Water evaporation is a ubiquitous natural process¹ that harvests thermal energy from the ambient environment. It has previously been utilized in a number of applications^2,3 including the synthesis of nanostructures⁴ and the creation of energy-harvesting devices^5,6. Here, we show that water evaporation from the surface of a variety of nanostructured carbon materials can be used to generate electricity. We find that evaporation from centimetre-sized carbon black sheets can reliably generate sustained voltages of up to 1 V under ambient conditions. The interaction between the water molecules and the carbon layers and moreover evaporation-induced water flow within the porous carbon sheets are thought to be key to the voltage generation. This approach to electricity generation is related to the traditional streaming potential⁷, which relies on driving ionic solutions through narrow gaps, and the recently reported method of moving ionic solutions across graphene surfaces^8,9, but as it exploits the natural process of evaporation and uses cheap carbon black it could offer advantages in the development of practical devices.

水蒸发是无处不在的自然过程¹，它从周围环境中收集热能。它先前已用于许多应用程序^2,3中，包括纳米结构⁴的合成和能量收集设备^5,6的创建。在这里，我们证明了从各种纳米结构碳材料表面蒸发的水可以用来发电。我们发现，在环境条件下，从厘米大小的炭黑片蒸发可以可靠地产生高达1 V的持续电压。水分子与碳层之间的相互作用以及多孔碳片内蒸发引起的水流被认为是产生电压的关键。这种发电方法与传统的流电势⁷有关，传统的流电势⁷依赖于通过狭窄的间隙驱动离子溶液，以及最近报道的使离子溶液在石墨烯表面上移动的方法^8,9但是，由于它利用了蒸发的自然过程并使用了廉价的炭黑，因此在开发实用设备方面可能具有优势。