Molecular-Scale Asymmetry Nanochannels for High-Efficiency Osmotic Energy Generation

Area of Science:

• Materials Science
• Nanotechnology
• Energy Harvesting

Background:

• Osmotic power generation utilizes ion gradients and membrane-based reverse electrodialysis to produce electrical energy.
• The efficiency of osmotic energy harvesting is critically dependent on ion permeability and selectivity across membranes.
• Two-dimensional (2D) heterogeneous interfaces offer potential for molecular-scale control over ion transport but remain underexplored.

Purpose of the Study:

• To design and investigate a 2D nanofluidic membrane with molecular-level asymmetric channels for enhanced ion transport.
• To evaluate the performance of this membrane in osmotic energy generators, focusing on ion selectivity and energy conversion efficiency.
• To elucidate the mechanism of ion transport through the designed asymmetric nanochannels.

Main Methods:

• Fabrication of a 2D nanofluidic membrane featuring molecular-level asymmetric channels.
• Characterization of the membrane's cation selectivity and ion conductivity.
• Testing the membrane in a reverse electrodialysis system for osmotic power generation, measuring output power density and energy conversion efficiency.
• Investigating ion transport mechanisms using advanced analytical techniques.

Main Results:

• The developed 2D membrane achieved a high cation selectivity coefficient of 0.985.
• Superior energy conversion efficiency of up to 47.1% was demonstrated in mixing artificial seawater and river water.
• An excellent output power density exceeding 20 W m^-2 was recorded.
• An interface-induced contiguous ion adsorption-diffusion mechanism for Na⁺ transport was uncovered.

Conclusions:

• The 2D nanofluidic membrane with asymmetric channels significantly enhances ion selectivity and conductivity for osmotic power generation.
• The asymmetric pore structure and charge distribution are key to selective ion adsorption and facilitated transport.
• This study provides fundamental insights into ion transport in asymmetric nanochannels and paves the way for advanced iontronics devices.