Metal-organic frameworks (MOFs) constitute an important class of complex functional materials relevant, amongst others, for sensing, catalysis, optoelectronics and energy storage and conversion applications. However, the growth process, particularly the nucleation phase and the early growth stages that govern the final material properties, are not fully understood yet. Such knowledge is crucial for the design of tailored bottom-up MOF fabrication protocols.
We characterize the initial stages of potential-controlled MOF growth as a function of applied substrate potential, electrolyte composition, substrate morphology and functional ligands in situ with unprecedented molecular topographic and chemical resolution. Based on the detailed mechanistic insight into the molecular interactions underlying (early stage) MOF growth thus gained, we can rationally design improved preparation protocols for MOFs with desired properties.
To rationally design electrocatalysts, detailed understanding of the interrelation between the electronic structure of speciﬁc surface sites and their reactivity is required. For example, the inﬂuence of domain boundaries between different catalytic materials or the importance of step edges in contrast to terraces has to be further elucidated on the (sub-)nanometer level. We employ EC-TERS to characterize the electro-active surface sites and the site-speciﬁc and potential-dependent pathways of electrocatalytic processes to further understand the development of improved electrocatalysts.
Many vital functions of living organisms like respiration, photosynthesis or nitrogen ﬁxation rely on the ability of complex metal-ion containing molecules called metalloproteins to induce and sustain ﬁnely tuned sequences of chemical processes by exchanging electrons with fellow molecules. We aim to employ EC-TERS to obtain a quasi-atomistic picture of metalloprotein redox behaviour to improve our understanding, for example, of the (mal)functioning of metalloproteins in relation to physiological diseases or biophysical processes. (Funded through the Boehringer Ingelheim Foundation Plus 3 Programme.)
The organization of water in proton or anion exchange membranes determines to a large extent the performance of fuel cells, affecting both ion transport and catalytic efficiency. Thus, establishing the molecular properties, such as spatial arrangement and chemical interactions, of water in fuel cell membranes provides a physico-chemical basis for an improved understanding of device performance.
With help of coherent anti-Stokes Raman spectroscopy (CARS), we want to quantify the water content inside the membrane and visualize its distribution in 3D with (sub)micrometer resolution. The high sensitivity of CARS provides millisecond temporal resolution and thus allows us to directly monitor how membrane flooding and dehydration processes proceed.