• Deposition methods govern the electrochemical performance of modified electrode • Structured protocol links electrode surface characterization to electrochemistry • Inkjet printing yields uniform functionalization versus drop-casting on electrodes • Coverage uniformity and layer thickness explain impedance and voltammetric response • Electrochemical response follows accessible active sites, not deposited mass The performance of functionalized electrochemical sensors is commonly linked to the intrinsic properties of the material used for electrode surface modification. However, the role of the deposition method itself is often overlooked, even though it critically defines the interfacial structure and batch-to-batch reproducibility. In addition, electrode functionalization is rarely accompanied by comprehensive surface characterization, which limits mechanistic interpretation and transferability of results. Here, we introduce a structured, multiscale characterization framework that isolates how deposition methods define the electrochemical interface on printed electrodes. A commercial screen-printed carbon electrode platform was functionalized with nitrogen-doped graphene acid using conventional drop-casting and inkjet printing as a controlled deposition strategy. Complementary local and electrode-scale analyses were used to quantify film homogeneity, thickness distribution, microtopography, wetting behavior, and coating integrity. These interfacial descriptors were systematically correlated with electrochemical performance using impedance spectroscopy and voltammetric benchmarking. Inkjet printing produced thin, laterally uniform coatings with enhanced wetting and significantly reduced electrode-to-electrode variability. In contrast, drop-casting resulted in edge-enriched films dominated by coffee-ring drying and pronounced interfacial heterogeneity. The electrochemical response was governed by the spatial accessibility and distribution of the functional layer rather than by the nominal deposited mass. This positions deposition technique among primary design parameters in electrochemical sensor development. The framework presented here provides a practical characterization and reporting protocol that supports reproducible and mechanistically interpretable optimization of functionalized electrochemical interfaces. Electrochemical performance is governed by how a functional layer is structured and coupled to the electrode: continuity, electronic connectivity, and mechanical robustness determine kinetics and reproducibility. Spatially resolved, complementary interface characterization is essential to translate surface architecture into reliable device performance.

Single-Atom Catalysts (SACs) are a hot topic in catalysis research. Nowadays, there is a growing attention in modelling the reactivity and activity of SACs towards several electrochemical reactions. The activity of SACs is strongly sensitive to the local coordination of the transition metal atoms. An aspect less explored is assessing their stability in electrochemical conditions. In this work, we performed a density functional theory investigation of SACs based on MoS 2 , a widely adopted supporting material, by focusing on the role of the local coordination to the stability. Our results are based on a dataset of fifteen transition metal atoms on four different possible coordinative sites. The stability of SACs in electrochemical conditions is predicted by using a recently proposed simple yet practical scheme within the formalism of Pourbaix diagrams [ ACS Catal. 14, 45 (2024) ]. When looking at the role of the metal, Pt-SACs are mostly stable, compatible with the large diffusion of these kinds of systems in experiments. Results show that the local coordination has a dramatic effect on stability. Most often the simple adsorption of metals on MoS 2 leads to unstable systems, unless noble atoms are considered. Moreover, stability improves when metal atoms occupy lattice S sites, but the most stable configurations refer to substitutional doping of Mo atoms. The results provided are validated against selected available experimental data. These results provide a further example of the crucial role of the local coordination in single-atom catalysis and may of help for the screening of potential candidates and could be used to help the understanding of the active phase in promising electrocatalysts.

• A leakless IL/poly(IL) gel electrolyte was evaluated for BPA detection • The IL/poly(IL) gel prevents BPA oxidation fouling and electrode passivation • Mild electrode polarisation yields 100% current retention over five SWV scans • This protocol works on Pt thin-film, Pt macrodisk and glassy carbon electrodes A novel anti-fouling strategy has been developed to fully prevent electrode passivation caused by the polymeric by-products from bisphenol A (BPA) electrochemical oxidation. In this work, we utilise a gelled electrolyte comprised of a mixture of an ionic liquid (IL, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C 2 mim][TFSI]) and a poly(ionic liquid) (poly(IL), poly(diallyldimethylammonium) bis(trifluoromethylsulfonyl)imide, poly[DADMA][TFSI]) to detect BPA. We demonstrate that the IL-based gelled electrolyte possesses an inherent anti-fouling effect, which can be further enhanced by applying mild electrode polarisation prior to BPA detection. Square wave voltammetry (SWV) measurements for BPA oxidation with electrode polarisation confirms the elimination of electrode fouling, demonstrating up to 100% of residual current values across five consecutive measurement cycles (RCV 1-5 ). The polarisation step was shown to be effective on both platinum and glassy carbon electrodes. As a proof-of-concept, electrochemical sensing experiments demonstrated a linear response to BPA concentrations from 200 to 1,200 µM, with a sensitivity of 2.4 nA/µM and a limit of detection of 44 µM.

• Complex capacitance is useful for adsorbed systems with fast electron transfers • CPE behaviour suggests frequency dispersion of surface concentrations • Gaussian distance distribution from the electrode causes log-normal rate distribution • Both CPE and rate distributions are evidenced in a giant electroactive rotaxane • Fast CV and EIS are very complementary techniques to assess these distributions Electrochemical analysis of adsorbed systems integrating redox centres in their structure often show deviations from ideal behaviours, revealing thermodynamic or kinetic distributions. In this work, we revisit theoretically the influence of the constant phase element (CPE), often introduced to fit data obtained by electrochemical impedance spectroscopy (EIS), together with distributions of the electron transfer rate constants between the electrode and electroactive entities. If such approaches have already been developed in EIS, we extend it in this study to ultrafast CV measurements, and further explore their physicochemical consequences. We thus propose on the one hand an interpretation of the CPE in terms of frequency dispersion of the charge transferred to the electrode, referred here as a “pseudo-Nernstian” model in EIS, and for which a mathematical derivation is suggested. It results in the variation of the apparent surface concentration with the time scale of the technique, probed in CV by the non-linear dependency of the voltammetric peak area with the scan rate. On the other hand, since the distance distributions of redox entities with the electrode lead to log-normal distributions of rate constants, the apparent rate deduced from the measurement may be biased, possibly explaining some discrepancies in the literature. Finally, we apply our model to reinterpret CV and EIS results obtained for giant rotaxanes bearing ten ferrocene centres adsorbed onto gold electrodes, demonstrating a good agreement between the techniques, and the potential for accessing complex mechanisms by time-resolved electrochemical measurements.