The electrochemical nitrate reduction reaction (NO3RR) presents a sustainable pathway to simultaneously address environmental nitrate (NO3−) pollution and decarbonize ammonia (NH3) production. While traditional constant-potential #electrocatalysis for NO3RR has been widely studied, it suffers from inherent limitations, including competing hydrogen evolution, intermediate desorption, mass transfer bottlenecks, etc. In response, pulsed #electrocatalysis, as an easily operable method, enables the regulation of reaction pathways by periodically varying applied potentials and can effectively overcome the limitations of constant-potential catalysis. However, research on pulsed catalysis in NO3RR remains fragmented, lacking systematic categorization. Consequently, this review provides a comprehensive overview of pulsed NO3RR systems, encompassing fundamental testing methodologies, #catalytic mechanisms, device configurations, in situ characterization techniques, and merits of pulsed strategy. Furthermore, the analysis outlines essential criteria for catalyst design to maximize the potential of pulsed strategy and emphasizes the need for enhanced research and refined investigations in existing pulsed NO3RR implementations.

Electrocatalytic nitrate reduction reaction (NO3RR) for the selective generation of ammonia (NH3) enables the removal of deleterious nitrate pollutants while simultaneously upcycling them into a value-added fertilizer. The development of nonprecious metal-derived catalysts such as those featuring copper (Cu) as earth-abundant alternatives for the state-of-the-art precious metal catalysts is of urgent need yet suffering from the activity–selectivity–durability trilemma. Rational design of molecular Cu complexes with well-defined coordination structures permitting systematic structure–activity relationship (SAR) investigations is key to addressing the challenge. Here, a series of molecular Cu(I) complexes with [2]catenane ligands are developed as NO3RR electrocatalysts for the first time. By engineering multiple cationic ammoniums on the catenane backbone, acceptance of the anionic nitrate substrate as well as the release of the cationic ammonium product are promoted, thereby facilitating a higher Faradaic efficiency and product selectivity toward ammonia via an 8e– pathway. Of note, the mutual Coulombic repulsion between the multiply charged ligands is overcome by the mechanical interlocking such that the catalyst integrity can be maintained under practical conditions. This report highlights the promise of employing mechanically interlocked ligands as a platform for customizing metal complexes as catalysts for redox processes involving multiple proton-coupled electron transfer steps.

Proceedings of the National Academy of Sciences, Volume 123, Issue 2, January 2026. SignificanceElectrocatalytic nitrate reduction reaction (NO3RR) offers a sustainable route for ammonia synthesis and nitrogen recycling, but its complex network of proton-coupled electron transfer steps has hindered comprehensive mechanistic ...