Descriptor-informed oxidant selection in pulsed electrochemical AOPs: Cathode-favored periodate activation enables selective sulfamethoxazole oxidation

Oxidant selection in electrochemical advanced oxidation processes remains largely empirical because molecular and interfacial factors governing activation are not quantitatively linked to degradation performance. Here, a descriptor-informed framework was developed to rationalize oxidant-dependent activation in pulsed electrochemical AOPs. Six oxidants or redox-active precursors were evaluated using sulfamethoxazole degradation, and four descriptors-the LUMO-HOMO gap, vertical electron affinity, adsorption energy, and Bader charge transfer-were correlated with apparent rate constants. The preliminary descriptor-informed analysis captured the oxidant-dependent activation trend and identified periodate (PI) as the most favorable oxidant. Under identical conditions, pulsed electrolysis/periodate (PE/PI) achieved 95.43% sulfamethoxazole (SMX) removal with a rate constant of 0.10631 min-1, outperforming pulsed electrolysis/peroxymonosulfate (PE/PMS) and PE/H2O2. Mechanistic experiments and density functional theory (DFT) calculations showed that the superior PE/PI performance arose from stronger cathodic adsorption, more efficient interfacial electron transfer, and contributions from 1O2-mediated non-radical oxidation and IO3•-associated radical oxidation, while freely diffusing •OH contributed only marginally. Matrix tests further indicated that PE/PI is better suited to relatively clean waters, whereas PE/PMS offers greater robustness in complex matrices. This work extends empirical oxidant comparison toward descriptor-informed interpretation of oxidant-dependent activation.