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.

碳已成为纳米流体中的一种独特材料，具有快速水传输、分子离子分离和高效渗透能转换的报道。由于缺乏对纳米级离子传输的基本了解，这些现象中的许多仍然等待适当的合理化，这只能在受控环境中实现。在这里，我们开发了“活化”二维碳纳米通道的制造。与具有“原始”石墨壁的纳米导管相比，这可以非常详细地研究纳米级离子传输。我们表明，活性碳纳米通道在表面带电、离子电导、流动电流和（表观）渗透电流方面优于原始通道几个数量级。详细的理论框架使我们能够将增强的跨活性碳纳米通道的离子传输归因于高表面电荷和低摩擦的最佳组合。此外，这证明了活性炭在从盐度梯度中收集能量的独特潜力，具有跨活性炭纳米通道的单孔功率密度，达到每平方米数百千瓦，超过替代纳米材料。