Bubbles are known to influence energy and mass transfer in gas evolving electrodes. However, we lack a detailed understanding on the intricate dependencies between bubble evolution processes and electrochemical phenomena.This review discusses our current knowledge on the effects of bubbles on electrochemical systems with the aim to identify opportunities and motivate future research in this area. We first provide a base background on the physics of bubble evolution as it relates to electrochemical processes. Then we outline how bubbles affect energy efficiency of electrode processes, detailing the bubble-induced impacts on activation, ohmic and concentration overpotentials.Lastly, we describe different strategies to mitigate losses and how to exploit bubbles to enhance electrochemical reactions. Context & ScaleElectrochemical reactors will play a key role in the electrification of the chemical industry and can enable the integration of renewable electricity sources with chemical manufacturing. Most large-scale industrial electrochemical processes, including chloro-alkali and aluminum production, involve gas evolving electrodes. The evolution of bubbles at the surface of redox reaction sites often lead to the reduction of the active electrode area, the increase of ohmic resistance in the electrolyte and the formation of undesirable concentration gradients. All of these effects result in energy losses which reduce the efficiency of electrochemical systems. This review synthesizes our current understanding on the relationship between bubble evolution and energy losses in electrochemical reactors. By presenting a thorough account on the state of the research in this area, we aim to provide a common ground for the research community to improve our understanding on the complex processes involved in multiphase electrochemical systems. Increasing our knowledge on the relationship between bubbles and electrochemistry will lead to new strategies to mitigate and exploit bubble-induced phenomena leading to design guidelines for high-performing electrochemical reactors.

This study provides insights into structure-property relationships of Nafion membranes swollen with organic sorbates, revealing correlations between sorbate polarity, ionomer domain structure, and ionic conductivity.Swelling, nanostructure, and ionic conductivity of Nafion in the presence of short-chain alcohols and alkanes was studied by infrared spectroscopy, X-ray scattering, and voltammetry. Nafion equilibrated with alkanes exhibited negligible uptake and nanoswelling, while alcohols induced nanoscopic-to macroscopic-swelling ratios that increased with alcohol polarity. In mixed-sorbate environments including organics and water, alcohols preserved the overall ionomer domain structure but altered the matrix to enable higher sorbate uptake. Alkanes did not demonstrably alter the hydrated nanostructure or conductivity. Identifying the impacts of organic sorbates on structure-property relationships in ionomers such as Nafion is imperative as membrane-based electrochemical devices find applications in emerging areas ranging from organic fuel cells to the synthesis of fuels and chemicals. File list (2) download file view on ChemRxiv Nafion Solvent draft-v7.docx (4.23 MiB) download file view on ChemRxiv SI-v2.docx (1.10 MiB)

Autonomous chemical process development and optimization methods use algorithms to explore the operating parameter space based on feedback from experimentally determined exit stream compositions. Measuring the compositions of multicomponent streams...

Green hydrogen production via water electrolysis can play a significant role in decarbonizing energy and multiple industrial processes. In this electrolysis process, water molecules are oxidized to produce oxygen in the anode, while protons are reduced to hydrogen in the cathode. Both of these electrochemical products are gaseous species that lead to bubble nucleation at the surface of electrodes. This bubble evolution phenomena results in substantial energy losses due to the blockage of ion conduction pathways, reduction of the available electrocatalytic area, and disruption of concentration gradients at the electrode–electrolyte interface. In this study, we implement a microfluidic water electrolyzer to elucidate the impacts of electrochemical reaction conditions and convective flows on bubble-induced overpotential losses. We show that high Reynolds (Re) number flows (i.e., Re > 20) mitigate the formation of large bubbles, resulting in minimal bubble-induced overpotential losses. For flows with smaller Re, periodic evolution of large bubbles leads to overpotential fluctuations on the order of ∼100 mV. Furthermore, to understand the impact of bubbles on concentration overpotentials, we use fluorescence microscopy and pH sensitive dyes to capture the spatiotemporal dynamics of pH gradients and correlate the strength and shape of these gradients to the applied potential and convective forces. We find that the presence of large bubbles at low Re can result in more severe concentration gradients that are affected by the hydrodynamic flows around the bubbles. The findings presented in this work provide insights into the effects of convective flows in mitigating bubble-induced overpotential losses.

ResumenLa configuración estructural y estratigráfica de la secuencia pre-Aptiense en la Cuenca del Oriente, se deriva del desarrollo de dos eventos tectónicos superpuestos. El primero pertenece a la aparición de un régimen extensional durante el Jurásico Medio-Valanginiense, representado por depresiones de hemi-graben y graben que constituyen los tres dominios tectónicos de la cuenca. En el graben Sacha-Shushufindi, el relleno sedimentario son representados por sedimentos volcaniclásticos continentales de la Formación Chapiza, parcialmente contemporáneos con la actividad del arco volcánico Jurásico Misahuallí (Tschopp, 1953), que se desarrolla en el margen occidental de la cuenca. Probablemente, la extensión está vinculada a los períodos de retroceso de un slab que se evidencia por el desarrollo de una zona de subducción y un control extensional en la región de arco posterior. El segundo episodio representa la inversión de fallas normales a inversas producidas a partir de una tectónica de compresión, lo que resulta en mega estructuras positivas (Anticlines Sacha y Shushufindi). L a e dad de l a i nversión p odría estar relacionada c on l a é poca volcánica Hauteriviense de la Formación Chapiza Superior o Miembro Yaupi, que se desarrollan en una sola operación contra la estructura invertida de Sacha. AbstractThe structural and stratigraphic configuration of the pre-Aptian sequence in the Oriente Basin, is derived from the development of two overlapping tectonic events. The first, belongs to the apperarance of an extensional regime during the Middle Jurassic-Valanginian, represented by half-graben and graben depressions that constitute the three tectonic domains of the basin. At the Sacha-Shushufindi graben the sedimentary filling are continental volcaniclastic sediments of the Chapiza Formation, partially contemporaneous whit the activity of the Jurassic Misahuallí volcanic arc (Tschopp, 1953), that is developed in the western margin of the basin. Probably the extension is linked to salb roll-back periods by the development of a subduction zone and an extensional control in the back-arc region. The second episode represents the inversion of normal to inverse faults produced from a compressive tectonics, which results in mega positive structures (Sacha and Shushufindi An ticlines). The age of the inversion could be related to the Hauterivian volcanic of the Upper Chapiza Formation or Yaupi Member, which are developed in onlap against the Sacha inverted structure.Structural and stratigraphic architecture of the pre-aptian sequence of the oriente basin ARTÍCULO ORIGINAL Recibido