LAUSR

Ambient electrocatalytic reduction of nitrate to ammonia (NO3RR) provides a reliable route for migrating nitrate pollutants and simultaneously generating valuable NH3. Most current efforts have focused on NO3RR under alkaline/neutral media with the low nitrate concentration range, while the investigation of NO3RR under acidic conditions in highly concentrated electrolyte is rarely reported, which ignores the strongly acidic environments in most industrial nitrate‐containing wastewaters and contradicts with the demands of actual large‐scale production. Herein, Ru‐doped TiO2 (Ru‐TiO2) nanosphere arrays are synthesized as ultra‐stable and highly active electrocatalysts for acidic NO3RR across wide nitrate concentrations (0.1−6 M). Benefitting from the combined electronic structure and lattice strain engineering by Ru doping, Ru‐TiO2 exhibits superior NH3 yield rate of 69.6 mg h−1 cm−2 and Faradaic efficiency of 98.8% in pH = 1 electrolyte with high nitrate concentration (6 M), boasting an impressive electrocatalytic stability of over 300 h at around −860 mA cm−2. Further, an alkaline‐acid hybrid zinc‐nitrate battery is assembled with Ru‐TiO2, which can achieve high open‐circuit voltage of 2.01 V and remarkable power density of 92.8 mW cm−2. This work provides new insights into the design of high‐performance NO3RR catalysts under environmentally‐relevant wastewater conditions close to industrial production.