Electrotunable Kapitza Resistance at Electrode-Water Interfaces: The Importance of Electrode Metallicity.

The electrolyte-water-metal interface plays a vital role in electrochemical processes within nanocapacitors and in thermal management in nanoscale devices. Understanding the microscopic origins of thermal transport at these nanomaterial-fluid interfaces is crucial for advancing technologies in areas such as electrochemical energy storage and thermoplasmonics. Here, we use constant potential molecular dynamics simulations with fully dynamic electrodes to create steady heat fluxes in confined solutions that can respond to changes in the interfacial electrostatic environment at constant voltages. Our findings reveal that the Kapitza Resistance (KR) can be adjusted by applying voltage, altering ionic strength through the addition of salt, and, importantly, varying the metallicity of the electrodes. We show that the KR decreases with increasing electrode polarization, and salt concentrations above one molal further improve this voltage response, particularly with high effective metallicity (highly polarizable) electrodes. We attribute this response to a synergistic effect induced by the presence of the ions next to the electrodes and the reorientation of a nanometer-thick layer of water that solvates the electrodes. We present in our work a large-scale, nonequilibrium analysis that provides predictions of conditions necessary to tune the KR by considering experimentally relevant factors, including electrode metallicity, capacitance, and bias voltage.