Precisely Ce-doped LaMnO3 produces thermally stable nanoparticles and efficient electron pathways for electrocatalytic wastewater to fertilizer conversion

Precise Ce doping stabilizes LaMnO 3 nanoperovskites during high-temperature calcination. • Ce-induced V O pinning suppresses coarsening and builds a Mn 3+ –O–Mn 3+ /V O network. • LCMO achieves 9623 μg h −1 cm −2 NH 3 yield and 96.4% FE in a flow cell. • Low-cost LCMO scales to 78 g and converts municipal wastewater to ammonium fertilizer. Precise control of the geometry and electronic states of high-temperature perovskites is crucial for efficient electrocatalytic nitrite reduction (NO 2 RR) to remove NO 2 − pollutants and enable green ammonia synthesis. In this work, an A-site Ce substitution strategy is established to steer high-temperature crystallization through (V O ) pinning, enabling defect–lattice co-programming of Ce–LaMnO 3 (LCMO) with a nanoscale Mn 3+ -rich active network. Importantly, a synthesis-to-reactivity mechanism is elucidated for high-temperature perovskite NO 2 RR catalysts, where V O pinning suppresses sintering-driven agglomeration while concurrent e g state activation mitigates electronically sluggish Mn sites. Density functional theory further shows that the formation of Mn 3+ −O−Mn 3+ network in conjunction with V O lowers the free-energy demand of key hydrogenation steps and accelerates NO 2 RR kinetics. In the flow cell, the optimized LCMO catalyst delivers an ammonia yield rate of 9623 μg h −1 cm −2 with Faradaic efficiency of 96.4%, ranking it among the most efficient catalysts reported for NO 2 RR. Notably, LCMO is scalable to 78 g per batch without detectable structural change and at a low estimated cost of ca. 1.5 USD g −1 , highlighting its industrial relevance. In a solar-powered system, it directly converts real municipal wastewater into ammonium fertilizer with an (NH 4 ) 2 SO 4 concentration of 1.8 g L −1 , establishing a scalable, solar-driven wastewater-to-fertilizer route for practical green ammonia stabilization. Download: Download high-res image (193KB) Download: Download full-size image Trace A site Ce in LaMnO 3 pins oxygen vacancies, blocks interparticle mass exchange, and locks smaller Mn 3+ -rich perovskite nanoparticles with a Mn 3+ –O–Mn 3+ /V O network that lowers NO 2 RR hydrogenation barriers. LCMO delivers 9623 μg h −1 cm −2 NH 3 at 96.4% FE at −0.8 V vs. RHE and in a flow converts wastewater into crystalline NH 4 F and (NH 4 ) 2 SO 4 .