Sm ³⁺ -Doped High-Surface-Area MnO x Film Electrodes for Selective Electrochemical Recovery of Mg ²⁺ from Salt-Lake Brines

Scalable magnesium-ion batteries (MIBs), regarding as the stored energy candidate for the requirement of carbon-neutral, are focused attention for the Mg 2+ extraction in the coexisting ion system. It is reported that the fabrication of a MnO x -based film electrode combination of the doping of samarium (Sm 3+ ) and the imprinting of magnesium (Mg 2+ ) via redox coprecipitation, achieving the high efficiency for Mg 2+ extraction from salt-lake brines. The optimal MgMnO x -1%Sm exhibits a high Mg 2+ adsorption capacity of 52.22 mg·g –1 due to the increasing specific surface area induced by the trace Sm 3+ doping and the unique Mg 2+ channel derived from the imprinted Mg 2+ . Moreover, the adsorption capacity can retain 89.53% of its initial capacity after 10 adsorption–desorption cycles and 89.45% of its electrochemical activity after 2000 cyclic voltammetry cycles (CVs). Density functional theory (DFT) calculations on an XRD-derived Mn 8 O 15 model reveal that Mg 2+ exhibits the strongest adsorption with an energy of −5.00 eV among Li +, Na +, and K +, rationalizing the experimentally observed preferential binding. Herein, it is revealed that the synergetic modulation of Sm 3+ doping and ion imprinting provides a highly effective and sustainable route for selective Mg extraction from salt-lake resources.