## 3 Results  
The results regarding the particle size distribution that were evaluated using scanning electron microscopy (SEM) are presented in Figure 3. The Pt nanoparticles are distinctly visible as bright contrast features in all examined samples, homogeneously distributed on the surface of the Magneli phase titanium oxide catalytic support. X-ray diffraction (XRD) analysis was employed to characterize the crystalline structure and orientation of the synthesized samples. This technique provides valuable insights into phase composition and structural integrity. Figure 4 presents the XRD spectra of the synthesized samples alongside the XRD pattern of the catalytic support, confirming the presence of characteristic peaks associated with the MPT phase in all examined samples. Platinum is predominantly observed in its crystalline form, with the main crystallographic orientations identified as (111) and (200). Additionally, secondary orientations, including (220), (311), and (222), are consistently detected, indicating a well-defined crystalline structure across all samples. These findings further validate the structural properties of the synthesized catalyst. Figure 4: XRD spectra of Pt/MPT samples with Pt content ranging from 10 wt.% to 40 wt.%. Figure 3: SEM images of Pt/MPT with the following Pt content: (**a**) 10 wt.%, (**b**) 20 wt.%, (**c**) 30 wt.%, and (**d**) 40 wt.%. Scale bar: 100 nm. To determine the particle size of the synthesized samples, the Scherrer equation was applied [51]. This method provides an estimation of crystallite size based on the broadening of X-ray diffraction peaks. The calculated particle sizes are summarized in Table 1.  
Particle sizes exhibit a noticeable range from 18 nm to 13 nm across all samples in the crystallographic orientation (111). In the case of the (200) orientation, the particle sizes are slightly smaller, ranging from 9 nm to 12 nm. The smallest particle size, indicative of a higher active surface area, is achieved in the (111) orientation for the Pt/MPT sample with a 40% wt. Pt content. Overall, there is a consistent trend of decreasing crystal size as the Pt percentage increases from Pt/MPT 10% wt. to Pt/MPT 40% wt., which was observed for both the (111) and (200) orientations. The BET method was employed to determine the specific surface area of the synthesized samples. The multi-point BET analysis was conducted within the relative pressure range of p/p0 = 0.05-0.3, and the single-point BET analysis was performed at p/p0 = 0.3. Pore volume measurements were taken at a relative pressure approaching 1 (p/p0 = 0.99). The average pore diameter was calculated by assuming cylindrical geometry for the pores, utilizing a relative pressure of p/p0 = 0.99. The obtained results are presented in Table 2.  
The surface area analysis of the synthesized Pt/MPT catalyst samples at 10% wt. and 20% wt. revealed comparable values from both multi-point and single-point measurements. These samples exhibited consistent total pore volume and average pore diameter without significant variations. By contrast, Pt/MPT samples at 30% wt. and 40% wt. demonstrated a notable decrease in surface area for both the multi- and single-point analyses. However, the total pore volume and average pore size diameter remained similar when compared to Pt/MPT at 10% wt. and 20% wt. The results unequivocally indicate that exceeding 20% wt. of Pt in the sample leads to a reduction in the surface area of the catalysts. Following the physicochemical characterization of the powder containing Pt and MPT, catalytic ink was prepared and applied onto flat, graphite-based electrodes for screening purposes in a three-electrode cell with a liquid electrolyte. The catalyst ink was applied using a spray technique employing an airbrush with an 8 mL buffer zone and a two-stage trigger control. The spray distance was maintained at 10 cm, and the pressure was regulated up to 1.5 bar.