Taming the thermodiffusion of alkali halide solutions in silica nanopores

Thermal fields give rise to thermal coupling phenomena, such as mass and charge fluxes, which are useful in energy recovery applications and nanofluidic devices for pumping, mixing or desalination. Here we use state of the art non-equilibrium molecular simulations to quantify the thermodiffusion of alkali halide solutions, LiCl and NaCl, confined in silica nanopores, targeting diameters of the order of those found in mesoporous silica nanostructures. We show that nanoconfinement modifies the thermodiffusion behaviour of the solution. Under confinement conditions, the solutions become more thermophilic, with a preference to accumulate at hot sources, or thermoneutral, with the thermodiffusion being inhibited. Our work highlights the importance of nanoconfinement in thermodiffusion and outlines strategies to tune mass transport at the nanoscale, using thermal fields.