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Heyi Xia1,2, Wanqi Zhou3, Xinyue Qu1

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Researchers discovered upstream proton diffusion in MXene/poly(vinyl alcohol) films generates electricity. This novel hydrovoltaic effect, driven by proton dissociation, powers devices using small water droplets and could harvest energy from sweat.

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Area of Science:

  • Materials Science
  • Nanotechnology
  • Electrochemistry

Background:

  • Downstream ionic transport in nanochannels generates streaming potentials, enabling hydrovoltaic devices.
  • Proton movement opposing water flow (upstream diffusion) has not been previously explored for electricity generation.

Purpose of the Study:

  • To demonstrate electricity generation via upstream proton diffusion in two-dimensional nanochannels.
  • To investigate the mechanism of proton dissociation and diffusion in MXene/poly(vinyl alcohol) films.
  • To develop a wearable energy-harvesting device utilizing this phenomenon.

Main Methods:

  • Fabrication of two-dimensional nanochannels using MXene/poly(vinyl alcohol) films.
  • Infiltration of water into nanochannels to induce proton dissociation.
  • Measurement of voltage generated by upstream proton diffusion.
  • Development and testing of a wearable device using skin sweat.

Main Results:

  • Upstream proton diffusion was confirmed as a mechanism for electricity generation.
  • A small water droplet (5 µl) generated ~400 mV for over 330 minutes.
  • The ultrathin and flexible film enabled the creation of a wearable energy-harvesting device.

Conclusions:

  • Upstream proton diffusion in MXene/poly(vinyl alcohol) nanochannels offers a novel pathway for hydrovoltaic energy generation.
  • The observed effect is driven by proton dissociation from surface functional groups and subsequent diffusion against water flow.
  • This technology holds promise for developing flexible, wearable devices for harvesting energy from environmental moisture, such as human sweat.