Charge-tunable Au₂₅ nanoclusters for electrochemical uranium extraction from seawater

Abstract

Atomically precise Au₂₅(SR)₁₈ (SR: thiol ligand) nanoclusters with adjustable charge states (−1, 0, +1) provide an ideal platform to explore the chemical properties of charged active sites and reveal the structure-ability relationship at a single-electron level. Owing to the different affinity of charged active sites towards specific reactants, it inspires us to investigate the adsorption ability of Au₂₅q nanoclusters (q = −1, 0, +1) towards UO₂²⁺, which are an important raw of nuclear energy. In this work, three Au₂₅⁻¹, ⁰, ⁺¹ nanoclusters with similar crystalline structures but different electron configurations are synthesized, and their uranium extraction ability is explored via the electrochemical pulse technique. First, theoretical calculations predict that Au₂₅⁻ has a stronger binding ability for UO₂²⁺ than Au₂₅⁰ and Au₂₅⁺. Then, the experimental results demonstrate that the Au₂₅⁻ nanoclusters display the best removal capacity, with a removal efficiency of >95% in simulated seawater with 1–20 ppm UO₂(NO₃)₂. The extraction capacity of Au₂₅⁻ can reach 887.9 mg g⁻¹, and the removal efficiency could be 88% in simulated seawater with 50 ppm UO₂(NO₃)₂. The excellent extraction performance of Au₂₅⁻ nanoclusters might be attributed to the enhanced capture of UO₂²⁺ through electronic attraction, which could further be effectively electro-reduced under an externally applied potential. This work deeply reveals the structure-ability relationship between metal nanoclusters and uranium extraction performance at a single-electron level, which can provide valuable guidance for developing efficient absorbents.