Breaking the trade-off with ordered nanochannels for higheffective osmotic energy conversion

Abstract

In the pursuit of high-performance osmotic energy conversion technologies, the trade-off between ion flux and selectivity poses a fundamental constraint. Here, we propose a "skeleton-guided self-assembly" strategy to fabricate high-performance laponite-XLS/negatively charged bacterial cellulose (X-NBC) composite membranes, in which edge-modified 2D nanosheets and a size-matched 1D scaffold jointly satisfy the two structural prerequisites of charge isotropy and lateral-size commensurability required for ordered assembly. By selecting pyrophosphate-edge-modified Laponite-XLS, in which the positively charged edge sites are intrinsically shielded, we exploit its isotropic electrostatic repulsion to suppress the conventional disordered "house-of-cards" stacking and enable highly ordered "face-to-face" parallel alignment along the one-dimensional NBC template. This architecture reconfigures internal channels into continuous low-tortuosity "ionic highways" with a height (~10 nm) closely matched to the Debye length, boosting ionic conductivity to 0.61 mS cm−1 (5.5-fold higher than pure NBC) while sustaining a high cation transfer number of 0.88 under a 500-fold salinity gradient through dilute-side Donnan exclusion. Consequently, the X-NBC membrane achieves a peak power density of 29.3 W m−2 under a 500-fold NaCl gradient with a 0.5 mm channel length, nearly 6 times the 5 W m−2 commercial benchmark. Combined with excellent biocompatibility (cell viability >99%), the membrane further demonstrates a measurable ion-selective response under physiologically realistic gradients, establishing a material foundation for passive, low-power implantable bioelectronic interfaces. This work provides a general design paradigm for engineering low-resistance, high-selectivity nanochannels in advanced energy and bioelectronic applications.