PCCP Blog

Gold has been revered by humanity for millennia as a decorative expression of status and a way to measure monetary wealth. It can be found pure, it doesn’t tarnish with use, and is easily worked. So far so good, and gold is still valued for those exact properties today. However, from a chemical perspective it was long considered inert, and other rarer, more expensively extracted metals became the darlings of catalysis. More recently, in a similar manner to the development of noble gas chemistry, there has been a surge of discovery and development in the uses of gold as a catalytic material.

Rodriguez and Koper provide a fascinating review of the surprising catalytic properties that have been discovered over the last few decades, with a focus on electrocatalysis. They gather up various findings from all over the world, consolidate them and tease out the recurrent themes. It seems that gold catalysts are not easily poisoned, which can only be a good thing, but can be very choosy about the types of reactions they will catalyse, with different surfaces even having different catalytic preferences. All this suggests an electrocatalyst with the potential to be highly tuneable. If that pricks your curiosity then I strongly suggest that you read this perspective article, which surely forms a useful basis for future investigations.

Electrocatalysis on gold
Paramaconi Rodriguez and Marc T. M. Koper
Phys. Chem. Chem. Phys., 2014, Advance Article
DOI: 10.1039/C4CP00394B

It is a problem that everybody is familiar with; the increasing levels of carbon dioxide present in the atmosphere as a direct consequence of the industrial activity of humanity are contributing to climate change. New carbon capture technologies are therefore big business and big politics, with enormous quantities of time, money and rhetoric devoted to the subject the world over. There is an expectation that scientists will somehow save the human population from itself, preferably quickly, safely, cheaply and without the general populace having to radically alter their lifestyles.

Whilst I’m not necessarily saying they’ve found the answer, Sun and co-workers have certainly hit on an idea that merits further exploration with their study of solid boron as a new candidate for carbon dioxide capture. Their calculations predict that the amphoteric nature of certain boron allotropes means that they will spontaneously form strong Lewis acid-base interactions with multiple carbon dioxide molecules per individual boron structure.

I’m sure that there are plenty of researchers out there who could experimentally verify the predictions of this computational study (which the authors state was motivated by the desire for somebody to do just that) and develop their findings to the potential benefit of the entire planet.

The only question, surely, is who will get there first?

By Victoria Parkes

Are you up for the challenge? Read the full details of this PCCP article now:

A computational study of carbon dioxide adsorption on solid boron
Qiao Sun, Meng Wang, Zhen Li, Aijun Du and Debra J Searles
DOI: 10.1039/C4CP00044G

t

If you enjoyed this, you may also be interested in our Faraday Discussion on Carbon Dioxide Utilisation which will take place in Sheffield in 2015 – find out more on the website.

Hydrogen demonstrates a staggering variation in its interactions with other materials. When it encounters metals, the norm is for it to dissociate and then chemisorb as atoms carrying a negative charge. It has already been established that this is not the case when hydrogen chemisorbs onto gold. It can chemically mimic gold atoms in clusters as gold has a high electron affinity and is isoelectronic to cationic hydrogen. Vetter et al. have conducted a study to determine whether this behaviour extends to the other coinage metals, despite their lower electron affinities.

The group employed high level calculations to predict the molecular orbitals of both the pure metal clusters and those where one of the metal atoms was replaced by hydrogen. They also recorded photoelectron spectra of the clusters so that their theoretical results might be backed by experimental findings, thus enabling a more thorough interpretation.

Their results are interesting, suggesting that although the charge on the hydrogen atom remains negative as one would expect at lower electron affinities, the structure of the cluster remains unperturbed, as in the gold case, when the original metal cluster is sufficiently large.  This naturally leads to speculation about the comparative reactivity of these monohydride clusters, and the authors’ findings on the subject are eagerly awaited.

by Victoria Parkes

Read the full story here:

Hydrogen mimicking the properties of coinage metal atoms in Cu and Ag monohydride clusters
Karsten Vetter, Sebastian Proch, Gerd. F. Ganteför, Swayamprabha Behera and Puru Jena
DOI: 10.1039/C3CP53561D

There can be no doubt that fullerene research is both interesting and varied; we have created carbon nanotubes from them, we can put things inside them, they have diverse medical uses, and recently evidence has been presented suggesting that they are found in space.  In this paper, Raggi et al. take a computational approach to investigate the dielectric properties of C₆₀, the smallest of the fullerene family, and the first to be predicted and discovered.

The results of their study are quite striking. They found that by varying the distance between the fullerene and the point charge, the surface charge density of C₆₀ can be manipulated. In other words, they predict that one could selectively polarise a fullerene molecule to a greater or lesser extent. They were also able to predict the separation parameters necessary in order to achieve this, including identifying the tipping point at which the charge distribution is expressed as a purely positive hemisphere and a purely negative hemisphere.

This study has important implications for future studies into fullerenes as it demonstrates that assuming a uniform surface charge density can only be valid above a certain threshold separation from the point charge. As well as being important to the understanding of fullerene-ion collisions, this new insight could potentially lead towards an understanding of fullerene fission mechanisms.

by Victoria Parkes

Read the full details of this exciting research in PCCP:

Surface-charge distribution on a dielectric sphere due to an external point charge: examples of C₆₀ and C₂₄₀ fullerenes
Gerardo Raggi, Anthony J. Stace and Elena Bichoutskaia
DOI: 10.1039/C3CP53522C