Introduction

Water’s structure remains one of science’s unresolved mysteries. Interfacial water, formed on material surfaces, exhibits long-range order and provides new insights into its elusive nature1,2,3,4. Its properties depend on humidity levels: at low humidity, water forms a flat single layer, while higher humidity creates hydrogen-bonded bilayers and ice-like hexagonal structures on materials like mica and silicon oxide. Recent studies have uncovered the existence of ordered water zones, known as self-organized water (SOWs), which extend up to several hundred micrometers near hydrophilic surfaces5,6,7. These zones differ markedly from bulk water, exhibiting unique characteristics such as the exclusion of solutes and nanoparticles. SOW water also displays distinct physical properties, including a higher refractive index, increased viscosity, and specific light absorption at 270 nm8,9,10,11. Notably, SOW water demonstrates charge separation, with regions adjacent to Nafion surfaces generating an electrical potential of approximately − 200 mV, indicative of net negative charges within the Self-organized water12. Similar charge separation has been observed in interfacial water on silicon oxide surfaces, driven by strong water-surface interactions13,14. These discoveries underscore the unusual behavior of SOW water and its potential significance for both scientific understanding and practical applications15. In addition, recent research has shown that electromagnetic energy can profoundly impact interfacial water. Ultraviolet (UV) radiation, for example, provides the energy required to dissociate interfacial water molecules into OH⁻ and H⁺ ions16. Infrared (IR) energy, which is prevalent on Earth, has been found to promote the expansion of Self-organized waters. Chai et al. reported that IR light, even at comparable power levels to visible and UV light, has a significantly stronger effect on enlarging SOWs17. Considering the inherent charge-separation potential of interfacial water, these findings suggest that electromagnetic energy may play a key role in regulating the properties and dynamics of interfacial water. Such insights could have far-reaching implications for understanding natural phenomena and advancing technological innovations.

The shift from fossil fuels to renewable energy sources is being accelerated by global warming. To facilitate this transition, it is crucial to develop economically viable alternatives to petrochemical processes across all sectors18. Hydrogen stands out as one of the most promising options for energy storage and distribution due to its high energy density, relatively simple chemical structure, and superior efficiency19,20,21. If hydrogen is produced through water electrolysis (WE) powered entirely by renewable energy, greenhouse gas emissions could be cut by up to 75%22. As a result, there is growing investment in research aimed at scaling up WE technology. At present, two main technologies are being explored: those based on liquid alkaline solutions and those using acidic solid electrolytes. Traditional alkaline electrolyzers, however, are limited by their inability to operate dynamically a key requirement for integrating with variable renewable energy sources23,24. Meanwhile, anion exchange membrane (AEM) electrolyzers, which rely on solid electrolytes, are not yet mature enough for large-scale deployment25,26. These technological challenges highlight the need for further advancements before widespread adoption can be achieved27. Present study is unique in its emphasis on self-organized water (SOW) and its function in improving HER performance, as opposed to other investigations that have investigated hydrophilic surfaces, interfacial water, and the impact of IR on water dynamics. Activation barriers are reduced and proton transport is facilitated by highly ordered molecular alignment at the electrode-electrolyte interface, which is shown by our work. Overpotential and current density have both shown considerable improvements in the upgraded system as compared to the unaltered one. We provide light on a hitherto unexplored process of proton-coupled electron transfer by showing how SOW stabilizes transition states via dipole alignment and affects local electric fields. This goes beyond earlier research. We contrast material-based approaches (such as doping or nanostructuring) with a focus on customizing interfacial water structures apart from electrode alterations, providing a supplementary strategy to more conventional approaches. We bridge the gap between studies of structured water in biological systems and their electrochemical applications and provide clear experimental evidence that SOW leads to improved electrolysis efficiency. Novel molecular-level insights into SOW production and its influence on HER kinetics have been revealed by state-of-the-art spectroscopy and modeling. Catalysis might benefit from water structures that are dynamically changeable, as shown by these findings.

Lastly, our study explores new avenues for optimizing low-cost, high-performance systems for HER and other proton-transfer processes like as oxygen evolution. These findings have larger implications for sustainable energy technology. A self-organized water electrolyzer, featuring PEO-coated platinum electrodes, is considered the most suitable system for short-term upscaling due to its efficiency, stability, and scalability. This system leverages the unique properties of Plasma electro oxidation (PEO) coatings, which enhance the performance of platinum electrodes by improving their catalytic activity and durability. The self-organizing nature of the electrolyzer ensures consistent and reliable operation, even under fluctuating conditions, making it ideal for integration with renewable energy sources such as solar and wind. Moreover, the use of PEO-coated platinum electrodes reduces the overall cost of the system by minimizing the amount of precious metals required while maintaining high electrochemical performance. This cost-effectiveness, combined with the system’s adaptability to various scales of operation, positions it as a leading candidate for rapid deployment in industrial and commercial applications. In the short term, this technology has the potential to address key challenges in hydrogen production, including energy efficiency and operational flexibility, paving the way for a more sustainable energy future.

In this study, we report the fabrication of a self-organized water (SOW)-based electrolyzer utilizing (PEO)-coated platinum (Pt) electrodes as both the anode and cathode for the sustainable generation of hydrogen (H₂) gas. The incorporation of infrared (IR) light into the SOW system provides the necessary driving energy to facilitate the dissociation of interfacial water molecules into hydroxide ions (OH⁻) and protons (H⁺). The PEO coating on the Pt electrodes enhances the exposure of highly active catalytic sites, thereby improving overall electrochemical performance. Furthermore, the inherent characteristics of the SOW system enable the formation of a continuous catalyst layer with abundant mass transport pathways and reduced electronic resistance within the catalyst layer. As a result, the SOW electrolyzer demonstrates exceptional catalytic stability, maintaining high performance for over 1,000 h of operation. This work highlights the critical role of multi-scale structural design in water electrolyzer development, offering novel insights into the creation of high-performance, cost-effective catalysts tailored for water-splitting applications. These findings pave the way for advancements in sustainable hydrogen production technologies, addressing key challenges in efficiency, durability, and scalability.

Results and discussion

Characterization of self organized water

Figure 1a-d, provides a visual representation of self-organized water (SOW) formed adjacent to a hydrophilic surface, specifically Nafion-324. The figure depicts the dynamic behavior of nanoparticles suspended in an aqueous medium several minutes after exposure to the hydrophilic surface. Initially, the nanoparticles were uniformly distributed throughout the aqueous phase, indicating no preferential interaction with the surface. However, over time, the nanoparticles migrated away from the hydrophilic interface, leaving behind a distinct Self-organized water (SOW) that expanded radially at a rate of approximately 1 μm/s28. This process ultimately stabilized, yielding a well-defined self-organized water zone with a width of around 245 μm. The self-organized water phenomenon observed here is not unique to Nafion surfaces but is a general characteristic of various hydrophilic materials29. Similar effects have been documented in the presence of hydrophilic metals, biological tissues, hydrogels, and other substrates, suggesting that the formation of SOW is a universal feature of water in contact with such surfaces. This behavior is considered to result in an orderly arrangement at the micrometer scale from the hydrophilic interface, which induces physical and chemical properties distinct from bulk water30. These include increased viscosity, higher refractive indices, and charge separation, as previously reported in the literature.

The expansion dynamics of the Self-organized water are influenced by factors such as surface chemistry, environmental conditions, and external stimuli like electromagnetic radiation31. For instance, infrared (IR) energy has been shown to enhance the growth of Self-organized waters, further emphasizing the role of energy input in modulating interfacial water behavior. The stability and reproducibility of these zones make them highly relevant for applications ranging from water purification to energy conversion systems.

Fig. 1
figure 1

(a-d) Microscopic analysis of self-organized water at the Nafion-324 membrane surface. nanoparticles were used to highlight distinctions.

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Figure 2, illustrates the effect of incident infrared (IR) light exposure on self-organized water (SOW) and protonated water (PW). To evaluate this impact, SOW was exposed to IR light at a fixed intensity, and expansion ratios were calculated by comparing the SOW dimensions post-IR irradiation to those of a control experiment conducted without IR exposure. As shown in Fig. 2b–d, increasing the thickness of SOW under an IR intensity of 50 µW leads to a significant expansion of both the SOW and protonated water (PW). Specifically, the SOW thickness increases from 245 μm to 1140 μm under IR irradiation, which not only enhances the spatial extent of the SOW but also amplifies the regions of negative and positive charge within the water. Water (H₂O) molecules exhibit a dipole moment due to the electronegativity difference between oxygen and hydrogen atoms, resulting in a partial negative charge (δ⁻) on the oxygen side and partial positive charges (δ⁺) on the hydrogen sides. Hydrophilic surfaces, such as Nafion, possess negatively charged functional groups (e.g., -SO₃⁻), which attract the positively charged hydrogen atoms of water molecules, thereby facilitating their adsorption. Upon exposure to infrared (IR) radiation, water molecules undergo resonant vibrations, specifically O-H stretching and bending modes, which absorb energy at characteristic frequencies. This energy absorption can transiently weaken or reorganize hydrogen bonds, leading to the partial dissociation of water molecules into protons (H⁺) and hydroxide ions (OH⁻) in the vicinity of the surface. Due to their larger size, OH⁻ ions become entrapped within the structured water (SOW) layer adjacent to the surface, while the smaller, more mobile H⁺ ions are repelled and migrate away from the Nafion surface32.

Fig. 2
figure 2

The effect of IR intensity on the expansion of self-organized water thickness at the Nafion-324 membrane surface with different time duration (a) 0 min, (b) 3 min (c) 8 min and (d) 12 min respectively.

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The SOW and protonated water (PW) adjacent to hydrophilic surfaces exhibit distinct properties compared to bulk water. These interfacial water zones are characterized by charge separation, with negative charges accumulating in the SOW region and positive charges localized in the protonated water (PW) region33. This phenomenon is driven by interactions between water molecules and the hydrophilic surface, leading to the formation of structured water layers with unique electrochemical properties. Such findings highlight the critical role of IR energy in modulating the structural and charge-related characteristics of interfacial water, offering insights into its potential applications in energy conversion, catalysis, and other advanced technologies.

Electrochemical characteristics of self-organized water (SOW) system

Figure 3 presents the results of an additional investigation into the electrochemical behavior of the self-organized water (SOW) region. This study was conducted using a three-electrode setup in a ferri-ferrocyanide redox system. Cyclic voltammetry was employed to probe electron transfer mechanisms, utilizing a redox probe composed of 5 mM K₂[Fe(CN)₆] dissolved in 0.1 M KNO₃. As depicted in Fig. 3a, the SOW system exhibited a significantly higher peak current (Ip) compared to bulk water. This observation suggests that the presence of SOW and protons near the hydrophilic surface enhances electron transfer between the electrode and the redox species, K₃[Fe(CN)₆]. This improvement can be attributed to the higher conductivity of the SOW system and its increased effective surface area. In bulk water, the oxidation and reduction of Fe²⁺/Fe³⁺ occur with relatively slow electron transfer due to limited ion diffusion toward the electrode surface. In contrast, within the SOW system, the ordered arrangement of ions near the hydrophilic surface facilitates faster electron transport, leading to more efficient redox reactions. To explore the influence of scan rate on the SOW system, the scan rate was varied from 20 mV s⁻¹ to 200 mV s⁻¹. Figure 3b and c illustrate the linear relationship between the scan rate and the anodic (Ipa) and cathodic (Ipc) peak currents. The correlation coefficients were determined to be R² = 0.9907 for Ipa and R² = 0.9594 for Ipc, indicating a strong linear dependence between the scan rate and the peak currents. These results confirm that the SOW system supports efficient electron transfer for the K₃[Fe(CN)₆] redox probe, likely due to the presence of positively charged species at the electrode interface. Collectively, these electrochemical investigations highlight the unique properties of the SOW system in facilitating enhanced charge transfer processes.

Fig. 3
figure 3

(a) Electro activity of bulk water and self-organized water systems (b and c) Scan rate variation and linear regression plot of current Vs ln V of self-organized water (SOW) electrolyzer.

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We further explored the application of the self-organized water (SOW) system for hydrogen production using a two-electrode cell in distilled water, as illustrated in Fig. 4. Figure 4a, demonstrates that the highest hydrogen (H₂) gas production was observed in the SOW arrangement and the SOW arrangement with infrared (IR) radiation. This enhanced performance is attributed to charge separation occurring near hydrophilic surfaces, which results in negative charges accumulating in the SOW region and positive charges in the protonated water (PW). Notably, IR radiation amplifies the extent of SOW and PW within the bulk water, thereby promoting H₂ gas generation at the electrode surface. To investigate the electron, transfer processes in the system, cyclic voltammetry was performed using 5 mM K₃[Fe(CN)₆] in 0.1 M KNO₃ as the electrochemical redox probe. As shown in Fig. 4b, the SOW arrangement with IR radiation exhibited a significantly higher peak current (Ip) compared to other configurations. This indicates that the presence of SOW and PW in the bulk solution enhances electron transfer between the electrode and the redox probe, likely due to the system’s superior conductivity and increased effective surface area.

Fig. 4
figure 4

(a) volume of H2 gas produced (b) electro activity of various systems (c and d) Scan rate variation and linear regression plot of current Vs ln V of SOW electrolyzer. (e and f) Scan rate variation and linear regression plot of current Vs ln V of SOW with IR radiation.

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The scan rate was systematically varied from 20 mV s⁻¹ to 200 mV s⁻¹ for both the SOW system and the SOW system with IR radiation. Figure 4c-f, reveal a linear relationship between the scan rate and the anodic (Ipa) and cathodic (Ipc) peak currents. For the SOW system, the correlation coefficients were R² = 0.9907 for Ipa and R² = 0.9594 for Ipc. In contrast, for the SOW system with IR radiation, the linear coefficients were R² = 0.9686 for Ipa and R² = 0.9615 for Ipc. These results demonstrate a strong linear dependence between the scan rate and peak currents, underscoring the consistency and reliability of the system. Electrochemical studies confirm that the SOW system with IR radiation facilitates efficient electron transfer for the K₃[Fe(CN)₆] redox probe. This enhanced performance can be attributed to the abundance of positively charged species present at the electrode interface, which promote rapid and effective charge transfer. Collectively, these findings highlight the potential of the SOW system, particularly when augmented by IR radiation, as a highly efficient platform for hydrogen production and other electrochemical applications.

Morphological features of PEO-Ti & Pt/Ti electrode

Plasma Electrolytic Oxidation (PEO) coatings on platinum (Pt)-coated titanium (Ti) electrode, PEO-coated Ti electrode (Figure S1 and 2) have distinctive morphological properties that have a substantial influence on the performance of the electrodes shown in Fig. 5a-f. The surface area may be increased and additional active sites for electrochemical reactions can be provided by these coatings, which can generate a range of nanoporous layers according to the desired characteristics. The regulated porosity that is generated by the PEO process makes the Pt/Ti electrode more suitable for applications such as fuel cells and catalyst support. This is because the PEO procedure makes it easier for reactants and products to diffuse during electrochemical processes. On Pt/Ti electrodes, PEO coatings often result in a surface that is more abrasive, which enhances the adherence of catalytic materials and facilitates the efficient movement of mass. This roughness adds to higher catalytic activity, which in turn makes it more efficient for chemical reactions that involve electrochemical reactions. Based on the particular requirements of the application, the thickness of the PEO coating can be adjusted to meet those requirements. Even while thicker coatings offer improved protection and durability, they also have the potential to alter mass transport qualities, which might potentially have an effect on the efficiency of reactions performed.

Fig. 5
figure 5

FE-SEM images of (a-f) PEO-Pt/Ti electrode. Elemental analysis results of (g) EDS spectra (h) elemental mapping of PEO-Pt/Ti electrode. PEO current: 1 A.

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In addition, EDX spectra and elemental mapping results in Fig. 5g-h confirms the presence of PT, O and Ti elements with high purity. In order to achieve consistent electrochemical performance, it is necessary to have a distribution of nanostructures, porosity, and surface roughness that is homogeneous throughout the whole electrode surface. In addition, the platinum nanoparticles or layer that is placed on the titanium substrate needs to be dispersed uniformly and thoroughly in order to guarantee that the catalytic characteristics of platinum are utilized to their utmost potential. When it comes to enabling electron transmission and enhancing overall performance, the interface between the PEO coating and the Pt/Ti electrode is an extremely important factor to consider. When it comes to electrochemical processes, having a specific interface is essential to their success. These morphological characteristics may be modified to enhance the performance of Pt/Ti electrodes in a variety of applications, such as electrocatalysis, fuel cells, and electrochemical water splitting. This is accomplished by adjusting the parameters of the PEO process. These individualized coatings are absolutely necessary in order to get the highest possible level of efficiency from the electrode in these cutting-edge technologies. Furthermore, the XRD pattern of the PEO-Pt/Ti sample is presented in Figure S3. The analysis reveals broad diffraction peaks at 2θ = 39.6°, 47.4°, and 67.1°, corresponding to the (111), (200), and (220) crystallographic planes, respectively. These peaks are consistent with the face-centered cubic (fcc) structure of platinum (Pt) and match the reference data provided in the JCPDS Card 04–0802. This confirms the presence of crystalline platinum in the sample.

Overall water splitting

To evaluate the practical electrochemical performance of overall water splitting in self-organized water (SOW), Fig. 6a, presents a schematic representation of an SOW electrolyzer utilizing PEO-coated platinum-titanium (PEO-Pt/Ti) electrodes as both the anode and cathode. As shown in Fig. 6b, the PEO-Pt/Ti||PEO-Pt/Ti system achieves a current density of 100 mA cm⁻² at a cell voltage of 3.1 V. Although this voltage is slightly higher than that reported for some advanced catalysts integrated into membrane electrode assembly (MEA) and proton exchange membrane (PEM) setups (Fig. 6c), the SOW electrolyzer offers significant advantages in terms of cost-effectiveness and simplicity while maintaining high efficiency for hydrogen production. These results underscore the potential of the SOW electrolyzer as a robust bifunctional catalyst, demonstrating exceptional performance for efficient water splitting to generate hydrogen (H₂) and oxygen (O₂). In addition to its efficiency, the PEO-Pt/Ti electrodes exhibit remarkable stability, maintaining consistent performance over 25 h at a fixed potential. PEO-Pt/Ti electrodes demonstrate stable performance for over 25 h under neutral pH (pH 7) conditions, which inherently mitigates many common degradation issues such as catalyst dissolution, corrosion, and structural degradation that are typically encountered in acidic or alkaline electrolysis systems. In contrast to conventional water electrolysis systems using commercial catalysts like Pt/C, IrO₂, and RuO₂—which often suffer from challenges such as oxidation, dissolution, or particle aggregation during extended operation, our neutral pH system significantly reduces these degradation pathways. This indicates that SOW-enhanced electrolysis not only improves performance but also offers a more stable and durable alternative for sustainable water splitting applications. This highlights their superior durability for long-term water splitting applications. To quantify hydrogen production, the water displacement method was employed in an H-type electrolytic cell using the PEO-Pt/Ti catalyst for both SOW and bulk water systems. As depicted in Fig. 6d and e, the volume of hydrogen collected at intervals of 0, 2, 4, 6, 8, and 10 min was measured. The results reveal significantly higher hydrogen production in the SOW electrolyzer compared to bulk water electrolysis. This enhanced performance is primarily attributed to the presence of the protonated water (PW)at the electrode surface, which facilitates more efficient charge transfer and gas evolution. In contrast, bulk water electrolysis exhibits comparatively lower hydrogen production.

Fig. 6
figure 6

(a) Schematic representation of SOW electrolyzer (b) Polarization curve of PEO-Pt/Ti||PEO-Pt/Ti before and after 1000 cycles. (c) Cell voltage comparison of reported catalyst at 100 mA/cm−2 (d) Volume of produced hydrogen in SOW electrolyzer at 3.5 V (e) Volume of produced hydrogen in bulk water electrolyzer at 3.5 V.

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Furthermore, the presence of H₂ and O₂ gases during overall water splitting (OWS) was confirmed using gas chromatography (GC) as shown in Figure S4. The separation of these gases is based on differences in molecular size, polarity, and their interactions with the stationary phase. As shown in Figure SI, distinct peaks for H₂ and O₂ are observed at retention times (RT) of 2 min and 6 min, respectively. The clear separation of these retention times provides conclusive evidence of successful hydrogen and oxygen generation during the electrolysis process. These findings collectively demonstrate the effectiveness of the SOW electrolyzer as a low-cost, durable, and high-performance system for sustainable hydrogen production through water splitting. To evaluate potential degradation, we conducted post-electrolysis structural analysis using scanning electron microscopy (SEM) after 25 + hours of continuous operation at pH 7. The SEM images revealed (Figure S5) that the electrode surface remained largely intact, exhibiting no significant morphological changes, cracks, or particle detachment. This observation underscores the excellent stability of the system under neutral pH conditions. The absence of noticeable degradation further suggests that the PEO (plasma electrolytic oxidation) layer effectively protects the Pt/Ti structure, preventing corrosion and minimizing catalyst loss. While SEM provides compelling evidence of structural stability, these findings are complemented by the consistent electrochemical performance observed throughout the experiment, reinforcing the robustness of the system under prolonged operation. Table S1 provides a comprehensive comparison of the SOW-enhanced PEO-Pt/Ti electrolyzer with other electrolyzers that have been described. It has excellent efficiency and stability, achieving 100 mA cm⁻² at 3.1 V while operating at neutral pH. The PEO-Pt/Ti system provides better endurance than traditional Pt/C, IrO₂, and RuO₂-based electrolyzers, which function in acidic or alkaline environments and have corrosion, catalyst dissolution, and high prices. Furthermore, the use of structured orientated water (SOW) improves proton transfer kinetics and reduces activation barriers in contrast to newly developed nanostructured catalysts. As shown in Table S1, the PEO-Pt/Ti electrolyzer offers a steady operation for more than 25 h, making it an economical, long-lasting, and environmentally responsible alternative for producing hydrogen.

Conclusion

We have successfully developed a novel self-organized water (SOW) electrolyzer employing a PEO-coated platinum-titanium (PEO-Pt/Ti) heterostructure electrode, demonstrating exceptional performance in the hydrogen evolution reaction (HER). The SOW system provides the driving energy necessary for the dissociation of interfacial water into hydroxide ions (OH⁻) and protons (H⁺). This catalyst leverages the synergistic interaction between the PEO-Pt/Ti heterostructure and the strategically optimized SOW to modulate electronic energy states, thereby enhancing the electrochemical active surface area, improving electrical conductivity, and reducing the activation energy barrier for catalytic reactions. Consequently, the electrode achieves current densities of 100 mA cm⁻² at a cell voltage of 3.1 V. Furthermore, the SOW-based water-splitting device constructed using this electrode exhibits significantly higher hydrogen (H₂) production at a cell voltage of 3.5 V, while maintaining stable operation for over 25 h. These results underscore the durability and efficiency of the system. This work not only introduces a novel design strategy for water electrolysis but also highlights the potential of integrating advanced electrode structural engineering with SOW systems to advance the development of high-performance electrocatalytic systems for practical applications. Such innovations pave the way for cost-effective and sustainable hydrogen production technologies.

Experimental

Materials

Sodium phosphate (Na₃PO₄), potassium hydroxide (KOH), chloroplatinic acid (PtCl₄), potassium nitrate (KNO₃), ethanol, and acetone were procured from Daejong Chemical Factory Co., Ltd. The Nafion-324 membrane was supplied by Dopant. All chemicals were used as received without any further purification.

Material Characterization

X-ray diffraction (XRD) analysis was carried out using a Rigaku Ultima IV diffractometer equipped with Cu Kα radiation (λ = 0.15405 nm). Field emission scanning electron microscopy (FESEM) images and energy-dispersive X-ray spectroscopy (EDS) data were obtained using a JEOL 7500 F FESEM system.

Electrochemical Measurements

Electrochemical measurements were conducted using a Princeton Applied Research workstation in a three-electrode configuration, with tap water serving as the electrolyte. An Ag/AgCl electrode (3 M KCl) and a platinum wire were used as the reference and counter electrodes, respectively, while a glassy carbon electrode (GCE) was employed as the working electrode for fundamental electrochemical studies. In contrast, water-splitting experiments were performed using PEO-coated Pt/Ti electrodes as both the anode and cathode and pure water was used as electrolyte.

Measurements of SOW

A segment of Nafion 324 membrane was carefully handled using tweezers, while a prepared nanoparticle solution was injected into the system via a syringe to ensure the removal of all air bubbles. The Nafion film was then positioned using the tweezers to ensure full immersion in a 35 mm × 10 mm Falcon polystyrene petri dish containing 3–4 mL of the nanoparticle suspension. In certain cases, the Nafion film was pre-hydrated by soaking it in a separate petri dish filled with 3–4 mL of deionized (DI) water for 15–30 min before the experiment. For control measurements of self-organized water (SOW), the pre-hydrated Nafion film was transferred to a fresh petri dish containing 3–4 mL of DI water mixed with nanoparticle. For experimental measurements, another piece of Nafion film was submerged in 3–4 mL of the test suspension. The petri dish, with the Nafion film oriented perpendicular to the optical axis, was covered and placed on the stage of a Bresser LCD microscope equipped with a 40× objective lens. SOW measurements were recorded once a steady-state SOW size was achieved, typically within 15 min after introducing the Nafion film to the suspension, though this duration was occasionally extended to 30 min. The dimensions of the SOW were analyzed using the graph tool in ImageJ (version 1.49v). Measurements were taken at 2–6 locations along each side of the Nafion film, and the mean SOW size was calculated from these readings. This methodical approach ensured precise and reproducible quantification of SOW dimensions under both control and experimental conditions.

Nanoparticle suspension

Polycarboxylate-coated nanoparticles with diameters of 0.5, 1, or 2 μm (Polysciences Inc.; #18327; 2.5% solids-latex) were utilized to determine the size of the Self-organized water (SOW). These nanoparticles were suspended in deionized (DI) water, which was obtained from a Barnstead D3750 Nanopure Diamond purification system (Dubuque, IA), producing type 1 high-performance liquid chromatography (HPLC)-grade water with a resistivity of 18.2 MΩ. The volume ratio of nanoparticles to DI water was maintained between 1:100 and 1:1000, depending on the experimental requirements. This ratio was kept constant throughout each experimental series to ensure consistency and eliminate potential variations caused by differences in concentration.

Electrochemical deposition of Pt/Ti

The Pt-coated titanium mesh electrode was fabricated using an electrochemical deposition technique. A reduction potential of −1.2 V versus Ag/AgCl was applied for 100 s during the deposition process. The electrolyte solution consisted of 0.1 M KNO₃ and 1 mM palladium chloride (PtCl₄) in an aqueous medium. After the deposition was completed, the electrode was thoroughly rinsed with deionized water to remove any residual electrolyte and subsequently allowed to dry naturally under ambient conditions.

Development of PEO-coated Pt/Ti electrode

PEO-coated Pt/Ti electrode, a solution of 10 g L⁻¹ Na3PO4 and 5 g L⁻¹ KOH was used as the electrolyte during the plasma electrolytic oxidation (PEO) coating process. The electrolyte was maintained at a temperature of 5–10 °C throughout the treatment. The PEO process was conducted under an alternating current (AC) power supply with a voltage of 380 V, a frequency of 60 Hz, and a current density of 22.12 A dm⁻². The PEO coatings were applied for 10 min to optimize the coating thickness and properties for the Pt/Ti electrode.