Sordello F, Odorici E, Hu K, Minero C, Cerruti M, Calza P
Department of Chemistry, University of Turin, Via Giuria, 5, I-10125 Turin, Italy.
Materials Engineering, McGill University, 3610 University St., Montreal, QC H3A 0C5, Canada.
Nanoscale. 2016 Feb 14;8(6):3407-15. doi: 10.1039/c5nr07257c.
The addition of graphene nanoplatelets (GNP) to TiO2 nanoparticles (NPs) has been recently considered as a method to improve the photocatalytic efficiency of TiO2 by favoring charge carrier separation. Here, we show that it is possible to improve the efficiency of GNP-TiO2 composites by controlling the shape, stability, and facets of TiO2 NPs grown on GNP functionalized with either COOH or NH2 groups, while adding ethylendiamine (EDA) and oleic acid (OA) during a hydrothermal synthesis. We studied the photocatalytic activity of all synthesized materials under UV-A light using phenol as a target molecule. GNP-TiO2 composites synthesized on COOH-functionalized GNP, exposing {101} facets, were more efficient at abating phenol than those synthesized on NH2-functionalized GNP, exposing {101} and {100} facets. However, neither of these composites was stable under irradiation. The addition of both OA and EDA stabilized the materials under irradiation; however, only the composite prepared on COOH-functionalized GNP in the presence of EDA showed a significant increase in phenol degradation rate, leading to results that were better than those obtained with TiO2 alone. This result can be attributed to Ti-OH complexation by EDA, which protects GNP from oxidation. The orientation of the most reducing {101} facets toward GNP and the most oxidizing {100} facets toward the solution induces faster phenol degradation owing to a better separation of the charge carriers.
最近，将石墨烯纳米片（GNP）添加到二氧化钛纳米颗粒（NPs）中被认为是一种通过促进电荷载流子分离来提高二氧化钛光催化效率的方法。在此，我们表明，在水热合成过程中添加乙二胺（EDA）和油酸（OA）时，通过控制在COOH或NH2官能化的GNP上生长的TiO2 NPs的形状、稳定性和晶面，可以提高GNP-TiO2复合材料的效率。我们以苯酚为目标分子，研究了所有合成材料在UV-A光下的光催化活性。在COOH官能化的GNP上合成的、暴露{101}晶面的GNP-TiO2复合材料在去除苯酚方面比在NH2官能化的GNP上合成的、暴露{101}和{100}晶面的复合材料更有效。然而，这些复合材料在光照下都不稳定。OA和EDA的添加使材料在光照下稳定；然而，只有在EDA存在下在COOH官能化的GNP上制备的复合材料在苯酚降解率上有显著提高，其结果优于单独使用TiO2时获得的结果。这一结果可归因于EDA对Ti-OH的络合作用，从而保护GNP不被氧化。最具还原性的{101}晶面朝向GNP，最具氧化性的{100}晶面朝向溶液，由于电荷载流子的更好分离，导致苯酚降解更快。
