Study on Strategy to Incorporate Carbon and Nitrogen in Nanostructured TiO2: Modification of Low Bandgap Initiated by Broad Spectrum Response and Its Photoelectrochemical Properties

A material of nitrogen, carbon-codoped TiO₂ (HITNC-1) with an unusual optical property in the near-infrared region is prepared at 800°C in NH₃ and CO₂ atmosphere. TEM results show semiconductor nanocrystals with grain size approximately in the range of 2~8 nm. HITNC-1 exhibits two strong absorption bands in near-infrared region, which is relative with the F-type color centers produced by the behaviors of Ti³⁺ trapping electrons and lies on the doping of N,C atoms into TiO₂ lattices. The results of the surface photovoltage spectrum indicate that the intensity of positive photovoltage signal is 20 times than raw TiO₂, and emerges a new signal in NIR region. The transient photovoltage results provide the investigation of dynamic behavior of photo-induced charge carriers in HITNC-1. Therefore, the photoelectrochemical properties clearly demonstrate that N,C-codoped TiO₂ at high temperature could induce the separation of e^- and h⁺ and harvest photons for optical property.