Efficient and Robust Photodegradation of Dichlorvos Pesticide by BiOBr/WO_2.72 Nanocomposites with Type-I Heterojunction under Visible Light Irradiation

Abstract

In this study, we developed novel BiOBr/WO_2.72 nanocomposites (abbreviated as BO/WO) and systematically investigated their photocatalytic degradation performance against the pesticide dichlorvos under visible light irradiation. The experimental results demonstrated that the BO/WO nanocomposites achieved an 85.4% degradation of dichlorvos within 80 min. In comparison, the BO alone achieved a degradation degree of 66.8%, and the WO achieved a degradation degree of 64.7%. Furthermore, the BO/WO nanocomposites retained 96% of their initial activity over five consecutive cycles, demonstrating exceptional stability. Advanced characterization techniques, such as high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) confirmed the composition and catalytic mechanism of the composite material. The findings indicated that the BO/WO nanocomposites, through their optimized Type-I heterojunction structure, achieved efficient separation and transport of photogenerated electron–hole pairs, significantly enhancing the degree of degradation of organophosphate pesticides. This research not only propels the development of high-performance photocatalytic materials, but also provides innovative strategies and a robust scientific foundation for mitigating global organophosphate pesticide pollution, underscoring its substantial potential for environmental remediation.

1. Introduction

As society progresses, the conflict between humans and nature intensifies, leading to a plethora of environmental issues, such as medical waste, water contamination, soil degradation, and crop pollution [1,2,3,4,5]. Among these issues, the extensive use of organophosphate pesticides in agricultural production exacerbates environmental pollution [6,7,8,9,10]. Dichlorvos, a highly effective organophosphate pesticide, is particularly concerning due to its high toxicity and stability, making it resistant to degradation in natural environments, thereby posing significant threats to ecosystems and human health [11]. To address this issue, photocatalytic technology has garnered widespread attention for its capacity to efficiently decompose organic pollutants under solar irradiation [12,13,14,15,16,17,18].

Photocatalytic technology harnesses light energy to excite semiconductor materials, generating highly reactive electron–hole pairs that oxidize and decompose organic pollutants, thus providing an eco-friendly treatment method [19,20,21,22,23,24,25,26]. The selection of photocatalytic materials is crucial in this process [27,28,29,30,31,32,33,34]. Common photocatalytic materials include TiO₂, ZnO, BiOBr (BO), and WO_2.72 (WO), among which BO and WO have exhibited outstanding performance due to their unique structures and excellent properties. BO, with its distinctive layered structure and narrow bandgap, can effectively absorb visible light, thereby enhancing photocatalytic efficiency [12]. Moreover, its layered structure facilitates the separation of photogenerated electron–hole pairs, reducing recombination rates. In contrast, WO demonstrates excellent photocatalytic performance due to its high electrical conductivity and unique electrochemical properties. The conductivity of WO promotes electron transfer, decreasing electron–hole recombination rates. Additionally, the oxygen vacancies in WO can alter the surface structure of the photocatalyst, increasing the number of surface active sites and enhancing surface reaction activity, further improving photocatalytic performance [11].

However, the inherent limitations of single materials constrain their further development, whereas composite materials can effectively address these issues [15,16,17,18,19,20]. For instance, Anh et al. demonstrated that combining CoWO₄ with g-C₃N₄ forms a Z-scheme heterojunction structure with superior photocatalytic properties. This structure promotes the effective separation of photogenerated electron–hole pairs, significantly reducing recombination rates and, thus, enhancing photocatalytic efficiency [13]. This composite material demonstrated a high degradation degree in the removal of the pesticide, diazinon. Similarly, Elhaddad et al. combined SnO₂ nanoparticles with g-C₃N₄, forming an excellent heterojunction structure that enhances light absorption and improves the mobility of photogenerated charge carriers, thereby increasing photocatalytic efficiency [14]. This composite material exhibited outstanding performance in degrading organic pollutants.

Inspired by the aforementioned composite materials, we developed and systematically examined novel BO/WO nanocomposites for their photocatalytic degradation of the pesticide dichlorvos under visible light irradiation. The experimental results demonstrated that the BO/WO nanocomposites achieved an 85.4% degradation of the dichlorvos within 80 min. This performance significantly surpassed those of the individual BO and WO, which achieved degradation degrees of 66.8% and 64.7%, respectively. Additionally, the BO/WO nanocomposites demonstrated remarkable stability, retaining 96% of their initial activity over five consecutive cycles. Advanced characterization techniques, such as high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR), were utilized to further elucidate the composition and catalytic mechanism of the composite material. The catalytic mechanism was identified as Type-I. The Type-I heterojunction structure facilitates the effective transfer of electrons from the conduction band of one material to the conduction band of another, thereby enhancing the separation of electron–hole pairs and improving overall photocatalytic performance. Consequently, the BO/WO nanocomposites, through their optimized Type-I heterojunction structure, achieved efficient separation and transfer of photogenerated electron–hole pairs, significantly enhancing the degradation of organophosphate pesticides. This investigation not only propels the advancement of high-performance photocatalytic materials, but also offers innovative strategies and a robust scientific basis for mitigating global organophosphate pesticide contamination, demonstrating substantial potential for environmental remediation.

2. Results

2.1. Diagram of Materials Synthesis Process

The synthesis routes for the WO, BO, and BO/WO nanocomposites are illustrated in Scheme 1. First, an appropriate amount of WCl₆ is added to 35 mL of ethanol, stirred for one hour, and subjected to hydrothermal treatment at 180 °C for 24 h. The resulting product is rinsed multiple times with ultrapure water, centrifuged, and finally calcined in a muffle furnace at 400 °C for 20 min in air to obtain WO nanomaterials. Subsequently, BO/WO nanocomposites are synthesized using WO as the substrate. An appropriate amounts of WO, Bi(NO₃)₃·5H₂O, and KBr are added to a mixture of 25 mL of ethylene glycol and 10 mL of water, stirred for 1 h, and then transferred to a reaction vessel for hydrothermal treatment at 110 °C for 10 h. After it is allowed to cool naturally, the resulting product is rinsed multiple times with ultrapure water and ethanol, centrifuged, and freeze-dried for 18 h to obtain BO/WO nanocomposites. The synthesis method for BO nanosheets is similar to that of BO/WO nanocomposites, albeit without the addition of WO; only appropriate amounts of Bi(NO₃)₃·5H₂O and KBr are included. All the detailed parameters mentioned above are listed in Table S1.

2.2. Analysis of Phase and Microscopic Morphology

Figure 1 presents the X-ray diffraction (XRD) patterns and Fourier-transform infrared spectroscopy (FT-IR) spectra of the BO, WO, and BO/WO nanocomposites. In panel (a), the XRD patterns of the BO, WO, and BO/WO are displayed. The BO sample exhibited high crystallinity, with diffraction peaks at 10.9° (001), 21.9° (002), 25.2° (101), 31.7° (102), 32.2° (110), 39.3° (112), 46.2° (200), 50.7° (104), 53.4° (211), 57.2° (212), 67.5° (220), 71.0° (214), and 76.8° (310), which corresponded well with the standard pattern for BiOBr (JCPDS no. 78-0348). Similarly, the WO sample showed distinct peaks at 23.4° (010), 26.2° (−503), 34.1° (−512), and 47.9° (020), which corresponded to the WO_2.72 phase (JCPDS no. 73-2177). The BO/WO composite material exhibited the crystalline planes of both BO and WO. Specifically, the BO crystalline planes included (001), (002), (101), (102), (110), (112), (200), (104), (211), (212), (220), (214), and (310), alongside the WO (010) plane. This indicates that the BO/WO nanocomposite material exclusively contained BO and WO phases without any extraneous peaks, signifying a high degree of purity in the synthesis of the sample.

Panel (b) presents the FT-IR spectra for the BO, WO, and BO/WO, revealing distinct features for each material: BO (red curve), BO/WO (green curve), and WO (blue curve). In the BO spectrum, the prominent absorption peaks at 3300–3700 cm⁻¹ and 1400 cm⁻¹ corresponded to O-H stretching and bending vibrations, indicating the adsorption of moisture or hydroxyl groups during preparation or storage. Additionally, the C-H stretching vibrations in the 2800–3000 cm⁻¹ range and the C-O stretching vibrations around 1070 and 1300 cm⁻¹ are likely to have originated from ethylene glycol or absorbed water. The bending vibrations of H₂O molecules observed in the 1500–1700 cm⁻¹ range further confirm the presence of surface-adsorbed water. The characteristic vibrations of Bi-O and Bi-Br in the 500–1000 cm⁻¹ range validate the crystalline structure of the BiOBr. In the WO spectrum, O-H vibrations were observed around 3300–3700 cm⁻¹ and 1400 cm⁻¹. Weak C-H stretching vibrations were present in the 2800–3000 cm⁻¹ range, and the faint C-O stretching vibrations around 1070 and 1300 cm⁻¹ were attributed to ethanol used during WO synthesis. However, these peaks were attenuated due to the high temperatures involved in the hydrothermal synthesis and subsequent calcination in a muffle furnace. The bending vibrations of H₂O molecules in the 1500–1700 cm⁻¹ range indicate surface-adsorbed water. The characteristic W-O vibrations in the 500–1000 cm⁻¹ range confirm the crystalline structure of the WO. The BO/WO composite exhibits the characteristic vibrations of O-H, C-H, and C-O, as well as the distinct vibrational features of both WO and BO in the 500–1000 cm⁻¹ range. Moreover, the significantly enhanced bending vibrations of the H₂O molecules in the 1500–2500 cm⁻¹ range for the BO/WO, compared to the pure BO and WO, suggest alterations in the surface properties and interactions within the composite material. For instance, the composite material, compared to its individual components, typically possesses a larger specific surface area and more adsorption sites, leading to greater molecular adsorption. This result indirectly corroborates the existence of the composite material, highlighting its potential advantages in photocatalytic applications.

To better examine the microstructures and elemental compositions of the synthesized samples, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses were conducted, as illustrated in Figure 2. The SEM images (Figure 2a–c) reveal distinct morphologies: the BO (Figure 2a) appears as stacked nanosheets with sizes ranging from 50 to 200 nm; the WO (Figure 2b) exhibits a flower-like structure composed of numerous nanorods, with diameters within the range of 10–20 nm; and the BO/WO nanocomposites (Figure 2c) display an interwoven structure of BO nanosheets and WO nanorods. The energy-dispersive X-ray spectroscopy (EDS) spectra shown in Figure 2d–f confirm the elemental compositions of the samples. Figure 2d shows that the BO consisted solely of Bi, O, and Br elements, with no impurity peaks. Figure 2e indicates that the WO contained only W and O elements, also without impurity peaks. Figure 2f reveals that the nanocomposite contained all the elements from the pure materials, with no impurity peaks, affirming the high purity of the synthesized samples, which is consistent with the results shown in Figure 1.

The TEM images in Figure 2g–i further elucidate the morphologies of the BO, WO, and BO/WO. Figure 2g depicts BO as nanosheets of varying sizes, stacked together, with dimensions ranging from 50 to 200 nm. Figure 2h shows WO clearly as nanoflower clusters assembled from nanorods, with diameters within the range of 10–20 nm and lengths of around 200 nm. In Figure 2i, the composite material demonstrates an interwoven structure of BO nanosheets and WO nanorods. Additionally, the HRTEM image in Figure 2i displays lattice fringes of WO (010) and BO (102), with spacings of 0.38 nm and 0.28 nm, respectively. The indistinct interface between the lattice fringes (highlighted by the bright yellow line) confirms the presence of heterojunctions, indicating the successful fabrication of the BO/WO nanocomposites. To provide a clearer observation of the interface, HRTEM images at 10 nm and 5 nm scales are shown in Figure S1. Figure S1a shows the composite material at a scale of 10 nm, where the yellow dashed circle highlights the interface between two distinct crystal phases. This region, outlined by the yellow dashed circle, is further magnified in Figure S1b. Figure S1b presents the composite material at a scale of 5 nm, with the red dashed circle distinctly marking the interface. This area, indicated by the red dashed circle, is magnified in the inset of Figure 2i.

2.3. X-ray Photoelectron Spectroscopy (XPS) Analysis and Specific Surface Area

Figure 3 displays the XPS spectra of the BO, WO, and BO/WO nanocomposites. As shown in the overview in Figure 3a, the BO/WO nanocomposite contained all the elements present in BO (Bi and Br) and WO (W and O). Additionally, surface-adsorbed carbon elements were observed. Figure 3b–e presents the high-resolution XPS spectra of core elements in the BO, WO, and BO/WO nanocomposites. In Figure 3b, the Br 3d spectra for the BO show Br 3d_3/2 and Br 3d_5/2 peaks at 69.9 eV and 68.6 eV, respectively; in the BO/WO nanocomposite, these peaks shifted to 69.6 eV and 68.4 eV, respectively. Figure 3c shows the O 1s spectra, where the peaks for the BO are at 530.0 eV, and those for the WO are at 530.7 eV, corresponding to lattice oxygen and surface-adsorbed oxygen, respectively. In the BO/WO nanocomposite, the O 1s peak is at 530.1 eV. Figure 3d presents the Bi 4f spectra, where the BO shows Bi 4f_5/2 and Bi 4f_7/2 peaks at 164.7 eV and 159.4 eV, respectively; these peaks in the BO/WO nanocomposite were at 164.6 eV and 159.3 eV, respectively. Figure 3e displays the W 4f spectra for the WO, with W 4f_5/2 and W 4f_7/2 peaks at 37.9 eV and 35.8 eV, respectively; these peaks shifted to 37.8 eV and 35.7 eV in the BO/WO nanocomposite. These results indicate that the peak positions of each element in the BO/WO nanocomposite were shifted relative to those in the pure BO or WO, confirming the presence of heterojunctions between the BO and the WO. This finding is consistent with the high-resolution TEM image in Figure 2i, further validating the successful synthesis of the BO/WO nanocomposite.

Figure S2a illustrates the photoluminescence (PL) intensities of the WO, BO, and their composite material, BO/WO, over a specific wavelength range. The WO (depicted by the blue curve) exhibited the lowest PL intensity, indicating that its oxygen vacancy states effectively trapped photogenerated electrons and holes, thereby significantly suppressing electron–hole recombination and enhancing photocatalytic efficiency. Conversely, the BO (depicted by the red curve) displayed the highest PL intensity, suggesting a higher recombination rate of photogenerated charge carriers, which results in lower photocatalytic efficiency. The PL intensity of the composite material, BO/WO (depicted by the green curve), lay between those of the WO and the BO, integrating the trapping states of WO and the light absorption properties of BO.

Figure 3f presents the specific surface area (S_BET) data for the three different catalysts, BO, WO, and BO/WO. The data specifically show that the S_BET of the BO was 11.7 m² g⁻¹, while that of the WO was 39.1 m² g⁻¹ and that of the BO/WO composite catalyst significantly increased to 52.6 m² g⁻¹. The increase in specific surface area indicates that the material’s surface provides more active sites, which is beneficial for enhancing photocatalytic performance. The BO/WO composite material, by combining the properties of BO and WO, formed a larger surface area. This structural advantage can promote the separation and transfer of photogenerated carriers, thereby enhancing the efficiency of the photocatalytic reaction. This result is consistent with the findings shown in Figure 1b, further confirming the significant potential of the BO/WO composite catalyst in photocatalytic applications.

2.4. Photocatalytic Activity and Stability Analysis

Figure 4 illustrates the photocatalytic performances of the BO, WO, and BO/WO nanocomposites. Specifically, as depicted in Figure 4a, the BO demonstrated a gradual decrease in the degradation of dichlorvos during the photocatalytic degradation process, although its overall degradation degree remained relatively low, achieving a degradation degree of 66.8% within 80 min. Figure 4b reveals that the BO/WO nanocomposite significantly enhanced the photocatalytic activity, markedly achieving a degradation degree of 85.4% within 80 min. Figure 4c shows the photocatalytic performance of the WO, which exhibited some degradation activity, achieving a degradation degree of 64.7% within 80 min. In summary, the BO/WO nanocomposite demonstrated superior degradation and notable photocatalytic activity in the degradation of organophosphorus pesticides compared to the BO and WO alone. This enhancement was attributed to the heterojunction structure between the BO and the WO, which effectively facilitates the separation of photogenerated electron–hole pairs, thereby reducing recombination rates and significantly improving photocatalytic efficiency.

Figure 5 illustrates the photocatalytic stability of the BO, WO, and BO/WO nanocomposites under visible light irradiation during the degradation of the dichlorvos. The upper panels (Figure 5a–c) display the photocatalytic degradation performances of the BO, BO/WO, and WO over four cycles, indicating that the BO/WO nanocomposite exhibited significantly higher photocatalytic degradation in each cycle compared to the pure BO and WO. The middle panels further show the extent of the degradation within each cycle, demonstrating that the BO/WO nanocomposite maintained a relatively stable degradation performance across multiple cycles. In contrast, the pure BO showed poor stability with gradually decreasing degradation degree over the cycles, while the WO, despite its relatively good stability, exhibited lower overall degradation. The lower panels analyze the changes in degradation degree across cycles, revealing that the BO/WO nanocomposite retained a high degradation degree even after four cycles, indicating exceptional stability.

Specifically, the BO/WO nanocomposite retained 96% of its initial activity after five consecutive cycles, showcasing its superior stability. Although the BO achieved a final degradation degree of 98%, it suffered from poor stability throughout the cycles. Conversely, the WO showed better stability throughout the cycles, but also showed a lower final degradation degree, of 92%. The BO/WO nanocomposite combines the advantages of both BO and WO, maintaining high degradation degree and excellent stability. In summary, the optimized heterojunction structure of the BO/WO nanocomposite not only provides outstanding performance in single-cycle photocatalytic degradation, but also demonstrates remarkable stability over multiple cycles, making it highly promising for the degradation of organophosphorus pesticides.

In the photocatalytic degradation of organic pollutants, different scavengers significantly impact the performance of the BO/WO catalyst. Figure 6 illustrates the variations in degradation degree of the BO/WO in the presence of isopropanol (IPA), ascorbic acid, triethanolamine (TEOA), and potassium bromate (KBrO₃). Specifically, the IPA, acting as a hydroxyl radical (·OH) scavenger, achieved a degradation degree of 31.7%. The ascorbic acid, as a superoxide radical (·O₂⁻) scavenger, resulted in a degradation degree of 34.7%. The TEOA, serving as a hole (h⁺) scavenger, achieved a degradation degree of 31.5%. The KBrO₃, acting as an electron (e⁻) scavenger, resulted in a degradation degree of 46.4%. These results elucidate that ·OH, ·O₂⁻, h⁺, and e⁻ all play pivotal roles in the photocatalytic degradation process. In particular, ·OH and h⁺ have a profound impact on the degradation degree, indicating their crucial role in the degradation of dichlorvos pesticide. This discovery underscores the necessity of considering various reactive species in the design of photocatalysts. Enhancing photocatalytic performance hinges on optimizing electron–hole separation and the effective utilization of reactive species.

Based on the above content, Figure S2b presents the apparent rate constants (k_app) derived from fitting the data of the WO, BO, and their composite material, BO/WO, under various conditions, as depicted in Figure 4 and Figure 6. The specific values were as follows: BO (0.0134 min⁻¹), BO/WO (0.0228 min⁻¹), WO (0.0128 min⁻¹), BO/WO-IPA (0.0058 min⁻¹), BO/WO-Ascorbic Acid (0.0052 min⁻¹), BO/WO-TEOA (0.0054 min⁻¹), and BO/WO-KBrO₃ (0.0067 min⁻¹). These data indicate that the BO/WO composite material exhibited the highest photocatalytic degradation degree in the absence of additives. The addition of various scavengers (IPA, ascorbic acid, TEOA, KBrO₃) significantly diminishes the photocatalytic degradation degree of the BO/WO composite, underscoring the roles of reactive species such as ·OH, ·O₂⁻, h⁺, and e⁻ in influencing the photocatalytic performance of the composite material. These findings are consistent with the previously mentioned results.

2.5. Optoelectronic Properties and Theoretical Calculations Analysis

Figure 7 details the optoelectronic properties and theoretical calculations of BO, WO, and their BO/WO nanocomposites. In Figure 7a, the UV-vis absorption spectra reveal that the WO exhibited substantial visible light absorption. Similarly, the BO demonstrated significant absorption in the visible range, with the BO/WO nanocomposite exhibiting a visible light absorption range that was intermediate between those of the BO and WO. Figure 7b,c displays the Tauc plots for the WO and BO, respectively. Based on Equation 1 [34], noted in the supporting information, and considering that BO is an indirect bandgap semiconductor, while WO is a direct bandgap semiconductor, the bandgaps for the WO and BO were determined to be 2.95 eV and 2.56 eV, respectively. Using Equations 2 and 3 [11], noted in the supporting information, the conduction and valence band positions for the BO were calculated to be 0.67 eV and 3.23 eV, respectively, while for the WO, they were 0.545 eV and 3.495 eV. These band positions suggest a Type-I heterojunction configuration in the BO/WO nanocomposite, which effectively facilitates the separation of photogenerated electron–hole pairs, thereby significantly enhancing its photocatalytic activity.

Figure 7d displays the electron paramagnetic resonance (EPR) spectrum of the BO/WO nanocomposite, showing characteristic peaks within the magnetic field range of 3450 G to 3540 G, indicating the presence of ·OHs. ·OHs play a crucial role in photocatalytic degradation due to their strong oxidizing ability, allowing them to rapidly attack organic pollutants and degrade them into harmless end products. Figure 7e,f shows the electrostatic potential profiles for WO and BO, respectively, with the WO having a work function of 4.745 eV and the BO having a work function of 5.103 eV. These differences in work function facilitate the formation of a Type-I heterojunction, effectively separating photogenerated electron–hole pairs, reducing recombination rates, and further enhancing photocatalytic efficiency. Combined with previous photocatalytic performance analyses, these results demonstrate that the BO/WO nanocomposite, through its optimized heterojunction structure, maintains a high degradation degree and excellent stability. It also exhibits superior light absorption capability and efficient charge carrier separation, making it highly promising for the degradation of organophosphorus pesticides, with significant performance advantages and potential.

2.6. Photocatalytic Response and Electrochemical Impedance Spectroscopy Analysis

Figure 8 presents the photocatalytic response and electrochemical impedance spectroscopy (EIS) analysis of the BO, WO, and BO/WO nanocomposites. Figure 8a shows the transient photocurrent responses of the BO, WO, and BO/WO nanocomposites under light irradiation. The results indicate that during the light on/off cycles, the BO/WO nanocomposite exhibited the highest photocurrent density, significantly surpassing those of the pure BO and WO. This demonstrates that the BO/WO nanocomposite possesses more efficient photogenerated electron–hole pair separation and transport capabilities, thereby enhancing its photocatalytic performance. Figure 8b displays the EIS Nyquist plots of the BO, WO, and BO/WO nanocomposites. It is evident that the BO/WO nanocomposite had the smallest semicircle diameter, indicating the lowest charge transfer resistance. This further confirms the superior performance of the BO/WO heterojunction structure in the separation and transport of photogenerated charge carriers. In summary, the BO/WO nanocomposite, through its optimized heterojunction structure, achieved the efficient separation and transport of photogenerated electron–hole pairs, thereby exhibiting superior performance in photocatalytic applications. These findings highlight the significant advantages of the BO/WO nanocomposite in enhancing photocatalytic activity and stability.

2.7. Photocatalytic Mechanism

Figure 9 illustrates the photocatalytic mechanism of the BO/WO nanocomposites, incorporating a Type-I heterojunction structure and the role of the noble metal, Pt. When light irradiated the BO/WO nanocomposites, the photon energy met or exceeded the bandgap energy of the material, causing photogenerated electrons to transition from the valence band (VB) to the conduction band (CB), leaving holes in the VB. The Type-I heterojunction structure between the BO and the WO effectively promotes the separation of the photogenerated electron–hole pairs, reducing their recombination rates, thereby enhancing the photocatalytic efficiency. Specifically, the valence band position of the BO was 3.23 eV, with a conduction band position of 0.67 eV, whereas the valence band position of the WO was 3.48 eV, with a conduction band position of 0.56 eV. With this band alignment, photogenerated electrons transferred from the CB of the WO to the CB of the BO, while photogenerated holes transferred from the VB of the WO to the VB of the BO. This bidirectional migration effectively reduces recombination and enhances photocatalytic activity.

During the photocatalytic process, photogenerated holes oxidize H₂O or OH⁻ to produce ·OH. These ·OH radicals possess potent oxidative capabilities, enabling them to swiftly attack and degrade organic pollutants, such as dichlorvos, converting them into CO₂, H₂O, and other innocuous substances. Throughout this process, the noble metal, Pt, gradually dissolved into the overall photocatalytic reaction, playing a pivotal role. Firstly, Pt nanoparticles acted as electron traps, capturing and storing photogenerated electrons, thereby further promoting the separation of electron–hole pairs and diminishing recombination rates. Secondly, the Pt exhibited high catalytic activity, accelerating the reaction of photogenerated electrons with reactants, thereby enhancing photocatalytic efficiency. Additionally, Pt can augment the light absorption capacity of the photocatalyst, extending the light response range and improving overall photocatalytic performance. Through the gradual participation and dissolution of the Pt, the photocatalytic reaction progressed incrementally, continuously improving reaction efficiency and stability. In summary, the BO/WO nanocomposites, through their optimized Type-I heterojunction structure and the synergistic effect of the noble metal, Pt, achieve the efficient separation and transport of photogenerated electron–hole pairs, significantly enhancing the photocatalytic degradation degree of organophosphorus pesticides, such as dichlorvos, thereby demonstrating superior photocatalytic activity and stability.

3. Conclusions

In this investigation, we successfully engineered BiOBr/WO_2.72 (BO/WO) nanocomposites, which demonstrated superior photocatalytic performance and stability in degrading organophosphate pesticides under visible light irradiation. The BO/WO nanocomposites effectively achieved an 85.4% degradation of dichlorvos within 80 min. This performance significantly surpassed those of the individual BO (66.8% degradation degree) and WO (64.7% degradation degree). Additionally, the BO/WO nanocomposites retained 96% of their initial activity over five cycles, showcasing exceptional cyclic stability. Advanced characterization techniques, such as HRTEM, XPS, and EPR, validated the composite’s composition and catalytic mechanism. The optimized Type-I heterojunction structure facilitated the efficient separation and transport of the photogenerated electron–hole pairs, significantly curtailing the recombination rates and enhancing the photocatalytic efficacy. The incorporation of the noble metal, Pt, further augmented the electron trapping and light absorption, thereby elevating the overall reaction efficiency and stability. This research not only propels the development of high-performance photocatalytic materials, but also proffers innovative strategies and a robust scientific foundation for mitigating global organophosphate pesticide contamination. These findings underscore the substantial potential of these materials for environmental remediation.