Tag: advanced photoemission

Novel protocol for mass production of nanowires

Novel protocol for mass production of nanowires

Nanotechnology is one of the major driving forces behind the technological revolution of this century and nanomaterials play a key role in this revolution. While the use of nanoparticles is widespread in industrial applications, the use of nanowires -wires with a diameter of only a few nanometres- is mostly reduced to scientific areas. The fields of biomedicine and permanent magnets would benefit from the cost-effective mass production of nanowires.

In a recent publication, researchers from the Universidad Complutense de Madrid (UCM) and various centres from the Consejo Superior de Investigaciones Científicas (CSIC), in collaboration with ALBA, have established a novel and sustainable synthesis protocol that allows obtaining a greater number of nanowires than conventional laboratory fabrication processes with considerably reduced production time and cost.

The goal of this project was to increase the production of metallic nanowires, reducing costs and timings to expand their applicability to industry. Due to the high costs associated with the high-purity aluminium normally used as the starting material, as well as with the low temperature and large anodization time, the commercial application of nanowires using anodized aluminium oxide is still limited by their fabrication process.

Read more on the ALBA website

Image: The CIRCE beamline (variable polarization soft X-ray beamline dedicated to advanced photoemission experiments)

Credit: ALBA

Catalytic role of oxygen-containing groups on carbon electrodes

Catalytic role of oxygen-containing groups on carbon electrodes

The electrochemical reduction of oxygen plays a significant role in many critical applications such as gas sensors, hydrogen peroxide electrosynthesis, and electrochemical energy storage. Oxygen reduction reaction (ORR) drives the operation of fuel cells and metal-air batteries. The latter potentially can provide the highest specific energy among energy storage devices.

To increase the ORR efficiency, a catalyst immobilized on (or mixed with) conductive support is introduced to the positive electrode composition. Usually, porous sp2-carbon materials, like graphene, serve as such supporting materials. Its electronic configuration (sp2) provides the sufficient electric conductivity to the positive electrode. Nevertheless, ORR proceeds too slowly on the neat surface of ideal sp2-carbon in the absence of a catalyst.

The role of graphene imperfections (vacancies, impurity atoms, and functional groups) on catalyzing ORR (mainly in aqueous media) has been under intense investigation during the last decades. However, little is known about the effect of oxygen functionalization of carbon onORR in aprotic media (lacking the acidic protons). The interest in this process, especially in the presence of metal ions in the electrolyte, is relevant for various aprotic metal-oxygen batteries (lithium, sodium, magnesium, etc.) which are now considered as the most promising electrochemical power sources due to their outstanding theoretical performance. For such devices carbon electrodes are highly attractive due to their light weight and low cost, and the effect of carbon surface chemistry on the processes occurring upon battery operation is of great importance.

The present research shows for the first time that oxygenation of carbon electrode surface does not affect the rate of one-electron oxygen reduction in aprotic media. At the same time, in Li+-containing electrolytes, oxygen groups enhance both the rate of electrochemical Li2O2 formation and carbon electrode degradation due to faster oxidation by lithium superoxide (LiO2) intermediate yielding carbonate species as a product.

The research is led by scientists from Lomonosov Moscow State University and the Semenov Institute of Chemical Physics, in collaboration with Friedrich–Alexander–Universität Erlangen-Nürnberg, IFW Dresden, Saint Petersburg State University, Donostia International Physics Center and Massachusetts Institute of Technology. 

Read more on the ALBA website

Image: C 1s core level spectra of a) pristine and b) oxidized graphene electrodes before and after discharge. C) Model spectroelectrochemical Li-O2 cell. D) Evolution of C 1s components’ ratios upon discharge for pristine and oxidized graphene.