Spin-state engineering of Co-doped LaMnO3 enhances N2 and H2O activation for chemical-looping ammonia synthesis

Ammonia is a crucial chemical and carbon-free energy carrier, but its industrial synthesis via the Haber–Bosch process requires harsh conditions and fossil-derived hydrogen. Alternative strategies are needed to achieve sustainable ammonia production under moderate conditions. H 2 O-based chemical looping ammonia synthesis (H 2 O-CLAS) enables hydrogen-free operation and decouples N 2 and H 2 O activation from scaling constraints, but remains hindered by high energy demand, inferior catalyst stability, and intrinsically challenging activation of N 2 and H 2 O. Here we demonstrate Co-doped LaMnO 3 as a durable and efficient H 2 O-CLAS catalyst, where nitrogen fixation occurs at 1000 °C and ammonia release proceeds at 600 °C under atmospheric pressure with a production rate of 866.01 µmol g −1 h −1 , outperforming state-of-the-art H 2 O-CLAS catalysts. Co doping modulates the d-band electronic structure of LaMnO 3 via spin-state engineering and enhances lattice oxygen mobility, thereby promoting N 2 and H 2 O activation, nitride formation, and hydrogen-bond interactions for ammonia formation. This work outlines a pathway toward sustainable ammonia synthesis with markedly reduced energy consumption and carbon emissions. Scheme. Illustration of spin-state modulation in Co-doped LaMnO 3 for chemical-looping ammonia synthesis. Download: Download high-res image (216KB) Download: Download full-size image