Reactive oxygen species formation at Pt nanoparticles revisited by electron paramagnetic resonance and electrochemical analysis

A combined electrochemical and electron paramagnetic resonance (EPR) procedure for the study of oxygen reduction reaction (ORR) intermediates generated at Pt nanoparticles (NPs) is validated in this work. Using spin-trap EPR complemented by electrochemical analysis, we show that we can detect and identify the free radicals that are produced during the ORR through trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) which are otherwise difficult to detect. Experiments with 5-(diethoxyphosphoryl)-5-methyl-1-pyrroline-N-oxide (DEPMPO) as spin trap show no evidence of (DEPMPO)-D-center dot-OOH and indicate that only (OH)-O-center dot radicals are trapped during the ORR. The results of this study serve as a functional proof-of-concept for further research on the identification of radical ORR intermediates in solution. We propose that our procedure can be used for a more rigorous quantification of free radicals involved in other electrochemical reactions.

Automated summary

The study validates a method combining electrochemical and electron paramagnetic resonance (EPR) techniques for investigating oxygen reduction reaction (ORR) intermediates at Pt nanoparticles. The results demonstrate the detection and identification of free radicals produced during ORR, providing a functional proof-of-concept for further research. The proposed procedure could enable a more rigorous quantification of free radicals in other electrochemical reactions.