An interdisciplinary collaboration between researchers at Case Western Reserve University and the University of Notre Dame has revealed a critical interaction that is occurring at this plasma-liquid interface in that the electrons in plasma actually serve to separate water, producing hydrogen gas.
In a paper set to appear as a Fast Track Communication in the Journal of Physics D: Applied Physics, David B. Go, assistant professor of aerospace and mechanical engineering at the University of Notre Dame, and his graduate student Paul Rumbach teamed with R. Mohan Sankaran, associate professor of chemical engineering at Case Western Reserve, and his undergraduate student Megan Witzke describe a series of experiments that revealed this new chemistry.
A plasma is an ionized gas, consisting of not only neutral gas molecules but also free electrons and charged ions. Though often thought of as very hot, microplasmas are a unique regime of plasmas that can be formed at atmospheric pressure and are considered "cold plasmas" because they are typically around room temperature. In most plasma-liquid studies, the focus has been on how the different gas species and photons (light) produced by the plasma interact with the liquid.
"Many researchers have revealed that reactive oxygen and nitrogen species in the plasma play an important role in the plasma-liquid interaction," Sankaran said, "But we've always thought that the electrons must be playing an important part. We had preliminary evidence that suggested that the plasma electrons would reduce various chemical species in the liquid but always believed that they must have been interacting with water as well. This study conclusively proves that the electrons directly interact with and electrolyze water."
Water electrolysis is the splitting of water into oxygen and hydrogen and usually occurs in an electrochemical cell with two metals electrodes. In their work Go and Sankaran replaced one of the metal electrodes with an atmospheric-pressure plasma jet. However, the result was that the plasma electrochemical cell acted like a traditional electrochemical cell.
"We found that at the plasma-liquid interface, the plasma formed a virtual cathode and electrons from the plasma reduced hydrogen ions to produce hydrogen gas while at the metal anode, oxidation formed oxygen gas. The reactions are the same as for a traditional electrochemical cell, except now the plasma jet plays the role of one of the electrodes," Go said.
While Go and Sankaran acknowledge that the plasma-liquid interaction is an incredibly complex phenomenon, they agree that this work fills in a crucial piece of the puzzle."As we continue to develop plasma jets for all kinds of applications, be they medical, environmental or for synthesizing materials," Go said. "It's crucial that we understand the fundamental chemistry that is occurring. The role of electrons has been somewhat overlooked, but we show that they play an important role and must be considered as we continue to try to understand these new microplasma devices."
David Go | EurekAlert!
The material that obscures supermassive black holes
26.09.2017 | Instituto de Astrofísica de Canarias (IAC)
Creative use of noise brings bio-inspired electronic improvement
26.09.2017 | American Institute of Physics
Controlling electronic current is essential to modern electronics, as data and signals are transferred by streams of electrons which are controlled at high speed. Demands on transmission speeds are also increasing as technology develops. Scientists from the Chair of Laser Physics and the Chair of Applied Physics at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have succeeded in switching on a current with a desired direction in graphene using a single laser pulse within a femtosecond ¬¬ – a femtosecond corresponds to the millionth part of a billionth of a second. This is more than a thousand times faster compared to the most efficient transistors today.
Graphene is up to the job
At the productronica trade fair in Munich this November, the Fraunhofer Institute for Laser Technology ILT will be presenting Laser-Based Tape-Automated Bonding, LaserTAB for short. The experts from Aachen will be demonstrating how new battery cells and power electronics can be micro-welded more efficiently and precisely than ever before thanks to new optics and robot support.
Fraunhofer ILT from Aachen relies on a clever combination of robotics and a laser scanner with new optics as well as process monitoring, which it has developed...
Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.
A warming planet
Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.
The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...
Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...
19.09.2017 | Event News
12.09.2017 | Event News
06.09.2017 | Event News
26.09.2017 | Information Technology
26.09.2017 | Physics and Astronomy
26.09.2017 | Life Sciences