Separation-Free High-Purity Hydrogen Production via the Mechanochemical Ammonia–Silicon Reaction under Mild Conditions

Ammonia (NH₃) has emerged as a promising hydrogen (H₂) carrier thanks to its high hydrogen content (17.6 wt %) and easy liquification. However, conventional NH₃ cracking requires high temperatures (400-600 °C) and additional gas separation processes, increasing the regeneration cost of high-purity H₂. Here, we develop a mechanochemical NH₃-silicon (Si) reaction that enables high-purity H₂ production under mild conditions (50.0 °C) without further separation. Utilizing dynamic mechanical actions, the mechanochemical NH₃-Si (MAS) reaction realized 100.0% NH₃ conversion, 100.0% H₂ purity, and a fast H₂ production rate of 102.5 mmol h^-1. The process simultaneously produced high-value silicon nitride (Si₃N₄) from end-of-life Si solar panels, demonstrating the strong economic competitiveness of the MAS reaction. Combining experimental and theoretical analyses, the dynamic evolution of Si nanoparticles was determined to be the key to efficiently extracting H₂ from NH₃ during ball milling.