Jahn-Teller Distortions Induced by in situ Li Migration in λ-MnO₂ for Boosting Electrocatalytic Nitrogen Fixation

Lithium-mediated electrochemical nitrogen reduction reaction (Li-NRR) completely eschews the competitive hydrogen evolution reaction (HER) occurred in aqueous system, whereas the continuous deposition of lithium readily blocks the active sites and further reduces the reaction kinetics. Herein, we propose an innovative in situ Li migration strategy to realize that Li substitutes Mn sites in λ-MnO₂ instead of evolving into the dead Li. Comprehensive characterizations corroborate that the intercalation of Li⁺ at high voltage breaks the structural integrity of MnO₆ octahedron and further triggers unique Jahn-Teller distortions, which promotes the spin state regulation of Mn sites to generate the ameliorative e_g orbital configuration and accelerates N≡N bond cleavage via e_g -σ and e_g -π* interaction. To this end, the resulted cationic disordered LiMnO₄ delivers the recorded highest NH₃ yield rate of 220 μg h^-1  cm^-2 and a Faradaic efficiency (FE) 83.80 % in organic electrolyte.