Electrolyte Switching Reveals Electric Double Layer Dynamics and Electrocatalytic Electrolyte Effects
Year: 2026
Type: preprint
Abstract: New insights into the electric double layer (EDL) under strongly driven electrocatalytic (EC) conditions are obtained by measuring its rearrangement kinetics in response to abrupt switching of bulk electrolyte composition (55 ms for complete exchange up to the ordered layers of the EDL) The aqueous alkaline hydrogen evolution reaction (HER) is used as a model EC system, motivated by its opposite alkali metal hydroxide effect: catalyst activity decreases with increasing cation radius on Pt (Li + > Na + > K + > Cs + ) whereas the trend is opposite for Au and Ag. Monitoring the constant potential HER current as the electrolyte composition is switched between two different cations (e.g. Li + and Cs + ) provides an overall kinetic picture as the EDL rearranges to accommodate the new cation. For both Pt, Au, and Ag, the transition time is asymmetric; switching from a smaller ionic radius to a larger one is faster than the reverse (e.g. 95 ± 31 ms for Li + → K + compared to 352 ± 38 ms for K + → Li + on Pt at -200 mV vs RHE). Transition times also increase with greater ionic radius difference between the cations and at more negative potentials. The transition time trends are consistent with more weakly hydrated cations having stronger electrostatic ion-electrode interactions and hence being slower to leave. EDL rearrangement kinetics appear unaffected by the simultaneously occurring HER. Mixing LiOH with the stickier K/CsOH electrolytes produced a smooth, continuous variation in HER kinetics with increasing K/CsOH fraction on Pt, Au, and Ag, even though we expect the closest ion plane (CIP) to be mostly K + /Cs + over the range. This shows that EDL structure beyond the CIP can also influence HER kinetics on Pt, Au, and Ag. Our work emphasizes the spatial extent of electrolyte influence which needs to be captured by theory.
Source: ChemRxiv
Authors: Calton J. Kong, Joel W. Ager
Institution: Lawrence Berkeley National Laboratory
Language: English
Field: Energy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7222996592