Self-Standing Porous Aromatic Framework Electrodes for Efficient Electrochemical Uranium Extraction

Abstract

Electrochemical uranium extraction from seawater provides a new opportunity for a sustainable supply of nuclear fuel. However, there is still room for studying flexible electrode materials in this field. Herein, we construct amidoxime group modified porous aromatic frameworks (PAF-144-AO) on flexible carbon cloths in situ using an easy to scale-up electropolymerization method followed by postdecoration to fabricate the self-standing, binder-free, metal-free electrodes (PAF-E). Based on the architectural design, adsorption sites (amidoxime groups) and catalytic sites (carbazole groups) are integrated into PAF-144-AO. Under the action of an alternating electric field, uranyl ions are selectively captured by PAN-E and subsequently transformed into Na2O(UO3·H2O)x precipitates in the presence of Na+ via reversible electron transfer, with an extraction capacity of 12.6 mg g-1 over 24 days from natural seawater. This adsorption-electrocatalysis mechanism is also demonstrated at the molecular level by ex situ spectroscopy. Our work offers an effective approach to designing flexible porous organic polymer electrodes, which hold great potential in the field of electrochemical uranium extraction from seawater.