ARC Centre of Excellence for Functional Nanomaterials, School of Chemical Engineering, The University of New South Wales, Sydney, NSW 2052, Australia.
ACS Appl Mater Interfaces. 2011 Oct;3(10):3988-96. doi: 10.1021/am2008568. Epub 2011 Oct 7.
The role titanate particle structure plays in governing its characteristics upon calcining and their ensuing influence on photocatalytic performance was investigated. Titanate nanotubes and nanoribbons were prepared by hydrothermal treatment of Aeroxide P25 and then calcined at temperatures in the range 200 - 800 °C. Heat treatment directly transformed the nanotubes to anatase while nanoribbon transformation to anatase occurred via a TiO(2)(B) intermediate phase. The nanoribbon structure also provided an increased resistance to sintering, allowing for retention of the original {010} facet of the titanate nanosheets up to 800 °C. The changing material properties with calcining were found to influence the capacity of the particles to photodegrade oxalic acid and methanol. The nanotubes provided an optimum photoactivity following calcination at 500 °C with this point representing a transition between the relative dominance of crystal phase and surface area on performance. The comparatively smaller initial surface area of the nanoribbons consigned this characteristic to a secondary role in influencing photoactivity with the changes to crystal phase dominating the continually improving performance with calcination up to 800 °C. The structural stability imparted by the nanoribbon architecture during calcination, in particular its retention of the {010} facet at temperatures >700 °C, advanced its photocatalytic performance compared with the nanotubes. This was especially the case for methanol photooxidation whose primary degradation mechanism relies on hydroxyl radical attack and was facilitated by the {010} facet. The effect was not as pronounced for oxalic acid due to its higher adsorption on TiO(2) and therefore greater susceptibility to oxidation by photogenerated holes. This study demonstrates that, apart from modulating sintering effects and changes to crystal phase, the titanate nanostructure influences particle crystallography which can be beneficial for photocatalytic performance.
研究了钛酸盐颗粒结构在煅烧过程中对其特性的控制作用及其对光催化性能的后续影响。通过水热处理 Aeroxide P25 制备了钛酸盐纳米管和纳米带，然后在 200-800°C 的温度下进行煅烧。热处理直接将纳米管转化为锐钛矿，而纳米带通过 TiO(2)(B)中间相转化为锐钛矿。纳米带结构还提供了更高的抗烧结能力，使得钛酸盐纳米片的原始{010}面在 800°C 下得以保留。随着煅烧的进行，材料特性的变化被发现会影响颗粒光降解草酸和甲醇的能力。纳米管在 500°C 煅烧后提供了最佳的光活性，这一点代表了晶体相和表面积对性能的相对优势之间的转变。纳米带相对较小的初始表面积使得这种特性在影响光活性方面处于次要地位，而随着煅烧温度升高至 800°C，晶体相的变化主导着性能的不断提高。纳米带结构在煅烧过程中赋予的结构稳定性，特别是在温度高于 700°C 时保持{010}面，提高了其光催化性能，与纳米管相比具有优势。对于甲醇光氧化尤其如此，其主要降解机制依赖于羟基自由基的攻击，而{010}面促进了这种攻击。对于草酸，由于其在 TiO(2)上的吸附较高，因此更容易被光生空穴氧化，因此这种影响并不明显。本研究表明，除了调节烧结效应和晶体相变化外，钛酸盐纳米结构还会影响颗粒结晶学，这对光催化性能有益。
