The Combination of Electronic Structure and Lattice Strain Engineering for Ultra‐Stable Acidic Nitrate Electroreduction at Highly Concentrated Electrolyte

Abstract Ambient electrocatalytic reduction of nitrate to ammonia (NO 3 RR) provides a reliable route for migrating nitrate pollutants and simultaneously generating valuable NH 3 . Most current efforts have focused on NO 3 RR under alkaline/neutral media with the low nitrate concentration range, while the investigation of NO 3 RR 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‐TiO 2 ) nanosphere arrays are synthesized as ultra‐stable and highly active electrocatalysts for acidic NO 3 RR across wide nitrate concentrations (0.1−6 M). Benefitting from the combined electronic structure and lattice strain engineering by Ru doping, Ru‐TiO 2 exhibits superior NH 3 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‐TiO 2 , 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 NO 3 RR catalysts under environmentally‐relevant wastewater conditions close to industrial production.