Rutar Melita, Rozman Nejc, Pregelj Matej, Bittencourt Carla, Cerc Korošec Romana, Sever Škapin Andrijana, Mrzel Aleš, Škapin Srečo D, Umek Polona
Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana, Slovenia ; Jožef Stefan International Postgraduate School, Jamova cesta 39, SI-1000 Ljubljana, SIovenia.
Slovenian National Building and Civil Engineering Institute, Dimičeva 12, SI-1000 Ljubljana, Slovenia.
Beilstein J Nanotechnol. 2015 Mar 27;6:831-44. doi: 10.3762/bjnano.6.86. eCollection 2015.
The influence of the reaction conditions during the transformation of hydrogen titanate nanoribbons to TiO2 nanoribbons on the phase composition, the morphology, the appearance of the nanoribbon surfaces and their optical properties was investigated. The transformations were performed (i) through a heat treatment in oxidative and reductive atmospheres in the temperature range of 400-650 °C, (ii) through a hydrothermal treatment in neutral and basic environments at 160 °C, and (iii) through a microwave-assisted hydrothermal treatment in a neutral environment at 200 °C. Scanning electron microscopy investigations showed that the hydrothermal processing significantly affected the nanoribbon surfaces, which became rougher, while the transformations based on calcination in either oxidative or reductive atmospheres had no effect on the morphology or on the surface appearance of the nanoribbons. The transformations performed in the reductive atmosphere, an NH3(g)/Ar(g) flow, and in the ammonia solution led to nitrogen doping. The nitrogen content increased with an increasing calcination temperature, as was determined by X-ray photoelectron spectroscopy. According to electron paramagnetic resonance measurements the calcination in the reductive atmosphere also resulted in a partial reduction of Ti(4+) to Ti(3+). The photocatalytic performance of the derived TiO2 NRs was estimated on the basis of the photocatalytic oxidation of isopropanol. After calcinating in air, the photocatalytic performance of the investigated TiO2 NRs increased with an increased content of anatase. In contrast, the photocatalytic performance of the N-doped TiO2 NRs showed no dependence on the calcination temperature. An additional comparison showed that the N-doping significantly suppressed the photocatalytic performance of the TiO2 NRs, i.e., by 3 to almost 10 times, in comparison with the TiO2 NRs derived by calcination in air. On the other hand, the photocatalytic performance of the hydrothermally derived TiO2 NRs was additionally improved by a subsequent heat treatment in air.
研究了钛酸氢纳米带转变为TiO₂纳米带过程中的反应条件对其相组成、形态、纳米带表面外观及其光学性质的影响。转变过程通过以下方式进行：(i) 在400 - 650℃的温度范围内，在氧化和还原气氛中进行热处理；(ii) 在160℃的中性和碱性环境中进行水热处理；(iii) 在200℃的中性环境中进行微波辅助水热处理。扫描电子显微镜研究表明，水热处理显著影响纳米带表面，使其变得更粗糙，而在氧化或还原气氛中基于煅烧的转变对纳米带的形态或表面外观没有影响。在还原气氛（NH₃(g)/Ar(g)流）和氨溶液中进行的转变导致了氮掺杂。通过X射线光电子能谱测定，氮含量随煅烧温度的升高而增加。根据电子顺磁共振测量，在还原气氛中煅烧还导致Ti(4+)部分还原为Ti(3+)。基于异丙醇的光催化氧化评估了所得TiO₂纳米带的光催化性能。在空气中煅烧后，所研究的TiO₂纳米带的光催化性能随锐钛矿含量的增加而提高。相比之下，N掺杂的TiO₂纳米带的光催化性能与煅烧温度无关。进一步比较表明，与在空气中煅烧得到的TiO₂纳米带相比，N掺杂显著抑制了TiO₂纳米带的光催化性能，即抑制了3至近10倍。另一方面，水热法制备的TiO₂纳米带的光催化性能通过随后在空气中的热处理得到进一步改善。
