Electricity generated by upstream proton diffusion in two-dimensional nanochannels

HY Xia and WQ Zhou and XY Qu and WB Wang and X Wang and RX Qiao and YK Zhang and X Wu and C Yang and BF Ding and LY Hu and Y Ran and K Yu and S Hu and JF Li and HM Cheng and H Qiu and J Yin and WL Guo and L Qiu, NATURE NANOTECHNOLOGY, 19, 1316-1322 (2024).

DOI: 10.1038/s41565-024-01691-5

The movement of ions along the pressure-driven water flow in narrow channels, known as downstream ionic transport, has been observed since 1859 to induce a streaming potential and has enabled the creation of various hydrovoltaic devices. In contrast, here we demonstrate that proton movement opposing the water flow in two-dimensional nanochannels of MXene/poly(vinyl alcohol) films, termed upstream proton diffusion, can also generate electricity. The infiltrated water into the channel causes the dissociation of protons from functional groups on the channel surface, resulting in a high proton concentration inside the channel that drives the upstream proton diffusion. Combined with the particularly sluggish water diffusion in the channels, a small water droplet of 5 mu l can generate a voltage of similar to 400 mV for over 330 min. Benefiting from the ultrathin and flexible nature of the film, a wearable device is built for collecting energy from human skin sweat.

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