Unveiling the key influencing factors towards electrode/electrolyte interface control is a long-standing challenge for a better understanding of microscopic electrode kinetics, which is indispensable to building up guiding principles for designer electrocatalysts with desirable functionality. Herein, we exemplify the oxygen evolution reaction (OER) via water molecule oxidation with the iridium dioxide electrocatalyst and uncovered the significant mismatching effect of pH between local electrode surface and bulk electrolyte: the intrinsic OER activity under acidic or near-neutral condition was deciphered to be identical by adjusting this pH mismatching. This result indicates that the local pH effect at the electrified solid–liquid interface plays the main role in the “fake” OER performance. This local pH effect on the OER electrode process is further verified by integrating a wide spectrum of analytical approaches. This study will accelerate the understanding of the local proton-induced effect on electrode interface processes and the development of advanced electrochemical activity.