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

Abstract

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 degrees 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 degrees 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.