Institute of Materials Chemistry
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Fundamentals

Mechanistic studies

We are interested in the complex mechanism of hydrogen evolution in heterogeneous photocatalysis. For this, we use a variety of techniques to characterize the photocatalyst (e.g. TEM, XPS, XRD, FTIR, BET, chemisorption) and system (e.g. on­line gas analyzer, GC, ATR flow cell,).

Recently, we focused on what we call “deactivation” of a photocatalyst: An early stage loss in activity in hydrogen evolution from aqueous methanol solutions. This phenomenon – to the best of our knowledge –  has not been reported in literature so far.

Process of Fluorescence quenching and effect of blocking layer

Investigating interfacial charge and energy transfer

The charge and energy transfer processes in nanocarbon-inorganic hybrids is vital to the improved properties but is still not clearly understood. Specifically, what is the maximum distance from which the charge transfer can occur? What is the ideal nanocarbon type/surface chemistry? How can the electron-hole lifetime be maximized?

To investigate the electron transfer from the inorganic material to the CNTs, we chose ZnO as the inorganic material due to its strong photoluminescent and photocatalytic properties. To investigate the charge transfer, we conduct fluorescence quenching and lifetime experiments. Introducing an Al2O3 blocking layer with variable thickness allows to determine the distance dependence of the ocurring interfacial processes. The required thin and conformal coatings are obtained by atomic layer deposition (ALD), which has proven to be the method of choice.

[ALD synthesis] N. Kemnade, C. J. Shearer, D. J. Dieterle, A. S. Cherevan, P. Gebhardt, G. Wilde, D. Eder, Nanoscale 2015, 7, 3028–3034; DOI:10.1039/C4NR04615C.