Berlin 2018 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 49: Soft Matter Physics: Emerging Topics, New Instruments and Methods

CPP 49.7: Vortrag

Mittwoch, 14. März 2018, 16:45–17:00, C 230

In-situ characterization of NiFeOOH for the oxygen evolution reaction using X-ray absorption spectroscopy — •Dorian Drevon — Albert-Einstein-Strasse 15, Berlin

Reducing global carbon emissions will require efficient catalysts for use in solar-to-fuel conversion processes, where electrochemical water oxidation is the key to a zero emission cycle. For this, understanding the fundamental processes of the oxygen evolution reaction (OER, 4OH- * O2 + 2H2O + 4e-) from a mechanistic perspective is an important goal for the design of highly efficient and functional electrocatalysts.

The Ni-Fe oxyhydroxide electrocatalysts are currently the most active OER catalysts in alkaline media Combining Ni and Fe leads to an excessive increase in the catalytic activity and a coincident change at the metal redox states, witnessing of the electronic interaction between Ni and Fe sites. However, the complexity of the metal redox activity have resulted in a debate regarding the OER active state in this electrocatalyst.

In-situ O K-edge X-ray and Fe,Ni L-edge absorption fine structure (XAFS) spectroscopy was used to investigate the electronic and structural change in the Nickel Iron electrocatalyst during the oxygen evolution reaction (OER). Above 0.5V versus Ag/AgCl, we were able to see the rise of pre-features at the Oxygen k-edge and post feature at the Nickel L-edge but they were absent in the Fe L-edge suggesting that Ni undergoes a change in its oxidation state from Ni(II) to of Ni(III,IV) when the catalysts becomes active.