Accelerated proton-coupled electron transfer kinetics of iron phthalocyanine for oxygen reduction via heteropoly blue clusters

Iron phthalocyanine (FePc) with tetracoordinated Fe-N 4 site shows promising activity for catalyzing the oxygen reduction reaction (ORR) in alkaline media. However, the consecutive proton-coupled electron transfer (PCET) steps with water as the proton donor and low electronic conductivity of FePc raise the kinetic barriers for device application. Herein, a significant effect of polyoxometalates (POMs) on the ORR kinetics of Fe-N 4 sites via surface coordination of FePc is revealed. POM clusters modulate the interactive steric/electronic environment of Fe-N 4 , leading to a low barrier for H 2 O cleavage to produce protons along with a high electron transfer rate, thereby accelerating the PCET steps of FePc. With precisely controlled electron charge of POM clusters, the influence and mechanism of heteropoly blue in promoting PCET steps of FePc relative to heteropoly acid are elucidated, and noticeably enhanced ORR activity and reaction current are achieved. These findings highlight the potential of POMs as ligands to optimize dynamics of Fe-N 4 atomic sites toward efficient alkaline ORR.