Enhancing nitrate electroreduction for ammonia production over electron-deficient Co3O4 with La doping regulation
Electrocatalytic nitrate reduction (NO3−RR) offers a dual solution for wastewater remediation and ambient ammonia synthesis, yet the competing hydrogen evolution reaction (HER) and sluggish eight-electron transfer limit Faradaic efficiency (FE) and yield. This study reports lanthanum-doped Co3O4 nanowire arrays on carbon cloth (La-Co3O4/CC) that achieve an NH3 FE of 96.36% and a yield of 537.44 μmol h−1 cm−2, markedly surpassing undoped Co3O4 (87.78%, 279.4 μmol h−1 cm−2). Density functional theory calculations reveal that La doping induces electron deficiency at Co sites, enhancing NO3− adsorption and optimizing hydrogenation energetics. A Zn–NO3− battery incorporating La-Co3O4/CC delivers a peak power density of 9.86 mW cm−2, demonstrating viable energy recovery. The catalyst maintains structural integrity over 24 h of continuous operation with negligible performance decay. This work establishes rare-earth doping as a rational strategy to overcome the intrinsic limitations of Co3O4 in nitrate electroreduction, providing a scalable pathway for decentralized ammonia production and nitrate removal.