Correction to Vaterite Dissolution: Mechanism and Kinetics.

[This corrects the article DOI: 10.1021/acs.jpcc.

Removing 65 Years of Approximation in Rotating Ring Disk Electrode Theory with Physics-Informed Neural Networks.

The rotating Ring Disk Electrode (RRDE), since its introduction in 1959 by Frumkin and Nekrasov, has become indispensable with diverse applications in electrochemistry, catalysis, and material science. The collection efficiency () is an important parameter extracted from the ring and disk currents of the RRDE, providing valuable information about reaction mechanism, kinetics, and pathways. The theoretical prediction of is a challenging task: requiring solution of the complete convective diffusion mass transport equation with complex velocity profiles.

Double Electrode Experiments Reveal the Processes Occurring at PEDOT-Coated Neural Electrode Arrays.

Neural electrodes have recently been developed with surface modifications of conductive polymers, in particular poly(3,4-ethylenedioxythiophene) (PEDOT), and extensively studied for their roles in recording and stimulation, aiming to improve their biocompatibility. In this work, the implications for the design of practical neural sensors are clarified, and systematic procedures for their preparation are reported. In particular, this study introduces the use of in vitro double electrode experiments to mimic the responses of neural electrodes with a focus on signal-recording electrodes modified with PEDOT.

The solubility product controls the rate of calcite dissolution in pure water and seawater.

Quantification of calcite dissolution underpins climate and oceanographic modelling. We report the factors controlling the rate at which individual crystals of calcite dissolved. Clear, generic criteria based on the change of calcite particle dimensions measured microscopically with time are established to indicate if dissolution occurs under kinetic or thermodynamic control.

Discovering Electrochemistry with an Electrochemistry-Informed Neural Network (ECINN).

Machine learning is increasingly integrated into chemistry research by guiding experimental procedures, correlating structure and function, interpreting large experimental datasets, to distill scientific insights that might be challenging with traditional methods. Such applications, however, largely focus on gaining insights via big data and/or big computation, while neglecting the valuable chemical prior knowledge dwelling in chemists' minds. In this paper, we introduce an Electrochemistry-Informed Neural Network (ECINN) by explicitly embedding electrochemistry priors including the Butler-Volmer (BV), Nernst and diffusion equations on the backbone of neural networks for multi-task discovery of electrochemistry parameters.

Rotating Disk Electrodes beyond the Levich Approximation: Physics-Informed Neural Networks Reveal and Quantify Edge Effects.

Physics-informed neural networks are used to characterize the mass transport to the rotating disk electrode (RDE), the most widely employed hydrodynamic electrode in electroanalysis. The PINN approach was first quantitatively verified via 1D simulations under the Levich approximation for cyclic voltammetry and chronoamperometry, allowing comparison of the results with finite difference simulations and analytical equations. However, the Levich approximation is only accurate for high Schmidt numbers ( > 1000).

Calcifying Coccolithophore: An Evolutionary Advantage Against Extracellular Oxidative Damage.

The evolutionary advantages afforded by phytoplankton calcification remain enigmatic. In this work, fluoroelectrochemical experiments reveal that the presence of a CaCO shell of a naturally calcifying coccolithophore, Coccolithus braarudii, offers protection against extracellular oxidants as measured by the time required for the switch-off in their chlorophyll signal, compared to the deshelled equivalents, suggesting the shift toward calcification offers some advantages for survival in the surface of radical-rich seawater.

AI facilitated fluoro-electrochemical phytoplankton classification.

Marine phytoplankton is extremely diverse. Counting and characterising phytoplankton is essential for understanding climate change and ocean health not least since phytoplankton extensively biomineralize carbon dioxide whilst generating 50% of the planet's oxygen. We report the use of fluoro-electrochemical microscopy to distinguish different taxonomies of phytoplankton by the quenching of their chlorophyll-a fluorescence using chemical species oxidatively electrogenerated in seawater.

Kinetics of Lipophilic Pesticide Uptake by Living Maize.

We report the uptake of a lipophilic fungicide into the cuticle of living leaves of young maize from droplets of a suspension concentrate. The action of a "coffee-ring" effect is demonstrated during fungicide formulation drying, and the fungicide particle distribution is quantified. We develop a simple, two-dimensional model of uptake leading to a "reservoir" of cuticular fungicide.

Single Calcite Particle Dissolution Kinetics: Revealing the Influence of Mass Transport.

Calcite dissolution kinetics at the single particle scale are determined. It is demonstrated that at high undersaturation and in the absence of inhibitors the particulate mineral dissolution rate is controlled by a saturated calcite surface in local equilibrium with dissolved Ca and CO coupled with rate determining diffusive transport of the ions away from the surface. Previous work is revisited and inconsistencies arising from the assumption of a surface-controlled reaction are highlighted.

Rapid Opto-electrochemical Differentiation of Marine Phytoplankton.

The use of electro-generated oxidants in seawater facilitates the discrimination of different plankton groups via monitoring the decay in real time of their chlorophyll-a (chl-a) fluorescence signals following potentiostatic initiation of electrolysis in their vicinity (Yang M.Chem. Sci.

Reversible Cyclic Voltammetry and Non-Unity Stoichiometry: The Ag/AgBr/Br Redox Couple.

The voltammetry of electrochemically reversible couples in which a soluble reactant is converted into an insoluble product is investigated computationally via simulation and, in the context of the Ag/AgBr/Brredox couple, experimentally. The voltammetric waveshape is characterized and, when analyzed via apparent transfer coefficient analysis, shown to give rise to apparent transfer coefficients very considerably in excess of unity, leading to the generic insight for the characterization of electrode reactions involving solution and solid phase reactants.

Electrode kinetics from a single experiment: multi-amplitude analysis in square-wave chronoamperometry.

The recently introduced technique of square-wave chronoamperometry (SWCA) is studied under conditions of progressively increasing height of potential pulses (square-wave amplitude) within a single experiment. In multi-amplitude square-wave chronoamperometry (MA-SWCA) a potential modulation consisting of square-wave forward and reverse potential pulses is imposed on a constant mid-potential; the amplitude of pulses increases progressively during the experiment. This allows the fast and reliable estimation of kinetic parameters at a constant pulse frequency in a single experiment, based on the resulting feature known as the amplitude-based quasireversible maximum.

Voltammetry of Carbon Nanotubes and the Limitations of Particle-Modified Electrodes: Are Carbon Nanotubes Electrocatalytic?

The use of carbon nanotubes (CNTs) as electrocatalysts is summarized; the limitations of using voltammetry based on CNT-modified electrodes is explained; and the role of mass transport, as well as electrode kinetics, with respect to dictating the voltammetric responses is discussed. The use of single-entity electrochemistry to at least complement, if not replace, ensemble voltammetry is advocated along with other caveats, notably purity, with respect to CNT voltammetry.

Quantifying the Extent of Calcification of a Coccolithophore Using a Coulter Counter.

Although, in principle, the Coulter Counter technique yields an absolute measure of particle volume, in practice, calibration is near-universally employed. For regularly shaped and non-biological samples, the use of latex beads for calibration can provide sufficient accuracy. However, this is not the case with particles encased in biogenically formed calcite.

Calcium Carbonate Dissolution from the Laboratory to the Ocean: Kinetics and Mechanism.

The ultimate fate, over the course of millennia, of nearly all of the carbon dioxide formed by humankind is for it to react with calcium carbonate in the world's oceans. Although, this reaction is of global relevance, aspects of the calcite dissolution reaction remain poorly described with apparent contradictions present throughout the expansive literature. In this perspective we aim to evidence how a lack of appreciation of the role of mass-transport may have hampered developments in this area.

Electrochemical Heterogeneity at the Nanoscale: Diffusion to Partially Active Nanocubes.

How does heterogeneity in activity affect the response of nanoparticles? This problem is key to studying the structure-activity relationship of new electrocatalytic materials. However, addressing this problem theoretically and to a high degree of accuracy requires the use of three-dimensional electrochemical simulations that have, until recently, been challenging to undertake. To start to probe this question, we investigate how the diffusion-limited flux to a cube changes as a function of the number of active faces.

Modeling Transcuticular Uptake from Particle-Based Formulations of Lipophilic Products.

We report a mathematical model for the uptake of lipophilic agrochemicals from dispersed spherical particles within a formulation droplet across the leaf cuticle. Two potential uptake pathways are identified: direct uptake via physical contact between the cuticle and particle and indirect uptake via initial release of material into the formulation droplet followed by partition across the cuticle-formulation interface. Numerical simulation is performed to investigate the relevance of the particle-cuticle contact angle, the release kinetics of the particle, and the particle size relative to the cuticle thickness.

Understanding Carbon Nanotube Voltammetry: Distinguishing Adsorptive and Thin Layer Effects via "Single-Entity" Electrochemistry.

Cyclic voltammetry of ensembles of nanotube-modified electrodes fails to distinguish between signals from electroactive material adsorbed on the tubes from those due to a thin-layer response of analyte material occluded in the pores of the ensemble. We demonstrate that the distinction can be clearly made by combining cyclic voltammetry with single-entity measurements and provide proof of concept for the case of b-MWCNTs and the oxidation of 4-hexylresorcinol (HR), where the increased signals seen at the modified electrode are concluded to arise from thin-layer diffusion and not adsorptive effects. The physical insights are generic to porous, conductive composites.

Anodic stripping voltammetry using underpotential deposition allows sub 10 ppb measurement of Total As and As(III) in water.

We report a sensitive stripping voltammetry method for the detection of total arsenic in aqueous solution using gold macroelectrodes based on the underpotential deposition (UPD) of As ad-atoms. The detection of As(III) or total arsenic can be selectively made by changing deposition potential, with detection of the total As content by deposition at high potential (- 1.3 V) and of As(III) by deposition at lower potential (- 0.

A Calibration-Free pH Sensor Using an In-Situ Modified Ir Electrode for Bespoke Application in Seawater.

A bespoke calibration-free pH sensor using an in situ modified Ir electrode for applications in seawater is reported. The electrochemical behaviour of an iridium wire in air-saturated synthetic seawater was studied and the formation of pH-sensitive surface layers was observed that featured three pH-sensitive redox couples, Ir(III/IV), IrOxOI-/IrOxOII-H, and H/H, where H is adsorbed hydrogen deposited at underpotential conditions. The amperometric properties of the electrochemically activated Ir wire were investigated using linear sweep voltammetry first, followed, second, by square wave voltammetry with the formation conditions in seawater for the optimal pH sensitivity of the redox couples identified.

Oxygen Reduction Reaction at Single Entity Multiwalled Carbon Nanotubes.

The electrocatalysis of the oxygen reduction reaction (ORR) in aqueous base (0.1 M KOH) by multiwalled carbon nanotubes (MWCNTs) is studied at the single entity level. Electroactive surface functionality is shown to facilitate significant electrocatalysis leading to peroxide formation which is seen to occur at lower potentials as compared to the voltammetric responses obtained at bare carbon macroelectrodes and at such electrodes modified with layers of carbon nanotubes.

The application of physics-informed neural networks to hydrodynamic voltammetry.

Electrochemical problems are widely studied in flowing systems since the latter offer improved sensitivity notably for electro-analysis and the possibility of steady-state measurements for fundamental studies even with macro-electrodes. We report the exploratory use of Physics-Informed Neural Networks (PINNs) as potentially simpler, and easier way to implement alternatives to finite difference or finite element simulations to predict the effect of flow and electrode geometry on the currents observed in channel electrodes where the flow is constrained to a rectangular duct with the electrode embedded flush with the wall of the cell. Several problems are addressed including the evaluation of the transport limited current at a micro channel electrode, the transport of material between two adjacent electrodes in a channel flow and the response of an electrode where the electrode reaction follows a preceding chemical reaction.

Experimental Voltammetry Analyzed Using Artificial Intelligence: Thermodynamics and Kinetics of the Dissociation of Acetic Acid in Aqueous Solution.

Artificial intelligence (AI) is used to quantitatively analyze the voltammetry of the reduction of acetic acid in aqueous solution generating thermodynamic and kinetic data. Specifically, the variation of the steady-state current for the reduction of protons at a platinum microelectrode as a function of the bulk concentration of acetic acid is recorded and analyzed giving data in close agreement with independent measurements, provided the AI is trained with accurate and precise knowledge of diffusion coefficients of acetic acid, acetate ions, and H.

Electro-oxidation of amino-functionalized multiwalled carbon nanotubes.

We report the electrochemistry of amino-functionalized multiwalled carbon nanotubes (MWCNTs-NH) in the pH range from 0.3 to 6.4 using quantitative cyclic voltammetry (CV) and single entity electrochemistry measurements, making comparison with non-functionalized MWCNTs.