Toward a Visible Light-Driven Photocatalyst: The Effect of Midgap-States-Induced Energy Gap of Undoped TiO2 Nanoparticles

• DOI: 10.1021/cs501539q
• Publication Date: 2014-12-01T18:40:07Z
• Authors: Houman Yaghoubi; Zhi Li; Yao Chen; Huong T. Ngo; Venkat R. Bhethan...; Babu Joseph; Shengqian Ma; Rudy Schlaf; Arash Takshi
• Keywords: Visible spectrum

TiO2 is one of the most promising candidate materials for clean-energy generation and environmental remediation. However, larger-than 3.1 eV bandgap perfectly crystalline confines its application to ultraviolet (UV) range. In this study, electronic optical properties undoped mixed-phase nanoparticles were investigated using UV inverse photoemission, low intensity X-ray photoelectron (XP), diffused reflectance spectroscopy methods. The facile solution-phase synthesized exhibited a midgap-states-induced energy gap only ∼2.2 eV. spectrum showed sub-bandgap absorption due existence large Urbach tail at 2.2 photoemission evidenced presence midgap states. enables be photoactive in visible gas-phase CO2 photoreduction test with water vapor under light illumination was studied which resulted production ∼1357 ppm gr–1(catalyst) CO ∼360 CH4, as compared negligible amounts standard (P25) sample. possessed Brunauer–Emmett–Teller (BET) surface area ∼131 m2 gr–1, corresponding Langmuir ∼166 gr–1. determined interplanar distances atomic planes by high-resolution transmission electron microscopy (HR-TEM) diffraction (XRD) methods consistent. A detailed elemental analysis XPS inductively coupled plasma mass spectrometry (ICP-MS) demonstrated that catalyst indeed undoped. catalytic activity can ascribed unique structure oxygen vacancy related defects high area.