Heterojunction Membranes With Enhanced Built‐in Electric Field for Sustainable Fluidic Electro‐Fenton Water Purification

ABSTRACT The sluggish interfacial electron transfer at the cathode significantly limits the efficiency of in situ H 2 O 2 electrosynthesis and the Fe(III)/Fe(II) redox cycle in electro‐Fenton (EF). Herein, heterojunction FeOCl@rGO electrocatalytic membranes (EMs) with an enhanced built‐in electric field (BIEF) were rationally designed employing an interface engineering approach. The BIEF optimizes the adsorption configuration of O 2 /H 2 O 2 and the d‐band center of Fe sites by instigating local charge redistribution and establishing a directional potential gradient at the heterointerface, which significantly promotes the on‐site synthesis of H 2 O 2 and the continuous regeneration of Fe(II). The BIEF‐enhanced EMs exhibit excellent EF performance across a wide pH range and in various natural water matrices, enabling rapid degradation of diverse organic pollutants with extremely low energy consumption (0.395 kWh m −3 order −1 ). Under continuous filtration operation, the pollutant removal efficiency approaches 100% at a unit cost of 0.0035 USD/liter. This heterojunction‐regulated BIEF strategy provides an important tool for regulating interfacial charge dynamics and H 2 O 2 activation in EF, showcasing great potential in energy‐efficient water purification.