity element leads to the emergence of a defect energy level, thereby contributing to a reduction in the bandgap width within the system. The presence of this impurity level facilitates electron transitions by serving as a “bridge”, thereby augmenting the likelihood of such transitions and enhancing the optical performance of the system. Figure 5c illustrates the electron density of states for Se-doped BiOIO₃, demonstrating that the contributions of Bi, O, and I to the system are largely consistent with those in intrinsic BiOIO₃. However, the incorporation of Se leads to an upward shift in the valence band, causing the Fermi level to traverse through it and exhibit typical characteristics of a p-type semiconductor. Additionally, this upward shift of the valence band also leads to a slight reduction in the bandgap. The electron density of states for Te-doped BiOIO₃, as shown in Figure 5d, exhibits a striking resemblance to that of Se-doped BiOIO₃. The incorporation of Te induces an upward shift in the valence band, thereby conferring p-type semiconductor characteristics upon the system. The conduction band also undergoes a downward shift, resulting in a significant reduction in the width of the bandgap due to the influence exerted by the Te-5s orbital. Consequently, the introduction of As, Se, and Te as dopants in BiOIO₃ leads to a reduction in the energy required for electron transitions, thereby indicating an augmentation in the optical performance of the systems.

3.4. The Two-Dimensional Electron Density and Bader Charges of BiOIO₃ and X-BiOIO₃

The electron density diagrams on the (100) plane of BiOIO₃ before and after doping are presented in Figure 6. It is evident that doping induces alterations in the distribution of electron clouds within the systems, implying a modification in atomic bonding. The introduction of an As atom into BiOIO₃ leads to a shift in the bonding between the As and O atoms due to the deviation in atomic positions, resulting in enhanced charge delocalization near the As atoms, as depicted in Figure 6b. Meanwhile, no significant alteration in the electron cloud distribution is observed for the Se-BiOIO₃ and Te-BiOIO₃ systems, as depicted in Figure 6c,d. However, when compared to intrinsic BiOIO₃, the Se atom demonstrates a higher degree of delocalization while enhancing the localization of the adjacent O atom. This suggests a transfer of electrons from the vicinity of the Se atom to the O atom. When one Te atom replaces one I atom, the degree of electron cloud overlap with the neighboring O atoms decreases, indicating a weakening in the bonding interaction between Te and its adjacent O atoms. Consequently, upon the substitution of I atoms by X atoms, the electron cloud undergoes varying degrees of changes, indicating that doping modifies the internal electron arrangement of the system and facilitates electron transfer [22]. The observed phenomenon can potentially be attributed to the disparity in non-metallic properties among the four atoms. In accordance with Pauling electronegativity, iodine (I) exhibits a higher electronegativity value of 2.66 compared to arsenic (As) at 2.18, selenium (Se) at 2.55, and tellurium (Te) at 2.1. Consequently, the non-metallic characteristics of these atoms follow the order I > Se > As > Te. Thus, upon the substitution of iodine atoms with X atoms, there is a reduction in electron cloud density near this position.

To further investigate the charge transfer dynamics in each system following doping, we employed the Bader charge method to analyze the charges of the oxygen atoms adjacent to the doping sites. The obtained results are presented in

Table 3. Bader charge of O atom near the doping site.

Model	The Charge of O Atoms
	O1	O2	O3	O4	Average
BiOIO3	6.8260	6.9150	6.9662	6.9119	6.9048
As-BiOIO3	7.0762	7.0254	6.9087	7.1356	7.0364
Se-BiOIO3	7.0203	7.0499	6.9736	7.0125	7.0141
Te-BiOIO3	7.0304	7.1611	7.0102	7.1411	7.0857

, with atomic numbers cross-referenced in Figure 1.

The table demonstrates a high degree of consistency in the charges of the four nearest oxygen atoms surrounding the I atom in intrinsic BiOIO₃, implying an even distribution of electrons among these oxygen atoms and a lack of significant distortion. Upon doping with the non-metal X, a pronounced distortion in the charge distribution of oxygen is observed. In comparison to the intrinsic BiOIO₃, the charges of the O atoms adjacent to the doping sites in the doped system are all elevated due to the higher electronegativity of I compared to that of the X atoms. This observation is consistent with electron density analysis findings. The table further demonstrates that variations in the doping element exert a significant influence on the dynamics of charge transfer. In As-BiOIO₃, electron transfer predominantly occurs towards the O₄ direction, whereas in Se-BiOIO₃, there is a relatively higher electron flux towards the O₂ direction; similarly, in Te-BiOIO₃, there is also a pronounced movement of electrons towards the O₂ direction. The charge transfer direction in the doped system has shifted compared to intrinsic BiOIO₃, owing to an increased degree of distortion induced by doping. This alteration in the internal charge distribution aligns with previous analytical findings. Hence, it is evident that non-metal X doping can effectively modify the electronic structure and enhance the distortion degree of the system, resulting in a greater deviation between positive and negative charges. Consequently, this strengthens the polarization field and modulates its optical properties [28].

3.5. Optical Properties of BiOIO₃ and X-BiOIO₃

3.5.1. Alignment with Band Structure Edges

The photocatalyst is evaluated in accordance with the relative position of its semiconductor conduction band maximum (CBM) and valence band (VBM) values in relation to the standard hydrogen electrode minimum (NHE). The determination of the band edge potential on the NHE scale typically relies on Equations (3) and (4) [29]. In both equations, X represents the absolute electronegativity of the material. The energy level of the free electron on the NHE scale, approximately 4.5 eV, is denoted as E_elec. Instead, E_g refers to the band gap of a semiconductor.

$$E_{VBM}=X-E_{elec}+0.5E_g$$

(3)

$$E_{CBM}=E_{VBM}-E_g$$

(4)

The valence band edge potential of BiOIO₃ and X-BiOIO₃ at the NHE scale is depicted in Figure 7. The CBM of BiOIO₃ and X-BiOIO₃ lies above the H⁺/H₂ potential, while the VBM is beneath the O₂/H₂O potential, suggesting that BiOIO₃ and X-BiOIO₃ possess the capability of water hydrolysis and oxygen generation. Nevertheless, due to the significant reduction in the bandgap width when Se is doped into BiOIO₃, the energy required for electron transition becomes smaller. Hence, it can be inferred that Se-BiOIO₃ has a superior water splitting photocatalytic activity among the four systems.

3.5.2. Absorption Spectrum

Doping significantly alters the optical properties of a crystal by introducing impurities that modify the electronic states within the system, thereby enhancing its light responsiveness and influencing its optical characteristics. In this study, we analyze optical absorption graphs and dielectric diagrams to investigate the changes in the optical characteristics of the doped systems.

The optical absorption coefficient α(ω) of a crystal can be determined by utilizing the real part ε_r(ω) and the imaginary part ε_i(ω) of the dielectric function, as demonstrated in Equations (5) and (6) [30].

$$\epsilon (\omega )={\epsilon }_r(\omega )+i{\epsilon }_i(\omega )$$

(5)

$$\alpha (\omega )=\sqrt{2}(\omega ){\left[\sqrt{{\epsilon }_r^2(\omega )+{\epsilon }_i^2(\omega )}-{\epsilon }_r(\omega )\right]}^{{\displaystyle \frac{1}{2}}}$$

(6)

Theoretically, the optical absorption coefficient of X-BiOIO₃ systems exhibits a remarkable enhancement within the visible light range, as illustrated in Figure 8. In comparison to intrinsic BiOIO₃, X-BiOIO₃ systems demonstrate a significant red shift towards lower energy levels, indicating an augmented light-responsive capacity. These findings suggest that the introduction of As, Se, and Te can significantly enhance the optical absorption capacity of this system. The comparative analysis reveals that among all doping systems, Se-BiOIO₃ exhibits the highest light absorption capacity, thereby indicating its superior photocatalytic potential.

3.5.3. Dielectric Function

The dielectric constant characterizes the response of materials to external energy. Figure 9a illustrates the calculated real part of the dielectric function for the four systems both before and after doping, highlighting the trend in the dielectric constant as it varies with incident light energy. The greater the dielectric constant, the stronger the system’s polarization capability and internal electric field strength. When the incident light energy approaches zero, the corresponding value on the vertical axis represents the static dielectric constant. In the figure, the static dielectric constant of the intrinsic BiOIO₃ is calculated at 4.929, whereas the static dielectric constants for the X-BiOIO₃ systems are recorded as 4.8798, 7.567, and 5.938, respectively. In comparison to intrinsic BiOIO₃, the dielectric constants of the doped systems exhibit notable variations. Specifically, the static dielectric constant of As-BiOIO₃ is lower than that of intrinsic BiOIO₃, suggesting that the incorporation of As diminishes the polarization capability of the system. However, this reduction amounts to only 1.20% relative to intrinsic BiOIO₃ and can be considered negligible. Additionally, the dielectric constants of Se-BiOIO₃ and Te-BiOIO₃ exhibit increases of 53.51% and 20.47%, respectively, compared to the intrinsic BiOIO₃. This suggests that doping with Se and Te alters the polarization capability of BiOIO₃, leading to an enhancement in internal electric field strength and the accelerated movement of charge carriers within the doped systems, thereby improving charge binding capacity, which aligns with the previous analysis.

Figure 9b illustrates the calculated imaginary part of the dielectric function before and after doping, revealing significant variations among the three X-BiOIO₃ systems within the 0–4 eV range. The imaginary part of the dielectric function represents the energy dissipated due to the induction of a large number of electric dipoles within the system in response to external energy stimulation. This value quantitatively reflects the degree of electronic transition, and its peak corresponds to the strengthened inter-band electronic transition of the system under the action of an external electric field. In addition, this value is also related to the probability of the system absorbing external energy [31]. Notably, Se-BiOIO₃ exhibits a small peak at 0.370 eV, reaching a maximum value of 2.5236 eV, attributed to an electron transition between the 4p state of Se and the 2p state of O. At 0.592 eV, a new peak is observed in the Te-BiOIO₃ system, attributed to the introduction of impurities that induce orbital hybridization and coupling at this energy level. In conclusion, the peak positions of the Se-BiOIO₃ and Te-BiOIO₃ systems following doping exhibit a tendency to shift towards the low-energy region. This observation aligns with the conclusions derived from band structure analysis and is also associated with the impurity levels introduced by doping. The doping of Se effectively reduces the bandgap of intrinsic BiOIO₃, enhances its light absorption coefficient, and strengthens the polarization electric field within the system. Consequently, it can be inferred that this system exhibits superior optical performance.

4. Conclusions

The energy band of intrinsic BiOIO₃ is calculated in this study using the PBE functional and MBJ functional based on the first principles of density functional theory. The results obtained under the MBJ functional exhibit superior agreement with experimental values. The X-BiOIO₃ systems demonstrate relative stability when calculated using the MBJ potential. In comparison to intrinsic BiOIO₃, the X-BiOIO₃ systems exhibit crystal lattice distortion, thereby facilitating the generation of localized potential differences within the system. The intensification of polarization promotes the adjustment of the bandgap. The bandwidth of X-BiOIO₃ reduces and the energy band distribution becomes denser. The diminished bandwidth and the denser energy levels of X-BiOIO₃ suggest that doping enhances the probability of electron transitions. The CBM of BiOIO₃ and X-BiOIO₃ lies above the H⁺/H₂ potential, while the VBM is beneath the O₂/H₂O potential, suggesting that BiOIO₃ and X-BiOIO₃ possess the capability of water hydrolysis and oxygen generation. The expansion of the light absorption range significantly enhances the optical performance of the system. In contrast, the Se-BiOIO₃ system exhibits the highest absorption coefficient within the visible light region, followed by that of the Te-BiOIO₃ system. Furthermore, both Se and Te doping can modify the polarization capability of BiOIO₃. Based on the aforementioned conclusions, it can be deduced that doping with the non-metallic element Se enhances the internal electric field strength, accelerates charge carrier generation within the system, improves charge binding capability, increases electron mobility, and ultimately elevates the photocatalytic efficiency of BiOIO₃-based materials, thereby paving a new pathway for the development of photocatalytic materials.