Heterogeneous Two-dimensional lamellar Ti3C2Tx membrane for osmotic power harvesting

Osmotic energy generated from salinity gradients has been recognized as a novel blue energy source. Membrane-based reverse electrodialysis (RED) is a promising strategy for harvesting electric power from salinity difference. However, practical RED process often suffers from the low energetic efficiency due to the inherent ion concentration polarization phenomenon. Here, a heterogeneous two-dimensional lamellar Ti3C2Tx membrane with asymmetric geometry and charge properties was designed. The diode-like transport behavior with unidirectional ion conduction was observed, suggesting a preferential transport direction in the Ti3C2Tx hetero-nanochannel. When applied as the osmotic energy generators, the heterogeneous Ti3C2Tx membranes produced a maximum output power density of 16 W/m2 on mixing the natural brine and river water, higher than the commercialization benchmark (5 W/m2). Theoretical calculations confirmed that the asymmetric membrane architecture achieved a balance between effectively weakening the concentration polarization and maintaining the high ion selectivity. This study is a significant step forward in the field of designing artificial nanofluidic membranes and highly efficient osmotic energy conversion systems.