## 3 Results and Discussion
### Bubble Growth and Departure Regimes
Once the contact line shortens sufficiently, buoyancy overcomes the pinning force, allowing the bubble to detach. To fully validate this hypothesis, experiments should be conducted on a transparent platinum layer (\(\sim\)5 nm thickness) to enable visualization of the triple contact line position, for example, using the total internal reflection technique. Such an analysis, planned for our future studies, is, however, complex and requires exceptional spatiotemporal resolution. The process of single bubble evolution at 3.1 V is presented in Figure 16, and the process is largely similar to the bubble evolution at 3.0 V.  
At potentials of \(\geq\)3.2 V, very large bubbles start to form on the surface, with diameters significantly exceeding the diameter of the microelectrode, as shown in Figure 9:1 The growth time of these bubbles is notably longer, reaching several seconds. Thus, their behavior was analyzed using a lower recording frequency. Figure 9:2 Growth of a single coalesced hydrogen bubble at 3.1 V.  
In Figure 18, electrical current density at the end of the measurement interval (at \(t\) = 200 s) is presented for all the measured potentials together with the departure frequency of large, coalesced bubbles (where applicable). Within the evaluated range of potentials, data can be divided into three regions, with the transition regions being divided into two sub-regions. These findings can be associated with bubble departure diameters and departure frequencies. [PERSON] et al. [29] previously defined three regions based on applied potential and the concentration of the electrolyte, namely sulfuric acid. They evaluated the same electrolyte at different concentrations between 0.1 and 1 mol L\({}^{-1}\) at potentials between 2 and 10 V. For the sulfuric acid concentration of 0.5 mol L\({}^{-1}\), they identified \"regime 1\" up to 4.7 V, \"regime 2\" between 4.7 and 10 V, and \"regime 3\" beyond 10 V. Based on their findings, all of our measurements were conducted in \"regime 1\", where bubble evolution is characterized by the growth of nearly spherical bubbles atop a carpet of micro-bubbles. Within this regime, both the position of the bubble apex and electrical current variations are monotonic, with no significant oscillations in current during the bubble growth cycle. Figure 9:3 Growth of a single coalesced hydrogen bubble at 3.2 V.  
Figure 9:4 Comparison of current density at the end of the experimental run for each measured potential. Values are divided into 3 regions, and region 2 is divided further into two subregions. We further explored the degree of bubbles coalescence within the evaluated electrical potential range using a 0.5 mol L\({}^{-1}\) sulfuric acid electrolyte. Based on qualitative observations from high-speed video recording and quantitative analysis of potentiostat measurements, we defined three distinct regions characterized by specific bubble behavior and current responses. In \"Region 1\", observed at applied potentials between 2.0 and 2.6 V, bubble formation is characterized by the emergence of isolated, nearly spherical bubbles with negligible coalescence. The electrical current density remains relatively stable, indicating minimal disruption due to bubble detachment. Hydrogen bubble departure frequency in this region could only be estimated by counting bubbles within a specified period, as no significant current oscillations were observed. \"Region 2\", identified as a transitional range of applied potentials from 2.6 to 3.2 V, exhibits increased bubble coalescence. Within this region, two subregions are identified. In subregion 2a, occurring at potentials in the lower part of this range, multiple bubbles coalesce and detach simultaneously, though not as a single entity. Specifically, several coalesced bubbles grow and detach from the surface simultaneously instead of coalescing into a single large bubble.