Synthesis And Photoelectric Performance Study Of Ultralong And Well-separated Single-crystal TiO₂ Nanowire Arrays

Photoelectrochemical(PEC)devices based on semiconductor materials,which can utilize clean solar energy,have broad application prospects in energy conversion and environmental governance.Electrodes are the core of these PEC devices because they bear the role of collecting carriers and providing a reaction interface.In recent years,one-dimensional(1D)structures such as nanorods,nanowires and nanotubes have been favored due to their unique properties in optics and electricity.The results show that the 1D nanowire(NW)arrays can offer a directed charge transport path to the electrode substrate,thus improving the charge transport property.For example,it has demonstrated that the electron transport properties of single-crystal TiO2 NW arrays are two orders of magnitude higher than that in the randomly packed nanoparticle(NP)films.However,to date,the synthesis of well-separated TiO2 NW arrays is limited to 3-4?m.Further increase the length result in NW arrays fusing to each other from the root and forming a compact layer due to the diameter grown fast simultaneously as the length of the nanowires grows.This not only reduces the aspect ratio and specific surface area,but also hinders their fast charge transport property,which further affects the performance of PEC devices.Thus,the growth of ultralong and well-separated 1D single-crystalline NW arrays is of great importance.Based on this background,the main research contents of this paper include the following two parts:First,ultralong well-separated NW arrays were synthesized by adjusting the growth conditions to regulate the growth rates of diameter and length of the NW.Finally we get well-separated single crystal rutile TiO2 NW arrays with a length of?10?m and an aspect ratio of approximately 100.Secondly,the PEC cell system was constructed based on the above ultralong and well-separated TiO2 NW arrays and the relationship between its ultralong well-separated single-crystal microstructure and charge transport property was studied.We reveal that the charge transport of the NW is 100 times faster than that of nanoparticle films and remarkably exhibits length-independence.The NW arrays with a length of?10?m used in PEC cell devices have 100%charge collection efficiency,which can be attributed to the well-separated architecture.