Enhancement Study of the Photoactivity of TiO₂ Photocatalysts during the Increase of the WO₃ Ratio in the Presence of Ag Metal

Abstract

Nanocomposites (NCs) consisting of 4%Ag/x%WO₃/TiO₂, with varied concentrations (x = 1, 3, 5, 7 wt.%) of WO₃, were successfully synthesized using the sol-gel process to examine their photocatalytic performance. The synthesized 4%Ag/x%WO₃/TiO₂ nanopowder was characterized using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (UV–vis DRS), photoluminescence (PL), and Brunauer–Emmett–Teller (BET) surface area analysis to elucidate its physicochemical properties. The photocatalytic evaluation revealed that the Ag/1%WO₃/TiO₂ nanocomposite exhibits 98% photoreduction efficiency for Cr(VI) after 2 h under visible light due to the impact of the plasmonic effect of Ag atoms. In addition, the Ag/4%WO₃/TiO₂ shows about 95% photooxidation efficiency for methylene blue (MB) dye after 4 h.

1. Introduction

Titanium dioxide (TiO₂) is renowned as a highly promising photocatalyst due to its advantages, such as its photostability, low cost, and non-toxicity [1,2]. However, its photocatalytic activity is limited to ultraviolet (UV) light due to its wide bandgap (3.20 eV), which constitutes only 3–5% of the total solar irradiance [3]. To address this, researchers have explored modifications like metal doping composites with other materials to shift its optical response into the visible range [4]. One effective approach involves doping TiO₂ with metals (e.g., Ag, Au, and Cr) and rare earth metals (Eu, Ce etc.) [5,6], or nonmetal atoms (e.g., N, S, and F). These modifications can trap electrons, enhance charge separation, and decrease the bandgap, potentially leading to new sunlight-driven photocatalysts [7,8,9,10]. Additionally, coupling TiO₂ with other semiconductors (such as SnO₂, and WO₃) can extend the photoexcitation energy range that improves pollutant photodegradation [11]. Fundamentally, WO₃ possesses a conduction band potential of +0.77 eV [12], enabling a new band position that efficiently receives photogenerated electrons from the conduction band of TiO₂. Therefore, introducing tungsten doping into TiO₂ matrices has resulted in higher electrical conductivity [13]. The exploration of TiO₂/WO₃ composites has emerged as a prominent area of research, driven by their promising properties and diverse functionalities. For instance, TiO₂-supported WO₃ has demonstrated remarkable efficacy as a heterogeneous catalyst for redox reactions [14]. Additionally, synthesizing highly ordered cubic mesoporous WO₃/TiO₂ thin films has enhanced photocatalytic activity compared to pure TiO₂ films [15]. Furthermore, studies by Reyes-Gil et al. (2013) and Reyes-Gil et al. (2015) highlighted the enhanced ion storage capacity and electrochromic activity of WO₃/TiO₂ nanostructures, underscoring the significance of composite materials in advanced applications [16,17]. Archana et al. (2014) also investigated the photocatalytic and electrical properties of WO₃-doped TiO₂ nanowires, revealing promising results for high-efficiency dye-sensitized solar cells [13]. These recent literature reviews provide valuable insights into the multifaceted properties of nanocomposites, offering a comprehensive understanding of their structural, optical, electrical, dielectric, and photocatalytic characteristics and paving the way for further advancements in diverse technological applications. Despite these advancements, challenges persist, particularly in supercapacitors and photocatalysis utilizing TiO₂-based materials. [18,19]. Additionally, TiO₂-based photocatalysts often suffer from relatively low photocatalytic efficiency and limited light absorption in the visible region [20], which restricts their practical applications. To address these challenges, incorporating Ag nanoparticles and WO₃ into TiO₂-based materials may offer promising solutions. Ag nanoparticles possess excellent electrical conductivity, which can enhance the charge transport within TiO₂ matrices. Li et al. prepared Ag/WO₃/TiO₂ nanowires via the hydrothermal technique [21]. They reported that the as-prepared composite photocatalysts showed greatly improved absorbance even in the infrared regime and dramatically improved photocatalytic activities toward methyl orange degradation in comparison to those of pure TiO₂ nanowires. In addition, the as-prepared Ag/WO₃/TiO₂ composite exhibited excellent recyclability for pollutant degradation. It is suggested that, with the synergetic help of WO₃ and Ag nanoparticles, more photogenerated electrons and hole pairs can be produced, participate in the photodegradation reaction, and enhance the photocatalytic activity dramatically [22]. Xu et al. used an aqueous sol-gel route for the preparation of nanostructured Ag-WO₃/TiO₂ [23]. Ag-WO₃/TiO₂ nanoparticles with a mixed phase (anatase/rutile) showed more excellent photocatalytic activity on the removal of MB than single-doped TiO₂, owing to their small particle size distribution, larger surface area, and higher absorbance of visible light [23]. Ag@TiO₂/WO₃ was synthesized using the sol-gel method and its photocatalytic activity was enhanced compared to its counterparts [24]. The rate of degradation of methylene blue (MB) using Ag@TiO₂/WO₃ was ~20 and ~25 times higher in contrast with pure TiO₂ and Degussa P25, respectively. This increase in the photocatalytic performance was because of the enhancement of light harvesting, a large amount of charge carrier injection due to the surface plasmon resonance effect exhibited by Ag nanoparticles under the irradiation of visible light, and a lower recombination rate due to the ease of charge carrier transfer through the junction between the two metal oxides [24]. Similarly, the addition of WO₃ to TiO₂ matrices can significantly enhance photocatalytic performance. WO₃ possesses a favorable electronic band structure and a high surface area, facilitating the charge transfer processes [25]. In photocatalysis, WO₃ acts as a co-catalyst, promoting the separation of photoinduced charge carriers and enhancing photocatalytic activity, particularly in the visible light region [26]. In this paper, we aim to see the impact of the variation of the %WO₃ weight ratio with 4% Ag doping on structural, optical, and photocatalytic properties of TiO₂ NPs. The pure and doped TiO₂ NPs were prepared using the facile sol-gel method and studied from the application point of view. The obtained results are discussed in different sections of the article. The composite revealed that the photoactivity was enhanced, which was clear from the photoreduction of Cr(VI) ions and photodegradation of MB dye.

2. Result and Discussion

The X-ray diffraction (XRD) technique confirmed the phase structure of the prepared nanocomposite samples. XRD patterns for pure TiO₂ and 4% Ag/x%WO₃/TiO₂ (x = 1, 3, 5, and 7%) nanocomposites are represented in Figure 1a. They revealed that all samples are related to the classic anatase structure of TiO₂, showing patterns at 2θ = 25.6°, 37.8°, 48.18°, 54.1°, 55.2°, 62.8°, 69°, and 70.5°, which are related to the (101), (004), (200), (105), (211), (204), (116), and (220) planes, respectively, and are matched to the stander card of TiO₂ [JCPDS#21-1272] [27,28]. The face-centered cubic metallic Ag crystal structure is associated with the diffraction peaks (200) and (220) at 44.48° and 64.68° (JCPDS# 87-0597), respectively. Incorporating various weight percentages of 1, 3, 5, and 7 wt.% of WO₃ onto 4% Ag/TiO₂ leads to the appearance of the diffraction peaks of WO₃ for 5% and 7% between 2θ = 23.5° and 25° for the (002), (020), and (200) planes. The slight shift in the characteristic peaks of TiO₂ at 2θ = 25.4°, shown in Figure 1b, could be attributed to the shrinking of the crystallite size due to the replacement of the Ti atom by the W atom. The W⁶⁺ ion can easily replace the Ti⁴⁺ ion in the TiO₂ lattice because the radius of W⁶⁺ is 62 pm smaller than Ti⁴⁺ ions, which equals to 68 pm [29]. It is important to investigate the microstructural parameters of any material synthesized at the nanoscale and to see the impact of doping on such parameters. Hence, herein we have investigated the impact of doping on the crystallinity of TiO₂, and we have estimated the crystallite size (D) values of the prepared nanocomposites for the most intense peak (101) using the Scherrer equation:

$$\mathrm{D}={\displaystyle \frac{\mathrm{k}\mathsf{\lambda }}{\mathsf{\beta }\mathrm{c}\mathrm{o}\mathrm{s}\mathsf{\theta }}}$$

(1)

where $\mathsf{\beta }$ denotes the full width at half maximum (FWHM), $\mathrm{k}$ is the shape factor with a value of 0.9, and $\mathsf{\lambda }$ represents the wavelength of the XRD source. The calculated D values of the prepared pure WO₃, pure TiO₂ NPs, and 4% Ag/x%WO₃/TiO₂ (with x = 1, 3, 5, and 7 wt.% of WO₃) nanocomposites are presented in

Table 1. The estimated values of D, δ, and ε.

Sample	D (nm)	δ	ε
Pure TiO2	17.01	3.45 × 10−3	9.27 × 10−3
WO3/TiO2	15.77	3.50 × 10−3	9.14 × 10−3
4%Ag/1%WO3/TiO2	15.94	3.93 × 10−3	9.90 × 10−3
4%Ag/3%WO3/TiO2	15.91	3.94 × 10−3	9.89 × 10−3
4%Ag/5%WO3/TiO2	14.50	4.75 × 10−3	10.8 × 10−3
4%Ag/7%WO3/TiO2	13.98	5.11 × 10−3	11.2 × 10−3

. The crystallite size values decrease systematically when the WO₃ dopant ratio increase in TiO₂. Also, the other parameters of the structure, such as the dislocation density (δ) and the microstrain $\left(\mathsf{\epsilon }\right)$, were calculated using FWHM for the most intense peak (101) and its angular position for the prepared samples by [30,31]:

$$\mathsf{\delta }={\displaystyle \frac{1}{{\mathrm{D}}^2}}$$

(2)

$$\mathsf{\epsilon }={\displaystyle \frac{\mathsf{\beta }}{4\mathrm{t}\mathrm{a}\mathrm{n}\mathsf{\theta }}}$$

(3)

The estimated values of δ and $\mathsf{\epsilon }$ are also presented in Table 1. The given values of δ after doping WO₃/TiO₂ with 4%Ag samples increase as the D values decrease. The δ values increase when increasing the WO₃ content, whereas the ε values vary between 11.2 × 10⁻³ and 7.55 × 10⁻³. These microstructural parameters indicate the impact of doping.

To confirm the changes in the prepared samples, Raman spectra for pure TiO₂ and 4% Ag/x%WO₃/TiO₂ (with x = 1, 3, 5, and 7 wt.% of WO₃) nanocomposites were recorded and are displayed in Figure 2.

The Raman spectra confirm the data extracted from the XRD graph that prove the anatase phase structure of pure TiO₂ and 4% Ag/x%WO₃-doped TiO₂ nanocomposites. The tetragonal anatase titania exhibits typical vibration modes, with the most active modes at 143, 196, and 637 cm⁻¹ corresponding to the Eg (symmetric stretching vibration) band, 395 cm⁻¹ related to the A1g (symmetric bending vibration) band, and 513 that corresponds to B1g (antisymmetric bending vibration) modes [32]. Moreover, there is a slight redshift to the lower wavenumber for the peak at 141 cm⁻¹ with an increase in the WO₃ weight ratio due to the insertion of a small radius of W⁶⁺ that equals 62 pm into the TiO₂ molecule that has a radius of Ti⁴⁺ ions equal 68 pm according to the number of the available vacancies, causing shrinking of the unit cell [32,33,34].

High-resolution transmission electron microscopy (HRTEM) images were recorded to clarify the structural attributes of pure TiO₂ and 4%Ag/x%WO₃/TiO₂ and nanocomposites (NCs), as shown in Figure 3.

Figure 3a,b prove that pure TiO₂ and 4%Ag/3%WO₃/TiO₂ exhibit a homogenous morphology, with a grain size within the approximate range of 10–15 nm. The average particle sizes for the pure TiO₂ and its composite have been determined from the histograms in Figure 3c,d, which show particle size distributions of 11 nm and 11.39 nm for TiO₂ and 4%Ag/3%WO₃/TiO₂, respectively. The HR images of the TiO₂ and the composite, which are shown in Figure 3e–h, expose the presence of fringes that were identified by SAED pattern lattice spacing values of 0.352 nm corresponding to the lattice spacing values of the (101) plane of anatase TiO₂, 0.38 nm that agrees with the (002) plane of monoclinic WO₃, and 0.23 nm for the (111) plane; these values are in agreement with the XRD results and previous reports [34,35,36,37].

Employing the N2 adsorption–desorption method described by Brunaure, Emmett, and Teller (BET), the physical adsorption of the produced samples was determined. The adsorption–desorption isotherms in Figure 4a display a type IV isotherm with mesopores and H2-type hysteresis loops, indicating that the processed samples are categorized as mesoporous materials [38,39,40,41,42]. The surface area and pore size distribution curves, obtained using the Barrett–Joyner–Halenda (BJH) method and shown Figure 4b, reveal that the pore size decreased with an increase in the WO₃ content (

Table 2. The estimated values of the bandgap, SA, PV and Pd.

	Bandgap (eV)	SA (m2/g)	PV [cm3 g−1]	Pd [nm]
Pure TiO2	3.2	66.21	0.2624	18.983
4%Ag/1%WO3/TiO2	2.72	62.56	0.2604	15.854
4%Ag/3%WO3/TiO2	2.40	48.98	0.0795	5.9162
4%Ag/5%WO3/TiO2	2.69	59.93	0.1806	12.003
4%Ag/7%WO3/TiO2	2.82	63.08	0.1852	11.475

) due to the incorporation of WO₃ particles into the pore of the TiO₂. However, at a higher 4% Ag/7%WO₃/TiO₂ content, the surface area increases again due to the sediment of the small-size WO₃ particles on the surface of the TiO₂. To evaluate the enhancement of the optical response of the prepared materials, UV–visible diffuse reflectance spectroscopy (UV-DRS) was employed. Figure 5a shows the absorbance spectra for pure TiO₂ and 4% Ag/x%WO₃/TiO₂ (with x = 1, 3, 5, and 7 wt.%) nanocomposites.

The absorption edge of pure TiO₂ was observed at 380 nm, indicating that the sample has a high bandgap; however, for 4% Ag/3%WO₃/TiO₂ nanocomposites, the bandgap was noticed to be lowest viz. 2.40 eV due to the redshift in the absorption edge (Figure 5a). The Ag and WO₃ particles on the surface of the TiO₂ contribute to the composite’s improvement [43].

The broad peaks ranged between 400 and 700 nm, especially in the 4% Ag/1%WO₃/TiO₂ sample (Figure 5a), due to plasmon-resonance Ag particles on the surface [24]. Furthermore, it was observed that with the increase in the WO₃ ratio, the plasmon peak decreased, and the absorption spectra around the heterojunction between WO₃/TiO₂ photocatalysts were wider and exhibited a redshift in comparison to the pristine titania [24]. The main source of this redshift is the lattice mismatch between the metal oxides, which leads to the formation of mid-gap states in the bandgap of titania.

The optical energy gap of the prepared samples was calculated using the Kubelka–Munk relation [44] as follows:

$$\mathrm{F}\left(\mathrm{R}\right)={\displaystyle \frac{{(1-\mathrm{R})}^2}{2\mathrm{R}}}$$

(4)

where R is the reflectance. In terms of F(R), Tauc’s equation adjusts the result to become [45]:

$$F\left(R\right)h\nu =A{(h\nu -E_g)}^n$$

(5)

E_g refers to the bandgap as mentioned above, $h\nu$ represents the energy of light, n = 1/2 is for the direct allowed transition, and n = 2 is for the indirect allowed transition.

As shown in Figure 5b, the energy gap was reduced as a result of the WO₃ particles being loaded onto the TiO₂ surface, according to the data in Table 2. The increase in WO₃ concentration on the surface of the TiO₂ composite contributes to the decrease of the energy gap and, consequently, increases the conductivity of the prepared materials. PL was employed to investigate the impact of the increase in the WO₃ ratio on the charge carrier trapping and transfer into the prepared composites. The emission spectra of pure TiO₂ and 4% Ag/x%WO₃/TiO₂ (with x = 1, 3, 5, and 7 wt.% of WO₃) nanocomposites are displayed in Figure 6. The prepared samples were excited at 380 nm to obtain the emission spectra and the result exhibited two luminescence emissions at 450 nm and 470 nm; according to the results, the emission peak at 450 nm was related to the surface defects. The composite and the analysis of the effectiveness of the charge carrier trapping and transfer through the knowledge of the bath of e−/h + pairs in semiconductors can be linked to particular electronic properties of the WO₃–TiO₂ nanocomposites [46]. However, the recombination of excited charge carriers on the WO₃ surface is responsible for the emission peak at 467 nm [47]. The results reveal that the PL spectra were decreased with an increase in the WO₃ weight ratio at 4% Ag/x%WO₃/TiO₂ (with x = 1, 3 wt.% of WO₃) nanocomposites, which means that there is an increase in the lifetime of the electrons at the exited state that gives a high photonic efficiency and photocatalytic activity [48,49]. On the other hand, when the WO₃ weight ratio increases to 5 and 7%, the impurity energy level works as a charge carrier recombination center, and the PL spectrum re-increases again, which decreases the photonic efficiency and photocatalytic activity [30,50].

The photocatalytic activity of pure TiO₂, WO₃/TiO₂, and with 4% Ag/x%WO₃/TiO₂ (with x = 1, 3 wt.% of WO₃) nanocomposites was studied using Cr(VI) as a heavy metal module photoreduction to nontoxic Cr (III). As presented in Figure 7a, the results demonstrate that the photoreduction efficiency of pure TiO₂ is 25%. Moreover, the photoreduction efficiency was nearly 95% in the 4% Ag/1%WO₃/TiO₂ sample. Nonetheless, the photoactivity was decreased after an increase of the 4% Ag/3%WO₃/TiO₂ to 78%, and re-increased again with 4% Ag/5%WO₃/TiO₂, reaching 95% in the presence of 4% Ag/7%WO₃/TiO₂. The obtained results are comparable with several previous reports [21,22,51,52,53,54,55,56] as provided in a comparative Table S1 (see supporting data). These changes are due to the two mechanisms’ impact on the catalyst activity. First, the pure TiO₂ activity is very small due to the wide bandgap of the TiO₂. The high activity of the 4% Ag/1%WO₃/TiO₂ sample is due to the impact of the plasmonic effect of the Ag metal that appeared clearly in the absorption graph. At the same time, the impact of the heterojunction between the TiO₂ and WO₃ molecules is very low. When the WO₃ molecule was increased to 3% and 5%, the impact of the plasmon effect was decreased. By contrast, the impact of the heterojunction between the TiO₂ and WO₃ molecules was increased till it reached 95% efficiency in the presence of the 4% Ag/7%WO₃/TiO₂ sample. Based on the pseudo-first-order model, the kinetics of Cr(VI) photoreduction over the synthesized photocatalysts were further explored as depicted in Figure 7b (Equation (6)) [21]:

$$\mathrm{Ln}\left({\displaystyle \frac{C_o}{C_t}}\right)=-k.t$$

(6)

where C_o and C_t are the Cr(VI) concentration at time zero and time t, and k is the rate constant. By fitting the ln (C_t/C_o) vs. t curves, the 4% Ag/1%WO₃/TiO₂ and 4% Ag/7%WO₃/TiO₂ nanocomposite appear to have a k value almost nine times greater than that of pure TiO₂, revealing that the Ag/WO₃/TiO₂ nanocomposite serves as an outstanding and efficient photocatalyst for the Cr(VI) photoreduction.

The other technique is to evaluate the organic waste degradation activity of the prepared photocatalysts using a photooxidation mechanism. Figure 8a shows the photodegradation efficiency of MB dye discharged into waterways from the textile industrial sector. The results exhibit that the 4% Ag/5%WO₃/TiO₂ catalyst shows improved degradation efficiency of MB to 85% after 30 min and 93% after 4 h. the efficiency of the sample refers to the impact of the heterojunction between the TiO₂ and WO₃, in addition to the impact of the plasmon effect of Ag that works as a trapping point for the photogenerated electron and holes [23]. Figure 8b shows the photodegradation rates of MB that exposed the photodegradation following the first-order kinetics. The optimum sample showed a photodegradation rate nine times higher than that of the pure TiO₂ sample.

3. Materials and Methods

3.1. Materials

Titanium (IV) isopropoxide (97%) was sourced from Alfa Aesar, Ward Hill, Massachusetts, U.S., and tungsten (VI) chloride (99.9%), Pluronic P123 (a poly (ethylene glycol)-poly(propylene glycol) copolymer with a molecular weight of approximately 5800), hydrochloric acid, ammonium hydroxide (NH₄OH) with a purity of >98%, and silver nitrate (AgNO₃) were procured from Sigma-Aldrich, Burlington, Massachusetts, United States.

3.2. Methods

3.2.1. Synthesis of Titanium Nanoparticle TiO₂ (NPs)

TiO₂ nanoparticles were synthesized using the sol-gel method. The procedure involved the following steps. First, 23.4 mL of titanium isopropoxide was mixed with 9.38 mL of hydrochloric acid (HCl) under stirring for 10 min, resulting in a clear solution. After that, 5 g of Pluronic (P123) dissolved into 76.04 mL of ethanol (97%) and was added to the above solution and stirred for 30 min. Second, an Ammonia solution was added to adjust the pH to ~8. The white precipitate was washed five times with distilled water and ethanol, dried for 24 h at 100 °C, and then annealed for 3 h at 450 °C.

3.2.2. Synthesis of (1, 3, 5 and 7% WO₃)/TiO₂ Nanocomposite

A calculated amount of tungsten precursor (tungsten (VI) chloride) was dissolved in ethanol and then added to the titanium isopropoxide solution to produce a (1, 3, 5, and 7% WO₃)/TiO₂ weight ratio. After that, the pH was adjusted using an ammonia solution, followed by washing and drying at 100 °C, and it was finally annealed for 3 h at 450 °C.

3.2.3. Synthesis of 4%Ag/x%WO₃/TiO₂

To prepare a 4% Ag-doped nanocomposite, the previously synthesized (1,3,5, and 7% WO₃)/TiO₂ samples were suspended in a solution containing 0.063 g AgNO₃ and exposed to UV irradiation for 24 h to produce 4% Ag (1, 3, 5, and 7% WO₃)/TiO₂. Finally, the samples were dried at 60 °C for 24 h.

3.3. Characterization Techniques

The crystal structure of the prepared samples was evaluated using an X-ray diffractometer (XRD-6000, Shimadzu, Kyoto, Japan) with Cu Kα radiation (λ = 1.5406 Å) operated at 40 kV and 30 mA. The synthesized nanoparticles’ photoluminescence (PL) spectra were examined using a spectrofluorophotometer (RF-5301 PC, SHIMADZU, Kyoto, Japan) operating at room temperature with an excitation wavelength of 380 nm. Optical characteristics and optical bandgaps were determined using a diffused reflectance spectrometer (DRS UV-3600, SHIMADZU, Kyoto, Japan). The surface morphology analysis of pure TiO₂ and the 4%Ag/x%WO₃/TiO₂ nanocomposite was performed using transmission electron microscopy (TEM JEM-2100F, Tokyo, Japan) that was employed to investigate particle sizes, shapes, and crystal planes. N₂ adsorption-desorption isotherms were employed to determine the specific surface area of the samples using a NOVA2000e apparatus (Quantachrome, Boynton Beac, FL, USA). Additionally, the photocatalytic activity of the prepared samples was illustrated via the photoreduction of Cr(VI) to Cr(III) using visible light irradiation (halogen lamp 1000 W, λ > 420 nm) set at a 20 cm distance above the reactor. In detail, 50 mg of catalyst was added into 50 mL of Cr(VI) solution (10 mg L⁻¹) and suspended and maintained at a constant pH of 3.0 using 100 μ of formic acid as a hole scavenger. The mixture was placed in darkness to reach equilibrium. After that, it was illuminated with visible light, and 2 mL of each interval was centrifuged to remove suspended solids. The aqueous solution of the Cr(VI) sample was determined at λ = 540 nm using the diphenylcarbazide (0.5%) (DPC) solution in acetone and 0.2 M of H₂SO that formed a violet color with Cr(VI) [56]. In addition, the catalytic activity for Cr(VI) reduction was evaluated using the formula (photocatalytic degradation = (1 − C_t)/Co), where C_o represents the initial concentration after the equilibrium experiment in the dark and C_t is the Cr(VI) concentration after the photoreduction process. Moreover, the photooxidation performance of the prepared materials was evaluated using MB dye as a module of the organic waste for the textile industrial sector. The oxidation efficiency was determined by withdrawing 2 ml of illuminated dye at each interval time and measuring the decreasing absorbance intensity of the dye using a spectrophotometer at λ = 664 nm using the same Cr(VI) degradation equation.

4. Conclusions

In our study, the synthesis of Ag/WO₃/TiO₂ nanocomposites with different concentrations of WO₃ particles via the sol-gel technique exhibited highly efficient photoactivity toward the two mechanisms of the photocatalyst performance. They show a good photoreduction of Cr(VI) ions that are converted to Cr(III) due to the impact of the plasmon effect of Ag. In addition, they exhibit a prerogative efficiency for the photo-oxidation of MB dye to CO₂ and H₂O.