Identifying Electrocatalytic Activity Sequence of Metal Phthalocyanines for the Hydrogen Peroxide Oxidation Reaction

The hydrogen peroxide oxidation reaction (HPOR) plays a vital role in the emerging H2-H2O2 cycle energy storage system, in which the rational design of HPOR electrocatalyst is essential for achieving high system efficiency. Herein, we establish the HPOR activity trends using structurally well-defined metal phthalocyanines (MPc) as model catalysts via a combined experimental and computational approach. The measured activity sequence follows the order of CoPc > FePc > MnPc > ZnPc > H2Pc > NiPc > CuPc based on their site-normalized exchange current (i0-s). Theoretical calculations indicate that the binding free energy of hydroperoxyl intermediate, HOO*, on MPc (ΔGHOO*) is the activity descriptor for HPOR. A volcano-type activity trend is observed by correlating the logarithm of i0-s (logi0-s) with the ΔGHOO* values and agrees with the theoretical predictions. This HPOR activity trend provides insights into the design of highly active electrocatalysts for HPOR and related energy applications.