Probing the Breathing of Reactive Electrical Double Layer

Fundamental understanding of the electrical double layer (EDL) under reactive conditions remains limited, hindering progress in electrocatalysis and energy conversion technologies. Herein, microscopic dynamics of the EDL during the hydrogen evolution reaction (HER) is probed using in-situ surface-enhanced infrared adsorption spectroscopy (SEIRAS). We demonstrate that the inner layer of the EDL contracts and then expands back in a positive-negative-positive potential cycle, a process we term “EDL breathing”. Challenging the classical static picture of the EDL, the contraction of inner layer significantly amplifies the strength of local electric field, revealing a nonlinear relationship between the local electric field and electrode potential. This work deepens our understanding of reactive electrocatalytic interfaces and provides novel insights into EDL dynamics, crucial for leveraging the EDL to advance green technologies.