Improving the Photo Electro Catalytic Degradation of Methylene Blue by Modified TiO<sub>2</sub>/ITO Photo Anodes

Alsaleh Almohammad, Jihad; Hashem, Mohammad; Alchaghouri, Hanan; Alghoraibi, Ibrahim

doi:https://doi.org/10.1155/2023/1722978

Journal of Nanomaterials

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Abstract Introduction Experimental Results and Discussion Conclusion Data Availability Conflicts of Interest References Copyright Related Articles

Research Article | Open Access

Volume 2023 | Article ID 1722978 | https://doi.org/10.1155/2023/1722978

Improving the Photo Electro Catalytic Degradation of Methylene Blue by Modified TiO₂/ITO Photo Anodes

Jihad Alsaleh Almohammad,¹Mohammad Hashem,¹Hanan Alchaghouri,¹and Ibrahim Alghoraibi^2,3

Academic Editor: Osman Ahmed Zelekew

Received03 Feb 2023

Revised03 May 2023

Accepted29 May 2023

Published15 Jun 2023

Abstract

TiO₂ photoanodes have gained significant attention for the removal of organic pollutants through photoelectrocatalytic processes, with the aim of developing a cost-effective and efficient method for improving the degradation of pollutants in surface water. This study investigated the effects of adding titanium nanooxide (Degussa P25) containing 70% anatase and 30% rutile phases on the properties of nanostructured TiO₂ photoanodes prepared on glass substrates (indium tin oxide (ITO)) using sol–gel/dip coating techniques The results obtained from ultraviolet–visible transmittance spectroscopy, electrochemical (EC) impedance spectroscopy, photocurrent, and atomic force microscopy analyses revealed that the addition of Degussa P25 improved the electrical conductivity of the TiO₂/ITO anode and reduced the optical bandgap from 3.50 to 3.35 eV, while the size of the titanium oxide particles decreased to about 75 nm. The EC impedance spectra measurement confirms that the addition of titanium nanooxide Degussa P25 improved the electrical conductivity for TiO₂/ITO anode. The photoelectrocatalysis (PEC) performance of the TiO₂ photoanodes was investigated via the degradation of methylene blue (MB) under UVA light irradiation. The AB photoanode (with the addition of Degussa P25) exhibited excellent PEC performance, with 95.9% color removal efficiency and 63% total organic carbon (TOC) removal efficiency, compared to 92% color removal efficiency and 56% TOC removal efficiency for the A photoanode (without the addition of Degussa P25). The kinetic constants (k) were 134 × 10⁻⁴, 110 × 10⁻⁴ (min⁻¹) for A and AB anodes, respectively, and the degradation of MB followed first-order kinetics for all anodes. The A and AB anodes were compared as electrodes for the degradation of MB using PEC, photocatalysis (PC), and EC technologies. Subsequently, The A and AB anodes were utilized as electrodes to compare the performance of PEC, PC, and EC technologies for the degradation of MB. The results showed that the AB anode exhibited higher efficiency in all PC technologies, with color removal (%) efficiencies of 95.9% (PEC), 33% (PC), and 21% (EC) compared to 92% (PEC), 28% (PC), and 19% (EC) for the A anode. Additionally, the photooxidation process had a 2.1% effect on the degradation of the initial MB concentration.

1. Introduction

Searching for solutions to the environmental pollution problem that is exacerbating day after day is an urgent need on the global stage. Huge amounts of pollutants generated from pharmaceutical and industrial processes have been discovered to have harmful and long-term impacts on our daily life [1–4]. Some of them are difficult to degrade due to their complex compositions, resulting in harmful residual pollutants in water [3, 5]. Several technologies and strategies, that are efficient and environmentally friendly, have been applied to the degradation of these pollutants, such as Fenton’s reaction [6], biological methods [7], and chemical oxidation [8]. However, these methods are often not energy efficient, or they secondarily pollute during the degradation of the primary waste since they are based on conventional wastewater treatments [3]. In this regard, photoelectrocatalysis (PEC), which is one of the most recent electrochemical (EC) advanced oxidation processes technology, offers a promising, efficient, and environmentally friendly approach for removing a wide spectrum of organic pollutants from wastewater and reduce the incidence of charge recombination and partially improve the limitations of photocatalysis (PC), which it uses suitable semiconducting materials as photoanodes [2–4, 9, 10]. Another interesting advantage of PEC is lower energy consumption when compared to anodic oxidation, which requires high potential/current to facilitate the degradation of organic [2]. In PEC, it is applying an external potential to a photocatalyst film supported on a conductive substrate that electrochemically aids the photocatalytic process. Through PC, the substrate helps expel the electrons that reach the conduction band (e⁻_CB) toward the external circuit, resulting a significant reduction in the challenge of rapid and spontaneous recombination of charge carriers (e⁻_CB/h⁺_VB) that is peculiar to PC and producing an increase in the electron transfer rate [3, 9, 10], as shown in Figure 1. Further, the holes generated in the valence band (h⁺_VB) react with water to produce (^·OH), the second strongest oxidant known after fluorine, which nonselectively reacts with most organics in water [4, 5, 9, 10]. When this technique is used to treat water contaminated with recalcitrant organic molecules, such as pharmaceuticals, total mineralization to water and carbon dioxide can be achieved over a period of time, or the molecules can be broken down to nontoxic organic molecules within a short period of time [3]. In other words, the efficiency of PEC in the degradation of organic pollutants in aqueous medium depends on the ability of photoanodes into generate in situ oxidizing reactive oxygen species [9–13]. Thus, the materials used to prepare a photoanode are an important factor in the photoelectrocatalytic process [11–14]. Figure 1 shows the mechanism of the photoelectron catalytic process using the TiO₂/indium tin oxide (ITO) anode and the reactions that occur on the surface.

The preparation of stable and reusable photocatalysts on conductive materials as a support is one of the most important steps in the development of PEC technology. Several kinds of semiconductors, particularly TiO₂, remained the most applied semiconducting photocatalyst as anodic material for photoelectrocatalytic degradation of organic compounds in water [2, 3]. TiO₂ is widely recognized as a favorable catalyst in the preparation of photoelectrodes for its advantages of nontoxicity, high reactivity, cost-effectiveness, easy synthesis, and chemical inertness [9, 10, 13]. TiO₂ occurs in three polymorphs, the stable rutile, metastable anatase, and brookite, showing different properties and bandgaps, i.e., 3.0, 3.22, and 3.23 eV, respectively [14]. Anatase reveals higher photocatalytic activity than rutile and brookite in many cases due to different lattice structures and electronic band structures [15].

Titanium oxide nanoparticles films can be prepared by several methods, such as magnetron sputtering [16], chemical vapor deposition [17], electrophoretic deposition (EPD) [10] sol–gel, dip-coating, spin-coating [9, 10], atomic layer deposition [18], and atmospheric plasma spray [19]. However, the sol–gel method is the most popular technique to synthesize TiO₂ thin-film photocatalysts [20] because it is an easy, simple, and cost-effective method that can be applied to all types of piles and sizes. In addition, it is a method that allows obtaining photoelectrodes with large internal surfaces, EC stability, and a high efficiency for the removal of organic pollutants and allows to achieve enough crystallinity to provide TiO₂ the desired combination of mechanical, catalytic, and optoelectronic properties, allowing it to achieve degradation efficiencies of contaminants between 70% and 100% during short treatment times [9]. All these techniques have been studied using different conductive substrates such as ITO, fluorine-doped tin oxide, titanium, stainless steel (SS), and recently boron-doped diamond (BDD) [2, 3, 9, 10, 21–24]. ITO-coated glass is made by spreading a thin and uniform layer of ITO over a glass substrate, making the glass have advantages (low resistance and highly transparent). Thus, the photoanode on an ITO glass (as a current conducting substrate) has a high efficiency for optical photons to pass through to generate holes and reduces the complexity of the processing unit. Many methods have been studied to improve the photocatalytic properties, such as doping with transition metals oxide [25] and noble metals [26, 27]. Doping with P25 is an effective and simple strategy for preparing and improving photocatalysts and enhancing the ability to degrade pollutants [28–30]. Sigcha-Pallo et al. [10] have used the EPD for papering a photoanode of titanium dioxide (TiO₂) nanoparticles (Degussa P25) onto a BDD substrate, applied in the degradation and mineralization of sodium diclofenac (DCF-Na) in an aqueous medium using PEC. The degradation and mineralization efficiencies of pollutants were between 80% and 100% during short treatment times [10]. The TiO₂/P25/ITO photoanode is one of the most promising photoanodes in PEC for wastewater treatment. The combination of the fabrication methods with sol–gel is an effective strategy to overcome the weaknesses of applying the sol–gel alone. Many studies have been concerned on the combination of the sol–gel with other techniques, for example, Carreño-Lizcano et al. [31] have prepared nitrogen-doped TiO₂/rGO (reduced graphene oxide) films by a sol–gel method and immobilized on SS by dip-coating technique to evaluate their photoelectrocatalytic activity in the phenol oxidation. The efficient phenol degradation was around 45% by using photoelectrocatalysis in comparison with other oxidation process as photolysis (1.5%), PC (21%), and electrocatalysis (24%) [31]. Alulema-Pullupaxi et al. [9] have combined sol–gel/spin-coating methods to synthesize a robust and stable (TiO₂/BDD) photoanode for studying the degradation of glyphosate by EC oxidation on BDD and photoelectrocatalysis on TiO₂/BDD in dark and ultraviolet (UV) light conditions. The glyphosate degradation was 2.3 times faster by photoelectrocatalysis on TiO₂/BDD relative to BDD.

Therefore, this work proposes the synthesis of TiO₂/ITO using a novel method combining sol–gel/dip-coating techniques with the addition of titanium nanooxide (Degussa P25).

The aim of this study is investigating the effect of adding Degussa P25 during the preparation of the photoanode on the surface morphology, EC, optical properties, and applying PEC technology to the degradation of methylene blue (MB). In addition, this study highlights the addition of P25 powders to a TiO₂/P25/ITO photoanode to improve the PEC performance, efficiency degradation of MB, operational ability, and enhance photocatalyst activity of the photoanode.

2. Experimental

2.1. Materials

According to the manufacturer’s specifications, Titanium dioxide (Degussa P25) comprises 70% anatase and 30% rutile phases, with an average particle size of this compound is approximately 25 nm and it exhibits a specific surface area of 48.3 m² g⁻¹ from N₂ adsorption at 77 K.

The following source: (MB, C.I.52015) from Scharlau Company (Barcelona-Spain) was used to prepare the artificially contaminated solutions of MB without any additional purification processes. Sodium sulfate Na₂SO₄ (95.0%) was purchased from Riedel_de Haen company, and used in the preparation of sol–gel titanium tetra isopropoxide (TTIP) purity, (97.0%), M = 284.22 and Triton X-100 from Scharlau Chemie, laboratory grade, M = 646.37 g mol⁻¹, D = 1.07 g cm⁻³, (Germany), ethanol from BDH (Germany) purity (99.2%), M = 46.01, and acetic acid from PRS (Spain) purity (98%). ITO glass of 50 Ω resistance, dimensions (3–10 cm), and thickness of 0.07 cm was bought from Aldrich (Germany). In addition, a cathode of nickel metal from Aldrich (Germany). Water for injections was also used in preparing samples and solutions.

2.2. Characterization

The morphology of the TiO₂ nanoparticles was characterized by an atomic force microscopy (AFM) (esayScan2, nanosurf), UV–visible (UV–Vis) spectroscopy studies were performed in order to determine the optical properties for wavelengths ranging from 300 to 800 nm using a Varian Carry 5000 (UV–VIS-IR), A UV–Vis spectrophotometer and total organic carbon (TOC) (Phoenix8000) were employed to monitor the degradation of MB. The point of zero charge pH_pzc, was determined by acid–base titration method following the procedure adopted previously [32] for a powder sample. The electrochemical impedance spectroscopy (EIS) was measured using an IVIUM-STAT.XR Potentiostat/Galvanostat with integrated high-performance frequency response analyzers for EIS measurements. With an excitation signal of 10 mV amplitude. The impedance vs frequency spectra was acquired at the open circular potential of the system in the dark and under UV illumination. The photocurrent densities were examined by linear sweep voltammetry measurements in a three-electrode EC system, using an Ag/AgCl as the reference electrode and Pt mesh as the counter electrode in a 1 M NaOH electrolyte.

2.3. Preparation of Photoanodes

Solution A was prepared by adding 1.5 mL surfactant agent Triton X-100, 10.2 mL acetic acid, 57 mL ethanol, and 5.4 mL TTIP and kept under vigorous stirring by ultrasonication for 3 hr. Solution B was prepared by adding 1 g titanium oxide (Degussa P25) to 10 mL of ethanol and 10 mL of water solution under continuous ultrasonic stirring. Solution B was added dropwise to solution A with constant stirring for a period of 1 hr to obtain solution AB.

ITO glass slides were rinsed with water and ethanol, calcined at 550°C to remove any impurities from the surface, and then immersed so that 8 cm from the conductor side was wetted by the sol via using the dipping electroplating device in solution A to obtain the photoanode A and another one in solution AB to obtain the photoanode AB. By programing the immersion time of 1 s and the drawing speed of 100 µm s⁻¹. Finally, the heat treatment takes place in two stages. The first stage raised the temperature to 100°C for 3 hr, and then the temperature was raised to 450°C at a speed of 15°C s⁻¹. The temperature was kept for 2 hr and then cooled down while maintaining the previous speed.

2.4. PEC Degradation of MB

The PEC degradation of MB was carried out in a homemade single-compartment cuboid transparent glass reactor Figure 2. In the PEC experiments, A and AB photoanodes acted as photoelectrodes and the Ni foils as cathodes (the geometric area in contact with the MB solution was 48 cm²). The distance between the two electrodes was 3.0 cm. The UVA light was supplied by two lamps; the first lamp (λ = 365 nm, 12 T5, 6 W, OSRAM, made in Italy) was placed inside the reactor parallel to the two electrodes. The second lamp (λ = 365 nm, 12 T8, 8 W, Hitachi, made in Japan) was placed outside the reactor and parallel to the two electrodes. A cooling water recirculation system was equipped to control the experimental temperature at 25°C. The distance between the inside lamp and the photoelectrode was 2 cm, and distance between the outside lamp and the photoelectrode was 6 cm. The concentration of MB was set as 25 mg L⁻¹, and 0.05 M of Na₂SO₄ was added to enhance the MB solution conductivity. Prior to irradiation, the two electrodes were vertically fixed in the reactor. Then 200 mL of MB is added to the reactor and stirred in the dark for 30 min to establish adsorption–desorption equilibrium. The potential in the PEC was controlled by a DC power supply. Samples were taken at specified intervals to follow the change of concentrations of solutions during treatment.

The removal efficiency is calculated as follows:where C₀, C (mg L⁻¹) the MB concentration initial and during the treatment process.

3. Results and Discussion

3.1. Characterization of TiO₂/ITO Anode

The AFM micrographs of TiO₂/ITO thin films deposited at room temperature after immersing in solutions A and AB are shown in Figure 3.

(a)

(b)

From AFM images, it is observed nonuniform unequal distribution grains were formed with a huge grain diameter of 125 nm, average area surface roughness (Sa = 20.2 nm), and area root-mean-square roughness (Sqrms = 31.1 nm) after immersing in solution A, while the grain carpet after immersing in solution AB showed homogeneous spherical shape formed on the surface of the film. The grains had relatively low narrow size distributions with low mean diameter (D = 75 nm) and high (Sa = 28.6 nm) and (Sqrms = 35.0 nm), respectively. In the case of formation, the thin film after the deposition of TiO₂ from solution AB. The film deposited from solution AB gave a better performance as a photoanode, and this is due to the fact that TiO₂ thin film on ITO has a good quality, high surface roughness, uniform, and completely covered the entire substrate surface area.

Comparing the grains size distribution histogram of A and AB thin films (as seen in Figure 4), we found that the film formed with solution (AB) is the most suitable case to form nanograins of TiO₂ with a small diameter and narrow size distribution which ranged from 30 to 185 nm. On the other hand, the TiO₂/ITO thin films prepared with solution A exhibit a large distribution and varied from 42 to 265 nm. The difference in grain size could be attributed to the presence of addition (Degussa P25) with nanoscale dimensions in solution AB, which affected the grain size formed during calcination.

(a)

(b)

3.2. Optical Properties

Absorbance measurements of anodes, Figure 5, were recorded in the range of 300–800 nm using a UV–Vis spectrophotometer (Varian carry 5000), allowing the calculation of the thickness and bandgap of A and AB photoanodes. The absorption coefficient was calculated using the relation α = ln (1/T)/t [33], where T is the transmittance and t is the thickness of the TiO₂ film. The thickness of the film was also calculated optically using a He–Ne laser. Tauc’s model is used for the optical bandgap’s (E_g) calculations [34]:where α, h, A, and represent the absorption coefficient, Planck’s constant, constant of proportionality, and frequency of light, respectively. n = 1/2 and two for indirect and direct transition, respectively [35]. Bandgap energy for A and AB anodes are determined by a slope of the curves on the x-axis, as exhibited as shown in Figure 6.

The bandgap energy was reduced from E_g = 3.52 to 3.35 eV when we added Degussa P25, which is closer to the reference value for the energy gap of anatase-type titanium oxide, E_g = 3.22 eV and Degussa P25 E_g = 3.15 eV reported in the literature [36–38], indicating a quantum size effect into bandgap. This shift of the TiO₂ film bandgap caused by quantum confinement in thin layers has been thoroughly explained in a publication by King et al. [39]. The decrease in the energy gap with the decrease in the size of the particles is an interesting result. Many studies indicate that the decrease in the size is accompanied by an increase in the energy gap when P25 is added [5, 30]. Other studies indicate slight changes in the energy gap when the size of the particle decrease; this may be due to the effect of surfactant material, the combination ratio of anatase and rutile phases in the sample, and the viscosity of the solution in sol–gel method [29, 30].

3.3. Photo EC Properties

The present study involved a photoelectrochemical investigation of anodes through EIS measurements under both UVA illumination (λ = 360 nm) and dark conditions. This investigation was conducted in a three-electrode cell that featured a flat quartz window opposite the working electrode, which had an exposed front face electrode area of 2 cm². The experimental setup employed Ag/AgCl as the reference electrode and a Pt wire as the working electrode.

Figures 7(a) and 7(b) depict the Nyquist plots obtained using a 10 mV amplitude at the open circuit potential within a frequency range of 10 Hz–100 KHz, with a decreasing scanning frequency order, first in the dark and then under UVA illumination. Nyquist plots convey information on the charge transfer process as the diameters of the semicircles are equal to the charge transfer resistance of a sample [40]. As seen in Figure 7, all plots obtained under UVA illumination exhibit semicircles similar to those obtained in the dark. Notably, the semicircle diameter of the anodes under illumination is smaller than that of the same films in the dark. This observation suggests that the charge transfer rate under illumination is higher than that in the dark for the anodes. For anode AB, obtained by the addition of titanium nanooxide Degussa P25, the charge transfer rate under both dark and illumination conditions is higher than that of anode A, indicating an enhanced charge conductivity. The charge transfer resistance can be determined by fitting the arc radius of the Nyquist curves according to the proposed equivalent circuit illustrated in Figure 7(c). The components of the circuit, R_s, CPE, and R_ct, represent the series resistance, constant phase element, and charge transfer resistance, respectively.

(a)

(b)

(c)

Figure 8 illustrates that no significant dark current was detected, even at high potential, while substantial photocurrent densities were observed under illumination on both A and AB photoelectrodes. It was observed that the photocurrent increased linearly with the applied potential bias until eventually reaching a plateau. Notably, the AB anode displayed significantly higher photocurrent density compared to the pristine A anode.

Based on the EIS and photocurrent measurements, it can be concluded that both anodes, with and without the addition of titanium nanooxide, exhibit significant photo-generated currents under UVA illumination, indicating their potential suitability as photoanodes. Furthermore, the AB anode displays a more active surface, which can be attributed to its higher surface roughness, uniform coverage of the substrate surface, and increased photocurrent density. These properties render it a promising candidate for use as a photoelectrocatalytic material electrode, which could play a crucial role in pollutant degradation.

3.4. Degradation of MB under UVA Light

Figure 9(a) illustrates the reduction of MB concentration over time using A and B anodes, while Figure 9(b)–9(f) presents the UV–Vis spectra of a 25 mg L⁻¹ MB solution at various time intervals (0–240 min). The initial spectrum (t = 0), depicted in Figure 9(b), exhibits the characteristic peak of MB at 664 nm, which gives the aqueous MB solution its blue color [41].

(a)

(b)

(c)

(d)

(e)

(f)

The obtained results are in concurrence with previously reported findings [42]. As the reaction proceeded, the reaction solution gradually lost its color, and the absorption maximum at 664 nm decreased while shifting towards a shorter wavelength, approximately 600 nm after 240 min, due to the formation of demethylated dyes [43]. After 60 min of reaction with MB, the λ_max of AB photoanode shifted to 654 nm, resembling that of Azure B (AB). After 120 min, λ_max shifted to 630 nm, which is similar to the λ_max of Azure A (AA). After 180 min, λ_max shifted to 615 nm, which corresponds to the λ_max of Azure C (AC), and after 240 min, λ_max shifted to 600 nm, which is comparable to the λ_max of Thionin (Th). These observations align with those reported in a publication by Yogi et al. [44]. The photocatalytic reaction mechanism involves the reaction of MB with generated HO^· radicals or h⁺, leading to the N-demethylation of its auxochromic dimethylamine groups. This demethylation results in the degradation of MB into a compound with a shorter absorption wavelength, along with H₂O and CO₂ [45]. Figure 10 shows the intermediates formed during the demethylation of MB in the PEC process using AB photoanode [44].

The treatment was performed at pH = 7, as indicated by our previous results, which showed that pH 7 provides the optimal MB dissociation value; since pHzpc TiO₂ < pH = 7 (as shown in Table 1), titanium oxide acquires a negative charge [46], which enhances the adsorption affinity for MB (a cationic dye). Our results are consistent with prior research indicating that the addition of P25 can enhance the photoanodes’ efficiency in degrading MB by improving the electron–hole pairs’ separation efficiency, photocatalytic activity, and PEC performance [28–30]. Furthermore, the AB photoanode’s operational durability was tested and found to withstand three cycles without breaking down or peeling off.

3.5. Kinetics of PEC Degradation of MB

In general, the PEC degradation of organic pollutants using TiO₂ film electrodes has been seen to follow first-order or pseudo-first-order kinetics and can be described by the Langmuir–Hinshelwood kinetic model. The kinetics data of the degradation of MB were analyzed using a first-order kinetic model [47].where C_t is the MB concentration (mg L⁻¹) at time t, C₀ is the MB initial concentration (mg L⁻¹), k is kinetic constants (min⁻¹), and t is the reaction time (min).

Table 1 presents the energy gaps, film thickness, pH zero-point charge, and the first-order kinetic constants for A and AB photoanodes during three cycles.

When the ln C₀/C vs time curve obtained at initial MB concentrations is plotted in Figure 11 for both anodes. The kinetic constant for the PEC degradation of MB using an AB anode was higher than that measured using an A anode (the former was 134 × 10⁻⁴ min⁻¹ and the latter was 110 × 10⁻⁴ min⁻¹) for the first cycle as shown in Table 1. These results show that the crystal structures of titanium oxide and E_g can significantly influence the kinetic constant of degradation on PEC.

3.6. Application of A and AB Photoanodes in Different Technologies

The photoanodes A and AB being used as working electrodes to study their efficiency in removing MB in some of advanced oxidation processes. A comparison was made between the PEC technology, the PC technology (without turning on the current), and the EC technology (no light source), with the same treatment unit, to degradation of MB using the A and AB photoanodes and compared it with exposing the solution to UVA rays only photooxidation (PO). After 4 hr, percentages of the color removal and TOC were 2.1% and 0.4%, respectively, when exposing 200 mL of MB solution (25 mg L⁻¹) to ultraviolet light. And it is only caused by the PO of MB. The results in Table 2 showed that after 4 hr of treatment, the anode AB showed a greater percentage of removal of color and total organic carbon than the anode A in whole treatments, in addition to the superiority of the PEC for the three cycles over all the studied techniques. Despite the formation of strong oxidants agents as h⁺, ^·OH in PEC and PC, the superiority of PEC in removing MB color is due to the possibility of transferring the formed electron through the external circuit to the cathode, which inhibits the recombination of an electron–hole [47], and increases the amount of oxidants formed and thus greater removal of MB color.

4. Conclusion

In this study, TiO₂ was prepared on ITO glass via the sol–gel method to produce photoanodes labeled as AB and A, with and without the addition of titanium dioxide nanopowder (Degussa, P25) 70% anatase and 30% rutile phases, respectively. The surface morphology, photo EC, and optical properties of the prepared anodes were characterized using AFM, EIS, and UV–Vis spectroscopy. The optical studies revealed that the bandgap energy (E_g) ranged from 3.50 to 3.35 eV, and the size of the titanium dioxide particles decreased from 125 to 75 nm. The PEC performance of anodes A and AB was investigated via the degradation of MB under UV light irradiation, with photoanode AB demonstrating excellent performance. The efficiency of color removal and TOC were 95.9% and 63%, respectively, while it was 92% and 56% for photoanode A (without the addition of Degussa P25). The degradation of MB followed first-order kinetics for all anodes. In conclusion, anode AB achieved a higher removal rate than anode A when used in PC, EC, and PEC technologies, with PEC demonstrating the greatest degradation of MB. The present study proposes that TiO₂/ITO films could be a promising candidate as photoanodes with photocatalytic activity for the photoelectrocatalytic degradation of pollutants in wastewater under UV light irradiation, as the photoanode showed excellent results, and the materials are commercially available.

Data Availability

The datasets used and/or analyzed during the current study are available from the corresponding author upon request.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

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Copyright © 2023 Jihad Alsaleh Almohammad et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Journal of Nanomaterials

Improving the Photo Electro Catalytic Degradation of Methylene Blue by Modified TiO2/ITO Photo Anodes

Abstract

1. Introduction

2. Experimental

2.1. Materials

2.2. Characterization

2.3. Preparation of Photoanodes

2.4. PEC Degradation of MB

3. Results and Discussion

3.1. Characterization of TiO2/ITO Anode

3.2. Optical Properties

3.3. Photo EC Properties

3.4. Degradation of MB under UVA Light

3.5. Kinetics of PEC Degradation of MB

3.6. Application of A and AB Photoanodes in Different Technologies

4. Conclusion

Data Availability

Conflicts of Interest

References

Copyright

Improving the Photo Electro Catalytic Degradation of Methylene Blue by Modified TiO₂/ITO Photo Anodes

3.1. Characterization of TiO₂/ITO Anode