This study deals with the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Ca2+ containing dimethyl sulfoxide (DMSO) on atomically smooth and rough platinum surfaces. We demonstrate via cyclic voltammetry, differential electrochemical mass spectrometry (DEMS) and rotating ring disk electrode (RRDE) investigations with variation of the electrode surface roughness and atomically surface structure, that the CaO/CaO2 adsorbate layer formation determines the ORR product distribution. We found that on Pt electrodes peroxide is formed on the clean electrode, whereas superoxide is formed at the adsorbate covered electrode. We furthermore identified four key parameters, which strongly affect the ORR product distribution. The electrode oxide interaction: A strong interaction shifts the product distribution to larger superoxide contribution. The alkaline earth metal oxide interaction: A strong interaction shifts the product distribution to larger peroxide contribution. The electrode surface area: A large electrode surface area delays the completion of the adsorbate layer and increases the peroxide contribution. Electrode surface defects: Defects allow for faster nucleation and thus foster the adsorbate formation, which finally leads to a larger superoxide contribution. Finally, reviewing earlier results of our group we provide a more general mechanism for the oxygen reduction alkaline earth metal cation containing DMSO, for a variety of electrode materials.

Towards a generalized ORR mechanism in M2+ containing DMSO – Oxygen reduction and evolution in Ca2+ containing DMSO on atomically smooth and rough Pt

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.