Efficient electrocatalytic nitrogen oxidation to nitrate by the self-assembly of supramolecular cucurbit[6]uril with a heteropolyacid

Abstract

Developing low-cost and sustainable catalytic systems to realize efficient nitrogen fixation has always been the pursued goal. Here, we report an efficient electrocatalyst synthesized via a simple self-assembly process from supramolecular cucurbit[6]uril (Q[6]) and a heteropolyacid for nitrogen oxidation. The as-prepared self-assembly material Q[6]-PMA with high stability and specific surface area shows a prominent activity in the electrocatalytic nitrogen oxidation reaction (NOR), affording a yield of nitrate (NO₃⁻) of up to 271.5 ± 5.6 μg h⁻¹ mg_cat⁻¹ with a Faraday efficiency (FE) of 71.2 ± 3.8%. The ¹⁵N isotope-labeling experiment confirmed that the nitrogen source of nitrate formation is derived from N₂. The results of the in situ XPS technique and in situ FITR experiments demonstrate that the molybdenum center of Q[6]-PMA is the main active site of the NOR and the corresponding cucurbit[6]uril unit is conducive to the stability of key intermediates.