In situ surface potential evolution along Au/Gd:CeO2 electrode interfaces

We present an investigation of electroactive Au/gadolinium doped ceria electrode interfaces under CO2/CO co-electrolysis environments using a combination of in situ high temperature scanning surface potential microscopy (HT-SSPM) and modified Poisson-Cahn (PC) models. Here charged surface adsorbate-oxygen vacancy interactions manifested in HT-SSPM potential profiles as small perturbations of opposite sign in reference to the applied biases. The positive deviation of surface potential on Au from applied cathodic biases is attributed to the work function difference between gold (ϕAu ∼ 5.31 eV) and graphitic carbon deposits (ϕC ∼ 5.0 eV) formed through CO disproportionation. The negative potential deviation from the applied anodic bias is attributed to negatively charged carboxylates. Results of the PC model confirmed the affinity of oxygen vacancies for the surface, thus supporting in situ experimental evidence of surface vacancy accumulation/depletion processes induced by cathodic/anodic biases.