Nano‐Si for On‐Demand H₂ Production: Optimization of Yield and Real‐Time Visualization of Si─H₂O Reaction Using Liquid‐Phase Transmission Electron Microscopy

Abstract Hydrogen (H₂), the most abundant element in the universe, has the potential to address the challenges of energy security and climate change. However, due to the lack of a safe and efficient method for storing and delivering hydrogen, its practical application is still in its infancy stages. To overcome this challenge, a promising solution is demonstrated in the form of on‐demand production of H₂ using nano‐Silicon (Si) powders. The method offers instantaneous production of H₂, yielding a volume of 1.3 L per gram of Si at room temperature. Moreover, the H₂ production yield and the rate can be effectively controlled by adjusting the reaction pH value and temperatures. Additionally, liquid‐phase transmission electron microscopy (LPTEM) is utilized in situ to demonstrate the entire reaction in real‐time, wherein H₂ bubble formation is observed and illustrated the gradual conversion of crystalline Si particles into amorphous oxides. Moreover, it is confirmed that the purity of the generated gas is 99.5% using gas chromatography mass spectrometry (GC‐MS). These findings suggest a viable option for instant H₂ production in portable fuel cells using Si cartridges or pellets.