New catalyst resists destructive carbon buildup in electrodes

Key challenges in the transition to sustainable energy include the long-duration storage of cheap, renewable electricity and the electrification of the heavy-freight transportation sector. Both challenges can be met using electrochemical cells. Solid oxide electrolysis cells are capable of highly efficient splitting of steam and CO2 to produce a synthetic H2–CO gas mixture (syngas), which can be converted into synthetic hydrocarbon transportation fuels using conventional industrial reactors. However, the efficiency of the process is limited by the risk of destructive carbon deposition inside the cells’ porous solid electrodes. A nickel catalyst is responsible for the carbon growth, but replacing this long-standing conventional catalyst has turned out to be highly challenging.

Now, researchers have used ambient-pressure x-ray photoelectron spectroscopy (APXPS) at ALS Beamlines 9.3.2 and 11.0.2 to probe the mechanisms by which carbon grows on different catalysts during CO2 electrolysis. Gadolinium-doped cerium oxide (GDC) is known to resist carbon growth, and the ambient-pressure experiments probed the degree and mechanism of this carbon resistance. The experimental data, subsequently confirmed by density functional theory calculations, revealed that the carbon atoms are energetically trapped by various oxygen species on the surface of GDC—a capability entirely lacking for nickel.

>Read more on the Advanced Light Source website

Image: Artistic representation of a nickel-based electrode as a broken down fuel pump and of a cerium-based electrode as a new, productive pump. Credit: Cube3D

The quest for atomic perfection in semiconductor devices

A research team, including scientists from MAX IV have reported in Nature Communications that the quest for atomic perfection in semiconductor devices was based on an oversimplified model.

Semiconductors are the fundamental building blocks of all modern electronics. Improvements to these materials could affect everything from the clock on our microwave to supercomputers used to crunch big data. The search to make them better involves looking at atomic level changes in semiconductor materials in order to understand how they could be improved, and even made perfect.

The problem with semiconductors and the way they are manufactured is that they need to be processed with metal contacts and thin insulating layers, and the interface between the semiconductor and these contacts contains a lot of defects which hamper device performance. If scientists can find a way to reduce the defects or eliminate them completely, then semiconductors could conceivably become faster and smaller. The problem is, these defects occur on the atomic scale and are very difficult to measure.

Scientists working at Max Lab, the predecessor to the newly built MAX IV, together with physicists from Lund University used the SPECIES beamline to investigate a common semiconductor synthesis method. Hafnium dioxide was deposited on the surface of indium arsenide and monitored using ambient pressure X-ray photoelectron spectroscopy (APXPS). The scientists were able to monitor the very first atomic layer that was deposited, and monitor the chemical reactions that were occurring as the process was underway.

>Read more on the MAX IV Laboratory website