Electrochemical nitrogen reduction reaction catalyzed by a cucurbit[6]uril-phosphomolybdic-copper cation hybrid

The electrocatalytic nitrogen reduction reaction (NRR) provides an energy-saving and environmentally friendly method to synthesize ammonia. Herein, a molybdenum-containing hybrid material (Q[6]-PMA-Cu) was prepared form the assembly of Keggin-type phosphomolybdic acid (PMA) with cucurbit[6]uril (Q[6]) and Cu2+ cations. Q[6]-PMA-Cu with multiple active sites and stable properties not only enables a high selectivity for NRR, but also shows a distinct advantage to suppress HER process, affording a high ammonia yield of 135.04±4.25 µg h−1 mgcat−1 with a Faradaic efficiency (FE) of 85.48±3.33%. 15N2 isotope labeling and control experiments were conducted to verified the nitrogen resource of ammonia formation. The results of experiments and DFT calculations demonstrates the reaction mechanism along the alternate association pathway, of which the metal active sites (Mo & Cu) play crucial role in electron transfer and the presence of hydrophobic Q[6] is responsible to inhibit side reaction of HER. •Q[6] provides hydrophobic sites, which inhibits HER and promotes NRR.•The multi-component synergistic effect of the hybrid improves the catalytic activity.•The NH3 yield of Q[6]-PMA-Cu was 135.04±4.25 µg h−1 mgcat−1, and the FE was 85.48±3.33%.