Towards understanding the nanofluidic reverse electrodialysis system: well matched charge selectivity and ionic composition

Cao, Liuxuan; Guo, Wei; Ma, Wen; Wang, Lin; Xia, Fan; Wang, Shutao; Wang, Yugang; Jiang, Lei; Zhu, Daoben

doi:10.1039/c1ee01088c

Cited by 185 publications

(156 citation statements)

References 58 publications

(62 reference statements)

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“…In nanofluidic systems, the asymmetric geometry functions not only as a pathway for molecular transportation, but also provides a geometric kinetic constraint that possibly induces a unidirectional diffusive flow through the nanopore [59,60]. Studies on the application of geometryinduced asymmetric diffusion for bio-inspired energy conversion and oil/water separation are currently underway in our lab [61][62][63][64].…”

Section: Resultsmentioning

confidence: 98%

Layer-by-layer removal of insulating few-layer mica flakes for asymmetric ultra-thin nanopore fabrication

et al. 2011

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We demonstrate an elaborate method to controllably fabricate ultra-thin nanopores by layer-by-layer removal of insulating few-layer mica flakes with atomic force microscopy (AFM). The fabricated nanopores are geometrically asymmetric, like an inverted quadrangular frustum pyramid. The nanopore geometry can be engineered by finely tuning the mechanical load on the AFM tip and the scanning area. Particularly noteworthy is that the nanopores can also be fabricated in suspended few-layer mica membranes on a silicon window, and may find potential use as functional components in nanofluidic devices.

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Section: Resultsmentioning

confidence: 98%

Layer-by-layer removal of insulating few-layer mica flakes for asymmetric ultra-thin nanopore fabrication

et al. 2011

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“…3a-c). It has been proven that the net diffusion current stems only from the charge separation and concentration distribution within the electrical double layer 24 , and therefore the total current can be expected to increase more rapidly within small pores in the double-layer overlap range compared with larger pore sizes (Fig. 3d).…”

Section: Letter Researchmentioning

confidence: 99%

Single-layer MoS2 nanopores as nanopower generators

Feng

Gräf

Liu

et al. 2016

Nature

978

855

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Making use of the osmotic pressure difference between fresh water and seawater is an attractive, renewable and clean way to generate power and is known as 'blue energy' 1-3 . Another electrokinetic phenomenon, called the streaming potential, occurs when an electrolyte is driven through narrow pores either by a pressure gradient 4 or by an osmotic potential resulting from a salt concentration gradient 5 . For this task, membranes made of two-dimensional materials are expected to be the most efficient, because water transport through a membrane scales inversely with membrane thickness 5-7 . Here we demonstrate the use of single-layer molybdenum disulfide (MoS 2 ) nanopores as osmotic nanopower generators. We observe a large, osmotically induced current produced from a salt gradient with an estimated power density of up to 10 6 watts per square metre-a current that can be attributed mainly to the atomically thin membrane of MoS 2 . Low power requirements for nanoelectronic and optoelectric devices can be provided by a neighbouring nanogenerator that harvests energy from the local environment 8-11 -for example, a piezoelectric zinc oxide nanowire array 8 or single-layer MoS 2 (ref. 12). We use our MoS 2 nanopore generator to power a MoS 2 transistor, thus demonstrating a self-powered nanosystem.MoS 2 nanopores have already demonstrated better water-transport behaviour than graphene 13,14 owing to the enriched hydrophilic surface sites (provided by the molybdenum) that are produced following either irradiation with transmission electron microscopy (TEM) 15 or electrochemical oxidation 16 . The osmotic power is generated by separating two reservoirs containing potassium chloride (KCl) solutions of different concentrations with a freestanding MoS 2 membrane, into which a single nanopore has been introduced 13 . A chemical potential gradient arises at the interface of these two liquids at a nanopore in a 0.65-nm-thick, single-layer MoS 2 membrane, and drives ions spontaneously across the nanopore, forming an osmotic ion flux towards the equilibrium state (Fig. 1a). The presence of surface charges on the pore screens the passing ions according to their charge polarity, and thus results in a net measurable osmotic current, known as reverse electrodialysis 1 . This cation selectivity can be better understood by analysing the concentration of each ion type (potassium and chloride) as a function of the radial distance from the centre of the pore, as we show here through molecular-dynamics simulations (Fig. 1b).We fabricated MoS 2 nanopores either by TEM 13 (Fig. 1c) Distance from the centre of the pore (Å)C max /C min = 1,000C max /C min = 500C max /C min = 100 LETTER RESEARCHosmotic current can be expected, owing to the long time required for the system to reach equilibrium. We measured the osmotic current and voltage across the pore by using a pair of Ag/AgCl electrodes to characterize the current-voltage (I-V) response of the nanopore.To gain a better insight into the performance of the MoS 2 nanopore power generator, ...

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“…In KCl solution, K + , which has the highest diffusion coefficient, yielded the maximum power, whereas LiCl yielded the lowest power. In this experiment, the highest power obtained was 45pW 11 . They also observed that the pH value of electrolyte influenced the surface charge of membranes or nanochannels 12 .…”

Section: Introductionmentioning

confidence: 93%

Energy Conversion From Salinity Gradient Using Microchip With Nafion Membrane

Chang

Yeh

et al. 2016

Int. J. Mod. Phys. Conf. Ser.

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When a concentrated salt solution and a diluted salt solution are separated by an ion-selective membrane, cations and anions would diffuse at different rates depending on the ion selectivity of the membrane. The difference of positive and negative charges at both ends of the membrane would produce a potential, called the diffusion potential. Thus, electrical energy can be converted from the diffusion potential through reverse electrodialysis. This study demonstrated the fabrication of an energy conversion microchip using the standard micro-electromechanical technique, and utilizing Nafion junction as connecting membrane, which was fabricated by a surface patterned process. Through different salinity gradient of potassium chloride solutions, we experimentally investigated the diffusion potential and power generation from the microchip, and the highest value measured was 135 mV and 339 pW, respectively. Furthermore, when the electrolyte was in pH value of 3.8, 5.6, 10.3, the system exhibited best performance at pH value of 10.3; whereas, pH value of 3.8 yielded the worst.

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Towards understanding the nanofluidic reverse electrodialysis system: well matched charge selectivity and ionic composition

Cited by 185 publications

References 58 publications

Layer-by-layer removal of insulating few-layer mica flakes for asymmetric ultra-thin nanopore fabrication

Layer-by-layer removal of insulating few-layer mica flakes for asymmetric ultra-thin nanopore fabrication

Single-layer MoS2 nanopores as nanopower generators

Energy Conversion From Salinity Gradient Using Microchip With Nafion Membrane

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