Direct growth of Cr-doped TiO2 nanosheet arrays on stainless steel substrates with visible-light photoelectrochemical properties

Abstract

Cr-Doped TiO₂ nanosheet arrays grown directly on a stainless steel substrate were successfully achieved by a simple and facile solvothermal reaction without adding Cr-dopant. The stainless steel substrate served as not only the site for the deposition of the TiO₂ film but also the Cr source. The Cr-doped TiO₂ film prepared at 180 °C for 36 h consists of ultrathin nanosheet arrays (a length of ∼860 nm) with a high surface area of 180.77 m² g⁻¹. The long reaction time results in a red shift of the absorption edges and also decreases in band gap energies due to a small amount of Cr³⁺ doping. The unique nanostructures and appropriate composition endowed the Cr–TiO₂ nanosheet arrays with excellent performances in photoelectrochemistry under UV illumination. The photocurrent densities under visible light illumination of the as-prepared Cr–TiO₂ nanosheet arrays are markedly enhanced after high-temperature calcination, which can be attributed to the improved crystallinity, wider visible light response, better binding force and increase of oxygen vacancies of the films.