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Electrochemical AFM is a powerful tool for the real‐space characterization of catalysts under realistic electrochemical CO2 reduction (CO2RR) conditions. The evolution of structural features ranging from the micrometer to the atomic scale could be resolved during CO2RR. Using Cu(100) as model surface, distinct nanoscale surface morphologies and their potential‐dependent transformations from granular to smoothly curved mound‐pit surfaces or structures with rectangular terraces are revealed during CO2RR in 0.1 m KHCO3. The density of undercoordinated copper sites during CO2RR is shown to increase with decreasing potential. In situ atomic‐scale imaging reveals specific adsorption occurring at distinct cathodic potentials impacting the observed catalyst structure. These results show the complex interrelation of the morphology, structure, defect density, applied potential, and electrolyte in copper CO2RR catalysts.

Summary Conventional polyolefin separators suffer from poor wettability to liquid electrolytes (LEs). Although some modified separators exhibit improved wettability, they are hydrophilic, causing inevitable moisture uptake. Trace water could result in poor performance and safety hazard of Li metal batteries. Here, we report a design idea of superLEphilic/superhydrophobic and thermostable separators by modifying the Celgard separator using silicone nanofilaments. The separator features low moisture uptake (∼0%), fast LE diffusion (454 ms), and high LE uptake (287.8%), LE retention rate, and Li+ conductivity. Consequently, the Li/LiFePO4 cells show high cycling stability (96.05% after 350 cycles), good rate performance (125 mA h g−1 at 5.0 C), low resistance, and stable open circuit voltage at 160°C. Moreover, the separator could improve performance of the other Li metal batteries with high-voltage cathodes and the LiFePO4/graphite pouch cells. This work provides an avenue for designing advanced separators by using bioinspired superwetting surfaces., Graphical Abstract, Highlights • A superLEphilic/superhydrophobic separator is first reported for Li metal batteries • The separator has low moisture uptake and could improve performance of Li/Li cells • The separator features fast LE diffusion, high LE uptake, and Li+ conductivity • The separator could enhance performance of high-voltage Li metal batteries, Chemistry; Electrochemistry; Nanoelectrochemistry; Materials Science; Energy Materials

International audience; This opinion paper details three typical cases in which new theoretical concepts need to be implemented in molecular electrochemistry in order to rationalize experimental results obtained in nanoscale cells or performed in new electrolytic media such as RTILs.

Enzymes are molecules that catalyze reactions critical to life. These catalysts are often studied in bulk water, where the influence of water volume on reactivity is neglected. Here, we demonstrate rate enhancement of up to two orders of magnitude for enzymes trapped in submicrometer water nanodroplets suspended in 1,2-dichloroethane. When single nanodroplets irreversibly adsorb onto an ultramicroelectrode surface, enzymatic activity is apparent in the amperometric current-time trace if the ultramicroelectrode generates the enzyme cofactor. Nanodroplet volume is easily accessible by integrating the current-time response and using Faraday's Law. The single nanodroplet technique allows us to plot the enzyme's activity as a function of nanodroplet size, revealing a strong inverse relationship. Finite element simulations confirm our experimental results and offer insights into parameters influencing single nanodroplet enzymology. These results provide a framework to profoundly influence the understanding of chemical reactivity at the nanoscale.

Cells modulate their homeostasis through the control of redox reactions via transmembrane electron transport systems. These are largely mediated via oxidoreductase enzymes. Their use in biology has been linked to a host of systems including reprogramming for energy requirements in cancer. Consequently, our ability to modulate membrane redox systems may give rise to opportunities to modulate underlying biology. The current work aimed to develop a wireless bipolar electrochemical approach to form on-demand electron transfer across biological membranes. To achieve this goal, we show that using membrane inserted carbon nanotube porins that can act as bipolar nanoelectrodes, we could control electron flow with externally applied electric fields across membranes. Before this work, bipolar electrochemistry has been thought to require high applied voltages not compatible with biological systems. We show that bipolar electrochemical reaction via gold reduction at the nanotubes could be modulated at low cell-friendly voltages, providing an opportunity to use bipolar electrodes to control electron flux across membranes. Our observations present a new opportunity to use bipolar electrodes to alter cell behavior via wireless control of membrane electron transfer.

Discerning the influence of electrochemical reactions on the electrode microenvironment is an unavoidable topic for electrochemical reactions that involve the production of OH− and the consumption of water. That is particularly true for the carbon dioxide reduction reaction (CO2RR), which together with the competing hydrogen evolution reaction (HER) exert changes in the local OH− and H2O activity that in turn can possibly affect activity, stability, and selectivity of the CO2RR. We determine the local OH− and H2O activity in close proximity to a CO2‐converting Ag‐based gas diffusion electrode (GDE) with product analysis using gas chromatography. A Pt nanosensor is positioned in the vicinity of the working GDE using shear‐force‐based scanning electrochemical microscopy (SECM) approach curves, which allows monitoring changes invoked by reactions proceeding within an otherwise inaccessible porous GDE by potentiodynamic measurements at the Pt‐tip nanosensor. We show that high turnover HER/CO2RR at a GDE lead to modulations of the alkalinity of the local electrolyte, that resemble a 16 m KOH solution, variations that are in turn linked to the reaction selectivity., Local affection: The abundance of gas diffusion electrodes (GDE) in modern electrochemistry has grown drastically, especially with the increasing interest in electrochemical reduction of CO2. Since several aspects of those electrodes and that reaction are not clarified yet, we herein couple assessment of the local reaction environment to the actual product distribution of the hydrogen evolution/CO2 reduction reaction system at Ag‐based GDEs.

Co3 O4 nanocubes are evaluated concerning their intrinsic electrocatalytic activity towards the oxygen evolution reaction (OER) by means of single-entity electrochemistry. Scanning electrochemical cell microscopy (SECCM) provides data on the electrocatalytic OER activity from several individual measurement areas covering one Co3 O4 nanocube of a comparatively high number of individual particles with sufficient statistical reproducibility. Single-particle-on-nanoelectrode measurements of Co3 O4 nanocubes provide an accelerated stress test at highly alkaline conditions with current densities of up to 5.5 A cm-2 , and allows to derive TOF values of up to 2.8×104 s-1 at 1.92 V vs. RHE for surface Co atoms of a single cubic nanoparticle. Obtaining such high current densities combined with identical-location transmission electron microscopy allows monitoring the formation of an oxy(hydroxide) surface layer during electrocatalysis. Combining two independent single-entity electrochemistry techniques provides the basis for elucidating structure-activity relations of single electrocatalyst nanoparticles with well-defined surface structure.

The active materials constitute the heart of any battery so that unambiguous determination of their intrinsic properties is of essential importance to achieve progress in battery research. A variety of in situ techniques with high lateral resolution has been developed or adapted for battery research. Surprisingly, nanoelectrochemistry is not attracting sufficient attention from the battery community despite the existing examples of relevant in situ and highly resolved spatiotemporal information. Herein, the important role of nanoelectrochemistry in battery research is highlighted to help encourage its use in this field. In the first part, two examples in which the use of nanoelectrochemistry is a must are provided, that is, determination of intrinsic kinetics of active materials and understanding of relationships between particle structure and electrochemical activity. In the second part, pros and cons of three mature nanoelectrochemistry techniques in battery research, that is, particle-on-a-stick measurements, nanoimpact measurements, and scanning electrochemical probe microscopy, are discussed providing representative examples., Spanish Government (MINECO) through the Research Challenges Programme (grant RTI2018-099228-A-I00) and Ramón y Cajal award (RYC2018-026086-I) as well as the NanoBat project. NanoBat has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement no. 861962.

Deterministic positioning and assembly of colloidal nanoparticles (NPs) onto substrates is a core requirement and a promising alternative to top down lithography to create functional nanostructures and nanodevices with intriguing optical, electrical, and catalytic features. Capillary-assisted particle assembly (CAPA) has emerged as an attractive technique to this end, as it allows controlled and selective assembly of a wide variety of NPs onto predefined topographical templates using capillary forces. One critical issue with CAPA, however, lies in its final printing step, where high printing yields are possible only with the use of an adhesive polymer film. To address this problem, we have developed a template dissolution interfacial patterning (TDIP) technique to assemble and print single colloidal AuNP arrays onto various dielectric and conductive substrates in the absence of any adhesion layer, with printing yields higher than 98%. The TDIP approach grants direct access to the interface between the AuNP and the target surface, enabling the use of colloidal AuNPs as building blocks for practical applications. The versatile applicability of TDIP is demonstrated by the creation of direct electrical junctions for electro- and photoelectrochemistry and nanoparticle-on-mirror geometries for single particle molecular sensing.

International audience; Electrochemical blocking is a type of single-entity electrochemical measurement particularly well adapted to the detection of insulating particles. The digital detection of ultralow concentrations of artificial entities such as polymer particles or biotargets such as proteins and bacteria represents an exceptional opportunity for sensing applications. In this review, we explore the latest development in the field of electrochemical blocking and propose some perspectives.

Electrochemical AFM is a powerful tool for the real‐space characterization of catalysts under realistic electrochemical CO2 reduction (CO2RR) conditions. The evolution of structural features ranging from the micrometer to the atomic scale could be resolved during CO2RR. Using Cu(100) as model surface, distinct nanoscale surface morphologies and their potential‐dependent transformations from granular to smoothly curved mound‐pit surfaces or structures with rectangular terraces are revealed during CO2RR in 0.1 m KHCO3. The density of undercoordinated copper sites during CO2RR is shown to increase with decreasing potential. In situ atomic‐scale imaging reveals specific adsorption occurring at distinct cathodic potentials impacting the observed catalyst structure. These results show the complex interrelation of the morphology, structure, defect density, applied potential, and electrolyte in copper CO2RR catalysts., Copper catalyst for electrochemical CO2 conversion has been unraveled in situ down to the atomic scale using electrochemical atomic force microscopy under highly gas‐evolving reaction conditions. Oxidized copper surfaces enter different morphological regimes in cathodic potential ranges down to −1.1 VRHE coupled with surface reconstructions and varying density of undercoordinated reaction sites.

Summary The key properties of yolk-shell architecture in improving electrochemical performance lies in its uniformity and the appropriate void space, which can expand/contract freely upon lithium alloying and leaching without damaging the outer shell, while being achievable with minimal sacrifice of volumetric energy density. Therefore, we developed a highly controllable strategy to fabricate a uniform porous germanium@polypyrrole (PGe@PPy) yolk-shell architecture with conformal Al2O3 sacrificial layer by atomic layer deposition (ALD) process. The PGe@PPy yolk-shell anode fabricated with 300 ALD cycles delivers excellent electrochemical performance: high reversible capacity (1,220 mA hr g−1), long cycle performance (>95% capacity retention after 1,000 cycles), and excellent rate capability (>750 mA hr g−1 at 32 A g−1). Electrodes with high areal capacity and current density were also successfully fabricated, opening a new pathway to develop high-capacity electrode materials with large volume expansion., Graphical Abstract, Highlights • Porous germanium@polypyrrole (PGe@PPy) yolk-shell architecture was developed • Precision expansion and void control make PGe@PPy stable during lithiation/delithiation • PGe@PPy electrode shows high rate and areal capacity, cycling stability, and current density • The full cell shows the stable capacity retention with high energy density, Nanoparticles; Nanoelectrochemistry; Materials Science; Energy Materials

Lithium (Li) dendrite formation is one of the major hurdles limiting the development of Li-metal batteries, including Li-O2 batteries. Herein, we report the first observation of the dendrite-free epitaxial growth of a Li metal up to 10-μm thick during charging (plating) in the LiBr-LiNO3 dual anion electrolyte under O2 atmosphere. This phenomenon is due to the formation of an ultrathin and homogeneous Li2 O-rich solid-electrolyte interphase (SEI) layer in the preceding discharge (stripping) process, where the corrosive nature of Br- seems to give rise to remove the original incompact passivation layer and NO3- oxidizes (passivates) the freshly formed Li surface to prevent further reactions with the electrolyte. Such reactions keep the SEI thin (

Recent literature has evinced a keen interest in porous electrodes. Numerous applications have been discussed and some aspects of the voltammetry investigated, a theoretical description of adsorption- and desorption processes though remains largely absent. The present study fills this important gap and provides a detailed analysis of the impact of adsorption on voltammetric electrode responses in porous materials. It is shown that in some cases, adsorption- and desorption processes may aid the detection of analytes while in other cases a planar unmodified electrode is superior in performance. Finally practical conclusions are drawn for the design of future experimental systems.

We study in real time the optical response of individual plasmonic nanoparticles on a mirror, utilized as electrodes in an electrochemical cell when a voltage is applied. In this geometry, Au nanoparticles are separated from a bulk Au film by an ultrathin molecular spacer. The nanoscale plasmonic hotspot underneath the nanoparticles locally reveals the modified charge on the Au surface and changes in the polarizability of the molecular spacer. Dark-field and Raman spectroscopy performed on the same nanoparticle show our ability to exploit isolated plasmonic junctions to track the dynamics of nanoelectrochemistry. Enhancements in Raman emission and blue-shifts at a negative potential show the ability to shift electrons within the gap molecules.

Hybrid magnetite/carbon quantum dots (MagNP/C-dots) were prepared and their characterization performed by high resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Because of their suitable magnetization and electrochemical properties, they were used as versatile electrode modifiers after magnetically confining onto screen printed carbon electrodes (SPE), with the aid of a miniature external magnet. The reported strategy introduces a convenient procedure for assembling modified electrodes, since the nanoparticles can be easily released by removing the magnet. The non-enzymatic magnetic biosensor showed excellent performance in the determination of NADH at the concentration range 2×10−7 to 5×10−6 mol L−1, exhibiting a sensitivity of 0.15 μmol L−1 and detection limit of 20 nmol L−1. The MagNP/C-dots /SPE sensor was also successfully applied for the determination of NADH in serum samples. The interference of typical biological molecules has also been investigated.

Near-infrared electrochemiluminescence (ECL) from Au-thiolate nanoclusters is activated by electrode reactions and enhanced by ethylenediamine tetraacetic acid (EDTA). The enhancement effect is higher at pH 7.4 than at more basic or acidic pHs. Magnesium ions are found to modulate the ECL signals through complexation with EDTA and the interaction with the Au nanoclusters. The chemical system and the signal modulation mechanism are believed to be generalizable and advantageous for future sensing and analysis applications with the following merits: 1) Ambient ECL without oxygen removal, 2) high enhancement at physiological pH values, 3) in the near-IR spectrum window with low interference, 4) rich and tunable redox activity of the Au nanoclusters, and 5) EDTA representing other ionophores or chelaters as versatile coreactants.

[Image: see text] Mass spectrometry imaging is a field that promises to become a mainstream bioanalysis technology by allowing the combination of single-cell imaging and subcellular quantitative analysis. The frontier of single-cell imaging has advanced to the point where it is now possible to compare the chemical contents of individual organelles in terms of raw or normalized ion signal. However, to realize the full potential of this technology, it is necessary to move beyond this concept of relative quantification. Here we present a nanoSIMS imaging method that directly measures the absolute concentration of an organelle-associated, isotopically labeled, pro-drug directly from a mass spectrometry image. This is validated with a recently developed nanoelectrochemistry method for single organelles. We establish a limit of detection based on the number of isotopic labels used and the volume of the organelle of interest, also offering this calculation as a web application. This approach allows subcellular quantification of drugs and metabolites, an overarching and previously unmet goal in cell science and pharmaceutical development.

Electrogenerated chemiluminescence (ECL) is a light emission phenomenon initiated by electrochemically generated radical species, which then undergo a series of electron transfer reactions. It leads to the final generation of an excited state that radiatively decays to the ground state. In this work, my goal was to develop fundamental aspects of ECL as well as analytical applications at different scales. In the first part, two supramolecular systems are studied. The ECL performances of spirofluorene derivatives based on trigonal truxene-core structure are investigated, focusing on the role of the different functional groups on the ECL properties. Then a bispyrene scaffold mounted on a constrained polyether macrocycle displaying intense excimer fluorescence has been selected to study the circularly polarized ECL. We show for the first time that ECL can discriminate enantiomers. In the second part of the thesis, annihilation ECL is enhanced by exploiting nanogap amplification. Furthermore, ECL imaging experiments enabled to demonstrate the increase in the performances of a bipolar electrochemistry system by employing a solid-state micropore configuration. Finally, the first steps in the development of a new ECL-based microscopy are presented. Using a unique ECL mechanism, which involves short-lifetime electrogenerated radicals, surface-confinement of ECL microscopy was demonstrated by cellular membranes’ imaging. ECL microscopy applied to cells imaging was further improved by adding a permeabilization step during cells labeling procedure. Disposable transparent carbon nanotube-based electrodes inkjet-printed on classic microscope glass coverslips, were used to image cells in both reflection and transmission configurations., L’électrochimiluminescence (ECL) est un phénomène d’émission de lumière obtenue suite à la génération d’espèces très réactives à l’électrode. Ces dernières vont subir une série de réactions de transfert d’électrons qui conduisent à la formation d’un état excité qui mène à l’émission finale de photons. La première partie de mon travail de thèse a porté sur l’étude de deux systèmes supramoléculaires. Les performances ECL d’un dérivé du spirofluorène et de trois composés modifiés avec un truxène comme partie centrale sont examinées. L’étude d’un deuxième système supramoléculaire, [18]-C-6bispyréne, a permis de démontrer une nouvelle propriété de l’ECL, maintenant capable de distinguer entre deux énantiomères, grâce à la détection du niveau de polarisation de l’émission ECL résultante. La combinaison entre ECL et systèmes confinés est présentée dans la deuxième partie de ma thèse. L’amplification du signal ECL par annihilation a été possible grâce à l’emploi d’un dispositif comprenant deux électrodes séparées par une distance de 100 nm. De plus, l’imagerie ECL a été utilisée pour mettre en évidence l’amélioration des performances de l’ECL bipolaire en utilisant une configuration comprenant un micropore planaire de 20 µm de long. Enfin, une nouvelle microscopie basée sur l’ECL a été développée. En perméabilisant la membrane cellulaire, l’ensemble de la cellule est visualisé par ECL. De plus, en se basant sur la distribution de l’émission ECL dans différents plans focaux, nous avons pu démontrer qu’une des caractéristiques fondamentales de cette nouvelle microscopie ECL est d’être confinée à la surface de l’électrode du fait des temps de vie limités des radicaux électro-générés. L’utilisation d’électrodes transparentes de nanotubes de carbone imprimés sur une lamelle de microscope a permis de réaliser l’imagerie ECL de cellules marquées aussi bien en réflexion qu’en transmission.

International audience; Nanoparticles (NPs) based electrochemical devices are generating a growing interest and optical microscopy has recently proven to be a powerful tool to apprehend their electrochemical behavior. Through several striking examples, this review demonstrates how label-free optical imaging coupled to an electrochemical actuation can be used to probe operando the physical and electrochemical properties of single NPs, with high resolution and sensitivity and without additional emitters. Such an approach can be particularly relevant to establish clear structure-motion/reactivity relationships required to optimize NPs exploited as electrode materials.

In this work, we develop a Bottom-Up Electrochemical Fabrication process of Conjugated Ultrathin Layers with Tailored switchable properties. To do so, we use ultrathin layers of covalently grafted oligo(bisthienylbenzene) (oligo(BTB)) as a switchable organic electrodes and perform 3,4-ethylenedioxythiophene (EDOT) oxidation on such organic layer. Adding only 3 nm of EDOT moieties (5 to 6 units) completely changes the switching properties of the layer without changing the surface concentration of the grafted electroactive species. As a consequence, a range of new materials, with tunable interfacial properties, is created through this bottom-up electrochemical process. They consist of oligo(BTB)-oligo(EDOT) di-block oligomers of various relative length grafted covalently on the underlying electrode. As an important result these ultrathin films retain reversible redox on/off switching and their switching potential can be finely tuned between 0.6 and -0.3 V/SCE despite an overall thickness that remains below 11 nm.

It is now possible to reliably measure single molecule conductance in a wide variety of environments including organic liquids, ultrahigh vacuum, water, ionic liquids, and electrolytes. The most commonly used methods deploy scanning probe microscopes, mechanically formed break junctions, or lithographically formed nanogap contacts. Molecules are generally captured between a pair of facing electrodes, and the junction current response is measured as a function of bias voltage. Gating electrodes can also be added so that the electrostatic potential at the molecular bridge can be independently controlled by this third noncontacting electrode. This can also be achieved in an electrolytic environment using a four-electrode bipotentiostatic configuration, which allows independent electrode potential control of the two contacting electrodes. This is commonly realized using an electrochemical STM and enables single molecule electrical characterization as a function of electrode potential and redox state of the molecular bridge. This has emerged as a powerful tool in modern interfacial electrochemistry and nanoelectrochemistry for studying charge transport across single molecules as a function of electrode potential and the electrolytic environments. Such measurements are possible in electrolytes ranging from aqueous buffers to nonaqueous ionic liquids. In this Account, we illustrate a number of examples of single molecule electrical measurements under electrode potential control use a scanning tunneling microscope (STM) and demonstrate how these can help in the understanding of charge transport in single molecule junctions. Examples showing charge transport following phase coherent tunneling to incoherent charge hopping across redox active molecular bridges are shown. In the case of bipyridinium (or viologen) molecular wires, it is shown how electrochemical reduction leads to an increase of the single molecule conductance, which is controlled by the liquid electrochemical gating. This has been referred to as to a "single molecule transistor configuration" with the gate voltage being provided by the controllable potential achieved through the electrochemical double layer. It is shown how the electrolyte medium can control such gating, with ionic liquids providing more efficient gate coupling than aqueous electrolytes. Control of the conductance of viologen molecular wires can also be achieved by encapsulating the viologen redox moiety within a molecular cage, thereby controlling its immediate environment. Molecular conductance can also be gated through multiple redox states. This has been shown for the redox moiety pyrrolo-tetrathiafulvalene, which undergoes single molecule electrochemical transistor gating through three redox states in molecular junctions. Charge transport through this junction follows a two-step hopping mechanism, demonstrating the role of the redox center in electron transfer across the molecular bridge. Recent electrolyte gating studies of rigid, conjugated redox-active metal complexes with tailored terpyridine coordinating ligands and anchors are also presented. These aforementioned studies have all been performed with gold electrode contacts. The Account concludes with recent data showing that it is now possible to study single molecule electrochemical gating with nickel electrodes. This opens up new perspectives for studying interfacial charge transfer with a wide variety of other electrode materials including semiconductor electrodes and also points toward future opportunities for coupling molecular spintronics and nanoelectrochemistry.

For the field of bioelectronics to make an impact on healthcare, there is an urgent requirement for the development of "wireless" electronic systems to enable modulation of chemistry inside of cells. Herein we report on an intracellular wireless electronic communication system. This is based on modulating the electrochemistry on gold nanoparticles without the nanoparticles having any physical electrical connection to a power supply at relatively low externally applied potentials. The system is made functional by modifying water-soluble gold nanoparticles (ws-AuNPs) with a Zn(II) meso-tetrakis(4-carboxyphenyl)porphyrin sodium salt (Na-ZnTCPP). Na-ZnTCPP modified ws-AuNPs are taken up by cells and are shown to be noncytotoxic. It is demonstrated that the redox state of the Zn-porphyrin modified gold nanoparticles is controlled, and a fluorescent output can be used to measure this during the application of an external electrical potential. When the porphyrin modified nanoparticles were located intracellularly and external potentials were applied, the same effect was observed. This provides an attractive "wireless" approach to develop bioelectronic devices for modulating and sensing cellular behavior.

Summary: Sodium ion capacitors (SICs) are designed to deliver both high energy and power densities at low cost. Electric double-layer capacitive cathodes are typically used in these devices, but they lead to very limited capacity. Herein, we apply a pseudocapacitive layered ferric vanadate (Fe-V-O) as cathode to construct non-aqueous SICs with both high energy and power densities. The Fe-V-O nanosheets cathode displays remarkable rate capability and cycling stability. The pseudocapacitive sodium storage mechanism of Fe-V-O, with over 83% of total capacity from capacitive contribution, is confirmed by kinetics analysis and ex situ characterizations. The capacitive-adsorption mechanism of hard carbon (HC) anode is demonstrated, and it delivers excellent rate capability. Based on as-synthesized materials, the assembled HC//Fe-V-O SIC delivers a maximum energy density of 194 Wh kg−1 and power density of 3,942 W kg−1. Our work highlights the advantages of pseudocapacitive cathodes for achieving both high energy and power densities in sodium storage devices. : Electrochemical Energy Storage; Energy Materials; Nanoelectrochemistry Subject Areas: Electrochemical Energy Storage, Energy Materials, Nanoelectrochemistry

We report striking time-dependent ion transport characteristics at nanoscale interfaces in current–potential (I–V) measurements and theoretical analyses., The dynamics of ion transport at nanostructured substrate–solution interfaces play vital roles in high-density energy conversion, stochastic chemical sensing and biosensing, membrane separation, nanofluidics and fundamental nanoelectrochemistry. Further advancements in these applications require a fundamental understanding of ion transport at nanoscale interfaces. The understanding of the dynamic or transient transport, and the key physical process involved, is limited, which contrasts sharply with widely studied steady-state ion transport features at atomic and nanometer scale interfaces. Here we report striking time-dependent ion transport characteristics at nanoscale interfaces in current–potential (I–V) measurements and theoretical analyses. First, a unique non-zero I–V cross-point and pinched I–V curves are established as signatures to characterize the dynamics of ion transport through individual conical nanopipettes. Second, ion transport against a concentration gradient is regulated by applied and surface electrical fields. The concept of ion pumping or separation is demonstrated via the selective ion transport against concentration gradients through individual nanopipettes. Third, this dynamic ion transport process under a predefined salinity gradient is discussed in the context of nanoscale energy conversion in supercapacitor type charging–discharging, as well as chemical and electrical energy conversion. The analysis of the emerging current–potential features establishes the urgently needed physical foundation for energy conversion employing ordered nanostructures. The elucidated mechanism and established methodology can be generalized into broadly-defined nanoporous materials and devices for improved energy, separation and sensing applications.