Direct measurement of the oxygen reduction reaction kinetics on iron phthalocyanine using advanced transient voltammetry

Platinum group metal (PGM)-free catalysts are promising candidates to replace PGM catalysts for the oxygen reduction reaction in fuel cells. While methodologies to determine the number of active sites are under intense development, experimentally quantifying the parameters governing the kinetics of the reaction remains rare, albeit its potential for paving the pathways for future catalysts development. The use of transient voltammetry to probe electrocatalytic reactions by varying the measurement timescales and quantifying the reaction parameters via detailed microkinetic models has shown immense success in uncovering hidden mechanistic insights, connecting theory and experiments. Here we present the application of Fourier-transformed alternating-current voltammetry for analysis of the oxygen reduction reaction electrocatalysis on a model PGM-free catalyst, iron-phthalocyanine, to decipher the kinetic and thermodynamic parameters governing the reaction. These parameters are used to shed light on the limiting steps governing the reaction and to present possible avenues to increase the performance of PGM-free catalysts. (Figure presented.)