An original selective and quantitative detection method for direct access to reactive oxygen species (ROS) generated in near-neutral aqueous solutions during transient electrochemical experiments is described herein. Several chemiluminescent probes, which were selected for their high selectivity toward ROS were used and the selective electrogenerated chemiluminescence (SECL) method was validated on several electrocatalytic materials known to exhibit different behaviors toward the oxygen reduction reaction (ORR); the examined electrodes consisted of platinum, Au(111), glassy carbon and boron-doped diamond (BDD). We first selected appropriate molecular probes that are suitable for use under electrochemical polarization conditions and that are chemiluminescent in the chosen aqueous solutions. The roles of the concentration, solubility and possible activation of the molecular probes were identified. Then, the information obtained by the simultaneous recording of the amperometric signal was correlated with the chemiluminescence intensity, which was measured with a highly sensitive photomultiplier tube (PMT). The experimental results were interpreted by constructing a potential vs. pH diagram for the oxygenated species. The complementary nature of the information about the mechanistic path of the ongoing mechanism of ORR on the different electrode materials allowed us to propose a unified scheme. A coupled proton electron transfer (CPET) mechanism can be invoked to explain the major differences observed from the identified reactive intermediates in relation to the electrocatalytic activity of the electrode materials.