Two-dimensional lamellar MXene/three-dimensional network bacterial nanocellulose nanofiber composite Janus membranes as nanofluidic osmotic power generators

• The Janus membranes composited with 2D lamellar MXene/3D network bacterial nanocellulose nanofiber were developed. • The preferred transport direction of the cations flows was identical under the different electrokinetic situations. • The implementation of artificial seawater and river water on the fully abiotic MXene/BNC Janus membrane can achieve an outstanding output power density of 0.91 Wm −2 . In the field of nanofluidic osmotic power generators, it has been an ultimate but seemingly distant goal to controllably fabricate the different-dimensional confined space including slits, network, nanochannels or their composition to control the ion transport. We demonstrated ion transport behaviors through ultimately 2D lamellar MXene/3D network bacterial nanocellulose nanofiber composite Janus membranes under the different transmembrane concentration gradient. The heterogeneous multilayers Janus membrane comprised effectively stacked hydrophobic MXene to hydrophilic bacterial nanocellulose (BNC). The asymmetric cations transport phenomena were explained in terms of asymmetric surface charges polarization in the confined space. Our results provided a facile and general strategy for studying the effects of membrane-scale confinement, which was important for the development of biomimetic energy conversion, ionic seizing, chemical sensing and other nanoscale technologies. We fabricate a bilayered heterogeneous MXene/BNC Janus membrane and demonstrate the asymmetric cations transportation phenomena in the confined slits therein. The cations prefer to transport from 2D silts to 3D network under electric field and the transmembrane concentration gradient