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 µl can generate a voltage of ~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.

自 1859 年以来，人们就观察到离子在狭窄通道中沿着压力驱动的水流运动，即所谓的下游离子传输，从而产生流动电势，并使得各种水力发电装置的诞生成为可能。相比之下，我们在这里证明了 MXene/聚乙烯醇薄膜二维纳米通道中与水流相反的质子运动（称为上游质子扩散）也可以发电。渗入通道的水导致质子从通道表面的官能团解离，导致通道内质子浓度较高，从而驱动上游质子扩散。再加上通道中特别缓慢的水扩散，5 µl 的小水滴可以在 330 分钟内产生约 400 mV 的电压。受益于薄膜的超薄和柔韧特性，可穿戴设备被设计用于从人体皮肤汗液中收集能量。