Solar Hydrogen Generation by a CdS-Au-TiO2 Sandwich Nanorod Array Enhanced with Au Nanoparticle as Electron Relay and Plasmonic Photosensitizer
Solar Hydrogen Generation by a CdS-Au-TiO2 Sandwich Nanorod Array Enhanced with Au Nanoparticle as Electron Relay and Plasmonic Photosensitizer
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DOI：
10.1021/ja503508g
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发表时间：
2014-06-11
影响因子：
15
通讯作者：
Wu, Nianqiang
中科院分区：
文献类型：
--
作者：
Li, Jiangtian;Cushing, Scott K.;Wu, Nianqiang
本文提出了一种三明治结构的cdau - tio2纳米棒阵列作为光电化学电池（PEC）的光阳极，用于劈水制氢。金纳米粒子夹在TiO2纳米棒和CdS量子点（QD）层之间，在提高太阳能-化学能转换效率方面发挥了双重作用。首先，Au纳米粒子作为电子继电器，在波长小于525 nm的光激发CdS量子点时，促进CdS和TiO2之间的电荷转移。其次，金纳米粒子作为等离子体光敏剂，使太阳能到氢的转换波长比cd的带边长，将光转换波长从525 nm延长到725 nm。Au的双重作用导致在全太阳光谱照射下，在0 V （vs AglAgCl）下的光电流为4.07 mA/cm(2)，最大太阳能-化学能转换效率为2.8%。对瞬态吸收光谱数据进行了反演分析，跟踪了异质结构中电子和空穴的转移，将弛豫动力学与潜在的耦合速率方程联系起来，揭示了陷阱态俄歇复合是界面电荷转移的主要因素。研究发现，金纳米粒子的加入增加了电荷转移寿命，降低了陷阱态俄格率，抑制了长时间的缩尺转移，并部分补偿了表面陷阱态的负面影响。最后，确定了等离子体热载流子的直接转移是等离子体能量传递的机制，并表明界面肖特基势垒高度调节等离子体热电子的转移和反向转移。电荷转移的瞬态吸收特性表明，在设计量子点敏化太阳能电池时，缺陷态是不可忽视的。这种简单的三明治结构将金纳米粒子的电学和光学功能结合在一个单一的结构中，这对设计高效的太阳能收集装置具有重要意义。
This paper presents a sandwich-structured CdSAu-TiO2 nanorod array as the photoanode in a photoelectrochemical cell (PEC) for hydrogen generation via splitting water. The gold nanoparticles sandwiched between the TiO2 nanorod and the CdS quantum dot (QD) layer play a dual role in enhancing the solar-to-chemical energy conversion efficiency. First, the Au nanoparticles serve as an electron relay, which facilitates the charge transfer between CdS and TiO2 when the CdS QDs are photoexcited by wavelengths shorter than 525 nm. Second, the Au nanoparticles act as a plasmonic photosensitizer, which enables the solar-to-hydrogen conversion at wavelengths longer than the band edge of CdS, extending the photoconversion wavelength from 525 to 725 nm. The dual role of Au leads to a photocurrent of 4.07 mA/cm(2) at 0 V (vs AglAgCl) under full solar spectrum irradiation and a maximum solar-to-chemical energy conversion efficiency of 2.8%. An inversion analysis is applied to the transient absorption spectroscopy data, tracking the transfer of electrons and holes in the heterostructure, relating the relaxation dynamics to the underlying coupled rate equation and revealing that trap-state Auger recombination is a dominant factor in interfacial charge transfer. It is found that addition of Au nanoparticles increases the charge-transfer lifetime, reduces the trap-state Auger rate, suppresses the long-time scale back transfer, and partially compensates the negative effects of the surface trap states. Finally, the plasmonic energy-transfer mechanism is identified as direct transfer of the plasmonic hot carriers, and the interfacial Schottky barrier height is shown to modulate the plasmonic hot electron transfer and back transfer. Transient absorption characterization of the charge transfer shows defect states cannot be ignored when designing QD-sensitized solar cells. This facile sandwich structure combines both the electrical and the optical functions of Au nanoparticles into a single structure, which has implications for the design of efficient solar-energy-harvesting devices.