This phenomenon is well documented and has been observed on various surfaces (Ni, Au, Pt, Pd, IrO2, RuO2) supported by O2−, Na+ and proton conducting solid electrolytes.
The EPOC effect was firstly discovered by M. Stoukides and C. Vayenas in the early 1980s and have been widely studied by various research groups for more than 100 heterogeneous catalytic reactions of mostly gaseous molecules.
Earlier mechanistic proposals for the EPOC phenomenon with solid electrolytes mainly emphasized tuning of the local work function of the surface of conductive catalysts by spilled-over species, which are in-situ generated during electrochemical polarization processes.
[3][4] It has been proposed that the spilled-over species can subsequently modulate the chemisorption strength between surface adsorbates (intermediates) and catalyst binding sites, thereby influencing the rate or selectivity of the target reactions significantly.
[10] Even though the perturbation of the local work function and tuning of surface binding strengths of intermediate species were suggested as the origin for the EPOC effects in the liquid electrolyte systems as similar to the EPOC examples of high-temperature solid electrolyte systems, thorough theoretical studies supported by clear experimental evidence have not been addressed.