Fig. 6: Mechanism analysis of secondary metal ion-induced electrochemical U(VI) reduction to U(IV) solid products.

a Selected snapshots from the MD simulation showing the K⁺/U(IV) interactions on Ga-N_x-C in ~100 ppm uranium-spiked potassium nitrate solution. b RDFs plots of U(IV)-K⁺, U(IV)-O, U(IV)-O(H₂O), and U(IV)-O(NO₃⁻), and their corresponding average coordination number. c MSD-time curves for the transport of U(IV)/K⁺ (showing the different diffusion coefficients). d Selected snapshots from the MD simulation showing the Ca²⁺/U(IV) interactions on Ga-N_x-C in ~100 ppm uranium-spiked calcium chloride solution. e RDFs plots of U(IV)-Ca²⁺, U(IV)-O, U(IV)-O(H₂O), and U(IV)-O(NO₃⁻), and their corresponding average coordination number. f MSD-time curves for the transport of U(IV)/Ca²⁺. g Selected snapshots from the MD simulation showing the Fe³⁺/U(IV) interactions on Ga-N_x-C in ~100 ppm uranium-spiked ferric nitrate solution. h RDFs plots of U(IV)-Fe³⁺, U(IV)-O, U(IV)-O(H₂O), and U(IV)-O(NO₃⁻), and their corresponding average coordination number. i MSD-time curves for the transport of U(IV)/Fe³⁺. j Selected snapshots from the MD simulation showing the Ce⁴⁺/U(IV) interactions on Ga-N_x-C in ~100 ppm uranium-spiked cerous nitrate solution. k RDFs plots of U(IV)-Ce⁴⁺, U(IV)-O, U(IV)-O(H₂O), and U(IV)-O(NO₃⁻), and their corresponding average coordination number. l MSD-time curves for the transport of U(IV)/Ce⁴⁺.