Efficient and selective uranium electrochemical extraction over flexibly engineered bi-functional Polypyrole@MoSe2@MXene

• The flexible ternary bi-functional composite PPy@MoSe 2 @MXene is designed for efficient uranium extraction. • Ion-exchange of PPy and pseudocapacitive intercalation between MoSe 2 and MXene synergistically promote uranium extraction. • In-situ Raman analysis verified the reduction of uranium species from U(VI) to U(IV). • DTF calculations further corroborated the high selectivity of PPy@MoSe 2 @MXene for uranium capture. The extraction of uranium from seawater is critical for addressing the global energy crisis by harnessing uranium resources. Capacitive deionization (CDI), an electrochemical extraction technique, shows significant promise for the selective capture of uranium by the merits of high efficiency, cost-effectiveness, and energy-saving characteristics. However, it is still a challenge for CDI to explore novel materials with high affinity for rapid extraction and recovery uranium. Herein, the ternary composite polypyrrole@MoSe 2 @MXene (PPy@MoSe 2 @MXene) is successfully designed with the bi-functional properties for uranium extraction. The pseudo-capacitive intercalation behavior promotes the swift transfer of uranium ions into the interlayer of MoSe 2 and MXene, while the ion-exchange capacities and nitrogen-rich active sites of PPy aid in reducing uranium from its hexavalent state U(VI) to the less soluble tetravalent state U(IV). Benefiting from this, the PPy@MoSe 2 @MXene composite demonstrates an impressive uranium extraction capacity of 659 mg g −1 and prominent reusability with 84 % capacity retention after 10 cycles. In-situ Raman spectroscopy further confirms the transformation of uranium species during the CDI process. The selectivity results in complex mixed solution and density functional theory (DTF) underscore that the high selective uranium extraction of PPy@MoSe 2 @MXene can be ascribed to the synergistic effect of PPy, MoSe 2 , and MXene, which provides convenient ions transfer pathway, abundant ion active sites, and reduced ion diffusion energy. This work provides a novel strategy for designing advanced bi-functional materials with enhanced uranium extraction capacity and selectivity from seawater.