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Upcoming seminars at the Ångström laboratory


May 9, 2018: Elodie Anxolabéhère-Mallart, Laboratoire d’Electrochimie Moléculaire, UMR CNRS, Université Paris Diderot

Time: 15:15 in the seminar room, Ångström laboratory, House 7, floor 1.

Title: Breaking and forming bonds with electrons and protons using earth abundant metal complexes as catalysts. 

Abstract: 

Our work relates to the development of processes for energy storage or new synthesis process. Our major goal is to develop efficient electro-catalysts for O2 activation, CO2 reduction or H2 evolution based on earth abundant transition metal catalysts. This requires deciphering the parameters that control the factors that govern the reactivity of the catalysts and the nature of the intermediates. We address this question through electrochemical methods coupled to spectroscopies (UV-vis, EPR) which provide insights into the mechanism of these fundamental catalytic reactions. 
We will present our last results on the synthesis, characterization and reactivity studies on M-peroxo and M-hydroperoxo (M = Mn, Fe) and will show how our electrochemical approach can give insights into the involved mechanisms (see scheme below).
We will also present recent results on molecular catalysis of electrochemical reduction of CO2 using Fe and Co complexes and H2 evolution using Co complexes.





May 16, 2018:  Yogi Surendranat, Department of Chemistry  MIT

Time: 15:15 pm in the seminar room, Ångström laboratory, House 7, floor 1.

Title: “Bridging Molecular and Heterogeneous Electrocatalysis Through Graphite Conjugation”

Abstract:The efficient interconversion of electrical and chemical energy requires catalysts capable of accelerating complex multi-electron reactions at electrified interfaces. These reactions can be carried out at the metallic surface sites of heterogeneous electrocatalysts or via redox mediation at molecular electrocatalysts. Molecular catalysts yield readily to synthetic alteration of their redox properties and secondary coordination sphere, permitting systematic tuning of their activity and selectivity. Similar control is difficult to achieve with heterogeneous electrocatalysts because they typically exhibit a distribution of active site geometries and local electronic structures, which are recalcitrant to molecular-level synthetic modification. However, metallic heterogeneous electrocatalysts benefit from a continuum of electronic states which distribute the redox burden of a multi-electron transformation, enabling more efficient catalysis. We have developed a simple synthetic strategy for conjugating well-defined molecular catalyst active sites with the extended states of graphitic solids. Electrochemical and spectroscopic data indicate that these graphite- conjugaterd catalysts do not behave like teir molecular analogoues, but rather as metalllic active sites with molecular definition, providing a unique bridge between the traditionally disparate fields of molecular and heterogeneous electrocatalysis.



Previous news and events


Feb 12: Andrea Pavlou, Julien Jacques, Nigar Ahmadova, Fikret Mamedov and Stenbjörn Styring published an article in Scientific reports: 

The wavelength of the incident light determines the primary charge separation pathway in Photosystem II

Abstract:Charge separation is a key component of the reactions cascade of photosynthesis, by which solar energy is converted to chemical energy. From this photochemical reaction, two radicals of opposite charge are formed, a highly reducing anion and a highly oxidising cation. We have previously proposed that the cation after far-red light excitation is located on a component different from PD1, which is the location of the primary electron hole after visible light excitation. Here, we attempt to provide further insight into the location of the primary charge separation upon far-red light excitation of PS II, using the EPR signal of the spin polarized 3P680 as a probe. We demonstrate that, under far-red light illumination, the spin polarized 3P680 is not formed, despite the primary charge separation still occurring at these conditions. We propose that this is because under far-red light excitation, the primary electron hole is localized on ChlD1, rather than on PD1. The fact that identical samples have demonstrated charge separation upon both far-red and visible light excitation supports our hypothesis that two pathways for primary charge separation exist in parallel in PS II reaction centres. These pathways are excited and activated dependent of the wavelength applied.


Nov. 30, 2017: The Swedish Energy Agency has granted funding for energy related basic research to: 
Johannes Messinger and Thomas Wågberg. 


Nov. 3, 2017: Luca D'Amario, Jens Föhlinger, Gerrit Boschloo and Leif Hammarström published an article in Chemical Science:

"Unveiling hole trapping and surface dynamics of NiO nanoparticles"

Abstract: The research effort in mesoporous p-type semiconductors is increasing due to their potential application in photoelectrochemical energy conversion devices. In this paper an electron–hole pair is created by band-gap excitation of NiO nanoparticles and the dynamics of the electron and the hole is followed until their recombination. By spectroscopic characterization it was found that surface Ni3+ states work as traps for both electrons and holes. The trapped electron was assigned to a Ni2+ state and the trapped hole to a “Ni4+” state positioned close to the valence band edge. The recombination kinetics of these traps was studied and related with the concept of hole relaxation suggested before. The time scale of the hole relaxation was found to be in the order of tens of ns. Finally the spectroscopic evidence of this relaxation is presented in a sensitized film.




Last updated April 23, 2018