Multiphysics simulation explaining the behaviour of evaporation-driven nanoporous generators

Evaporation-induced electricity generation in porous nanomaterials has recently attracted considerable attention due to relatively high produced voltages and wide operating conditions. Here, we present a combined study of computational and experimental work exploiting finite-element method simulations to find the critical parameters influencing the performance of such generators. The simulated behaviour is found to agree with the experimental data within typical variation of the measurements. We find that the electrical power produced by the generator depends not only on the properties of the porous material, but also on the surrounding environment of the generator. Particularly, the pore size and geometry are found to have a significant influence on the output power, highlighting the importance of accurate characterization of the samples and careful control of the laboratory conditions when performing experimental work. Increasing the pore size from 5 to 20 nm improves the simulated output voltage from 0.12 to 0.47 V, while increasing the ambient humidity to 100% will prevent voltage generation completely. The obtained results can guide the future design of generators based on water evaporation induced capillary flow in a nanoporous carbon black film, leading to more efficient power production.