Introduction

In recent years, there has been an increasing interest in the use of nanomaterials in various fields such as biomedical [1], sensor technology [2] and eco-friendly materials [3] by changing their shape and properties [4,5,6,7,8,9]. Several synthetic methods have been used to adjust the size and shape of the titanium dioxide (TiO2) nanomaterials. The size and shape of the TiO2 morphologies have revealed the unique physical and chemical properties of the TiO2 and found its potential to be widely applied in scientific and commercial areas [10,11,12]. Recently, TiO2 photocatalysts have attracted much attention because of their self-cleaning [13], solar cells [14] and promising applications in biomedical and environmental areas [3, 15,16,17]. In particular, TiO2 has produced beneficial results for the environment because of its photocatalytic properties [18,19,20,21,22,23,24]. Semiconductor morphology has a significant effect on the photoelectrochemical (PEC) and photocatalytic (PC) performances of TiO2 photocatalysts [25,26,27,28,29,30,31]. Scientists have been working to further develop these superior properties of TiO2 films. Nanotubes [32], nanowires [33] and porous nanostructures [34] produced by considering shape and size control are critical for increasing the potential of photocatalytic and photoelectrocatalytic activities.

TiO2 films can be produced on Ti substrates using methods such as vacuum evaporation [35], chemical vapor deposition [36], magnetron sputtering [37], sol–gel [38] and electrochemical anodization [39, 40]. Electrochemical anodization has been identified as a more efficient and cost-effective method for the formation of TiO2 layers on titanium substrates [23, 41, 42]. For nearly a century, protective or decorative oxide layers on metal surfaces have been created using electrochemical anodization of the appropriate metals[43]. Typically, two electrodes are used to perform anodization. The metal foil or sheet that is being anodized is inserted into the electrolyte and linked as the anode to the positive terminal of a DC power source. Platinum plates or rods are typically utilized as the counter electrode (cathode), while other materials like carbon can also be employed [43, 44]. Electrochemical conditions, particularly the anodizing voltage and time solution parameters such as the pH, water content, and electrolyte composition, generally impact the morphology and structure of the porous layers[45].

TiO2 has three different phase/crystal lattice structures; rutile-tetragonal, anatase-tetragonal and brookite-orthorhombic [46]. These crystal structures are rutile with the most stable structure and can be obtained using various growth methods. However, the anatase is less stable and less dense than rutile [47]. Although it seems to have an anatase disadvantage in terms of stability, it has the advantage of being photocatalytically advantageous according to the rutile because of the highest number of photoactivities of the electron–hole pairs [48].

The surface area is an important factor affecting the photocatalytic activity of a porous TiO2 layer prepared by anodic oxidation [49, 50]. A photocatalytic reaction is a concept related to surface morphology that is independent of the particle or film structure. Therefore, the surface area/volume ratio plays an important role in photocatalytic performance [51, 52]. The photocatalytic activity of porous TiO2 obtained by anodizing is very high because of the high surface area/ratio [32, 53, 54]. Therefore, the production of films with rough and excess surface area allows us to obtain structures with superior photocatalytic performance. The individual effects of each surface morphology related parameter were investigated. Also, practical applications of this material are limited to low surface area; therefore, many efforts have been made to improve the surface area by developing porous structures using different anodization parameters [25, 55, 56] and also measurements of numerical analysis are very important for surface morphological properties [9, 57,58,59]. Photocatalytic performance is affected by anodization parameters such as pH [19], time [32], voltage [60], and electrolyte type [20].

When we look at previous studies in the literature, it is seen that the effect of time or voltage in the anodizing process has been studied [25, 61, 62]. However, among these effects, the effect of the surface area parameter on the photocatalytic activity in the porous structure does not appear with a scientific calculation method. All existing studies have only been conducted by interpreting the photocatalytic efficiency from SEM images. The important point here is the numerical measurements made with the image analysis program. There is no study in which morphological features were examined in detail with any image analysis program and correlated with photocatalytic properties according to our knowledge. It is thought that revealing features such as area fraction, equal diameter, circularity, feret (min and max), and elongation terms of the nanopores may be very useful for theoretical calculations for photocatalytic applications in the future. In this regard, the aim of our study is to produce TiO2 films produced by anodizing at different times and voltages, analyze the electron microscope images in detail, and correlate them with the properties of the films. Especially, the correlation of the TiO2 pore properties with photocatalytic properties is our source of motivation. In line with these purposes, anodization productions were carried out within the periods of 15–480 min by applying 5–80 V. The structural, morphological, and photocatalytic properties of the produced samples were characterized, examined, and associated.

Experimental studies

The nanostructured TiO2 films

Cylindrical rods of commercially pure titanium (ASTM grade 2) were cut into 25 mm and 5 mm thickness. They were mechanically polished using 120 to 2000 sandpapers and ultrasonically cleaned with acetone, ethanol and distilled water for 15 min. Before starting the anodizing process, the samples were kept in an acid bath consisting of a mixture of nitric acid (HNO3) and hydrofluoric acid (HF) solutions for 10 s to remove the oxide layer on the surfaces. The experiment was carried out in two steps with 12. For step 1, the first six samples were subjected to electrochemical anodization for 60 min at room temperature, 1 M Na2SO4/5 wt.% NH4F, at voltages of 5 V, 10 V, 20 V, 40 V, 60 V, 80 V, respectively, as shown in Fig. 1. 1 M Na2SO4 / 5 wt.% NH4F electrolyte was chosen according to the previous article [20]. The best sample of the voltage varying samples was determined by the photocatalytic performance. In the second step, six samples were anodized for 15, 30, 60, 120, 240, 480 min at 40 V, which was determined as the best photocatalytic performance among the first step. All the procedures and parameters used in the experiments are listed in Table 1. After the anodizing process was completed, all samples were heat treated at 500 °C for 2 h in air atmosphere to improve oxide crystallinity and conversion to anatase, as reported in some similar studies [63].

Fig. 1
figure 1

Schematic of the working steps, including the anodization TiO2 films, heat treatment process and photocatalytic test

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Table 1 Sample abbreviations according to the voltage and anodization time parameters
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X-ray diffraction patterns of all samples were recorded to identify the phase structures using an X-ray diffractometer having a CuKα characteristic radiation source (XRD, Thermo-Scientific, ARL Kα). Diffraction patterns were acquired in the range of 10°- 80° with a scanning rate of 2°/min. The X-ray radiation of Cu-Kα was set at 45 kV and 44 mA. The surface morphology of the samples was monitored using a scanning electron microscope (SEM, JEOL 6060). An accelerating voltage of 5–10 kV was used for the SEM imaging. All samples were examined at higher magnifications to obtain more details from the samples. Contact angle measurements of water wetting were performed using a manual optical tensiometer (Theta Lite) for Steps 1 and 2.

Photocatalytic measurements

Photocatalytic experiments were performed to investigate the photocatalytic performance of TiO2 films. The photocatalytic activities of the TiO2 films were measured using a UV light source (Osram, UltraVitalux E27, 300W) for the degradation of methylene blue (MB) solutions. Methylene blue was exposed to UV at a concentration of 10–5 M and at a pH of 8 in a closed environment at a distance of 10 cm from the light source. The absorption spectrum of MB, which is required for photocatalytic calculations, was taken from the beaker in which the samples were in a solution with a 3 ml. syringe, and their measurements were performed sequentially. The calculation of this absorption spectrum was also carried out using a Shimadzu_UV 1240 spectrophotometer by looking at the characteristic peak of MB at 664 cm.

In the calculation of the photocatalytic measurements, the first measurement was taken by keeping the samples in the dark for 1 h. Thus, photocatalytic equilibration was achieved. 1 h absorption and desorption of all samples were performed under UV light with intermittent measurements.

The Beer-Lambert equation was used for the photocatalytic calculations [64, 65].

$$n=\left(\frac{{C}_{0}-C}{{C}_{0}}\right)\times 100$$
(1)

C0 and C are the initial and final concentrations of the MB solution, respectively. Photocatalytic degradation performance was obtained using the Lambert Beer Law for different voltage samples (step 1) and different times (step 2). Thus, photocatalytic efficiency is an important issue for determining any catalyst to be transferred into a device for industrial applications. Considering these facts, the photocatalytic efficiencies of the prepared TiO2 thin films were compared.

Results and discussion

XRD

XRD analysis was carried out to examine the crystal structures after annealing at 500 °C for 2 h. XRD analysis was performed for the 40 V sample with the best photocatalytic result of the group of samples (step 1) applied with different voltages. XRD results were given over the anodization time variable. XRD patterns of different times as 15 min, 30 min, 60 min, 120 min, 240 min, 480 min; 15, 30, 60, 120, 240, 480 are shown in Fig. 2., respectively.

Fig. 2
figure 2

XRD diffraction patterns of the nanostructured TiO2 films according to the anodization times

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Anatase appears in all calcined samples. A different phase structure, such as rutile and brookite, is not observed. The diffraction peaks at 2θ value of 25.24°, 38.2°, 48.12°, 62.83°, 70.55° and 76°, which are related to crystal planes of (101), (004), (200), (204), (220) and (215), respectively, correspond to the anatase crystalline structure of TiO2 (JCPDS Card No:12- 1272). With crystalline cell constants of a = 3.783 Å and c = 9.51 Å, all of the very sharp peaks could be indexed as anatase TiO2, and these values are essentially consistent with the stated values found on Joint Committee on Powder Diffraction Standards (JCPDS) card No. 04–0477.

The peak (101) at 2θ = 25.24° is the characteristic peak for the anatase phase of nanostructured TiO2 films. The detected peaks at 2θ = 35.2 and 2θ = 40.18 belong to the Ti element and they come from Ti substrate.

Morphological characterizations

The surface morphologies of the samples produced at different voltages and anodizing times are shown in Fig. 3 and Fig. 4, respectively. Nanoporous surface morphologies were aimed in the study, and considering the scale in the SEM images, this goal was achieved. Let us detail the morphologies of the samples (in Fig. 3) anodized for 1 min under different voltages in the range of 5–80 V. We observe that the desired nanoporous structures are obtained especially in the samples produced by applying 20 V, 40 V, and 60 V (see Fig. 3 (c), (d), and (e)). Although there are nanopores with insignificant diameters at low voltages such as 5 V and 10 V (Fig. 3 (a), (b)), it is impossible to say that the desired nanoporous structure is formed. Although comparisons will be made with the numerical data below, it can be clearly seen from Fig. 3 that the pore diameter increases with increasing voltage value similar to that reported in the literature [66,67,68]. This was also supported by calculations using an image analysis program. By increasing the voltage value to 80 V, the nanoporous morphology deteriorates and the pores merge into more rod-like morphology (see Fig. 3 (f)).

Fig. 3
figure 3

SEM images of the nanostructured TiO2 films according to the different anodization voltages

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Fig. 4
figure 4

SEM images of the nanostructured TiO2 films according to the different anodization times

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The SEM and photocatalytic results of the samples produced at different voltage values were examined and the best voltage parameter was determined to be 40 V. In Fig. 4, SEM images of samples anodized between 15 and 480 min under 40 V are presented.

When the morphologies are examined in general (Fig. 4), there are more superficial and small-diameter pores in short anodizing times, whereas the pore depth and diameter increase with increasing anodizing time. When looking at the literature studies, it is seen that these structures are compatible with the data obtained and at the same time, numerical measurements related to pore structures have been obtained with the image analysis program. These data support the SEM results.

Random nanopores were formed on the surface during the 15-min anodization process (Fig. 4 (a)). It is noteworthy that the pores started to become denser as the anodizing time increased to 30 min (Fig. 4 (b)). In addition, rough bumps on the surface began to be observed. Notably the pore density increased noticeably with the increase in the anodizing time to 60 min (Fig. 4 (c)). A serious morphological change was observed after 120 min of the anodization process. Especially, the surfaces of the samples that were anodized for 120 and 240 min. turned into more tubular structures (see Fig. 4 (d) and (e)). An indentation difference was observed between the tubes with 240 min anodization (Fig. 4 (e)), it is seen that the surface becomes flatter with 480 min of anodization, but the pore diameter becomes quite large (Fig. 4 (f)).

Morphological features of the samples obtained from the LUCIA image analysis program using SEM images are given in Table 2. To interpret the equal diameter and circularity properties in more detail, graphs depending on the production voltage and time are drawn and are presented in Fig. 5. First, the area fraction (Af) property can be defined as the ratio of the total pore area [69] to the entire surface area (At) in the related SEM image.

Table 2 Morphological properties of the samples produced at different anodization parameters
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Fig. 5
figure 5

Graphical presentation of the equal diameter, circularity properties of according to (a) anodization voltages and (b) times

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$${A}_{f}={A}_{p}/{A}_{t}$$
(2)

Af is an important parameter for revealing the anodizing process. The knowledge of how much porous morphology is obtained can affect the surface properties such as photocatalytic and wetting angles. As shown in Table 2, Af values increase with an increase in the anodizing time and voltage value. The only exception is seen in the 80 V sample, which was anodized with the maximum voltage value. The pore ratio, which was 0.61% at the 5 V, increased in parallel with the increase in voltage value, to 39.14% at 40 V and 43.15% at 60 V. The reason for the decrease in AF at 80 V could be the deterioration of the porous morphology. It can be seen that there is an increase from 5.67% to 68.75% at the Af value depending on the anodization time. The only exception in terms of the anodizing time parameter was observed in the sample anodized for 60 min.

$${E}_{q}=\sqrt{(4.Area/\pi }$$
(3)

The equal diameter (Eq) is a size feature derived from the area. It determines the diameter of the circle having the same area as the corresponding object (see formula 3). Eq is another important data for anodized surface morphology characterization like Af (it can even be said to be the most important). When the results in Table 2 and Fig. 5 are examined, the pore diameters of almost all samples are less than 100 nm. Therefore, it is proven that nanoporous structures are obtained after the anodization process. Increasing the anodizing voltage caused the pore diameter to increase from 23.67 nm to 105 nm. As shown in Fig. 5 (a), an increase at the voltage value from 20 to 40 V resulted in a remarkable increase in the pore diameter. Because the spherical pore morphology deteriorated in the sample produced at 80 V, a change was observed in the Eq curve. It is observed that greater changes in Eq values are observed with increasing anodization time. When the anodizing time increased from 15 to 60 min, an increase in Eq value, a decrease in the range of 60–120 min, and an increase in the range of 120–480 min were observed. This situation can be associated with the oxide formation and dissolution at the surface during the anodizing process [70, 71]. While the lowest Eq value was obtained in the 5 V sample with the lowest anodizing voltage, the highest Eq value was observed in the 120-min sample with the longest anodizing time.

Circularity is 1 (100%) only for a circle and all other shapes are characterized by the circularity of less than 1. It is a derived shape measure calculated from the area and perimeter.

$$Circularity=4.\pi .A/({P}^{2})$$
(4)

where A is the area and P is the perimeter value of the object. It is seen that different voltage values cause pore shapes with a circularity between 41.63% and 66.7% (see Table 2 and Fig. 5 (a)). Depending on the voltage parameter, the highest circularity was obtained in the sample produced at 40 V, while the worst was obtained in the sample produced with at 80 V. It can be observed that the circularity curve peaks at 40 V according to Fig. 5 (a). When the time-dependent circularity graph in Fig. 5 (b) is examined, a peak is observed in the sample produced at 40 V in 60 min (which is the same sample in the voltage part). It is seen that long anodizing processes such as 120, 240, and 480 min. reduce the circularity to very low values approximately 24%. This situation can be associated with the transformation of the morphology from a porous structure to a more tubular structure. It is thought that differences occur between the heights of the tubes growing from the surface and that they cannot provide shape stability.

The terms minimum and maximum Feret (Fmax and Fmin, respectively) and elongation are related to each other. The minimum Feret value is the minimum value of the set of Feret's diameters while the maximum Feret is the maximal value. The Elongation is determined as a ratio of the Fmax and Fmin features (5).

$$Elongation={F}_{max}/{F}_{min}$$
(5)

If the shape of the object is spherical, the elongation value is 1. Therefore, the Elongation property is inversely proportional to the circularity property. The highest elongation value was obtained for the 40 V sample as 1.36. That is, the morphology farthest from the rod-like morphology and closest to the spherical shape was obtained in the 40 V sample. The highest Elongation value was obtained for the 80 V sample produced at the highest voltage. As can be observed from Fig. 3 (f) the nanoporous morphology deteriorates and the pores merge into a more rod-like morphology. Therefore, the sample has a high elongation value of 1.95.

Contact angle measurement

The wettability performance plays a critical role because of the contact between the solution and the surfaces of the samples. If the wetting angle is less than 90°, it is hydrophilic, if it is greater than 90°, it is hydrophobic [72].

The contact angle values realized in the two steps are shown separately in Fig. 6 and Fig. 7 for nanostructured TiO2. The low contact angle indicates good compatibility/interaction between the surface and solution, thereby indicating wettability. The main reason why the samples of two-step production exhibit different contact angle values is the fact that they have different nanostructured surfaces [72, 73].

Fig. 6
figure 6

Contact angle for all different voltage nanostructured TiO2 samples

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Fig. 7
figure 7

Contact angle for all different time nanostructured TiO2 samples

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It has been observed that the morphologies showing more organized and uniformly distributed surfaces compared to each other show a hydrophilic structure, i.e., a much better wettability angle. Exposure of ions to the solution at different voltages and at different times in the anodizing process resulted in surfaces with different nanostructure sizes and diameters.

To obtain TiO2 surfaces in the form of more stable nanotubes, production conditions with parameters showing low wettability properties will be much more efficient [74, 75]. The wettability showed a direct correlation with the photocatalytic properties obtained for the first step fabrication involving different voltage values. In the 40 V sample that the surface with the lowest wetting angle shows the highest efficiency of dissolution. In the continuation, this situation is followed by the 60 V sample. With the increasing voltage, the electrical mechanism positively affected the chemical process of the oxidation mechanism formed by anodization and provided the formation of low-angle contact surfaces until 40 V, after which the electrical mechanism negatively affects the surface morphology according to the contact angle (see Fig. 6). Compared with the morphological features in Table 2, it can be seen that the maximum circularity value, which is an important parameter to determine the change in pore structure, is 66.7% at 40 V. Afterwards, it was determined that this value decreased with increasing voltage, which is supported by the morphological differences in Fig. 3.

For the sample of 40 V, which is the most efficient voltage value in terms of photocatalytic and surface properties, this time it was anodized to examine the effects of different times. Here, too, the compatibility of the photocatalytic efficiency with the effect of the time and the contact angle draws attention. Low contact angle correlates with increasing time. When the photocatalytic performance increases with the surface area, it shows that the interaction of free oxygen ions with the porous surface plays an important role. While completing the electrochemical process that will reach the desired surface porous structure in low times of 15 min, 30 min, high porous surface wettability was positively affected in 60 min and liquid-surface penetration was realized more efficiently (see Fig. 7). It can be seen in Fig. 4 that the pore diameters increase with increasing time, negatively affecting the wettability. Based on Table 2, it can be seen that while equal diameter and circularity values increase up to 60 min, which is important for surface penetration, they decrease after 60 min.

Photocatalytic activities

Voltage effect of photocatalytic activities

Photocatalytic kinetic value and dissolution of nanotube TiO2 samples produced at different voltages Figs. 8 and 9. These results indicate that the anodization voltage is a parameter that affects the photocatalytic degradation of methylene blue [22]. The photocatalytic kinetic and dissolution values obtained by subjecting the 40 V sample that showed the best result to the anodizing process at different voltages (Step 1). All absorbance measurements were performed by considering the characteristic peak at the 664 cm wavelength of MB. Keeping it in the dark did not make a significant difference in terms of dissolution (it can be ignored).

Fig. 8
figure 8

Voltage kinetic constants of the nanostructured TiO2 films

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Fig. 9
figure 9

Degradation diagram of the nanostructured TiO2 films for different voltages

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The nanostructured TiO2 sample anodized with 40 V in 1 M Na2SO4/5 wt.% NH4F solution showed the best photocatalytic result due to electrochemical reaction. Therefore, it shows that with the 40 V sample, which has the best photocatalytic efficiency 80% efficiency, the voltage increase has a positive effect to a certain extent, but then the optimum morphology is lost. The 60 V sample also exhibited high photocatalytic activity. The similarity of their morphology between them is related to the increased porosity of the O2 free ions finding more space to interact.

It can be seen in Fig. 3. that the porous structure is not formed sufficiently at low voltage values. It was observed that the increased voltage value was clearly seen in the first 20 V value. However, these pores are also quite small. Equal diameters (nm) are (a) 5 V = 23.64 nm, (b) 10 V = 26.85 nm and (c) 20 V = 29.73 nm. When Fig. 5 and Table 2 are examined, it is seen that the sample with the highest photocatalytic efficiency (d) 40 V and (e) 60 V is related to its equal pore diameters and circularity. They have values of 96.81 nm equal diameter and 66.7% circularity, 104.36 nm and 53.39% circularity, respectively. The change in the pore structure is understood from the diameter and circularity values, and it is seen that the structure transforms from pore to tube after 60 V. This adversely affects the photocatalytic performance. The ordered porous structure shows much better photocatalytic activity than the tubular structure [23].

Time effect of photocatalytic activities

Considering the time factor for the second step, as shown in Figs. 10 and 11, it can be seen that the production at different times affects the photocatalytic dissolution performance.

Fig. 10
figure 10

Degradation diagram of the nanostructured TiO2 films

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Fig. 11
figure 11

Degradation diagram of the nanostructured TiO2 films for different times

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To determine the anodizing time with the best photocatalytic efficiency for 40 V, which is the best photocatalytic sample of the 1st step, six different times were produced and the photocatalytic properties were determined. The surface structure of each sample is shown in Fig. 3. It can be seen that the porous structure deteriorated after 60 min of sample and left its place in the tubular structure. Simultaneously, it was observed that the diameter values also changed by looking at the values in both Fig. 5 and Table 2. The influences of these process parameters were evaluated and the photocatalytic activity of the sample anodized for 60 min was the highest of all samples.

Tube length increases with the increasing anodization time [25]. The photocatalytic efficiency of the porous structure decreases as it moves to the tubular structure [76]. Considering the equal diameter and circularity values, the 60 min sample with 96.81 nm and 66.7% has the smoothest pore structure. Although the 480 min sample has a high equal diameter of 127.12 nm, its circularity value is low (24.87%), indicating low photocatalytic efficiency.

A process showing how the step-by-step photocatalytic degradation mechanism works for MB [77, 78].

$${TiO}_{2}+hv\to {Ti{O}_{2} (e}^{-}+{h}^{+})$$
(4)
$$Dye+Ti{O}_{2}({h}^{+})\to Oxidantion\; process$$
(5)
$$Ti{O}_{2}({h}^{+})+{H}_{2}O\to O{H}^{.}+{H}^{+}+Ti{O}_{2}$$
(6)
$$Ti{O}_{2}({h}^{+})+O{H}^{-}\to {TiO}_{2}+O{H}^{.}$$
(7)
$$Dye+Ti{O}_{2}\left({e}^{-}\right)\to Reduction\; Process$$
(8)
$$Ti{O}_{2}\left({e}^{-}\right)+{O}_{2}\to Ti{O}_{2}+{O}_{2}^{.-}$$
(9)
$${O}_{2}^{.-}+{H}^{+}\to H{O}_{2}^{.}$$
(10)
$$H{O}_{2}^{.}+H{O}_{2}^{.}\to {H}_{2}{O}_{2}+{O}_{2}$$
(11)
$${H}_{2}{O}_{2}+{O}_{2}^{.-}\to O{H}^{.}+O{H}^{-}+{O}_{2}$$
(12)
$$Dye+O{H}^{.}\to Degradation\; Products$$
(13)

The degradation mechanism steps are as follows: (1) absorption of light, (2) separation of excited electron and holes, (3) migration of the photo-generated charge carriers to the surface of the catalyst and (4) undergo redox reaction via adsorbed reactants [79].

Conclusion

In summary, nanostructured anatase TiO2 films were successfully prepared at different anodization voltages and times by anodizing them at constant electrolyte concentrations, followed by 2 h calcination at 500 °C. Anatase appears in all calcined samples. It can be stated that a different phase structure, such as rutile and brookite, is not observed. The surface properties of the samples were significantly affected by the anodization parameters. Surface roughness was observed to increase with the increasing voltage to limit of 40 V and anodization time also affected to the morphology and photocatalytic properties. In particular, increasing time denotes performance of photocatalytic efficiency. This situation shows, the titanium samples modified by changing the preparation conditions exhibited different morphologies and pore structures. The photocatalytic activities of nanostructured anatase TiO2 films were compared for photodegradation of the MB solution under UV–visible light irradiation. The influences of these process parameters were performed and the photocatalytic activity of the sample anodized for 60 min was the highest of all samples. This titania can be readily utilized to meet application expectations in areas such as gas sensors, photocatalysis and photovoltaic cells. Especially TiO2 nanostructure usually has a significant surface-to-volume ratio and unidirectional electrical channel. While the studies carried out so far have been based only on the surface-volume relationship, in this study, a wide range of parameters (Table 2) belonging to the available surface morphology were also taken into account and their relationship with photocatalytic properties was evaluated. With this study, it has been possible to calculate how the anodizing voltage and time affect the surface morphology through the values calculated in Table 2, and the existing photocatalytic efficiency studies will be able to shed light on the future studies from a scientific point of view by considering these data.