Polyaniline (PANI) has shown substantial interest in analytical chemistry as an electrochemical proton pump for pH modulation in water and soil systems. In this work, we present a reagent-free electrochemical setup employing 3D PANI-coated stainless steel (PANI-SS) mesh arrays, which enable efficient pH control in both bulk and small-volume aqueous samples at the milliliter scale. The custom-designed electrochemical cell with a total volume of 40 mL featured multiple PANI-SS meshes as working electrodes, a screen-printed carbon counter electrode, and an Ag/AgCl reference electrode. The 3D mesh architecture substantially enhanced the electroactive surface area, allowing rapid and scalable proton delivery. A single PANI-SS mesh can release ~3 µmol of protons within 200 s at 0.4 V, lowering the pH of an unbuffered 40 mL NaCl solution from ~5.3 to ~4.3. By further increasing the number of meshes to four, the pH decreased to 3.36 in unbuffered solution and 3.89 in brackish water, respectively. In addition, we explore the applicability of the PANI mesh system to selectively acidify samples containing 5% sediment to a targeted pH of 4-5, which is crucial for certain bioreaction uses. These performances demonstrated the system’s ability to provide effective proton transfers, achieving significant acidification without the use of chemical reagents. Moreover, with excellent reversibility and ability to be electrochemically regenerated using diluted acidic mining leachates, PANI-SS meshes offer a sustainable alternative to the traditional acidification concept using conventional acids, aligning with the principles of circular chemistry. Therefore, the obtained results are crucial for the future development of similar PANI-based systems in their applications as efficient and environmentally friendly electrochemical proton pumps.

Electrochemical proton pumps based on conductive polymers provide a promising route for localized pH modulation in analytical and environmental applications. In this work, we present a comparative study of polyaniline (PANI) and its copolymer, poly(aniline-co-o-aminophenol) (PANOA), focusing on their structural, morphological, and electrochemical properties, which are relevant to their proton pumping performance. The local microscopic variations in their surface topography, morphology and conductivity are studied by employing scanning electrochemical microscope (SECM), while detailed characterization using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) reveals significant differences in films’ porosity, stability, and doping behavior that directly influences their acidification efficiency and spatial proton distribution. PANI films with a porous, swelling-prone structure enable broad and intense proton release, but also complicate precise pH monitoring. In contrast, PANOA films demonstrate compact and morphologically stable structures, offering more localized and controllable pH modulation. To resolve the local proton gradients generated by these films, we employ a PANI-based ultramicroelectrode (UME) pH sensor integrated into a SECM platform, enabling micrometer-scale resolution of pH changes near the film surface. This approach offers a novel methodology for investigating interfacial proton dynamics and contributes to a deeper understanding of how polymer structure influences proton pump functionality. The dual application of PANI polymer as both a proton pump and a pH sensor demonstrates its versatility, providing valuable insights into the design of next-generation electrochemical platforms for pH modulation.

Electrochemical proton pumps based on conductive polymers provide a promising route for localized pH modulation in analytical and environmental applications. In this work, we present a comparative study of polyaniline (PANI) and its copolymer, poly(aniline-co-o-aminophenol) (PANOA), focusing on their structural, morphological, and electrochemical properties, which are relevant to their proton pumping performance. The local microscopic variations in their surface topography, morphology and conductivity are studied by employing scanning electrochemical microscope (SECM), while detailed characterization using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) reveals significant differences in films’ porosity, stability, and doping behavior that directly influences their acidification efficiency and spatial proton distribution. PANI films with a porous, swelling-prone structure enable broad and intense proton release, but also complicate precise pH monitoring. In contrast, PANOA films demonstrate compact and morphologically stable structures, offering more localized and controllable pH modulation. To resolve the local proton gradients generated by these films, we employ a PANI-based ultramicroelectrode (UME) pH sensor integrated into a SECM platform, enabling micrometer-scale resolution of pH changes near the film surface. This approach offers a novel methodology for investigating interfacial proton dynamics and contributes to a deeper understanding of how polymer structure influences proton pump functionality. The dual application of PANI polymer as both a proton pump and a pH sensor demonstrates its versatility, providing valuable insights into the design of next-generation electrochemical platforms for pH modulation.