Bioinspired Ti 3 C 2 T x MXene-Based Ionic Diode Membrane for High-Efficient Osmotic Energy Conversion.

Bioinspired asymmetric nanofluidic ion channels with ionic diode behavior that can boost the osmotic energy (so-called blue energy) conversion are highly desirable, especially if they can be easily constructed and modified. Two-dimensional (2D) metal carbides and nitrides, known as MXenes, combine hydrophilic surfaces and tunable surface charge properties, providing a shortcut to prepare asymmetric nanofluidic ion channels. Here, we report a mechanically robust, flexible, and scale-up-friendly asymmetric Ti 3 C 2 T x MXene-based ionic diode membrane with a highly rectified current and demonstrate its potential use in reverse electrodialysis osmotic energy conversion. Under the salinity gradient of synthetic seawater and river water, our ionic diode membrane-based generator's power density is 8.6 W m -2 and up to 17.8 W m -2 at a 500-fold salinity gradient, outperforming the state-of-the-art membranes. The design of MXene-based ionic diode-type membrane provides a facile and general strategy in developing large-scale 2D nanofluidics and selective ion transport.