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Friday, 14 February 2020

Movement of a liquid droplet on MoS2 generates over 5 volts of electricity


Japanese scientists have developed an energy capture device that generates more than 5 volts of electricity from a single drop of liquid rolling downhill. It was already known that a sheet of graphene can generate electricity from the movement of a liquid on its surface. However, the output voltage is limited to about 0.1 volts, which is not enough to drive electronic devices.

The result was much better using molybdenite , or molybdenum disulfide (MoS2), as the active material in the nanogenerator, allowing to reach just over 5 volts of electricity from a drop of liquid rolling over the surface of the thin and flexible material - molybdenite is one of the stars of ultrafine electronics , surpassing graphene in several ways.

This voltage is important because it is at the level required for any electronic circuit, but the current generated by a single drop is also miniscule, with peaks of six nanowatts, which directs the nanogenerator for applications where there are continuous flows of liquids.



"To use MoS2 for the generator, it was necessary to form a large-area single-layer MoS2 film on a plastic film. With conventional methods, however, it was difficult to grow MoS2 uniformly on a large-area substrate," says Professor Ohno of the Institute of Materials and Systems for Sustainability at Nagoya University. "In our study, we succeeded in fabricating this form of MoS2 film by means of chemical vapor deposition using a sapphire substrate with molybdenum oxide (MoO3) and sulphur powders. We also used a polystyrene film as a bearing material for the MoS2 film, so that we were able to transfer the synthesized MoS2 film to the surface of the plastic film quite easily."

Harvesting Energy

The harvest of energy , incorporated in nanogenerators capable of transforming small amounts of naturally occurring energy (by light, heat and vibration) into electricity, is gaining attention as a method to power the Internet of Things (IoT) devices.

This technology is expected to have applications, for example, in autonomous and self-powered sensors, which will be able to work continuously without any concern with power or battery change.

The newly developed generator is flexible enough to be installed on the curved inner surface of plumbing, and is thus expected to be used to power IoT devices used in liquids, such as self-powered rain gauges and acid rain monitors, as well as water quality sensors that can generate power from industrial wastewater while monitoring it.



Professor Ohno says, "Our MoS2 nanogenerator is able to harvest energy from multiple forms of liquid motion, including droplets, spraying, and sea waves. From a broader perspective, this device could also be used in applications involving hydrodynamics, such as generating electricity from rainwater and waterfalls."


Bibliography:

Article: High output voltage generation of over 5 V from liquid motion on single-layer MoS2

Authors: Adha Sukma Aji, Ryohei Nishi, Hiroki Ago, Yutaka Ohno

Magazine: Nano Energy

Vol .: 68, 104370

DOI: 10.1016 / j. nanoen.2019.104370

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