Enhanced Electrochemical Oxygen Evolution Reaction Enabled by Ni Cavity-Arrayed Electrodes

The water electrolysis is mostly limited by the slow kinetics of the oxygen evolution reaction (OER) including the interfacial electron and mass transfer and autoionization reactions. Especially in the neutral pH condition, slow rate of the autoionization reaction of water molecules also limits the electrolysis. The vibrational strong coupling, where the matter excitation is coupled to the cavity vacuum field mediated by a virtual photon, can be expected to modulate the physicochemical properties of water. Here, we utilized the cavity-arrayed electrode for the promotion of the OER. The OER activities of Ni cavity-array electrodes were evaluated from the oxygen bubble growth behavior. The Tafel slopes from the bubble analyses were modulated from 120 mV per decade to 30 mV per decade and the OER activity was enhanced by the cavity-arrayed electrode. This enhancement was explained with regards to the acceleration of autoionization of water molecules under the vibrational strong coupling. This study demonstrates that the cavity systems modulate the thermodynamic equilibrium of water autoionization under the vibrational strong coupling of liquid water at room temperature, leading to enhanced OER.