Understanding the electric double-layer from molecular dynamics
Applied electrochemistry plays a key role in many technologies, such as batteries, fuel cells, supercapacitors or solar cells. It is therefore at the core of many research programs all over the world. Yet, fundamental electrochemical investigations remain scarce. In particular, electrochemistry is among the fields for which the gap between theory and experiment is the largest. From the computational point of view, this is due to the difficulty of combining a realistic representation of the electrode electronic structure and of the electrolyte structure and dynamics. Over the past decade we have developed a classical molecular dynamics code that allows to simulate electrochemical cells . In a first step, the electrodes were modeled as perfectly screening metals with a constant applied potential between them. Recently, we have extended this approach in order to account for the degree of metallicity of the electrode (i.e. from semimetals to perfect conductors), using a semi-classical Thomas-Fermi model . In parallel, we have recently shown that it is possible to replace the constant applied potential method by using the finite field method to a system with a slab geometry .
These simulations have allowed us to gain strong insight on supercapacitors, which are electrochemical devices that store the charge at the electrode/electrolyte interface through reversible ion adsorption. From the comparison between graphite and nanoporous carbide-derived carbon electrodes, we have elucidated the microscopic mechanism at the origin of the increase of the capacitance enhancement in nanoporous carbons . More recently, we have focused on innovative electrolytes which involve small amounts of water dissolved in ionic liquids or organic solvents for applications in catalysis .
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