Potential-gated Co-Cu dual-atom cascades for selective oxygen-to-radical conversion for energy-efficient water purification

Electro-Fenton (EF) oxidation efficiency has been constrained by the difficulty of balancing in-situ H 2 O 2 generation with subsequent catalytic activation on a structurally ill-defined interface. In this work, we designed dual-atom catalysts (DACs) to decouple these two steps through adjacent, functionally differentiated active centres operating synergistically. A precisely engineered Co-Cu-N 2 O 4 coordination was obtained via a polymerisation-pyrolysis directed molecular-transformation route. During EF catalysis, the Co-Cu-N 2 O 4 motif drives bidirectional electronic redistribution between the Co and Cu sites, enabling an efficient oxygen-reduction cascade. Specifically, the Co site selectively mediates H 2 O 2 electrosynthesis via two-electron reduction, which is subsequently activated at the adjacent Cu site through OOH⁎ dissociation to form high-valent Cu(III)-OH species and hydroxyl radicals (•OH). Operando ATR-FTIR captures a previously unresolved potential-gated redistribution of OOH⁎ adsorption: at 0.20 V, OOH⁎ preferentially adopts a Cu-associated adsorption configuration favourable for Cu(III)-OH and •OH formation, whereas more negative potentials favour a Co-associated OOH⁎ configuration, triggering the unproductive H 2 O-formation pathway. When integrated into an electrified flow-through membrane reactor, the system achieves >90% single-pass removal of sulfamethoxazole (SMX) and maintains stable operation for over 100 h. This work provides design principles for dual-atom interfaces and reveals the molecular-level cooperation that enables efficient cascade environmental electrocatalysis.