Abstract
The excessive use of fossil fuels has dramatically increased the concentration of CO2 in the atmosphere. Global warming has become more serious and made a significant impact on the climate change and ecological environment. Therefore, the reduction of atmospheric CO2 is an urgent issue. The use of photocatalyst to convert CO2 into hydrocarbons can not only reduce atmospheric CO2 but also develop new energy sources. In this study, free-standing open-ended TiO2 nanotube array has been successfully fabricated by raising the voltage at the end of anodization process. Compared with the close-ended structure, the flow-through nanotube structure facilitate the reactants to flow into the inside of the tube. Moreover, in order to absorb more visible light, we doped nitrogen into TiO2 to modify the band gap by annealing under urea ambient (ON-TiNT). The degradation of TiNT catalyst was tested by the photodegradation of methylene blue solution under UV irradiation. The complete decoloration of methylene blue solution by the OA-TiNT was observed in 4 hours with a degradation efficiency about 1.45 times of the CA-TiNT. For CO2 photoreduction experiment, the methanol yield by OA-TiNT was 1.7 times of the CA-TiNT, whereas ON-TiNT was 1.6 times of the CN-TiNT under Xe lamp irradiation. Our results show that open-ednded TiNT provides the increase of the methanol yield which might be attributed to the increased reaction surface area after removing the bottom cap of close-ended TiNT.