Centre for Nanoscience and Nanotechnology, ITER, SOA University, Bhubaneswar-751 030, Odisha, India.
Nanoscale. 2018 Oct 21;10(39):18540-18554. doi: 10.1039/c8nr06158k. Epub 2018 Sep 21.
The present article presents an in-depth discussion on the state-of-the-art multifarious roles of Au nanoparticles and their associated charge anti-recombination process in burgeoning photocatalysis research. Hexagonal-phase ZnTiO was fabricated through a sol-gel auto-combustion method by optimizing the calcination temperatures. To further improve the charge separation efficiency and visible light induced photocatalytic activity of pristine ZnTiO, we designed a new type of Au/ZnTiO nanocomposite by a precipitation-deposition method. The photocatalytic activities of the Au/ZnTiO nanocomposites were substantiated by evaluating the rate of hydrogen evolution under both UV and visible light illumination. The photocatalytic activity of the Au/ZnTiO nanocomposites rises proportionally with an increase in Au content up to 1.5 wt% under UV light illumination and it produce around 285 μmol h of H which is approximately 2.6 times higher than that produced by pristine ZnTiO. Therefore, the Au nanoparticles present on the surface of ZnTiO act as electron acceptors, leading to an increase in the rate of generation and separation of charge carriers. This process helps to enhance the congregation of electrons on Au nanoparticles through the Schottky junction. The obtained results are very consistent with steady-state PL and UV light induced photocurrent measurements. Conversely, such a trend was not detected under visible light illumination. The visible light induced photocatalytic activity of Au/ZnTiO nanocomposites increases with a rise in Au content up to 1 wt% and thereafter decreases with further Au loading. Therefore, the initial increment in photocatalytic activity is due to the generation, separation and participation of a large number of SPR-induced charge carriers and thereafter decreases due to the recombination of SPR-generated charge carriers because of the formation of defect sites at the Au and ZnTiO interface. That the excess Au loading causes the recombination of SPR charge carriers was well explained by undertaking SPR-induced TRPL analysis and this result is directly followed up with the results of visible light induced photocurrent and EIS measurements. The Au/ZnTiO nanocomposites with optimal Au loading (1 wt%) delivered an amazingly high rate of hydrogen evolution i.e. 108 μmol h with an energy conversion efficiency of 7.14%, whereas pristine ZnTiO shows negligible activity under visible light illumination.
本文深入探讨了金纳米粒子的多种最新角色及其在新兴光催化研究中的相关电荷反复合过程。通过优化煅烧温度，采用溶胶-凝胶自燃烧法制备了六方相 ZnTiO。为了进一步提高原始 ZnTiO 的电荷分离效率和可见光诱导光催化活性，我们通过沉淀-沉积法设计了一种新型的 Au/ZnTiO 纳米复合材料。通过评估在 UV 和可见光照射下的氢气产生速率，证实了 Au/ZnTiO 纳米复合材料的光催化活性。在 UV 光照射下，Au/ZnTiO 纳米复合材料的光催化活性随着 Au 含量的增加而呈比例增加，当 Au 含量为 1.5wt%时，产生约 285 μmol h 的 H，约为原始 ZnTiO 的 2.6 倍。因此，ZnTiO 表面的金纳米颗粒作为电子受体，增加了载流子的生成和分离速率。这一过程有助于通过肖特基结增加 Au 纳米颗粒上电子的聚集。得到的结果与稳态 PL 和紫外光诱导光电流测量非常一致。相反，在可见光照射下没有检测到这种趋势。在 Au 含量增加到 1wt%时，Au/ZnTiO 纳米复合材料的可见光诱导光催化活性增加，然后随着 Au 负载的进一步增加而降低。因此，光催化活性的初始增加是由于大量 SPR 诱导载流子的生成、分离和参与，而由于 Au 和 ZnTiO 界面处缺陷位的形成，SPR 生成的载流子的复合导致光催化活性随后降低。过多的 Au 负载导致 SPR 电荷载流子的复合，这可以通过进行 SPR 诱导的时间分辨光致发光（TRPL）分析得到很好的解释，这一结果与可见光诱导光电流和 EIS 测量的结果直接相关。具有最佳 Au 负载（1wt%）的 Au/ZnTiO 纳米复合材料产生了惊人的高氢气产生速率，即 108 μmol h，能量转换效率为 7.14%，而原始 ZnTiO 在可见光照射下几乎没有活性。
