Descriptor-informed oxidant selection in pulsed electrochemical AOPs: Cathode-favored periodate activation enables...

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.