Osmotic Power Generation with Positively and Negatively Charged 2D Nanofluidic Membrane Pairs

Abstract

In nature, hierarchically assembled nanoscale ionic conductors, such as ion channels and ion pumps, become the structural and functional basis of bioelectric phenomena. Recently, ion‐channel‐mimetic nanofluidic systems have been built into reconstructed 2D nanomaterials for energy conversion and storage as effective as the electrogenic cells. Here, a 2D‐material‐based nanofluidic reverse electrodialysis system, containing cascading lamellar nanochannels in oppositely charged graphene oxide membrane (GOM) pairs, is reported for efficient osmotic energy conversion. Through preassembly modification, the surface charge polarity of the 2D nanochannels can be efficiently tuned from negative (−123 mC m−2) to positive (+147 mC m−2), yielding strongly cation‐ or anion‐selective GOMs. The complementary two‐way ion diffusion leads to an efficient charge separation process, creating superposed electrochemical potential difference and ionic flux. An output power density of 0.77 W m−2 is achieved by controlled mixing concentrated (0.5 m) and diluted ionic solutions (0.01 m), which is about 54% higher than using commercial ion exchange membranes. Tandem alternating GOM pairs produce high voltage up to 2.7 V to power electronic devices. Besides simple salt solutions, various complex electrolyte solutions can be used as energy sources. These findings provide insights to construct cascading nanofluidic circuits for energy, environmental, and healthcare applications.

Fabrication of Bio‐Inspired 2D MOFs/PAA Hybrid Membrane for Asymmetric Ion Transport

“…As shown in Figure E, when the concentration gradient is 1 to 10 3 , the power density is increasing gradually. The maximum output power value of P max is 1.6 W m −2 at a concentration gradient of 10 3 , which is comparable to some previous works …”

Photo-switchable two-dimensional nanofluidic ionic diodes

“…27 Via a mild thermal annealing process, 28 the hydrophilic GOMs can be stabilized in water or in saline for months. The thickness of the GOMs is about 15 μm.…”

Anomalous Pore‐Density Dependence in Nanofluidic Osmotic Power Generation

“…[17] Therefore, the numeric pore density turns into an essential parameter. [20,21] The underlying mechanism remains unexplored in the literature. How-ever, recent experimental observations show that the commonlyused linear amplification method largely overestimates the actual performance, [18,19] compared with those experimental results obtained directly on porous materials.…”