Adv. Mater. http://doi.org/gc7shv (2018)

Energy harvesting from water is of significant interest due to the abundance and sustainability of this natural resource. However, flowing water is frequently required for energy converters to generate large amounts of electricity. Now, Peng and co-workers report a power generation system based on carbon materials that can efficiently harvest electricity from stationary pure water.

First, oxygen-modulated carbon nanotube (OCNT) yarns are prepared by an oxygen microplasma treatment. The oxygen modulated sp2-hybridized carbon systems exhibit stronger surface polarization than the pristine CNT (PCNT) yarns, as evidenced by X-ray adsorption studies. Then, the OCNT yarns are connected to PCNT yarns and immersed in quiescent water. The device works like a battery, in which the OCNT yarns, PCNT yarns and pure water act as the cathode, the anode and the electrolyte respectively. In the device, an open circuit voltage up to hundreds of millivolts is generated and a short-circuit discharging electric current reaches the microampere level. Interestingly, this ‘battery’ is rechargeable and can be turned on and off repeatedly without affecting the open circuit voltage. Furthermore, the demonstrated energy generator is capable of powering personal electronics.