64434 2026 eng 1 18 703 article Elsevier Inc. 1 -- -- -- High-concentration, steric stabilizer free colloids and particularly their electrochemical behavior remains almost unexplored. Herein, we report on the electrochemistry (cyclic voltammetry, impedance spectroscopy, etc.) of highly concentrated aqueous colloidal dispersion up to 800 g/L of citrate-capped ∼11 nm Fe3-xO4 nanoparticles (NPs) without background electrolyte on glassy carbon electrodes. X-ray photoelectron spectroscopy was applied to analyze the reaction products. Solid-state Fe(II)/Fe(III) conversion was concluded to determine the cathodic and anodic faradaic reactions of the particles, with the currents depending on approximately square root of the concentration. The electrochemical reactions are coupled with the electrophoretic transfer of the negatively charged NPs on toward the anode, with the ohmic-type behavior in the bulk demonstrated by the nearly linear voltametric cathodic curves and frequency-independent impedance above ∼10–100 Hz. Accumulation and clogging of the NPs retards diffusion near anode. Hydrogen and especially oxygen evolution are arrested, and very large oxidation overpotentials result in extraordinary wide, up to 12 V, electrochemical window of water stability. The findings shed light onto basic features of the electrochemistry of high-concentration colloids without added electrolyte and their potential applications in redox flow batteries, electrophoretic deposition and beyond. Journal of Colloid and Interface Science 0021-9797 10.1016/j.jcis.2025.139247 urn:nbn:de:kobv:b43-644340 true journal-article https://www.elsevier.com/tdm/userlicense/1.0/ crossref PersonAuthorFirstName_1,PersonAuthorLastName_1,PersonAuthorFirstName_2,PersonAuthorLastName_2,PersonAuthorFirstName_3,PersonAuthorLastName_3,PersonAuthorFirstName_4,PersonAuthorLastName_4,PersonAuthorFirstName_5,PersonAuthorLastName_5,PublisherName,TitleMain_1,Language,TitleParent_1,ArticleNumber,Volume,PublishedYear,IdentifierIssn,Enrichmentlocal_crossrefLicence doi-import 03.11.2025 Creative Commons - CC BY-NC - Namensnennung - Nicht kommerziell 4.0 International Yuri Mikhlin Anya Muzikansky Melina Zysler Andreas Thünemann David Zitoun eng uncontrolled Nanoplastics eng uncontrolled SAXS eng uncontrolled Small-angle X-ray scattering Ingenieurwissenschaften und zugeordnete Tätigkeiten 6 Materialchemie 6.5 Synthese und Streuverfahren nanostrukturierter Materialien Material Verlagsliteratur Datei für die Öffentlichkeit verfügbar ("Open Access") Wissenschaftliche Artikel der BAM Advanced Materials Bundesanstalt für Materialforschung und -prüfung (BAM) https://opus4.kobv.de/opus4-bam/files/64434/Mikhlin_Journal_of_Colloid_and_Interface_Science_2026_703_139247.pdf