Electrochemical impedance spectra of RuO₂ during oxygen evolution reaction studied by the distribution function of relaxation times

In this work, the distribution function of relaxation times (DFRT) of a RuO₂ catalyst is determined by Impedance Spectroscopy Genetic Programming (ISGP). The resulting DFRT plots contain three peaks that vary with the overpotential. This discloses the presence of various electrochemical phenomena at different relaxation times in the catalyst. The effective resistance to charge transfer during the oxygen evolution reaction (OER) is small at low overpotential but becomes dominant at high overpotential. Moreover, we can track the change in each peak after a stability test: the resistance to both the production rate of intermediates and charge transfer show an increase while the solution resistance is almost constant. Hence, ISGP opens a new avenue for analyzing catalysts and providing detailed information about the resistance contributed by various phenomena.