Interfacial Electronic Modulation in 1D Peapod-like CuO@TiO ₂ Nanotubes for Accelerated Nitrate-to-Ammonia Electrosynthesis

The widespread implementation of the electrochemical nitrate reduction reaction (NO3RR) is fundamentally hindered by the “nitrite-poisoning” effect, where the persistent accumulation of NO2– intermediates blocks active sites and triggers parasitic hydrogen evolution. Herein, we report a robust strategy to circumvent this kinetic bottleneck through the rational design of one-dimensional (1D) peapod-like CuO@TiO2 heterostructured nanotubes (HNTs). This hierarchical architecture, synthesized via a scalable electrospinning-calcination route, features a unique spatially confined interface that facilitates unidirectional electron pumping from the TiO2 scaffold to the CuO peapods. Comprehensive in situ investigations reveal that this interfacial electronic coupling simultaneously stabilizes low-valence Cu+ species and induces a high density of interfacial oxygen vacancies (Ov). The synergy between these features collectively tunes the adsorption energetics of nitrogenous species, effectively steering the reaction from the sluggish nitrite-dominated pathway toward a rapid relay reduction to ammonia. Consequently, the CuO@TiO2 HNTs deliver a remarkable NH4+ Faradaic efficiency of 93.5% and a competitive yield rate of 0.49 mmol h–1 cm–2 at industrially relevant potentials, alongside exceptional long-term durability. This work provides a transformative blueprint for the development of interface-engineered catalysts for high-efficiency nitrogen upcycling and sustainable chemical manufacturing.