Liquid flow over monolayer graphene has been experimentally demonstrated to generate an induced voltage in the flow direction in the laboratory of the College of Information Science and Electronic Engineering, Zhejiang University. The research team led by Mr. Lin Shisheng highlighted the crucial role of the underlying substrate in the electricity-generating process. This study will offer theoretical implications for the development of nanogenerators or graphene-related devices.
Graphene is the thinnest material in the known universe, but it can efficiently conduct electricity and electrons in graphene can move with a speed of 1,000 km/s. These properties open up much room for imagination. In 2011, scientists put forward the theoretical possibility of harnessing graphene-water to generate electricity, but its scientific mechanism has constantly been a matter of much debate. However, there are significant discrepancies in the reported results with non-ionic liquid: the observed voltage responses with deionized (DI) water vary from lab to lab under presumably similar flowing conditions. Although there has been tremendous research into graphene in recent years, the development of applications has made little improvement.
“Because graphene is extremely thin, we have to use supporting materials to build graphene devices. However, in terms of the interaction between water and graphene, there has been little concern over the role of the substrate,” Lin Shisheng said. Here, a graphene-piezoelectric material heterostructure is proposed for harvesting energy from water flow; it is shown that the introduction of a piezoelectric template beneath graphene results in an obvious voltage output up to 0.1 V even with DI water.
This potential arises from a continuous charging–discharging process in graphene, which is suggested to be a result of a relatively retarded screening effect of the water for the generated piezoelectric charges than that of the graphene layer, as revealed by first-principles calculations. This work considers a dynamic charge interaction among water, graphene, and the substrate, highlighting the crucial role of the underlying substrate in the electricity-generating process, which will greatly enhance understanding of the flow-induced voltage and push the graphene-water nanogenerator close to practical applications.
The relevant research was published online in Advanced Functional Materials on February 3, 2017, with Zhang Huikai as the first author and Lin Shisheng as the corresponding author.