Abstract
Carbon has emerged as a unique material in nanofluidics, with reports of fast water transport, molecular ion separation and efficient osmotic energy conversion. Many of these phenomena still await proper rationalization due to the lack of fundamental understanding of nanoscale ionic transport, which can only be achieved in controlled environments. Here we develop the fabrication of ‘activated’ two-dimensional carbon nanochannels. Compared with nanoconduits with ‘pristine’ graphite walls, this enables the investigation of nanoscale ionic transport in great detail. We show that activated carbon nanochannels outperform pristine channels by orders of magnitude in terms of surface electrification, ionic conductance, streaming current and (epi-)osmotic currents. A detailed theoretical framework enables us to attribute the enhanced ionic transport across activated carbon nanochannels to an optimal combination of high surface charge and low friction. Furthermore, this demonstrates the unique potential of activated carbon for energy harvesting from salinity gradients with single-pore power density across activated carbon nanochannels, reaching hundreds of kilowatts per square metre, surpassing alternative nanomaterials.
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Data availability
The data supporting the findings of this study are available within the paper and its Supplementary Information files. Source data are provided with this paper and are available at https://figshare.com/s/2aabcab85d33123a3af3.
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Acknowledgements
L.B. thanks R. Netz and B. Rotenberg for fruitful discussions. We thank the Institut des Matériaux de Paris Centre (IMPC FR2482) for servicing the XPS instrumentation, as well as A. Walton for his help with XPS measurements and valuable discussions. L.B. acknowledges funding from the EU H2020 Framework Programme/ERC Advanced Grant agreement number 785911-Shadoks and ANR project Neptune. A.S. acknowledges funding from the EU H2020 Framework Programme/ERC Starting Grant agreement number 637748-NanoSOFT. L.B. and A.S. acknowledge support from the Horizon 2020 programme through Grant number 899528-FET-OPEN-ITS-THIN. K.S.V. acknowledges the Marie Curie Individual Fellowship from the EU H2020 Framework Programme, through grant number 836434, GraFludicDevices. A.K. acknowledges the Ramsay Memorial Fellowship and also funding from the Royal Society research grant RGS/R2/202036. B.R. acknowledges the Royal Society fellowship and funding from the EU H2020 Framework Programme/ERC Starting Grant number 852674 AngstroCAP. This work has received the support of the Institut Pierre-Gilles de Gennes (programme ANR-10-IDEX-0001-02 PSL and ANR-10-LABX-31).
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L.B. and A.S. designed and directed the project. T.E. and K.S.V. contributed equally; they fabricated the devices, with input from A.N. and A.S. Device fabrication and characterization was contributed by B.R. and A.K. With input from L.B. and A.S., T.E. and K.S.V. performed experiments and carried out analysis. L.B. performed the theoretical analysis. L.B., K.S.V., T.E. and A.S wrote the manuscript. All authors contributed to discussions.
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Emmerich, T., Vasu, K.S., Niguès, A. et al. Enhanced nanofluidic transport in activated carbon nanoconduits. Nat. Mater. 21, 696–702 (2022). https://doi.org/10.1038/s41563-022-01229-x
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DOI: https://doi.org/10.1038/s41563-022-01229-x
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