Upgrading of nitrate to hydrazine through cascading electrocatalytic ammonia production with controllable N-N coupling.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 39362840.
- Also identified by DOI 10.1038/s41467-024-52825-1 and PMC identifier 11450151.
- Licence recorded as CC BY-NC-ND.
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Abstract
Nitrogen oxides (NO<sub>x</sub>) 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<sub>x</sub> to multi-nitrogen products (e.g., N<sub>2</sub>H<sub>4</sub>) via precise construction of a single N-N bond. Herein, we propose a strategy for NO<sub>x</sub>-to-N<sub>2</sub>H<sub>4</sub> under ambient conditions, involving electrochemical NO<sub>x</sub> upgrading to NH<sub>3</sub>, followed by ketone-mediated NH<sub>3</sub> to N<sub>2</sub>H<sub>4</sub>. It can achieve an impressive overall NO<sub>x</sub>-to-N<sub>2</sub>H<sub>4</sub> 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<sub>2</sub>CN* intermediates formed on WO<sub>3</sub> catalysts acted as pivotal monomers to drive controlled N-N coupling with high selectivity, facilitated by lattice-oxygen-mediated dehydrogenation. Additionally, both WO<sub>3</sub> catalysts and DPK mediators exhibit favorable reusability, offering promise for green N<sub>2</sub>H<sub>4</sub> synthesis.