Molecular Electrochemistry Research Articles

Molecular Electrocatalysis under Finite Diffusive Mass Transport Conditions. An Analytical Approach

AbstractMolecular electrocatalysis has emerged as a crucial branch of molecular electrochemistry, finding applications across various fields such as energy generation, electroanalysis, and electrosynthesis. In recent years, the study of these processes within confined spatial domains, has been increasingly frequent. However, a significant gap exists in the theoretical understanding of the interplay between different kinetics (redox and chemical) and mass transport under these conditions, and how their combined effects influence the electrochemical response. As a first step to address the aforementioned gap, this manuscript presents a theoretical expression for the current‐potential‐time response of a catalytic reaction occurring under finite diffusive conditions. The results indicate that, when the chemical kinetics is not fast, there are significant differences in electrochemical responses due to mass transport influences. Thus, in the case of bounded finite diffusion, a loss of efficiency in the process is observed, resulting in lower currents compared to those corresponding to semi‐infinite diffusive conditions. The validity of well‐known methods, such as the analysis of the current plateau or the foot of the wave under stationary conditions, is discussed. Experimental validation of these results is also provided through the study of the oxidation of Solketal mediated by the oxidation of TEMPO radical.

Nickel-Catalyzed Intramolecular Hydrosilylation of Alkynes: Embracing Conventional and Electrochemical Routes.

Nickel-catalyzed intramolecular hydrosilylation can be efficiently achieved with high regio- and stereoselectivities through two distinct methodologies. The first approach utilizes a conventional method, involving the reduction of nickel salt (NiBr2-2,2'-bipyridine) using manganese metal. The second method employs a one-step electrochemical reaction, utilizing the sacrificial anode process and NiBr2bipy catalysis. Both methods yield silylated heterocycles in good to high yields through a syn-exo-dig cyclization process. Control experiments and molecular electrochemistry (cyclic voltammetry) provided further insights into the reaction mechanism.

Autonomous closed-loop mechanistic investigation of molecular electrochemistry via automation

Electrochemical research often requires stringent combinations of experimental parameters that are demanding to manually locate. Recent advances in automated instrumentation and machine-learning algorithms unlock the possibility for accelerated studies of electrochemical fundamentals via high-throughput, online decision-making. Here we report an autonomous electrochemical platform that implements an adaptive, closed-loop workflow for mechanistic investigation of molecular electrochemistry. As a proof-of-concept, this platform autonomously identifies and investigates an EC mechanism, an interfacial electron transfer (E step) followed by a solution reaction (C step), for cobalt tetraphenylporphyrin exposed to a library of organohalide electrophiles. The generally applicable workflow accurately discerns the EC mechanism’s presence amid negative controls and outliers, adaptively designs desired experimental conditions, and quantitatively extracts kinetic information of the C step spanning over 7 orders of magnitude, from which mechanistic insights into oxidative addition pathways are gained. This work opens opportunities for autonomous mechanistic discoveries in self-driving electrochemistry laboratories without manual intervention.

Electrifying Carbon Capture by Developing Nanomaterials at the Interface of Molecular and Process Engineering.

ConspectusCarbon capture is an indispensable step toward closing the anthropogenic carbon cycle. However, the large-scale implementation of conventional thermochemical carbon capture technologies is hindered by their low energy efficiency, limited sorbent stability, and complexity in infrastructure integration. A mechanistically different alternative, commonly known as electrochemically mediated carbon capture (EMCC), has garnered increasing research traction over the past few years and relies on electrochemical stimuli instead of thermal or pressure swings for the capture and release of carbon dioxide (CO2). Compared to conventional methods, EMCC can be operated under mild conditions driven by intermittent renewable energy sources and has a flexible design to meet the multiscale demands of carbon capture, offering a potentially sustainable, energy-efficient, and cost-effective solution to CO2 concentration from dilute mixtures or the ambient environment.Nanomaterials have played a crucial role in carbon capture research. For instance, nanoporous materials can provide increased free volumes, surface areas, and active sites for carbon capture through physical or chemical adsorption from the gaseous phase. In contrast, EMCC relies on chemical absorption via acid-base interactions using solubilized CO2 in electrolytes. Therefore, most EMCC sorbents and mediators explored so far have been developed as molecules rather than nanomaterials. In recent years, our team has been focusing on electrifying the carbon capture processes at the molecular, materials, and process levels. We seek to address the most pressing issues associated with EMCC, either in fixed-bed or flow systems, that prevent their practical use. These issues include parasitic reactions with molecular oxygen, insufficient electrode capacity utilization, sorbent crossover, etc. To address these problems, there is an urgent need to develop rationally designed nanomaterials at the interface of molecular electrochemistry and device engineering. This Account provides an overview of recent progress on developing new chemistries and engineering batch/continuous processes for EMCC. We discuss the limitations of current EMCC technology and emphasize why nanomaterials are critical for electrifying carbon capture. First, we introduce the design principles for EMCC sorbents based on redox-active organic CO2 carriers and discuss metrics for their performance evaluation. Second, we showcase how molecular design can tackle problems of sorbent solubility, oxygen stability, and electrolyte compatibility in EMCC. Third, we discuss the early results of nanomaterials as solid sorbents in fixed-bed systems, nonswelling membranes for flow systems, and high-surface-area gas-liquid contactors. Finally, building on the foundation we established through our prior work, we offer perspectives on future directions for nanomaterials to help address the challenges in EMCC.

Electrochemical lossy mode resonance for detection of manganese ions

In this work we propose electrochemical lossy mode resonance (eLMR) as a powerful method for the detection of manganese (Mn) ions. The sensor is based on a simple planar waveguide (sodalime glass coverslip) coated with a thin layer of indium tin oxide (ITO) to obtain an optical resonance effect. Simultaneously, the ITO layer served as the working electrode in the cathodic stripping voltammetry (CSV) of Mn. The eLMR sensor is capable of simultaneously performing electrochemical (EC) and optical measurements, specifically lossy mode resonance (LMR), to monitor the growth of the adsorbed Mn layer on the ITO electrode and the electrochemically modulated diffusion layer. For Mn2+ ions, a limit of detection (LoD) of 1.26 ppb has been demonstrated using the EC method, whereas the optical method exhibited a LoD of 67.76 ppb. The results obtained indicate significant potential for application in molecular electrochemistry and studies focused on electrified interfaces.

On the evaluation of metal-corrosion inhibitor interactions by adsorption isotherms

Aiming to provide a wide perspective on metal-corrosion inhibition modeling the classical, modern and the so-called functional surface dependency adsorption isotherms were reviewed in order to clarify the working frameworks from either physical or chemical bonding continuous that best apply on various electro-chemical circumstances. This way, from the fashioned Langmuir isotherm, to its multi-scalar versions: the Freundlich isotherm to Temkin isotherm suitable for heterogeneous metal surfaces have been discussed. As such, the Flory - Huggins and Bockris - Swinkels isotherms allow the evaluation of the number of adsorbed water molecules replaced by one inhibitor molecule. The El-Awady isotherm is highlighting the number of layers of inhibitor molecules from the metal-solution interface. The Volmer isotherm is accounting for the possibility of adsorbate molecules to move from one adsorption site to another, in the absence of any lateral effects. The Dubinin-Radushkevich isotherm recently used in corrosion studies models the corrosion inhibitors via the adsorption energy Eads. All of presently considered isotherms may contribute in better characterizing nano-materials and surface processes via molecular electrochemistry and metal-ionic interaction on a hierarchical inclusive analytical framework.

Editorial overview: Organic and molecular electrochemistry section (2022)- electrosynthesis, electrocatalysis, electroanalysis, and molecular device

Editorial overview: Organic and molecular electrochemistry section (2022)- electrosynthesis, electrocatalysis, electroanalysis, and molecular device

Molecular electrochemistry. An overview of a cross-field: Electrochemistry/spectroscopic/theoretical integrated approach

This work summarizes state-of-the-art results achieved by combining, in a synergetic approach, the outcome obtained by electrochemical, spectroscopic and theoretical methods. A number of selected case-studies are reported, where such a synergetic approach enables to draw a complete picture of complex experimental systems. Finally, the relevance of the combined experimental and theoretical approach in solid-state electrochemistry, a territory amidst novel concepts in solid-state electronics, is recapped. • Electrochemical, spectroscopic (UV-Vis and vibrational: specroelectrochemistry SEC) and theoretical integrated approach. • Interface aspects between solid-state molecular electrochemistry and applications in the field of electronics. • A quite recent in situ Raman spectro-electrochemistry, μSEC Raman, is briefly surveyed. • Ab-initio Molecular Dynamics results to probe the reaction mechanism at a molecular level.

Electrochemical Mechanistic Analysis from Cyclic Voltammograms Based on Deep Learning.

For decades, employing cyclic voltammetry for mechanistic investigation has demanded manual inspection of voltammograms. Here, we report a deep-learning-based algorithm that automatically analyzes cyclic voltammograms and designates a probable electrochemical mechanism among five of the most common ones in homogeneous molecular electrochemistry. The reported algorithm will aid researchers' mechanistic analyses, utilize otherwise elusive features in voltammograms, and experimentally observe the gradual mechanism transitions encountered in electrochemistry. An automated voltammogram analysis will aid the analysis of complex electrochemical systems and promise autonomous high-throughput research in electrochemistry with minimal human interference.

A DFT and SERS study of synergistic roles of thermodynamics and kinetics during the electrocatalytic reduction of benzyl chloride at silver cathodes

The reductive cleavage of carbon-halogen bonds is one of the classical model systems of concerted versus non-concerted bond breaking electron transfer in molecular electrochemistry, but most studies did not consider the influence of adsorption of reaction intermediates on this phenomenon. We performed density functional theory (DFT) calculations to understand the electrochemical reduction of benzyl chloride at silver electrodes through predicting the surface adsorption effect of the reactant and of follow-up intermediates and analyzing the energetics of the overall dissociative electron transfer. The ensuing DFT calculations of surface-enhanced Raman spectroscopic (SERS) signals provided some key information for characterizing different surface species at different potentials at the molecular level. The most intense and broad spectral peak observed near 800 cm−1 in the electrochemical SERS was thus assigned to the CH2 wagging vibration closely associated with the co-adsorption of benzyl radical and chlorine. After the dissociation of the C-Cl benzyl chloride bond, the chloride anion adsorbs at the three-fold hollow site on silver electrodes, as indicated by a low vibrational frequency and a weak Raman signal. Conversely, the formed benzyl radical intermediate is found to adsorb at the top site with the characteristic vibrational frequency and strong Raman intensity. DFT calculations further confirmed that the kinetic effect underlying the electrocatalytic activity of silver electrodes is closely associated with the intrinsic energy barrier and the dissociative adsorption state of benzyl radical and chlorine on silver electrodes. Finally, we discuss the fundamental meaning of the kinetic rate constant of the first-step dissociative electron transfer for benzyl chloride on silver electrodes based on the different electron transfer models, indicating the synergistic roles of thermodynamics and kinetics.

Electrode‐supported and free‐standing bilayer lipid membranes: Formation and uses in molecular electrochemistry

AbstractThis short review is aimed at emphasizing the recent most prominent advances in the electrochemical investigation of the interactions of molecules with purely lipid bilayers. The first part which deals with electrode‐supported bilayer lipid membranes is articulated around the nature of electrode material with a focus on mercury to celebrate this special issue entitled “100 years from polarography to contemporary electrochemistry”. The second part is devoted to suspended or free‐standing bilayer lipid membranes that are robust models to investigate the passive transport of molecules. It is notably shown that molecular electrochemistry methods such as cyclic voltammetry, square wave voltammetry, amperometry, electrochemical impedance spectroscopy, or electrochemiluminescence are well‐adapted for the investigation of molecules/lipids interactions or the passive transport of molecules. These various techniques bring meaningful information notably on molecule/lipid interactions and transport modes across phospholipids.

Editorial overview: Organic and Molecular Electrochemistry (2021) Molecular electrochemistry—leading towards a carbon-free society

Editorial overview: Organic and Molecular Electrochemistry (2021) Molecular electrochemistry—leading towards a carbon-free society

In Memoriam of Jean‐Michel Savéant (1933–2020)

In Memoriam of Jean‐Michel Savéant (1933–2020)

Electrochemically induced electron transfer through molecular bridges

In this Opinion, we address some of the most important results obtained electrochemically in the area of intramolecular electron transfer (ET). The focus is on freely diffusing molecular systems in which a donor D and an acceptor A are separated by a well-defined bridge B (D-B-A systems). B can be a saturated spacer, a delocalized bridge, or the more complex peptide backbones. As to the acceptors, the selected examples encompass species that can be charged reversibly but a special emphasis is on ETs associated with the concerted cleavage of a sigma bond (dissociative ETs). Our goal is to showcase the essential background, the most appropriate electrochemical tools and methodologies, and a series of selected examples where molecular electrochemistry has provided invaluable information on the mechanisms of intramolecular ET and electronic communication through bridges.

Electrochemical Kinetic Study of [Cp*Rh] Complexes Supported by Bis(2-pyridyl)methane Ligands

Redox-induced reactions of organometallic complexes are ubiquitous in molecular electrochemistry and electrocatalysis research. However, a detailed knowledge of the kinetic parameters associated wi...

The strong potential of organic and molecular electrochemistry

The strong potential of organic and molecular electrochemistry

Preface—JES Focus Issue on Organic and Inorganic Molecular Electrochemistry

Preface—JES Focus Issue on Organic and Inorganic Molecular Electrochemistry

How molecular electrochemistry may shine light by designing electrofluorochromic compounds

Luminescence and electrochemistry have been intimately associated for a long time in the framework of electrochemiluminescence, where the electrochemical signal triggers light emission through a redox reaction. More recently another aspect of this coupling has been developed in electrofluorochromism, where electrochemistry is used to monitor photoluminescence processes. This review aims to highlight some molecular structures allowing emission properties to be tuned electrochemically through either redox-active luminophores or dyads in which a redox moiety can (de)activate the luminescence of a nearby unit. The working principle and main applications are also briefly discussed.

Quinone-based molecular electrochemistry and their contributions to medicinal chemistry: A look at the present and future

Abstract Molecular electrochemistry is closely linked to life sciences. Electron transfers play important roles in the bioactivation of redox-active drugs, in their metabolism/catabolism, and in their targeted release at precise destinations and frequently promote their ligand–target interactions. Altogether, this rich chemistry and the complexity of cellular environments and biocompartmentation often impede full investigation in situ of the whole chain of processes that sustain their therapeutic applications. Conversely, electrochemical ex situ investigations of drug properties and interactions performed in aqueous/aprotic/micellar/membrane/cell-mimetic media, combined with in vitro and in vivo data, are expected to provide extremely useful information on these processes. Therein, considering the ubiquitous case of quinones, we exemplified how such strategies allow controlling their beneficial or negative impact on cellular environments.

Self-Limited Grafting of Sub-Monolayers via Diels-Alder Reaction on Glassy Carbon Electrodes: An Electrochemical Insight.

The grafting of molecular monolayers is critical for the functionalization of surfaces. In molecular electrochemistry, the surface modification of electrodes and the way molecules are attached to the electrode surface are highly critical to electron transfers and electrochemical reactions. In this paper, sub-monolayers were covalently grafted onto glassy carbon (GC) electrodes via Diels–Alder cycloaddition with two soluble dienophiles, that is, propargyl bromide and ethynyl ferrocene. Such an approach is clean (no by-product, no catalyst/additive) and occurs under mild conditions by heating at 50 °C in toluene for few hours. The as-modified electrodes were thoroughly characterized by FTIR, XPS, and cyclic voltammetry using both millimetric GC electrodes and ultra-microelectrodes. Cyclic voltammetry gave access to surface coverage and clearly evidenced the covalent grafting of sub-monolayers. The grafting of functional sub-monolayers via Diels–Alder cycloaddition could be easily extended to various functionalities and carbons to prepare electrochemical sensors or electrocatalytic surfaces.