High-Performance Laponite/TEMPO-Oxidized Cellulose Nanofibers/Poly(vinyl alcohol) Composite Membrane for Salinity Gradient Power Generation

Amidst growing global energy challenges, salinity gradient energy has emerged as a promising renewable resource derived from the controlled mixing of fresh and salt water. Its efficient harvesting, however, relies on advanced nanofluidic membranes featuring high ion selectivity, low internal resistance, and mechanical robustness. In this study, a high-performance composite membrane was fabricated via an evaporation-induced self-assembly strategy using laponite (LAP), TEMPO-oxidized cellulose nanofibrils (T-CNF), and poly(vinyl alcohol) (PVA). The resulting membrane architecture synergistically integrates several key features: a high-surface-charge framework from T-CNF, nanochannels with interlayer spacing finely tuned by LAP nanosheets to enhance selective ion transport, and a robust network cross-linked by PVA, yielding a tensile strength of 77 MPa. Under a 50-fold salinity gradient (0.01 M/0.5 M KCl), the membrane exhibits a high cation selectivity of 0.87 and an outstanding power density of 1.57 W·m–2. Moreover, it demonstrates excellent long-term stability, showing <11% attenuation over 9 days of continuous operation, corresponding to an energy conversion efficiency of 27.6%. These results highlight a durable, high-performance membrane that offers a viable strategy for sustainable salinity gradient power generation.