Harris Jonathan, Silk Ryan, Smith Mark, Dong Yusong, Chen Wan-Ting, Waterhouse Geoffrey I N
School of Chemical Sciences, The University of Auckland, Auckland 1010, New Zealand.
The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington 6140, New Zealand.
ACS Omega. 2020 Jul 22;5(30):18919-18934. doi: 10.1021/acsomega.0c02142. eCollection 2020 Aug 4.
This study systematically evaluates the performance of a series of TiO nanoflower (TNF) photocatalysts for aqueous methylene blue photo-oxidation under UV irradiation. TNF nanoflowers were synthesized from Ti(IV) butoxide by a hydrothermal method and then calcined at different temperatures ( = 400-800 °C) for specific periods of time ( = 1-5 h). By varying the calcination conditions, TNF-T-t photocatalysts with diverse physicochemical properties and anatase/rutile ratios were obtained. Many of the TNF-T-1 photocatalysts demonstrated remarkable activity for aqueous methylene blue photo-oxidation at pH 6 under UV excitation (365 nm), with activities following the order TNF-700-1 > TNF-600-1 > TNF-500-1 > TNF-400-1 ∼ P25 TiO ≫ TNF-800-1. The activity of the TNF-700-1 photocatalyst (99% anatase, 1% rutile) was 2.3 times that of P25 TiO at pH 6 and 14.4 times that of P25 TiO at pH 4. Prolonged calcination of the TNFs at 700 °C proved detrimental to dye degradation performance due to excessive rutile formation, which reduced the photocatalyst surface area and suppressed OH generation. The outstanding activities of TNF-700-1 and TNF-600-1 are attributed to their hierarchical nanoflower morphology which benefitted UV absorption, a near-ideal anatase crystallite size for efficient charge separation, and their unusually low isoelectric point (IEP = 4.3-4.5).
本研究系统评估了一系列TiO纳米花（TNF）光催化剂在紫外光照射下对水溶液中亚甲基蓝进行光氧化的性能。TNF纳米花由丁醇钛（IV）通过水热法合成，然后在不同温度（400 - 800°C）下煅烧特定时间（1 - 5小时）。通过改变煅烧条件，获得了具有不同物理化学性质和锐钛矿/金红石比例的TNF-T-t光催化剂。许多TNF-T-1光催化剂在紫外光激发（365 nm）下，于pH 6时对水溶液中亚甲基蓝的光氧化表现出显著活性，其活性顺序为TNF-700-1 > TNF-600-1 > TNF-500-1 > TNF-400-1 ∼ P25 TiO ≫ TNF-800-1。TNF-700-1光催化剂（99%锐钛矿，1%金红石）在pH 6时的活性是P25 TiO的2.3倍，在pH 4时是P25 TiO的14.4倍。由于过度形成金红石，导致光催化剂表面积减小并抑制了羟基生成，在700°C下对TNF进行长时间煅烧被证明对染料降解性能不利。TNF-700-1和TNF-600-1的出色活性归因于其分级纳米花形态，这有利于紫外光吸收、具有接近理想的锐钛矿微晶尺寸以实现有效的电荷分离，以及其异常低的等电点（IEP = 4.3 - 4.5）。
