Enhanced Mass Transport Research Articles

Visualizing 4D Pore-Scale Gas Transport in Operating PEM Electrolyzers Using X-Ray Computed Tomography

Mass transport losses in polymer electrolyte membrane (PEM) electrolyzers are predominantly caused by the accumulation of oxygen gas within the pores of the porous transport layer (PTL), hindering reactant water delivery to reaction sites (1). To enhance mass transport and optimize electrolyzer performance, a comprehensive understanding of the mechanisms driving oxygen gas transport in the PTL is required. Numerous studies have utilized various imaging techniques - including optical, neutron, and X-ray radiography to elucidate the evolution and transport of oxygen gas in the multiphase flow regime during PEM electrolyzer operation (2). However, these techniques only capture two-dimensional (2D) images, resolving average gas distributions rather than a holistic pore-scale quantification. Few studies have used three-dimensional (3D) imaging to resolve the dynamic microscale distributions of oxygen gas in the PTL. Understanding the impact of key parameters affecting 3D oxygen gas transport, such as PTL morphology, will allow for tailored pore-scale material optimization for enhanced gas transport and improved performance of PEM electrolyzers.This study presents a non-destructive operando imaging approach using X-ray computed tomography (CT), enabling the visualization of transient 3D oxygen gas evolution and transport in the PTL of a PEM electrolyzer. Using state-of-the-art synchrotron X-rays, high temporal and spatial resolutions were achieved to capture the pore-scale formation and growth of oxygen gas pathways within the PTL at various operating conditions. Electrochemical performance of an in-house designed electrolyzer cell was also characterized while acquiring tomographic images to investigate the impact of observed transport mechanisms on performance. The methodology presented in this work showcases the capability of using X-ray CT to visualize the complex interfacial multiphase flow in PTLs. Findings from this study will provide valuable insight towards pore-scale material optimization of clean energy porous materials aimed at curtailing the costs of green hydrogen production.

Simultaneous heat and mass enhancement in mixed convective flow of power-law fluid using hybrid nanoparticles

Heat conduction and solute diffusion in fluid have been used for modeling of simultaneous heat and mass transportation in non-Newtonian fluid obeying the power-law rheological constitutive model. For thermal and mass transport enhancement, nanoparticles (Cu and AlO ) are dispersed in a mixture of water and ethylene glycol (EG). Mathematical models with correlations for physical properties are solved numerically via the finite element method (FEM). Wall shear stress on the surface of the pipe is enhanced when the intensity of the magnetic field rises. The wall shear stress reduces as positive buoyancy force increases. However, when the buoyancy force is negative , the wall shear stress increases. When the Grashof number is raised, the heat transfer rate at the pipe's surface tends to rise. Similarly, as the Schmidt number rises, the mass flux rises as well. Numerical outcomes have predicted that the motion of fluid becomes fast as the curvature parameter is increased. Favorable Buoyancy force increases the thickness of momentum boundary layer flow, whereas opposing Buoyancy force is responsible of a decrease in thickness of momentum boundary layer flow. Joule heating is responsible of an increase in the thermal boundary layer. Wall shear stress on the surface of the pipe is enhanced when the intensity of the magnetic field is increased.

Ambient electrochemical nitrogen fixation with aqueous V2O5 nanodots in a fluidized electrocatalysis system

We report a fluidized electrocatalysis system using V2O5 nanodots (V2O5 NDs) electrocatalyst dispersed in aqueous electrolyte for efficiently ambient electrocatalytic nitrogen reduction reaction (NRR) and nitrogen oxidation reaction (NOR). Compared to the conventional catalyst-immobilized approach, the V2O5 NDs catalyst with such fluidized approach exhibits superior bifunctional activities toward NRR and NOR, affording a high NH3 yield of 575.3 μg h−1 mg−1 and a faradaic efficiency (FE) of 28.7 % for NRR and a high NO3– yield of 1388.0 μg h−1 mg−1 and a FE of 12.6 % for NOR, respectively. The high bifunctional activities of V2O5 NDs are originated from the abundant oxygen vacancies as the active sites for the adsorption and activation of N2, affirmed by the DFT calculations. Furthermore, a theoretical model is built by the Monte Carlo simulation to confirm the important role of nanodots-incorporated fluidized approach in enhancement of mass transport and regeneration of active sites.

Electro‐kinetically enhanced mass transport of charged macro‐solutes through a microchannel with porous walls

AbstractElectrokinetics of the solute transport across the porous walls of micro channel is important from its practical application but less explored. Transport of the charged macro‐solutes across perm‐selective walls in a microchannel is investigated. The extended Nernst–Planck equation describes the charged macro‐solutes distribution in the mass transfer boundary layer over the porous wall. The transverse electromigration of the charged macro‐solute either augments or suppresses the concentration polarization and the permeation rate depending on the wall and solute surface potential (attractive or repelling). The wall potential is screened due to the electrical double layer interaction of the wall and charged solute. It is observed that the charged solute concentration over the channel wall enhances by two times in case of oppositely charged interactions (unlike solute and channel wall) compared to like charges. The findings of this study can facilitate understanding of electrokinetic based drug delivery and separation systems involving charged solutes.

Rapid and low-cost synthesis of ZSM-5 zeolite nanosheet assemblies for conversion of methanol to gasoline

Nanoscale zeolites with short diffusion paths show significantly enhanced mass transportation and easier accessibility for active sites in catalysis compared to microsized zeolites. However, the high cost and complex process involved in existing synthetic methods limit their application, so the development of a rapid and low-cost synthesis technology is of great significance. Herein, ZSM-5 zeolite nanosheet assemblies (Z5-NS-t) are rapidly synthesized by a microwave irradiation (MW) assisted seed-induced method using low-cost polyhexamethylene biguanide hydrochloride (PHMB) as a crystal growth inhibitor of the b-axis. The crystallization kinetics of the resultant materials and the formation mechanism of ZSM-5 zeolite nanosheets, as well as the influence of physico-chemical properties on their catalytic performance for the methanol-to-gasoline (MTG) reaction, are systematically investigated. Compared with the ZSM-5 nanoparticle assemblies (Z5-NP-60), which are synthesized by using the same method except for the addition of PHMB, Z5-NS-180 nanosheets with an approximate density of strong Brønsted acid sites exhibit excellent catalytic performance in the MTG reaction, giving rise to a high gasoline selectivity of 73.2% at a methanol conversion of 99.9% and a large amount of external carbon deposits. This is attributed to the synergy of accessibility of acid sites located in the pore intersections and the shorter diffusion paths for coke precursors out of the zeolite channel. This study provides an effective strategy for the synthesis of ZSM-5 nanosheets as catalysts for the MTG reaction, and it is expected to be applied for the synthesis of other zeolite nanosheets for important catalytic processes.

Numerical study of enhancement of heat and mass transport in the flow of power-law hybrid nano liquid under chemical reaction

Ethylene glycol with nanoparticles behaves as a non-Newtonian fluid and its rheology can be best described by the power-law rheological model. Further, hybrid nanoparticles are responsible for anti-oxidation, anti-evaporation, and anti-aging. Therefore, their dispersion in ethylene glycol is considered as these properties make the nanofluid stable. This article examines the impact of hybrid nanoparticles on the thermal enhancement of ethylene glycol as it is a worldwide used coolant. Moreover, simultaneous effects of temperature and concentration gradients, Joule heating, viscous dissipation, thermal radiations, and Bouncy forces are modeled and models are solved numerically using the finite element method (FEM). An increase in temperature due to composition gradient and an increase in concentration due to temperature gradient are observed. A significant increase in the Ohmic phenomenon with an increase in the intensity of the magnetic field is observed. The thermal performance of ethylene glycol is much improved due to simultaneous dispersion of hybrid nanoparticles relative to the thermal performance of ethylene glycol with mono nanoparticles only. Highlights The simultaneous dispersion of and in ethylene glycol is recommended to improve and optimize its thermal conductivity. Hence, and -ethylene glycol is a better coolant. The use of the Newtonian rheological model for ethylene glycol (when nanoparticles are dispersed in it) is an appropriate model. Therefore, to capture accurate information from numerical/theoretical analysis, the power-law constitutive model is suggested as it is an appropriate model and that is why is used in this study. -ethylene glycol is more heat generative than -ethylene glycol. This is the draw back with –-ethylene glycol when it is used as an engine coolant. The property of ––ethylene glycol to generate heat may cause over heating in the engine en used as a coolant. Thus, it is recommended to use non-heat generating fluids as base fluids.

A homogeneous multi-species transport model for porous TiO2 photoanode of photocatalytic fuel cell

Understanding the characteristics of multi species transport coupled with photoelectrochemical reaction occurring in the porous TiO2 photoanode of photocatalytic fuel cell remains a fundamental challenge. In this work, therefore, a theoretical model describing the hole/electron/organics/ion transport coupled with photoelectrochemical reaction is developed. Numerical results are in good agreement with experimental data. Besides, effects of various design and operation parameters on the photoanode performance are systematically studied. The photoanode performance improves with increasing the light intensity and decreasing the wavelength under the illumination from the substrate/photoanode interface due to more photo-excited electron-hole pairs and enhanced photon absorption, respectively. Increasing the supplied methanol and hydroxyl ion concentrations can boost the photoanode performance because of enhanced mass transport that accelerates photoelectrochemical reaction. When the photoanode is illuminated from the substrate/photoanode interface to the photoanode, increasing the photoanode thickness leads to an improvement in the photoanode performance because more photons are absorbed to photo-excite more electron-hole pairs. But too large thickness shows ignorable contribution to the photoanode performance. While for the illumination from the photoanode/electrolyte interface to the photoanode, the photoanode performance decreases with increasing the photoanode thickness due to increased electron transfer resistance. This work provides a deep understanding of various species transport characteristics coupled with photoelectrochemical reaction, which is useful for the design and operation of the photoanode.

Mass transport enhancement in direct formic acid fuel cell with a novel channel design

Direct formic acid fuel cells (DFAFCs) are a subtype of polymer electrolyte membrane fuel cells (PEMFCs) fed with liquid formic acid, which is an environmentally benign, low flammable chemical, with a higher volumetric energy density than compressed hydrogen, and can potentially be easily incorporated into the common gasoline infrastructure. Considering the laminar flow of formic acid in bipolar plate channels and the lower diffusivity of formic acid compared with gases, mass transport enhancement becomes crucial in improving the DFAFC performance. This study used computational fluid dynamics modeling to identify fuel starvation zones and uneven formic acid concentration distribution at the reaction surface in the DFAFC system with a standard channel design with serpentine arrangement. A new channel design (with right-angled trapezoidal baffles) was proposed based on the numerical simulations of hydrodynamic conditions at the anode side for various formic acid flow rates. This design enhances the uniformity in formic acid concentration distribution at the reaction surface and increases the convective fluxes between the neighboring channels in the serpentine arrangement. It was experimentally confirmed that the maximum power density of the DFAFC significantly increased for the proposed design compared with results of previous studies on hydrogen PEMFCs; an increase of 711.11 % was observed for the flow of 1 ml⋅min−1 of 9.0 M formic acid. This work underlines the advantage of CFD modeling in prototyping a new fuel cell channel design to enhance mass transport to the reaction surface and decrease concentration polarization.

Dynamic actuation enhances transport and extends therapeutic lifespan in an implantable drug delivery platform

Fibrous capsule (FC) formation, secondary to the foreign body response (FBR), impedes molecular transport and is detrimental to the long-term efficacy of implantable drug delivery devices, especially when tunable, temporal control is necessary. We report the development of an implantable mechanotherapeutic drug delivery platform to mitigate and overcome this host immune response using two distinct, yet synergistic soft robotic strategies. Firstly, daily intermittent actuation (cycling at 1 Hz for 5 minutes every 12 hours) preserves long-term, rapid delivery of a model drug (insulin) over 8 weeks of implantation, by mediating local immunomodulation of the cellular FBR and inducing multiphasic temporal FC changes. Secondly, actuation-mediated rapid release of therapy can enhance mass transport and therapeutic effect with tunable, temporal control. In a step towards clinical translation, we utilise a minimally invasive percutaneous approach to implant a scaled-up device in a human cadaveric model. Our soft actuatable platform has potential clinical utility for a variety of indications where transport is affected by fibrosis, such as the management of type 1 diabetes.

From Ensemble Electrochemistry to Nano‐Impact Electrochemistry: Altered Reaction Selectivity

AbstractSelective electrochemical production of valued chemicals is of significant importance but remains a great challenge in chemistry. Conventional approaches for enhancing reaction selectivity focus on the improvement of the catalysts themselves. In this work, we systematically studied the reaction kinetics and mass transport behavior of LaNiO3 nanocubes (LaNiO3 NCs) catalyzed hydrogen peroxide reduction reaction (HPRR) at ensemble and single nanoparticle levels using nano‐impact electrochemistry (NIE). We find that the selectivity of HPRR was altered at individual random‐walk nanoparticles as compared to their ensemble counterpart without changing the reaction kinetics, due to the significantly enhanced mass transport at single nanoparticles. This discovery offers the scope of new catalytic approaches for engineering electrochemical reactions in general.

From Ensemble Electrochemistry to Nano‐Impact Electrochemistry: Altered Reaction Selectivity

Selective electrochemical production of valued chemicals is of significant importance but remains a great challenge in chemistry. Conventional approaches for enhancing reaction selectivity focus on the improvement of the catalysts themselves. In this work, we systematically studied the reaction kinetics and mass transport behavior of LaNiO3 nanocubes (LaNiO3 NCs) catalyzed hydrogen peroxide reduction reaction (HPRR) at ensemble and single nanoparticle levels using nano-impact electrochemistry (NIE). We find that the selectivity of HPRR was altered at individual random-walk nanoparticles as compared to their ensemble counterpart without changing the reaction kinetics, due to the significantly enhanced mass transport at single nanoparticles. This discovery offers the scope of new catalytic approaches for engineering electrochemical reactions in general.

Life sciences discovery and technology highlights

Life sciences discovery and technology highlights

From ensemble electrochemistry to nanoparticle-impact electrochemistry: Altered reaction process and possible applications

Nanoparticle-impact electrochemistry (NIE) is an electroanalytical method based on the stochastic collisions of individual nanoparticles onto an inert ultramicroelectrode. In this article, we overview different characteristics of NIE-based reactions from their ensemble counterpart, that is, enhanced mass transport, intermittent working mode, and reduced reaction time scale. A particular interest is focused on the survey of the resulting changes in the reaction process regarding enhanced reaction efficiency and rate, altered selectivity, and improved catalyst stability. A summary of the application prospect of NIE is followed, and existing challenges are provided.

Development of Ti/TiOx foams for removal of organic pollutants from water: Influence of porous structure of Ti substrate

Ti/TiOx foams were obtained from plasma spraying technique using different porous Ti substrates. They were then applied for removal of organic pollutants from water by electro-oxidation. Effectiveness of these anodes was investigated using linear sweep voltammetry, probe molecules, quenchers and model pollutants. It was emphasized that surface morphology should allow for homogeneous coating of the surface in order to promote non-selective •OH-mediated oxidation of recalcitrant organic pollutants. Porous structure was also the key parameter for mass transport enhancement. Coarse roughness with characteristic scale that is larger than the diffusion boundary layer was more suitable in stirred-tank reactor. Flow-through application of Ti/TiOx foam further enhanced mass transport and allowed for 3.9- and 1.9-times enhancement of the degradation kinetic of paracetamol compared to Ti/TiOx plate and BDD plate, respectively. This work gives new insights on the role of porous structure of substrate for development and application of suitable electrodes in water treatment.

Protozeolite-Seeded Synthesis of Single-Crystalline Hierarchical Zeolites with Facet-Shaped Mesopores and Their Catalytic Application in Methanol-to-Propylene Conversion.

Hierarchical zeolites integrating intrinsic micropores with secondary meso- and/or macropores afford superior catalytic properties for enhanced mass transportation and more accessible active sites. The mesopores generated by using mesoporogens or framework etching are usually irregular with abundant defective sites and low hydrothermal stability. Here, using protozeolite nanoparticles as seeds, we succeeded in the synthesis of single-crystalline hierarchical ZSM-5 zeolites with hexagonal mesopores faceted by complete microporous frameworks. The protozeolites played a key role in the formation of faceted mesopores achieved via intraparticle ripening process. Thanks to the unique texture properties and more accessible acid sites at the open location, the as-prepared zeolites exhibited remarkedly long lifetime (18 h) and high propylene selectivity (52.7 %) with propylene/ethylene ratio of 3.64 in the methanol-to-propylene reaction (WHSV=12.5 h-1 ) compared to the counterparts.

Protozeolite‐Seeded Synthesis of Single‐Crystalline Hierarchical Zeolites with Facet‐Shaped Mesopores and Their Catalytic Application in Methanol‐to‐Propylene Conversion

AbstractHierarchical zeolites integrating intrinsic micropores with secondary meso‐ and/or macropores afford superior catalytic properties for enhanced mass transportation and more accessible active sites. The mesopores generated by using mesoporogens or framework etching are usually irregular with abundant defective sites and low hydrothermal stability. Here, using protozeolite nanoparticles as seeds, we succeeded in the synthesis of single‐crystalline hierarchical ZSM‐5 zeolites with hexagonal mesopores faceted by complete microporous frameworks. The protozeolites played a key role in the formation of faceted mesopores achieved via intraparticle ripening process. Thanks to the unique texture properties and more accessible acid sites at the open location, the as‐prepared zeolites exhibited remarkedly long lifetime (18 h) and high propylene selectivity (52.7 %) with propylene/ethylene ratio of 3.64 in the methanol‐to‐propylene reaction (WHSV=12.5 h−1) compared to the counterparts.

Tuning Electrode-Membrane Interface for Highly Efficient Polymer Electrolyte Membrane Fuel Cells

Polymer electrolyte membrane fuel cells (PEMFCs) are typically comprised of porous electrodes with randomly distributed mixtures of Pt/C catalyst and ionomer formed during the ink deposition process. The randomness of catalyst particles, ionomer films, and voids, create a non-ideal disordered electrode structure with high tortuosity. These intrinsic characteristics of conventional electrodes create significant challenges during PEMFC operation. These challenges include: 1) low catalyst utilization; 2) high O2 transport resistance to catalyst through the ionomer and pores of carbon support; and 3) limited electronic/protonic conductivities. To improve the performance of the PEMFC electrode, we have previously shown that structured electrodes based on a patterned membrane surface can increase the interfacial area between the electrode and the membrane, enhancing mass transport at high current densities, and augmenting its ionic conductivity.[1][2] In this work, we will present further optimization of these type of structured electrodes using free-standing architectures, reduced ionomer content, and new catalyst deposition processes. More importantly, these newly tuned electrode structures can improve the performance of PEMFCs by maximizing three-phase boundaries and optimizing the electron, proton, gas, and water transport paths. Acknowledgement: We gratefully acknowledge support from the Laboratory Directed Research & Development Program at Los Alamos National Laboratory. Reference: [1] S. K. Babu, R. Mukundan, D. A. Cullen, and J. S. Spendelow, “Co-Axial Nafion Nanowire Electrode.” ECS, Oct. 15, 2019.[2] S. K. Babu, J. S. Spendelow, and R. L. Borup, “Meso-Structured Array Electrode for Polymer Electrolyte Fuel Cells.” ECS, Oct. 03, 2017.

(Digital Presentation) Hydrophilic and Hydrophobic Carbon Nanotubes Combined into a Buckypaper As an Electrode for Li-O2 Batteries

With the decreasing costs of wind and solar power, these two energy sources are set to gain a sizeable share of the electricity market in the next years. To cope with the intermittency of these electricity sources, grid operators are required to develop new, inexpensive, and efficient energy storage facilities. One of the technologies being considered for such application is the Li-O2 battery, whose main advantage compared to state-of-the-art lithium-ion batteries is the prospect of higher energy density which might lead to decreased installation costs. Nevertheless, these batteries depend upon efficient mass transport of O2 inside the electrode to present suitable power density. In this work, a mix of hydrophilic and hydrophobic carbon nanotubes (CNT) was used to produce an O2 electrode with enhanced mass transport properties. Hydrophobic CNT were prepared via thermal treatment under Ar atmosphere at 850 °C for 2 h. Hydrophilic CNT were prepared via refluxing in 7 mol L-1 HNO3 solution for 4 h (~120 °C). Raman spectroscopy was used to analyze the quality of both types of CNT. Different proportions of hydrophobic and hydrophilic CNT were dispersed in solution with a surfactant using a probe sonicator. The solution was filtered using a 0.22 μm membrane and vacuum to produce a buckypaper. Batteries were assembled in a glove box using a Li electrode, a separator membrane (glass fiber), and the buckypaper as the O2 electrode. Galvanostatic discharge tests were carried out at different currents to analyze the impact of different qualities of CNT used in the making of the O2 electrode in the increasing demand for O2 in the battery at high currents. Scanning electron microscopy images were used to compare the morphology of the different electrodes before and after discharge. Results are expected to demonstrate a new method to increase the mass transport rates for O2 in Li-O2 batteries.The authors gratefully acknowledge the support from FAPESP (the Sao Paulo Research Foundation, Grant Numbers 2018/16663-2 and 2017/11958-1), Shell, the strategic importance of the support given by ANP (Brazil’s National Oil, Natural Gas and Biofuels Agency) through the R&D levy regulation, and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001.

(Invited) Redox Flow Battery Innovation

Flow battery innovations should offer significant improvements in performance, without compromising the durability / lifetime, and be cost-effective and scalable. The presentation will review some of the progress that has been made to enhance flow battery performance, and will discuss a number of recent innovations that aim to deliver these characteristics. These will include: Magnetic flowable electrodes applied in a polysulfide-iodide flow battery.Using flow through the current feeder to enhance mass transport and enable dendrite free zinc deposition in the zinc-iodide flow battery.Graphene modified membrane for enhanced power density. Flowable electrodes have emerged as a novel concept for high energy density batteries. To date, in most cases the flowable solid phase includes a redox active energy storage material, for example in zinc-nickel, sodium-sulfur, and lithium-sulfur systems [1-3]. In contrast, we have demonstrated the use of a carbon – magnetite nanocomposite which acts as an electrocatalyst but is not redox active [4,5]. This nanomaterial can be dispersed in the electrolyte and circulated through the battery to enhance the performance of a conventional static electrode. The magnetic characteristics of the nanocomposite can also be exploited, by using a magnetic field to assemble a high surface area electrode comprising a percolating network of the nanomaterial on the current feeder. The electrode also can be removed by releasing the magnetic field at the current feeder, and after being washed out of the cell the nanocomposite can be separated in a magnetic field. This enables replacement of the active electrode without the need to dismantle the cell.Zinc-iodide flow batteries offer high energy density due to the high aqueous solubility of the ZnI2. However, the power density that can be achieved is limited by potential for the dendritic growth of zinc deposits, and as zinc metal builds up in the cell the areal capacity is limited. We have found that by drawing some of the electrolyte through the current feeder, improved performance can be obtained [6]. This enables operation at higher power density and the denser uniform deposit should enable increased areal capacity.We attempted to reduce crossover in the all-vanadium redox flow battery by using a graphene modified nafion membrane. However, we found that the addition of the graphene reduced the losses in the battery and enabling a significant increase in the power density and discharge capacity. Currently we are working to optimize and scale up the membrane modification process, and to explore the mechanism of performance enhancement. References G. Zhu et al. (2020) High-energy and high-power Zn–Ni flow batteries with semi-solid electrodes. Sustainable Energy Fuels, 4, 4076-4085.Yang et al. (2018) Sodium–Sulfur Flow Battery for Low-Cost Electrical Storage. Advanced Energy Materials, 11, 1711991.Suo et al. (2015) Carbon cage encapsulating nano-cluster Li2S by ionic liquid polymerization and pyrolysis for high performance Li–S batteries. Nano Energy, 13, 467-473.Rahimi, A.M. Dehkordi, E.P.L. Roberts (2021) Magnetic nanofluidic electrolyte for enhancing the performance of polysulfide/iodide redox flow batteries. Electrochimica Acta, 309, 137687.Rahimi, A.M. Dehkordi, H. Gharibi, E.P.L. Roberts (2021) Novel Magnetic Flowable Electrode for Redox Flow Batteries: A Polysulfide/Iodide Case Study. Ind. Eng. Chem. Res., 60, 824-841.F. ShakeriHosseinabad et al. (2021) Influence of Flow Field Design on Zinc Deposition and Performance in a Zinc-Iodide Flow Battery. ACS Applied Mat. & Interfa

(Digital Presentation) Catalytic Interruption Mitigates Edge Effects in the Characterization of Heterogeneous, Insulating Nanoparticles

Single entity electrochemistry encompasses a broad collection of techniques that are used to detect and characterize single, freely diffusing analytes in solution1,2. A particular scheme in this field, “blocking” nanoimpacts, has expanded the scope of electrochemistry to the study of redox-inert materials. Here, as a particle adsorbs, it prevents charge exchange between the microelectrode with a freely diffusing electroactive redox mediator. The interpretation of these blocking results, however, is often complicated by “edge effects,” in which enhanced mass transport to the edges of microelectrodes leads to uneven current distributions3,4. To overcome this problem we introduce here the use of electrochemical amplification5. That is, we employ electrocatalytic amplification to drive a current increase, moving the rate limiting step in current generation away from the electrode surface, reducing the geometric impact of the electrode’s edges. Finite element simulations indicate that the rapid chemical kinetics introduced by this approach contributes to the amplification of the electronic signal to restore analytical precision and reliability detect and characterize the heterogeneity of nanoscale electro-inactive materials. Using this approach, which we have termed “electrocatalytic interruption,” we achieve significantly improved precision in the determination of particle size distributions.6 References Quinn, B. M.; van’t Hof, P. G.; Lemay, S. G. Time-Resolved Elec-trochemical Detection of Discrete Adsorption Events. J. Am. Chem. Soc. 2004, 126 (27), 8360–8361. https://doi.org/10.1021/ja0478577.Bard, A. J.; Faulkner, L. R. Electrochemical Methods: Fundamentals and Applications, 2nd ed.; Wiley: New York, 2001.Compton, R. G.; Banks, C. E. Understanding Voltammetry (Third Edition); World Scientific, 2018.Deng, Z.; Elattar, R.; Maroun, F.; Renault, C. In Situ Measurement of the Size Distribution and Concentration of Insulating Particles by Electrochemical Collision on Hemispherical Ultramicroelectrodes. Anal. Chem. 2018, 90 (21), 12923–12929. https://doi.org/10.1021/acs.analchem.8b03550.Bonezzi, J.; Boika, A. Deciphering the Magnitude of Current Steps in Electrochemical Blocking Collision Experiments and Its Implica-tions. Electrochimica Acta 2017, 236, 252–259. https://doi.org/10.1016/j.electacta.2017.03.090.Chung, J.; Hertler, P.; Plaxco, K.W.; Sepunaru, L. J. Am. Chem. Soc. 2021, https://doi.org/10.1021/jacs.1c04971. Figure 1