Highly Photoactive Titanium Dioxide Supported Platinum Catalyst: Synthesis Using Cleaner Ultrasound Approach

: Catalysts increase reaction rates; however, the surface area to volume ratio of catalysts has a vital role in catalytic activity. The noble metals such as platinum (Pt) and gold (Au) are expensive; despite this, they have proven their existence in catalysis, motivating the synthesis of supported metal catalysts. Metal catalysts need to be highly dispersed onto the support. In this investigation, an ultrasound approach has been attempted to synthesise highly photoactive titanium dioxide (TiO 2 ) nanoparticles by the hydrolysis of titanium tetraisopropoxide in an acetone/methanol mixture. To enhance its photocatalytic activity, TiO 2 was doped with Pt. The synthesised photocatalyst was characterised by techniques such as particle size analysis (PSA), XRD, FE-SEM, TEM, and EDX. The enhancement in the surface characteristics of Pt-doped TiO 2 compared with bare TiO 2 support was conﬁrmed with Brunauer–Emmett–Teller (BET) analysis. The enhanced surface area and uniformity in particle size distribution at the nanoscale level were due to the effects of ultrasonic irradiation. The obtained results corroborated the size and composition of the synthesised catalysts. The size of the catalysts is in the nanometre range, and good dispersion of Pt catalysts over the TiO 2 support was observed. The UV-Visible spectroscopy analysis was performed to study the optical properties of the synthesised TiO 2 and Pt/TiO 2 photocatalysts. An increase in the absorbance was noted when Pt was added to TiO 2 , which is due to the decrease in the band gap energy.


Introduction
Photocatalysis is a technique that harnesses the available abundant solar energy; in it, a photon drives a chemical reaction in the presence of a catalyst. The process is ecofriendly and non-hazardous [1] and is one of the most preferred methods for purifying the pollutants in the atmosphere and aquatic systems [2]. Titanium dioxide (TiO 2 ) is a widely used photocatalyst, considering its good catalytic activity, high stability, low cost, and suitable band gap energy [3,4], and hence is beneficial in many applications such as oxidation reactions [5], solar cells [6], hydrogen production [7], water treatment [8,9], and degradation of pollutants [10].
Various dopants are impregnated into TiO 2 to extend the sensitivity in the visible spectral range [11]. This process also helps in minimising the surface charge transfer [12]. The metal catalysts doping/impregnation concept has been gaining more importance recently. Here, the primary catalyst is dispersed on a suitable support, obtaining stable nanoparticles (NPs) and reducing costly metal utilisation [13]. Metals used include niobium [6], copper and nickel [7], iron [8], cobalt [12] silver [14], chromium [15], molybdenum [16], vanadium [17], silver [18], ruthenium, and platinum [19]. The Schottky barrier formed between TiO 2 and metal dopant acts as a source of electron traps or recombination sites to increase the efficiency of TiO 2 [20]. Among the above, platinum (Pt) doped TiO 2 gives better photocatalytic activity, extending the light absorption to the visible band [21,22]. There are broad-spectrum applications of Pt-doped TiO 2 , especially in the degradation of dye [23,24], decomposition of phenol [11], and solar energy utilisation [25]. Even though Pt is expensive and has limited commercial usage, it can be compensated for by immobilising suitable supports like TiO 2 [25]. Various methods are available for doped TiO 2 syntheses, such as sol-gel [26,27], suspension impregnation [28], solid-state reaction [29], sonochemical synthesis [19], and hydrothermal method [30] to manipulate the NPs' shape, size, and other physical properties. In the sonochemical synthesis, the ultrasound-induced chemical effect is attributed to the temperature rise caused by alternating compression and rarefaction cycles of acoustic cavitation. The hot spots are formed due to the rapid formation of the bubbles, their growth and collapse in the liquid media resulting in the metal ions reduction to metals and metal oxides. The sonochemical technique provides local temperatures of more than 5000 K, pressures more than 20 MPa, and a very high cooling rate during cavitation bubble collapse, causing special and unique properties for NPs [31].
Very little literature is available for the Pt doped TiO 2 NPs synthesis using the sonochemical method. Teoh et al. [32] reported a one-step Pt/TiO 2 synthesis using a flame spray pyrolysis reactor with controlled crystallite size and surface area. The synthesised particles exhibited rutile and anatase phases. Shanmugam and Gedaken [33] reported the synthesis of Pt NPs on mesoporous anatase TiO 2 using the ultrasound-assisted polyol reduction method. The obtained particles were in the range of 100 to 200 nm and were employed for the oxygen reduction reaction. Neppolian et al. [34] reported synthesising Pt, graphene oxide (GO), and TiO 2 photocatalyst. Initially, TiO 2 particles were synthesised using the pH swing method. Later, the ultrasound-assisted hydrothermal method was employed to obtain GO-TiO 2 NPs. Graphene oxide was initially dispersed in a water and ethanol solution mixture and sonicated for 2 h, and the required amount of TiO 2 was then added. To this known wt% of Pt was doped using the photochemical reduction method.
Bedolla et al. [35] synthesised Pt/TiO 2 utilising acid-treated TiO 2 dispersed in isopropyl alcohol using a sonicator probe. At the same time, Pt precursor (H 2 PtCl 6 ) was sonicated in an ultrasonic bath. The two solutions were mixed, to which sodium borohydride reducing agent was added and subjected to sonication. A black precipitate was formed after sonicating for 20 min. The surface area of the synthesised catalyst from BET analysis is 193 m 2 /g. The synthesised particles were used as catalysts in direct methanol fuel cell applications. Abdulrazzak et al. [36] reported the synthesis of Pt-impregnated TiO 2 coated on carbon nanotubes using the sonochemical hydration-dehydration method. TiO 2 particles were uniformly distributed on the carbon NPs surface, then coated by Pt NPs. In all the reports, the particle sizes of Pt/TiO 2 synthesised by ultrasound methods are more than 50 nm. By contrast, in this study, the synthesised particles were with the size of <20 nm.
The available research work done earlier showed that the size of Pt/TiO 2 NPs is in the range of 50 nm or more. This study aims to synthesise anatase phase Pt-doped TiO 2 NPs with a particle size less than 20 nm using an ultrasound approach. The synthesised particles are characterised using transmission electron microscopy and particle size analyser to study the particle size, X-ray diffraction to study the phase structure, BET analysis to study the pore size, and EDS to study the composition. The data obtained are compared with the available literature as and when required.

Photocatalytic Activity of TiO 2 and Pt/TiO 2
The UV Visible spectroscopy analysis was performed to study the optical properties of the synthesised TiO 2 and Pt/TiO 2 photocatalysts. Figure 1 shows the UV-Vis spectroscopy of TiO 2 NPs and Pt-doped TiO 2 NPs. The spectra were obtained in the wavelength range of 200 to 1100 nm. No changes in the spectral absorbance were observed beyond the wavelength of 400 nm. From Figure 1, strong absorption was observed in the wavelength range below 400 nm. This is due to the band gap absorption of TiO 2 . An increase in the absorbance has been observed when Pt is added to TiO 2 . This is attributed to the decrease in the band gap energy [37]. The band gap energy calculated from the UV spectrum of TiO 2 is 3.2 eV [38]. In comparison, the band gap energy for the Pt/TiO 2 decreases to 2.89 eV when TiO 2 is doped with platinum. The mechanism for the photocatalytic activity with a decrease in band gap is shown in Figure 2.
The UV Visible spectroscopy analysis was performed to study the optical properties of the synthesised TiO2 and Pt/TiO2 photocatalysts. Figure 2 shows the UV-Vis spectros copy of TiO2 NPs and Pt-doped TiO2 NPs. The spectra were obtained in the wavelength range of 200 to 1100 nm. No changes in the spectral absorbance were observed beyond the wavelength of 400 nm. From Figure 2, strong absorption was observed in the wavelength range below 400 nm. This is due to the band gap absorption of TiO2. An increase in the absorbance has been observed when Pt is added to TiO2. This is attributed to the decrease in the band gap energy [37]. The band gap energy calculated from the UV spectrum o TiO2 is 3.2 eV [38]. In comparison, the band gap energy for the Pt/TiO2 decreases to 2.89 eV when TiO2 is doped with platinum. The mechanism for the photocatalytic activity with a decrease in band gap is shown in Figure 3.    The UV Visible spectroscopy analysis was performed to study the optical properties of the synthesised TiO2 and Pt/TiO2 photocatalysts. Figure 2 shows the UV-Vis spectroscopy of TiO2 NPs and Pt-doped TiO2 NPs. The spectra were obtained in the wavelength range of 200 to 1100 nm. No changes in the spectral absorbance were observed beyond the wavelength of 400 nm. From Figure 2, strong absorption was observed in the wavelength range below 400 nm. This is due to the band gap absorption of TiO2. An increase in the absorbance has been observed when Pt is added to TiO2. This is attributed to the decrease in the band gap energy [37]. The band gap energy calculated from the UV spectrum of TiO2 is 3.2 eV [38]. In comparison, the band gap energy for the Pt/TiO2 decreases to 2.89 eV when TiO2 is doped with platinum. The mechanism for the photocatalytic activity with a decrease in band gap is shown in Figure 3.

Mechanism of Doping of Noble Metal Pt on the Surface of TiO 2
TiO 2 NPs function better under UV rays considering their large band gap [39]. However, they suffer from the fast recombination of excited electrons and holes [40]. Hence, TiO 2 NPs are modified to be better utilised in the visible range. Figure 2 illustrates the mechanism of the band gap decrease of TiO 2 because of the impregnation of Pt. The recombination of the electron-hole pair was reported to be retarded significantly due to the deposition of noble metals such as Au and Pt on TiO 2 . This phenomenon assists in extending the wavelength response to the visible range [41][42][43][44]. Figure 3 shows the particle size obtained from dynamic light scattering analysis for TiO 2 and TiO 2 -supported Pt photocatalyst. Both show a single peak corresponding to uniform particle size distribution. The size distribution of TiO 2 support is observed to be between 15 nm and 120 nm. The average particle size of TiO 2 particles is about 37 nm, whereas, in the case of TiO 2 -supported Pt catalysts, it increased slightly to 43 nm. The particle size analysis facilitates analysing the distribution of the synthesised photocatalyst. However, it failed to give the crystallinity and morphology of the obtained particles. Hence XRD and TEM analyses were employed. The size of the synthesised support and photocatalyst in the nano range (<50 nm) can be attributed to turbulence and intense shear effects of the ultrasound-induced cavitation.

Particle Size Analysis of TiO 2 Support and TiO 2 Supported Pt Photocatalyst
TiO2 NPs function better under UV rays considering their large band gap [39]. ever, they suffer from the fast recombination of excited electrons and holes [40]. H TiO2 NPs are modified to be better utilised in the visible range. Figure 3 illustrat mechanism of the band gap decrease of TiO2 because of the impregnation of Pt. T combination of the electron-hole pair was reported to be retarded significantly due deposition of noble metals such as Au and Pt on TiO2. This phenomenon assists in ex ing the wavelength response to the visible range [41][42][43][44]. Figure 4 shows the particle size obtained from dynamic light scattering analy TiO2 and TiO2-supported Pt photocatalyst. Both show a single peak corresponding t form particle size distribution. The size distribution of TiO2 support is observed to tween 15 nm and 120 nm. The average particle size of TiO2 particles is about 3 whereas, in the case of TiO2-supported Pt catalysts, it increased slightly to 43 nm particle size analysis facilitates analysing the distribution of the synthesised photoca However, it failed to give the crystallinity and morphology of the obtained par Hence XRD and TEM analyses were employed. The size of the synthesised suppo photocatalyst in the nano range (<50 nm) can be attributed to turbulence and intense effects of the ultrasound-induced cavitation.  Both the XRD spectrum of TiO2 supported Pt and TiO2 are identical. The l any diffraction peak of Pt on the Pt-doped TiO2 catalyst reveals that Pt is well disp and in smaller quantities. Sharp peaks for TiO2 demonstrate the strong crystalline n of the particles [45]. However, compared to TiO2, slight peak broadening could b served in the case of Pt-impregnated TiO2. This might be due to the presence of Pt surface of TiO2 NPs. The crystallite size of TiO2 NPs, calculated using Scherrer's for is 10.132 nm, whereas, for the TiO2 supported Pt catalyst, it increased to 13.43 nm increase of the average particle size of TiO2 by doping with Pt might be due to the po and inclusion of Pt (IV) with Ti (III) in TiO2 lattice. The smaller crystallite size of th is confirmed by the presence of a large BET surface area (129 m 2 /g). The surface char isation of TiO2 and Pt/TiO2 was evaluated with Brunauer-Emmet-Teller (BET) anal Figure 6, and the outcomes are reported in Table 1. The specific surface area of TiO   [45]. However, compared to TiO 2 , slight peak broadening could be observed in the case of Pt-impregnated TiO 2 . This might be due to the presence of Pt on the surface of TiO 2 NPs. The crystallite size of TiO 2 NPs, calculated using Scherrer's formula, is 10.132 nm, whereas, for the TiO 2 supported Pt catalyst, it increased to 13.43 nm. The increase of the average particle size of TiO 2 by doping with Pt might be due to the position and inclusion of Pt (IV) with Ti (III) in TiO 2 lattice. The smaller crystallite size of the NPs is confirmed by the presence of a large BET surface area (129 m 2 /g). The surface characterisation of TiO 2 and Pt/TiO 2 was evaluated with Brunauer-Emmet-Teller (BET) analysis in Figure 5, and the outcomes are reported in Table 1. The specific surface area of TiO 2 NPs is calculated as 71 m 2 /g. Interestingly, with the Pt doping on TiO 2 , an enhancement in the specific surface area could be noticed, which is in line with the earlier observation [46].         Field emission scanning electron microscopy (FE-SEM) gives the topographical information (10× to 300,000×). In the present synthesis, the particles were characterised with Catalysts 2022, 12, 78 6 of 11 a magnification of 50,000×, a scale of 1.0 µm, and 100,000× and 500 nm. They have been reported in Figures 6 and 7 for TiO 2 and Pt/TiO 2 , respectively. FE-SEM analysis (Figure 4) shows that the TiO 2 particles are spherical, and Pt doping on the TiO 2 support did not change the morphology significantly (Figure 7). The morphology of Pt photocatalyst with TiO 2 support remains spherical. Field emission scanning electron microscopy (FE-SEM) gives the topographical information (10× to 300,000×). In the present synthesis, the particles were characterised with a magnification of 50,000×, a scale of 1.0 µm, and 100,000× and 500 nm. They have been reported in Figures 7 and 8 for TiO2 and Pt/TiO2, respectively. FE-SEM analysis ( Figure 5) shows that the TiO2 particles are spherical, and Pt doping on the TiO2 support did not change the morphology significantly ( Figure 8). The morphology of Pt photocatalyst with TiO2 support remains spherical.

TEM Analysis of TiO2 and Pt/TiO2
The microjets formed due to ultrasonic cavitation prevent the agglomeration of crystals and result in smaller crystal size and uniform particle size and shape [47]. The TEM images of the TiO2 also confirmed the high degree of dispersion. The images (Figure 9a,b) clearly show that the Pt catalysts exhibit a uniform distribution over the TiO2 support. The Pt/TiO2 presents uniform dispersion of Pt on the TiO2 surface. The mean particle size of pure TiO2 was observed to be between 10 and 12 nm. The average particle size of Pt doped on TiO2 NPs was found to be less than 15 nm confirming the nanoscale of supported metal catalyst for its photocatalytic effectiveness. The covalent radius of Pt is 1.30 Å, and for Pt 2+ and Pt 4+ , it is 0.80 and 0.65 Å, respectively. Titanium has an ionic radius of 0.68 Å in the Ti 4+ state. Hence, Pt 4+ ion is conveniently inserted into the TiO2. Interestingly, the Pt 4+ ions doping does not distort the photocatalyst [48]. Field emission scanning electron microscopy (FE-SEM) gives the topographical information (10× to 300,000×). In the present synthesis, the particles were characterised with a magnification of 50,000×, a scale of 1.0 µm, and 100,000× and 500 nm. They have been reported in Figures 7 and 8 for TiO2 and Pt/TiO2, respectively. FE-SEM analysis ( Figure 5) shows that the TiO2 particles are spherical, and Pt doping on the TiO2 support did not change the morphology significantly ( Figure 8). The morphology of Pt photocatalyst with TiO2 support remains spherical.

TEM Analysis of TiO2 and Pt/TiO2
The microjets formed due to ultrasonic cavitation prevent the agglomeration of crystals and result in smaller crystal size and uniform particle size and shape [47]. The TEM images of the TiO2 also confirmed the high degree of dispersion. The images (Figure 9a,b) clearly show that the Pt catalysts exhibit a uniform distribution over the TiO2 support. The Pt/TiO2 presents uniform dispersion of Pt on the TiO2 surface. The mean particle size of pure TiO2 was observed to be between 10 and 12 nm. The average particle size of Pt doped on TiO2 NPs was found to be less than 15 nm confirming the nanoscale of supported metal catalyst for its photocatalytic effectiveness. The covalent radius of Pt is 1.30 Å, and for Pt 2+ and Pt 4+ , it is 0.80 and 0.65 Å, respectively. Titanium has an ionic radius of 0.68 Å in the Ti 4+ state. Hence, Pt 4+ ion is conveniently inserted into the TiO2. Interestingly, the Pt 4+ ions doping does not distort the photocatalyst [48].

TEM Analysis of TiO 2 and Pt/TiO 2
The microjets formed due to ultrasonic cavitation prevent the agglomeration of crystals and result in smaller crystal size and uniform particle size and shape [47]. The TEM images of the TiO 2 also confirmed the high degree of dispersion. The images (Figure 8a,b) clearly show that the Pt catalysts exhibit a uniform distribution over the TiO 2 support. The Pt/TiO 2 presents uniform dispersion of Pt on the TiO 2 surface. The mean particle size of pure TiO 2 was observed to be between 10 and 12 nm. The average particle size of Pt doped on TiO 2 NPs was found to be less than 15 nm confirming the nanoscale of supported metal catalyst for its photocatalytic effectiveness. The covalent radius of Pt is 1.30 Å, and for Pt 2+ and Pt 4+ , it is 0.80 and 0.65 Å, respectively. Titanium has an ionic radius of 0.68 Å in the Ti 4+ state. Hence, Pt 4+ ion is conveniently inserted into the TiO 2 . Interestingly, the Pt 4+ ions doping does not distort the photocatalyst [48].  Figure 10 depicts the EDX analysis for the TiO2-supported Pt catalyst obtained using ultrasound. The strong peaks of titanium (41.28 wt%) and oxygen (55.51 wt%) in the spectra indicate that the concentration of support (TiO2) is higher compared with Pt catalyst (3.21 wt%), as Pt is an expensive catalyst, and its lower percentage and good dispersion on the support is expected. The chemical composition of Pt/TiO2 from the EDX analysis is shown in Table 2.

Synthesis of TiO2 as the Support: Ultrasound Approach
TiO2 NPs were synthesised using an ultrasound approach. To initiate the reaction, TTIP (10 mL) was mixed with acetone and methanol (2 mL each) in a 250 mL beaker and  Figure 9 depicts the EDX analysis for the TiO 2 -supported Pt catalyst obtained using ultrasound. The strong peaks of titanium (41.28 wt%) and oxygen (55.51 wt%) in the spectra indicate that the concentration of support (TiO 2 ) is higher compared with Pt catalyst (3.21 wt%), as Pt is an expensive catalyst, and its lower percentage and good dispersion on the support is expected. The chemical composition of Pt/TiO 2 from the EDX analysis is shown in Table 2.

Energy Dispersive X-Ray Analysis (EDX) (Pt/TiO 2 )
Catalysts 2022, 12, x FOR PEER REVIEW 7 (a) (b) Figure 9. TEM images (a) TiO2 (b) TiO2 supported Pt catalyst synthesised using acoustic cavit Figure 10 depicts the EDX analysis for the TiO2-supported Pt catalyst obtained u ultrasound. The strong peaks of titanium (41.28 wt%) and oxygen (55.51 wt%) in the tra indicate that the concentration of support (TiO2) is higher compared with Pt cat (3.21 wt%), as Pt is an expensive catalyst, and its lower percentage and good dispe on the support is expected. The chemical composition of Pt/TiO2 from the EDX analy shown in Table 2.

Synthesis of TiO2 as the Support: Ultrasound Approach
TiO2 NPs were synthesised using an ultrasound approach. To initiate the reac TTIP (10 mL) was mixed with acetone and methanol (2 mL each) in a 250 mL beake

Synthesis of TiO 2 as the Support: Ultrasound Approach
TiO 2 NPs were synthesised using an ultrasound approach. To initiate the reaction, TTIP (10 mL) was mixed with acetone and methanol (2 mL each) in a 250 mL beaker and subjected to sonication. After initial mixing of TTIP, methanol, and acetone, dropwise addition of 50 mL NaOH was initiated in the presence of ultrasound. The sonicator was operated in batch mode (2 s on and 1 s off) and was initially carried out for 30 min and then continued for another 15 min. The extended 15 min sonication was performed to ensure 100% conversion of TTIP. The formed white precipitate was filtered, dried, and calcination was carried out at 500 • C for 4 h. Earlier reports indicate that the calcination of TiO 2 NPs between 600 • C and 850 • C lead to either brookite, anatase, or rutile phase [49].

Synthesis of TiO 2 Supported Pt Catalyst
For the synthesis of TiO 2 -supported Pt photocatalyst, TiO 2 support was obtained, as indicated in the previous section. For the doping of Pt catalyst, 70 mL polyvinyl propylene (PVP) (beaker A) dopant solution was prepared by dissolving PVP (10 mL) in Milli-Q water (70 mL). From the prepared PVP solution, 10 mL was taken in another beaker (beaker B), to which 0.5 g potassium hexachloroplatinate (K 2 PtCl 6 ) and 0.75 g TiO 2 was dissolved. The solution in beaker B was kept under stirring for 6-8 h for proper dispersion. The remaining 60 mL PVP solution was taken in another beaker (beaker C), to which 0.037 g sodium borohydride (NaBH 4 ) reducing agent was added. The solution in beaker B and beaker C was mixed and sonicated using an ultrasound probe (Dakshin ultrasonic probe sonicator, frequency 22 kHz, with the total power supply of 130 W) for 2 h to ensure the completion of the reaction. Figure 10a shows the synthesis pathway, whereas Figure 10b,c shows the reaction mixture before and after sonication, respectively. The reaction completion was confirmed by the changes in the solution colour (black). The synthesised particles were separated from the solution by centrifugation (9000 rpm and 10°C for 12 min) and were dried at 150 • C.

Characterisation
A UV-visible spectrometer (Analytik Jena, PECORD 210 PLUS) was employed to find the band gap energy of the synthesised TiO2 and Pt/TiO2 particles. The particle size analysis (PSA) of the synthesised support and photocatalyst was carried out using the dynamic light scattering method with Malvern Zetasizer (Nano S90 version 7.02). X-ray dif-

Characterisation
A UV-visible spectrometer (Analytik Jena, PECORD 210 PLUS) was employed to find the band gap energy of the synthesised TiO 2 and Pt/TiO 2 particles. The particle size analysis (PSA) of the synthesised support and photocatalyst was carried out using the dynamic light scattering method with Malvern Zetasizer (Nano S90 version 7.02). X-ray diffraction studies were performed to identify the phase and determine the crystallite size of the TiO 2 and Pt-doped TiO 2 . Bruker D8 advanced X-ray diffractometer, operated in reflection mode, was used to record the XRD spectra with CuKα as the X-ray source with the wavelength of 0.154 nm. The spectra were recorded for 2θ between 10 • and 90 • with a step size of 0.019, and the corresponding intensity values were plotted against 2θ (degree). FE-SEM (TESCAN model Vega 3 LMU) was used primarily to study the surface morphology where the sample was spread over a substrate and analysed. The morphology and size of the synthesised TiO 2 support and TiO 2 -supported Pt photocatalyst were evaluated using FEI-TechnaiTE-20 and JEOL JEM-2100F field emission transmission electron microscope operated at 200 kV. The surface characteristics of the support TiO 2 and TiO 2 -supported Pt catalyst were evaluated through Brunauer-Emmett-Teller (BET) analysis. The nitrogen adsorption-desorption method was used to estimate the particle surface area, pore size and volume. The BET analysis was carried out using the NOVA 1200 (Quantachrome) instrument at 77.3 K. The samples were degassed under vacuum conditions at 353 K for 4 to 5 h to remove the adsorbed gases and moisture before the analysis.

Conclusions
In this study, a photoactive TiO 2 catalyst was synthesised with an ultrasound approach to improve the photocatalytic performance of TiO 2 , and it was doped with a noble metal Pt. The impregnation helps to reduce the band gap and effective utilisation as a photocatalyst in the visible range. The synthesised TiO 2 and Pt impregnated TiO 2 photocatalyst exhibit a crystal size of less than 10 nm. The FE-SEM analysis showed that doping Pt onto titanium does not change the morphology. The uniform dispersion of a small quantity of Pt on the TiO 2 support was confirmed using TEM analysis and corroborated by EDX spectra which exhibits a less intense peak of Pt. The nanoscale synthesis is attributed to the intense shear effect arising from ultrasound cavitation. The enhancement in the surface properties of TiO 2 due to the addition of Pt was evaluated in terms of an increase in the surface area of the synthesised photocatalyst. Thus, the ultrasound approach can be considered greener and more energy-efficient for synthesising highly active photocatalysts.