Pulsed electrolysis controls sequential accumulation and conversion of key intermediates over zinc-based metal organic framework for enhanced nitrate electroreduction to ammonia.

The electrochemical nitrate reduction reaction (NORR) to ammonia offers a promising approach for wastewater treatment and ammonia synthesis. However, the generation of various by-products, such as nitrite ions (NO), and the occurrence of the competitive hydrogen evolution reaction (HER) complicate reaction pathways, causing unwanted electrical energy consumption and reducing the product selectivity. Herein, we introduce a pulse electrolysis approach to control the sequential accumulation and conversion of NO intermediates during the NORR using a conductive rod-like zinc-based metal organic framework (Zn-MOF) electrode with precise atomic structures. This strategy substantially improves both the yield and Faraday efficiency (FE) of NH production relative to constant-potential electrolysis. After a long-term stability test, the high-purity ammonia product in the electrolyte was successfully extracted via an argon (Ar) stripping process, showing a practical way to turn wastewater nitrate into valuable ammonia-derived products. This study presents a promising strategy for rationally designing metal organic framework (MOFs) electro-catalysts with precise atomic structures and controlling complex reactions, thereby minimizing side reactions, significantly boosting nitrate-to-ammonia conversion efficiency.