Pt based materials are used extensively in heterogeneous catalytic processes, but are notoriously susceptible to poisoning by CO. In contrast, highly dilute binary alloys formed of isolated Pt atoms in a Cu metal host, known as PtCu single-atom alloys (SAAs), are more resilient to CO poisoning during catalytic hydrogenation reactions. In this article, we describe how CO affects the adsorption and desorption of H2 from a model PtCu(111) SAA surface and gain a microscopic understanding of their interaction at the Pt atom active sites. By combining temperature programmed desorption and scanning tunneling microscopy with first principles kinetic Monte Carlo we identify CO as a Pt site blocker that prevents the low temperature adsorption and desorption of H2, the so-called molecular cork effect, first realized when examining PdCu SAAs. Intriguingly, for the case of PtCu, H2 desorption occurs before CO release is detected. Furthermore, desorption experiments show a non-linear relationship between CO coverage of the Pt sites and H2 desorption peak temperature. When all the Pt atoms are saturated by CO a very sharp H2 desorption feature is observed 55 K above the regular desorption temperature of H2. Our simulations reveal that the origin of these effects is the fact that desorption of just one CO molecule from a Pt site facilitates the fast release of many molecules of H2. In fact, just 0.7 % of the CO adsorbed at Pt sites has desorbed when the H2 desorption peak maximum is reached. The release of H2 from CO corked PtCu SAA surfaces analogous to the escape of gas from a pressurized container with a small puncture. Given that small changes in CO surface coverage lead to large changes in H2 evolution energetics the punctured molecular cork effect must be considered when modeling reaction mechanisms on similar alloy systems.
Angelos has accepted a position in Cambridge, and so the ICE group is moving! It’s going to be a reasonably slow multi-year phase transition. You can find more information in the official announcement. Congratulations, Angelos, and all the best for this exciting new opportunity!
Angelos has appeared on Clarivate’s ‘Highly Cited Researchers’ list for the second year in a row. Inclusion on the list is based on the number of recent publications that ranked in the top 1% by citations in a given field and year. For further details see: https://www.ucl.ac.uk/news/2019/nov/ucl-academics-named-global-list-influential-researchers Congratulations!
Martin won the Marshall Stoneham prize for his PhD thesis on “Merging data-driven and computational methods to understand ice nucleation”. It is awarded by the Condensed Matter & Materials Physics Group (CMMP) for outstanding postgraduate research. Well done!
The second annual Materials & Molecular Modelling (MMM) Hub Conference and User Meeting took place on 3-4 September. Many excellent talks demonstrated how the computational resources provided by the MMM Hub are used to tackle challenges in many areas of biological, chemical, and physical research. This was also illustrated by more than 50 posters, spanning […]
Last weekend, the ICE group gathered in York for the International Materials Simulation Workshop. Current and former members as well as collaborators talked about their recent projects and discussed how to tackle society’s big challenges, utilize advancements in methodology and make the most of fruitful collaborations. The meeting highlighted the diverse range of problems that […]
The ICE group will be participating in the Castle Triathlon series for the third year in a row. This time, three relays teams are going to compete at Castle Howard, near York, on 21 July. They will be swimming, cycling and running a combined distance of roughly 280 km! As part of the tradition, the […]
A 2-year postdoc position is available in the Condensed Matter Physics group at the University of Manchester. The project will be carried out in collaboration with the ICE group and involves developing and applying theoretical models to understand the anomalous dielectric behaviour of water under confinement (Fumagalli et al. Science 360, 1339-1342, 2018). You can […]
Angelos set a new world record for the “fastest marathon dressed as a scientist (male)” at this year’s London Marathon, finishing in 3:22:51. Congratulations! He also managed to raise more than £3000 in support of WaterAid, an international charity working to provide clean water and decent toilets to people all over the world. Many thanks […]
The ICE group has a new member: Julia will be working on C-H activation at single-atom alloy catalysts. The project involves collaboration with Michail Stamatakis from UCL’s Department of Chemical Engineering. We hope you will have a pleasant and productive time in the ICE group!
In a recently published Nature Reviews Chemistry article, titled “Surface premelting of water ice”, Ben Slater and Angelos review the current understanding of the quasi-liquid layer (QLL) that forms on the surface of ice. The review describes how advances in experimental and computational techniques furthered our understanding in the years since Faraday first postulated the […]