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

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 mu g h-1 mgcat-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. A supramolecular self-assembler of cucurbit[6]uril-phosphomolybdic acid with a multi-valence state is constructed to realize an efficient nitrogen oxidation reaction.