Upgrading of nitrate to hydrazine through cascading electrocatalytic ammonia production with controllable N-N coupling

Nitrogen oxides (NO x ) play important roles in the nitrogen cycle system and serve as renewable nitrogen sources for the synthesis of value-added chemicals driven by clean electricity. However, it is challenging to achieve selective conversion of NO x to multi-nitrogen products (e.g., N 2 H 4 ) via precise construction of a single N-N bond. Herein, we propose a strategy for NO x -to-N 2 H 4 under ambient conditions, involving electrochemical NO x upgrading to NH 3 , followed by ketone-mediated NH 3 to N 2 H 4 . It can achieve an impressive overall NO x -to-N 2 H 4 selectivity of 88.7%. We elucidate mechanistic insights into the ketone-mediated N-N coupling process. Diphenyl ketone (DPK) emerges as an optimal mediator, facilitating controlled N-N coupling, owing to its steric and conjugation effects. The acetonitrile solvent stabilizes and activates key imine intermediates through hydrogen bonding. Experimental results reveal that Ph 2 CN* intermediates formed on WO 3 catalysts acted as pivotal monomers to drive controlled N-N coupling with high selectivity, facilitated by lattice-oxygen-mediated dehydrogenation. Additionally, both WO 3 catalysts and DPK mediators exhibit favorable reusability, offering promise for green N 2 H 4 synthesis.