Structure and hydrogen generation mechanism of Si-based agent

Highlights: • Si-based agent generates a high amount of hydrogen in bowels condition. • For hydrogen generation from Si-based agent, OH⁻ ions are the reacting species. • The Si 2p peak for SiO₂ greatly increases with the hydrogen generation reaction time. • The increase in the shift of the Si 2p peak for SiO₂ is attributable to charging. • Si-based agent has 2> structure. Si-based agent fabricated from Si powder generates a high amount of hydrogen by reactions with weak alkaline solutions for long periods (e.g., more than 500 mL/g hydrogen at pH8.5 and 36 °C for 24 h). The hydrogen generation rate greatly increases with pH, indicating that the reacting species is OH⁻ ions. In the Si 2p XPS spectra of Si-based agent, peaks due to suboxide species and SiO₂ are present. The suboxide layer is present near the Si core, and the SiO₂ layer outside of the suboxide layer. The charging effect caused by photoemission largely shifts the Si 2p peak due to SiO₂ while the shifts induced by charging are much lower for suboxide species. This phenomenon is well explained by the silicon oxide structure that SiO₂ is present outside of the suboxide species.