Interfacial Mechanisms of Hydroxyl Radicals in Electrochemical Advanced Oxidation

The performance of electrochemical advanced oxidation processes (EAOP) is governed by the nature of the electrode material, with catalytic activity intrinsically linked to the generation of hydroxyl radicals that initiate oxidation. Here, using boron-doped diamond (BDD), widely recognized for its high hydroxyl radical yield, and platinum (Pt) as a contrasting reference electrode, we combine grand canonical density functional theory with machine learning molecular dynamics to investigate the generation, stabilization, and decay of OH• radicals at electrochemical interfaces. For BDD and Pt systems examined here, our calculations support an outer-sphere electron transfer pathway for OH• generation and indicate that the key difference between the two electrodes lies in the subsequent interfacial consumption of OH•. Although hydroxyl binding on BDD is stronger than on Pt, surface-bound OH* species on BDD are chemically inert and do not exhibit radical character. As a result, BDD suppresses OH• recombination with surface OH*, increasing the relative availability of OH• in the interfacial region. In contrast, on Pt electrodes, OH* possesses radical character that promotes rapid radical recombination and consequently limits catalytic oxidation efficiency. This study identifies suppressed interfacial OH• recombination as a key factor controlling OH• availability and EAOP performance, suggesting that surface shielding against radical quenching could serve as a design strategy for next-generation oxidation anodes.