Paper-Mill Waste Reinforced Nanofluidic Membrane as High-Performance Osmotic Energy Generators

Nanofluidic membranes consisting of 2D materials and polymers are considered promising candidates for harvesting osmotic energy from river estuaries owing to their unique ion channels. However, micron-scale polymer chains agglomerate in the nanochannels, resulting in steric hindrance and affection ion transport. Herein, a nanofluidic membrane is designed from MXene and xylan nanoparticles that are derived from paper-mill waste. The demonstrated membrane reinforced by paper-mill waste has the characteristics of green, low-cost, and outstanding performance in mechanical properties and surface-charge-governed ionic transport. The MXene/carboxmethyl xylan (CMX) membrane demonstrates a high surface charge (ζ-potential of −44.3 mV) and 12 times higher strength (284.96 MPa) than the pristine MXene membrane. The resulting membrane shows intriguing features of high surface charge, high ion selectivity, and reduced steric hindrance, enabling it high osmotic energy generation performance. A potential of the nanofluidic membrane is ≈109 mV, the corresponding current of up to 2.73 µA, and the output power density of 14.52 mW m⁻² are obtained under a 1000-fold salt concentration gradient. As the electrolyte pH increases, the power density reaches 56.54 mW m⁻². This works demonstrate that CMX nanoparticles can effectively enhance the properties of the nanofluidic membrane and provide a promising strategy to design high-performance nanofluidic devices.