Hierarchical TiO2–Si nanowire architecture with photoelectrochemical activity under visible light illumination

Abstract

Bandgap engineering of TiO₂ is a substantial strategy for efficient water splitting in the visible light range. Introducing dopants and hydrogenation have been found effective for that purpose. In this paper, we report the development of a hierarchical three dimensional TiO₂–Si nanowire (NW)-based photoelectrochemical (PEC) anode with visible light photochemical activity. The TiO₂ NWs were synthesized using a surface reaction-limited pulsed chemical vapor deposition method (SPCVD) with unbalanced TiCl₄ and H₂O precursors. Dangling Ti–Cl and Ti–OH groups inside TiO₂ NW crystals were suggested to be the reason for band narrowing and visible light absorption. The NW structure with a large aspect ratio was formed via the oriented attachment mechanism, which offered a super-high surface area density. This in situ crystal decoration approach opens a new window to tailoring electrical properties of TiO₂ for wider spectrum solar energy harvesting and conversion.