Visualizing dynamic evolution of surface electrochemical potential on solid-state electrolyte via spatially resolved photoelectron measurementsOA

The dynamic evolution of surface electrochemical potential of the electrolyte plays a key role in the performance of solid-state electrochemical devices,while its real-time characterization remains challenging.Here,we visualize the dynamic evolution of the surface electrochemical potential on yttria-stabilized zirconia(YSZ)in a planar AuYSZAu model cell,using spatially resolved photoelectron-based techniques including photoemission electron microscopy(PEEM)and micro-region X-ray photoelectron spectroscopy(μ-XPS).PEEM reveals two sequential reaction fronts in YSZ under cathodic polarization,corresponding to the evolution of the chemical potential of oxygen ions,with a faster propagation speed on the top surface and a slower one in the near-surface region.XPS measurements quantitatively reveal the time-dependent electric potential distribution across YSZ surface.COMSOL simulations confirm the presence of a stronger electric field at the top surface,particularly at the advancing reaction fronts,compared to the near-surface region.The critical role of the electric field in driving surface reactions is further supported by the enhanced reactions observed at the tips of the zigzag-shaped electrode edges.This work offers mechanistic insights into the coupling between electrochemical potential dynamics and electrolyte reactions.