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CCI Solar Events - March, 2018 Pick date

1 PM

CCI Cybermeeting - Zhaoyu Jin, Bard Group - UT Austin

01:00 PM to 02:00 PM, March 8, 2018

Location: eZuce

Surface Interrogation of Manganese Oxide Oxygen-Evolving Catalysts by Scanning Electrochemical Microscopy

Although numerous spectroscopic studies and other ex-situ or in-situ approaches have revealed much about transition-metal oxide catalysts for water oxidation, they are generally limited to bulk film measurements that provide little information about the real surface sites and intermediates in direct contact with water that are responsible for the actual electrocatalytic activity. Surface interrogation scanning electrochemical microscopy (SI-SECM) provides a good approach for the direct quantification and time-resolved detection of surface active sites and intermediates on the catalyst.

In this meeting, we will talk about an application of SI-SECM on studying the electrodeposited manganese oxide (MnOx) catalyst with mixed valence in neutral electrolyte (pH = 7.0). First, the quantification of the surface Mn site density will be presented to show how the oxidation state of Mn changes with potential. In addition, a high-valent intermediate Mn(V) that is able to chemically oxidize water has been found as the turnover center by redox titration at the higher potential after the generation of Mn(IV).

Next, investigation of oxygen-evolving kinetics on Mn(V) illustrates two behaviors of sites with different reaction rate constant. We will discuss the structural effect of the deposited MnOx related to the “fast” and “slow” kinetic site.

Finally, since the electrosynthesis potential has been reported as a critical condition for the activity of the catalysts, results from the “fast” site fraction and total site density will help design and develop more efficient Mn-based catalysts.