Silicon Suboxides as Driving Force for Efficient Light-Enhanced Hydrogen Generation on Silicon Nanowires

Efficient light-stimulated hydrogen generation from top-down produced highly doped n-type silicon nanowires (SiNWs) with silver nanoparticles (AgNPs) in water-containing medium under white light irradiation is reported. It is observed that SiNWs with AgNPs generate at least 2.5 times more hydrogen than SiNWs without AgNPs. The authors' results, based on vibrational, UV-vis, and X-ray spectroscopy studies, strongly suggest that the sidewalls of the SiNWs are covered by silicon suboxides, by up to a thickness of 120 nm, with wide bandgap semiconductor properties that are similar to those of titanium dioxide and remain stable during hydrogen evolution in a water-containing medium for at least 3 h of irradiation. Based on synchrotron studies, it is found that the increase in the silicon bandgap is related to the energetically beneficial position of the valence band in nanostructured silicon, which renders these promising structures for efficient hydrogen generation.

Automated summary

This study reported efficient light-stimulated hydrogen generation from highly doped n-type silicon nanowires (SiNWs) combined with silver nanoparticles (AgNPs) in water-containing medium under white light irradiation. The SiNWs with AgNPs generated at least 2.5 times more hydrogen than those without AgNPs, and the SiNWs' sidewalls were found to be covered by silicon suboxides with stable semiconductor properties. Based on synchrotron studies, the increase in the silicon bandgap was attributed to the energetically beneficial position of the valence band in nanostructured silicon, making them promising structures for efficient hydrogen generation.