Negatively Charged Catalytic Centers on MXene for Sustainable Uranium Recovery

Efficient and selective uranium extraction from wastewater remains a significant challenge, primarily because conventional adsorbents exhibit low affinity for UO₂²⁺, while most catalytic centers are either neutral or positively charged, creating a fundamental charge incompatibility with the target ions. To overcome this, we adopted an integrated adsorption-electrocatalysis strategy using a freestanding membrane electrode (ZMOM), fabricated via electrostatic self-assembly of Ti₃C₂T_x MXene and zinc molybdate (ZMO). The key innovation lies in employing molybdate ions as bifunctional units that combine a negatively charged surface for electrostatic attraction of UO₂²⁺ with oxygen-bridged configurations that serves as integrated catalytic sites. This synergy enables continuous capture and molybdenum-mediated redox conversion (U⁶⁺ ↔ U⁵⁺), leading to the precipitation of insoluble Na₂O(UO₃·H₂O)_x for easy recovery. Under the square-wave exchange (SWE) method, the optimized ZMOM-2 electrode achieves a high uranium extraction capacity of 1641.78 mg/g at -5 V from a 100 mg/L solution and retains 98.78% of its capacity over five consecutive cycles. This work establishes a new design principle that integrates adsorption sites and anionic catalytic centers into a single material, offering an efficient and robust route for uranium resource recovery.