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

Abstract

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 generatio