Surface‐Engineered Molybdenum Oxide with Cucurbit[6]uril for Enhanced Nitrogen Reduction Electrocatalysis

Electrocatalytic nitrogen reduction (NRR) offers a sustainable pathway for ammonia (NH 3 ) production but is challenged by the low solubility of N 2 in aqueous electrolytes, the high energy barrier of N 2 activation, and the competing hydrogen evolution reaction (HER). Herein, cucurbit[6]uril (CB[6]) is immobilized onto the surface of molybdenum oxide (CB[6]@MoO 2 ). The CB[6]@MoO 2 catalyst exhibits a high NH 3 production rate of 27.7 µg h −1 mg −1 and a FE of 25.3% at −0.35 V (vs. RHE) with a 0.1 M Cs 2 SO 4 solution as the electrolyte in a flow cell, significantly outperforming bare MoO 2 (7.1 µg h −1 mg −1 , 3.7%). Mechanistic studies reveal that the immobilized CB[6] on MoO 2 forms a host–guest complex with N 2 with the assistance of alkaline metal cations (e.g., Cs + ) as dynamic “lids”, concentrating and stabilizing N 2 within its hydrophobic cavity and inducing an interfacial electric field that facilitates N≡N bond activation, while the hydrophobic cavity of CB[6] enables excluding overwhelming water to suppress HER. The synergy of CB[6] on the MoO 2 surface through hydrophobic modification, selective N 2 molecular encapsulation, and local polarized electric field enhancement for N 2 activation dramatically improves NRR efficiency, demonstrating a supramolecular surface‐engineering strategy to address key limitations in aqueous NRR catalysis.