Enhancing the Catalysis of Oxygen Reduction Reaction via Tuning Interfacial Hydrogen Bonds

Abstract Proton activity at the electrified interface is central to the kinetics of proton-coupled electron transfer (PCET) reactions for making chemicals and fuels. Here we employed a library of protic ionic liquids in an interfacial layer on Pt and Au to alter local proton activity, where the intrinsic ORR activity was enhanced up to 5 times, exhibiting a volcano-shaped dependence on the pKa of the ionic liquid. The enhanced ORR activity was attributed to favorable proton transfer kinetics for strengthened hydrogen bonds between the ionic liquid to the ORR product with comparable pKa. This proposed mechanism was supported by in situ surface-enhanced Fourier-Transform Infrared Spectroscopy and our simulation of PCET kinetics based on computed proton vibrational wavefunction at the H-bond interface. These findings highlight opportunities in using non-covalent interactions of hydrogen bond structures and solvation environments at the electrified interface to tune the kinetics of ORR and beyond.