Gas bubbles evolving on electrodes during water-electrolysis are blocking active reaction area, thus hindering mass transfer and raising Ohmic resistance. Unlike earlier models that prescribe a uniform current density on the wetted part of the electrode, we resolve the primary electric field, which allows the current density and the interfacial gas production to respond to the geometry of the electrode and the temporal evolution of the bubbles. Using three-dimensional geometrical volume-of-fluid (VOF) simulations with phase change in Basilisk, we examine the growth of single-bubbles on electrodes of different size and of multiple bubbles growing on arrays of catalytic electrode islands. The non-uniform current density and the associated Ohmic resistance significantly affect the growth dynamics. Unlike the case of a single bubble, the outer bubbles in case of electrode islands tend to drift outward during growth, thus delaying full electrode coverage and sustaining current. Footprint tracking and a theoretical analysis show that this drift is governed by the liquid advection driven by the growth of neighboring bubbles, scaling with their separation 1/d2, and modulated by the current-density asymmetry. These results show how electrode patterning and bubble spacing can be exploited to tailor the electric field distribution and reduce bubble-induced resistive losses during water electrolysis.
Understanding electric fields at electrode/electrolyte interfaces strongly influences electrocatalytic processes, yet their characterization at high current densities is often hindered by gas evolution that interferes with physical and electromagnetic probes. Herein, a custom electrochemical flow cell is presented that suppresses bubble nucleation by directing a high-velocity jet of electrolyte toward the electrode surface through an internal nozzle. This enables in situ Raman spectroscopy and determination of electric field strengths at electrode/electrolyte interfaces under elevated current densities relevant to electrolysis and fuel cell applications. Video analysis shows that electrolyte flow reduces hydrogen bubble coverage on platinum (Pt) thin-film electrodes by85–88%. This enables stable Raman measurements at current densities up to 25 mA cm⁻², nearly two orders of magnitude higher than in a stagnant cell. Under reduced bubble coverage, graphene supported on Pt and gold (Au) electrodes exhibits Stark shifts in the graphene G-band corresponding to electric field strengths up to 10⁶ V cm⁻¹. The measurements reveal substrate-dependent behavior, including a ≈0.4 V shift in the graphene charge-neutrality point for Graphene/Pt relative to Graphene/Au. We propose a framework in which substrate work function, proton adsorption, and electrostatic gating collectively govern potential-dependent graphene doping and interfacial electric field strength at the electrode/electrolyte interface
Electrochemical control of interfacial tension enables the extrusion of gallium-based liquid metals into high-surface-area nonspherical geometries relevant to electrocatalysis and hydrogen production. Here, liquid metal wires with diameters down to ∼500 nm are produced using quartz nanopipettes under moderate anodic polarization in an alkaline electrolyte. A morphology map identifies the operating window for continuous wire formation, distinct from droplet and blob regimes. The current response displays a previously unreported transient behavior, reaching three distinct maximum current density levels depending on the wire residence time. A model coupling the time-dependent liquid metal/electrolyte interfacial area with kinetic current density expressions accurately reproduces the transients and yields steady-state current densities, relaxation time constants, and an effective interfacial pseudocapacitance. Oxidation charge analysis reveals three distinct initial oxide growth rates, consistent with the characteristic residence time regimes, while kinetic analysis quantifies the corresponding oxide-induced overpotential losses. These results define a practical lower size limit of ∼500 nm for electrochemical liquid metal wire fabrication and establish a quantitative framework for their use in high-surface-area electrochemical reactors.
Electrochemical CO2 reduction reaction (eCO2RR) is a promising technology for carbon utilization, yet achieving high product selectivity and long-term stability remains a critical challenge. In this study, we investigated the performance and surface stability of Cu electrodes modified with Ag nanoparticles using a spray-coating method. While a bare Cu reference electrode exhibited an initial starting period dominated by hydrogen evolution before shifting toward hydrocarbon production after two hours, the Ag-spray-coated Cu electrode demonstrated immediate and stable catalytic activity. Electrode potential remained stable throughout the 12 h evaluation, in contrast to the negative shifts observed with the bare Cu electrode. Ambient pressure hard X-ray photoelectron spectroscopy (AP-HAXPES) revealed that while the bare Cu surface remained metallic, the Ag-spray-coated Cu surface existed as Cu2O during the reaction. The enhanced selectivity and stability are attributed to a spillover mechanism, where CO generated on the Ag nanoparticles migrates to adjacent Cu2O sites, inhibiting hydrogen evolution and facilitating efficient reduction to methane and ethylene from the onset of electrolysis. These findings demonstrate that surface modification via nanoparticle spray coating is a highly effective strategy for achieving selective and stable CO2 conversion on bimetallic catalysts.
To improve the performance of lithium-ion batteries, electrode particles have been designed in various morphologies, with the cylindrical structure being one of the more common electrode particle shapes. However, compared to conventional spherical particles, the advantages of cylindrical particles have not been fully understood. This study develops an electrochemical-mechanical coupled model for the two morphologies of electrode particles—cylindrical and spherical—to analyze and compare their diffusion-induced stresses and electrochemical performance. The results show that the stress levels in cylindrical electrode particles are safer than spherical electrode particles as the particle size decreases. Under potentiostatic operation or the same charge/discharge rates, cylindrical particles demonstrate inferior charge state of charge (SOC) compared to spherical particles at larger sizes, but the disparity diminishes progressively as particle dimensions decrease. Under the same charging/discharging current magnitudes, cylindrical electrode particles have a higher charge SOC, and that increases with a higher aspect ratio. Consequently, the design of slender cylindrical electrode particles offers a promising strategy to simultaneously improve both electrochemical performance and mechanical stability in lithium-ion batteries.
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