Power generation in Janus nanopores: Insights from All-atoms MD simulations.

By means of large-scale all-atoms molecular dynamic simulation, this work explores the physical mechanism for ionic current rectification (ICR) and energy extraction in asymmetrically charged "Janus" membranes. The asymmetry in these membranes promotes a directional ionic conduction that can be exploited to generate current from a gradient in salinity.

The results we present in this work show excellent agreement with the experimental ICR and power extraction performances reported for membranes of the same size and charge. We found ICR correlates with an accumulation of ions inside the pore in the active state compared to the inactive state. In contrast, the electric potential was almost identical in all the tested conditions. These findings support the "accumulation-depletion" mechanism proposed for ICR.

In our simulations, water orients anisotropically, with a larger average dipole moment at the ionic depleted regions. Water molecules align their dipoles towards the charged walls so that the dipole-induced interactions dominate the physics at the pore's surface.

The results of this work confirm that ICR is not limited to pore radii below the Debye length, which opens membrane design possibilities to more accessible fabrication processes.