Department of Chemistry, William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Small. 2014 Nov;10(22):4760-9. doi: 10.1002/smll.201401298. Epub 2014 Jul 2.
Single-crystalline and branched 1D arrays, ZnO nanowires/nanodisks (NWs/NDs) arrays, are fabricated to significantly enhance the performance of photoelectrochemical (PEC) water splitting. The epitaxial growth of the ZnO NDs with large exposed polar facets on ZnO NWs exhibits a laminated structure, which dramatically increases the light scattering capacity of the NWs arrays, especially in the wavelength region around 400 nm. The ND branching of the 1D arrays in the epitaxial fashion not only increase surface area and light utilization, but also support fast charge transport, leading to the considerable increase of photocurrent. Moreover, the tiny size NDs can facilitate charge separation and reduce charge recombination, while the large exposed polar facets of NDs reduce the external potential bias needed for water splitting. These advantages land the ZnO NWs/NDs arrays a four times higher power conversion efficiency than the ZnO NWs arrays. By sensitizing the ZnO NWs/NDs with CdS and CdSe quantum dots, the PEC performance can be further improved. This work advocates a trunk/leaf in forest concept for the single-crystalline NWs/NDs in array with enlarged exposure of polar facets, which opens the way for optimizing light harvesting and charge separation and transport, and thus the PEC water splitting.
为了显著提高光电化学（PEC）水分解的性能，制备了单晶和支化一维阵列 ZnO 纳米线/纳米盘（NWs/NDs）阵列。在 ZnO NWs 上外延生长具有大暴露的极性面的 ZnO NDs 呈现层状结构，这极大地增加了 NWs 阵列的光散射能力，特别是在波长约 400nm 的区域。一维外延生长的 ND 支化不仅增加了表面积和光利用率，而且支持快速电荷输运，导致光电流的显著增加。此外，小尺寸的 NDs 可以促进电荷分离并减少电荷复合，而 NDs 的大暴露的极性面则减少了水分解所需的外部电位偏置。这些优势使 ZnO NWs/NDs 阵列的功率转换效率比 ZnO NWs 阵列高四倍。通过用 CdS 和 CdSe 量子点敏化 ZnO NWs/NDs，可以进一步提高 PEC 性能。这项工作提倡在具有扩大的极性面暴露的单晶 NWs/NDs 阵列中采用树/叶的概念，为优化光捕获和电荷分离和输运以及 PEC 水分解开辟了道路。
