A method for adjusting nitrogen doping amount in anatase TiO2 single crystals with well-faceted shape and micron size

A new approach was developed to adjust N doping amount in anatase single crystals with well-faceted shape and micron size, using a novel liquid dopant from the chemical recycling of the wasted supernatant solution in our previous experiments. The dependence of microstructure and property evolution on N doping amount was investigated systematically. The results show that all prepared N-doped samples are pure anatase with the morphology of truncated octahedral bipyramid including both {001} and {110} reactive facets. With the increase of N doping, the single crystals become angular and the thickness decreases, the aggregation of crystals increases, the photo-absorption capacity in visible region is enhanced and the absorption band edge is gradually red-shifted. The photocatalytic efficiency of the samples for the degradation of methylene blue (MB) or phenol under visible light irradiation gradually increases, but when the volume of dopant increases to 2 ml, the photoactivity of TiO2 decreases. The optimal volume of N dopant is 1 ml and A(6:1) shows the highest photodegradation rate. The effective N doping of wasted supernatant is mainly due to the previously formation of Ti-N linkage, and hence a N doping mechanism is proposed. This work provides a new opportunity for in-situ modification of anatase single crystals with well-faceted shape and micron size, and hence, a basis for development of some advanced materials, for example porous single crystals.