Proton flow battery advances hydrogen power

Researchers have developed a concept hydrogen battery based simply on storing protons produced by splitting water.

The novel concept developed by researchers at RMIT University advances the potential for hydrogen to replace lithium as an energy source in battery-powered devices.

The proton flow battery concept eliminates the need for the production, storage and recovery of hydrogen gas, which currently limit the efficiency of conventional hydrogen-based electrical energy storage systems.

Lead researcher Associate Professor John Andrews, from RMIT's School of Aerospace, Mechanical and Manufacturing Engineering, said the novel concept combined the best aspects of hydrogen fuel cells and battery-based electrical power.

"As only an inflow of water is needed in charge mode - and air in discharge mode - we have called our new system the 'proton flow battery'," Associate Professor Andrews said.

"Powering batteries with protons has the potential to be a much more economical device than using lithium ions, which have to be produced from relatively scarce mineral, brine or clay resources.

"Hydrogen has great potential as a clean power source and this research advances the possibilities for its widespread use in a range of applications - from consumer electronic devices to large electricity grid storage and electric vehicles."

The concept integrates a metal hydride storage electrode into a reversible proton exchange membrane (PEM) fuel cell.

During charging, protons produced from splitting water are directly combined with electrons and metal particles in one electrode of a fuel cell, forming a solid-state metal hydride as the energy storage. To resupply electricity, this process is reversed.

Published in the International Journal of Hydrogen Energy (January, 2014), the research found that, in principle, the energy efficiency of the proton flow battery could be as high as that of a lithium ion battery, while storing more energy per unit mass and volume.

The published paper is the first to articulate and name the proton flow battery concept, and the first to include an experimental preliminary proof of concept.

"Our initial experimental results are an exciting indicator of the promise of the concept, but a lot more research and development will be necessary to take it through to practical commercial application," Associate Professor Andrews said.

Source: http://www.rmit.edu.au/browse;ID=6wpkdgvja13n;STATUS=A

2-proton bit controlled by a single copper atom

Just a single foreign atom located in the vicinity of a molecule can change spatial arrangement of its atoms. In a spectacular experiment, an international team of researchers was able to change persistently positions of the nuclei of hydrogen atoms in a porphycene molecule by approaching a single copper atom to the molecule.

A subatomic bit formed by two protons tunnelling inside a simple organic molecule can be switched by approaching a single copper atom to the molecule. A spectacular experiment to demonstrate the phenomenon was carried out by a team of researchers from the Fritz-Haber-Institute of the Max-Planck-Gesellschaft (FHI) in Berlin, the University of Liverpool (UL) and the Institute of Physical Chemistry of the Polish Academy of Sciences (IPC PAS) in Warsaw. The experiment was reported in a paper published in "Nature Chemistry", one of the most prestigious chemical journals.

In the study the researchers made use of specific properties of the porphycene molecule. Porphycene (C20H14N4) is a porphyrin derivative. Chemical compounds belonging to this group occur naturally. They are found, e.g., in human blood, where they are involved in reactions related to oxygen transport. Their molecules have a form of planar carbon rings with hydrogen atoms outside and four nitrogen atoms inside, located in the corners of a tetragon.

In the centre of a porphycene molecule, in an empty space surrounded by nitrogen atoms, there are two protons (i.e., nuclei of hydrogen atoms) that can move between the nitrogens. It is interesting that both protons are always displaced together. The research carried out for over a decade by Prof. Jacek Waluk's team (IPC PAS) suggests that the movement of protons is not simply a displacement in space. The protons change their positions due to quantum tunnelling effect: making use of the uncertainty principle they just disappear at one place and reappear in another.

In the Berlin FHI laboratory the porphycene molecules provided by Prof. Waluk's team were deposited individually onto the surface of a perfect copper crystal. The job was not easy and required development of appropriate techniques – without them porphycene molecules tended to form groups (aggregates).

The subsequent step were the experiments under high vacuum and at very low temperature (5 K, which means five degree above the absolute zero). A single porphycene molecule laying on the copper substrate was observed with a scanning tunnelling microscope. The instrument allowed for recording changes in electron density of the molecule, and thus for monitoring changes of its shape. The images obtained with this technique allowed to determine current positions of both protons. Therefore the researchers were able to observe the movement of atoms inside the molecule in the course of a chemical reaction.

"We were pretty much surprised to find that after depositing on the copper substrate, hydrogen ions in porphycene molecule formed a configuration that was never observed so far, in spite of many, many years of research on this compound. Instead of being located in opposite corners of the tetragon formed by nitrogen atoms, both protons took positions next to each other. Quite surprisingly we found a new porphycene tautomer!", comments Prof. Waluk.

Using a tip of the scanning tunnelling microscope, in subsequent attempts a single copper atom was moved closer to the porphycene molecule, from different sides. It turned out that depending on the position of the copper atom, both protons in porphycene, moving between the nitrogen atoms, were located once on one side, and then on the other side of the molecule. Thus, the porphycene molecule acted as a binary switch, controlled with a single copper atom only. A change in position of the copper atom by less than a ten-billionth of a meter was sufficient to initiate the transition between the states.

The research carried out by the team from the FHI, the UL and the IPC PAS proves that the vicinity of a molecule can substantially affect its physical and chemical properties. The results of the study show that, under certain conditions, the environment of molecules should be controlled with atomic precision. On the other hand, the observed sensitivity to changes in the environment opens the way for development of methods for regulation of processes occurring in single molecules.

"It seems likely that the molecule's sensitivity to its vicinity found by us is a common phenomenon in nature. The phenomenon can be exploited, for instance, in designing nanomachines processing information on a single-molecule level", sums up Prof. Waluk.

This press release was prepared thanks to the NOBLESSE grant under the activity "Research potential" of the 7th Framework Programme of the European Union.

The Institute of Physical Chemistry of the Polish Academy of Sciences was established in 1955 as one of the first chemical institutes of the PAS. The Institute's scientific profile is strongly related to the newest global trends in the development of physical chemistry and chemical physics. Scientific research is conducted in nine scientific departments. CHEMIPAN R&D Laboratories, operating as part of the Institute, implement, produce and commercialise specialist chemicals to be used, in particular, in agriculture and pharmaceutical industry. The Institute publishes approximately 200 original research papers annually.

Source: http://www.ichf.edu.pl/

Proton's Weak Charge Determined for First Time

Researchers have made the first experimental determination of the weak charge of the proton in research carried out at the Department of Energy's Thomas Jefferson National Accelerator Facility (Jefferson Lab).

The results, accepted for publication inPhysical Review Letters, also include the determinations of the weak charge of the neutron, and of the up quark and down quark. These determinations were made by combining the new data with published data from other experiments. Although these preliminary figures are the most precise determinations to date, they were obtained from an analysis of just 4 percent of the total data taken by the experiment, with the full data analysis expected to take another year to complete.

The weak force is one of the four fundamental forces in our universe, along with gravity, electromagnetism and the strong force. Although the weak force acts only on the sub-atomic level, we can see its effects in our everyday world. The weak force plays a key role in the nuclear reaction processes that take place in stars and is responsible for much of the natural radiation present in our universe.

The Q-weak experiment was designed by an international group of nuclear physicists who came together more than a decade ago to propose a new measurement at Jefferson Lab. They proposed the world’s first direct measurement of the proton's weak charge, denoted by the symbolthis represents the strength of the weak force's pull on the proton, a measure of how strongly a proton interacts via the weak force. Since the weak charge of the proton is precisely predicted by the Standard Model, which is a well-tested theoretical framework that describes the elementary particles and the details of how they interact, it is an ideal parameter to measure experimentally as a test of the Standard Model.

To perform the experiment, the scientists directed a very intense beam of electrons into a container of liquid hydrogen. The electrons were longitudinally polarized (spinning along or opposite their direction of motion). Electrons that made only glancing collisions with the protons (elastic scattering, where the proton remained intact) emerged at small angles and were deflected by powerful electromagnets onto eight symmetrically placed detectors.

The weak force is far weaker than the electromagnetic force. In classical terms, one might think of this as for every one million electrons that interact with the protons via the electromagnetic force, only one will interact via the weak force.  Physicists measured those few weak interactions by exploiting an important difference between the two forces - the weak force violates a symmetry known as parity, which reverses all spatial directions and turns our right-handed world into a left-handed one. In an opposite-parity world, the electrons spinning with their axes along their direction of motion would interact with protons via the electromagnetic force with the same strength. Where the weak force is concerned, electrons with right-handed spin interact differently than left-handed ones. By keeping all other parameters of the experiment the same, and only reversing the polarization direction of the electron beam, scientists can use the difference or “asymmetry” of the measurements between two polarization directions to isolate the effect of the weak interaction. The goal is to measure this difference, only ~200 parts per billion, as precisely as possible. This precision is equivalent to measuring the thickness of a sheet of paper laid atop the Eiffel Tower.

The initial analysis of the Q-weak experimental data yielded a value forthat is in good agreement with the Standard Model prediction. However, the collaboration has 25 times more data than was used in this initial determination. The final result should provide a rigorous experimental test of the Standard Model, providing constraints on new physics at the scale of energies being explored at the Large Hadron Collider at CERN in Europe.

"Readers should view this result primarily as a first determination of the weak charge of the proton. Our final publication will be focused on implications with respect to potential new physics," says Roger Carlini, a Jefferson Lab staff scientist and spokesperson for the Q-weak Collaboration.

The Q-weak experiment was originally approved in January 2002. A nearly year-long installation period for experimental equipment began in 2009, which was followed by a two year period of data collection during 2010-2012.

Numerous technical achievements in the last decade made this experiment possible. These include the high-current, high-polarization, extremely stable electron beam provided by Jefferson Lab's Continuous Electron Beam Accelerator Facility; the world's highest-power cryogenic hydrogen target; extremely radiation-hard Cerenkov detectors; ultra-low noise electronics to read out the signals and precisely measure the beam current; and a system which measures the beam polarization to better than 1 percent using a back-scattered laser. These technical achievements have yielded an astonishingly small total uncertainty of 47 parts per billion for the data published so far.  

The Q-weak collaboration consists of 97 researchers from 23 institutions in the U.S., Canada, and Europe. The experiment was funded by the U.S. Department of Energy Office of Science, the U.S. National Science Foundation and the Natural Sciences and Engineering Research Council of Canada. Matching university contributions were also provided by The College of William and Mary, Virginia Tech, George Washington University and Louisiana Tech University. Technical support was provided by TRIUMF, MIT/Bates and Jefferson Lab.

Jefferson Science Associates manages Jefferson Lab for the DOE Office of Science. The Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit http://science.energy.gov/.

Source: https://www.jlab.org/news/releases/protons-weak-charge-determined-first-time