Interfacially Stitched Bilayer Anodes Enforce Surface-Confined Hydroxyl Radical Chemistry in Complex Wastewater

Abstract

Electro-oxidation technology holds great promise for wastewater treatment, yet its practical application remains hindered by insufficient selectivity in oxidative species generation and limited electrode stability under harsh operating conditions. Here, we devise a layer-by-layer anion–cation engineering strategy to fabricate an Sb–F-stitched SnO2 bilayer anode (SF–SnO2 BA), in which a fluorine-regulated SnO2 catalytic layer is interfacially anchored onto a dense Sb–SnO2 interlayer coated on a Ti foam scaffold. This hierarchically stitched architecture simultaneously modulates interfacial charge transport and stabilizes the catalytic layer, leading to markedly enhanced electrocatalytic oxidation performance across a broad pH range (1–11). When integrated into a scalable flow-through electro-oxidation system, SF–SnO2 BA enabled highly efficient mineralization (>80%) of four representative industrial wastewaters at low energy consumption. Furthermore, the system also demonstrated remarkable operational durability, sustaining high mineralization efficiency (60–80%) over 14 consecutive days during continuous treatment of real aniline wastewater from a coal chemical plant. In situ spectroscopic investigations coupled with theoretical calculations collectively elucidated that water molecules are initially oxidized on the SF–SnO2 BA surface to form Sn–OH intermediates, which are subsequently transformed into Sn–O species at elevated potentials. Notably, the cooperative F···Sn–O* structural motif directs the generation of surface-confined •OH, which acts as the dominant oxidative species for pollutant degradation. This interfacially stitched bilayer anode offers a viable route toward green and sustainable electrochemical oxidation technologies for practical wastewater treatment.