3D nanostructured N-doped TiO2 photocatalysts with enhanced visible absorption

Abstract

Considering the environmental issues, it is essential to develop highly efficient and recyclable photocatalysts in purification systems. Conventional TiO₂ nanoparticles have strong intrinsic oxidizing power and high surface area, but are difficult to collect after use and rarely absorb visible light, resulting in low photocatalytic efficiency under sunlight. Here we develop a new type of highly efficient and recyclable photocatalyst made of a three-dimensional (3D) nanostructured N-doped TiO₂ monolith with enhanced visible light absorption. To prepare the sample, an ultrathin TiN layer (∼10 nm) was conformally coated using atomic layer deposition (ALD) on 3D nanostructured TiO₂. Subsequent thermal annealing at low temperature (550 °C) converted TiN to anatase phase N-doped TiO₂. The resulting 3D N-doped TiO₂ showed ∼33% enhanced photocatalytic performance compared to pure 3D TiO₂ of equivalent thickness under sunlight due to the reduced bandgap, from 3.2 eV to 2.75 eV through N-doping. The 3D N-doped TiO₂ monolith could be easily collected and reused at least 5 times without any degradation in photocatalytic performance.