Sequential H<sub>2</sub>O<sub>2</sub> Production and Activation via Dual-Cathode Flow-Through Electrocatalysis for Efficient and Sustainable Water Treatment.

Abstract

Conventional electrochemical water treatment typically focuses on anodic oxidation or cathodic reduction. In contrast, highly efficient anode-cathode synergy can achieve effects beyond the capability of either single electrode, enabling low-carbon and sustainable pollutant removal. Herein, we developed a reagent- and aeration-free system for continuous ·OH generation by integrating anodic O₂ evolution with cathodic H₂O₂ production and activation cascades in a dual-cathode stacked flow-through electrochemical reactor. Low-cost graphite felt (GF) and stainless-steel mesh (SSM) cathodes selectively facilitated O₂/H₂O₂ and H₂O₂/·OH conversions. The stacked flow-through design established a self-sustaining ·OH production pathway, driving O₂ transport from the anode to the GF cathode for H₂O₂ generation, followed by directional H₂O₂ delivery to the SSM cathode for ·OH formation. Compared to a single-cathode system, the dual-cathode design maintained high Cr(VI) reduction (>95%) while enhancing Ni-EDTA decomplexation and total organic carbon (TOC) removal by up to 41% and 70%, respectively. Under optimized conditions (2.5 V, 2.5 mL/min), the dimensionally stable anode (DSA)/GF-SSM stacked flow-through system achieved 100% Cr(VI) detoxification, 99.9% Ni-EDTA decomplexation, and 50.8% TOC mineralization. Moreover, it demonstrated exceptional longevity and industrial scalability through continuous operation for 50 days. This study presents a feasible energy-efficient ·OH generation strategy, offering a practical, sustainable, and environmentally friendly solution for treating complex wastewater.