Mechanoluminescence-Enhanced Ammonia Synthesis via Mechanochemical Nitrate Reduction.

Abstract

The Haber-Bosch process remains the dominant method for ammonia (NH₃) synthesis, but it is highly energy-intensive and environmentally burdensome. Nitrate reduction to ammonia (NRA) presents a promising dual-function alternative, enabling both sustainable NH₃ production and environmental remediation. However, current NRA methods, primarily photocatalytic and electrocatalytic, depend heavily on external energy inputs (light or electricity), limiting their deployment in off-grid or distributed settings. Here, we report a mechanoluminescence (ML)-enhanced mechanocatalysis strategy for mechanically driven NRA using Mn-doped CaZnOS (Mn-CaZnOS) as an efficient mechano-catalyst. Under mechanical stimulation, Mn-CaZnOS generates a synergistic cascade of piezoelectric and photoexcitation effects that facilitate the NRA process. This ML-enhanced system achieves a notable NH₃ yield rate of 5.4 μmol g^-1 h^-1 with exceptional stability over 100 h. Mechanistic investigations, including isotope labeling, kinetic isotope effect, and electron spin resonance, confirm the reaction pathway and identify hydrogenation as the rate-limiting step. Kelvin probe force microscopy and density functional theory calculations reveal that mechanical stimuli induce piezopotential, enriching local NO₃^- concentration and enhancing proton-coupled charge transfer. Additionally, the electronic structure of the active sites is modulated to enhance intermediate adsorption and reduce the energy barrier for NH₃ formation. This work establishes ML-assisted mechanocatalysis as a mechanically driven platform for sustainable ammonia synthesis and environmental cleanup.