Department of Chemistry, Emory University , Atlanta, Georgia 30322, United States.
J Am Chem Soc. 2014 May 28;136(21):7708-16. doi: 10.1021/ja5023893. Epub 2014 May 14.
Semiconductor-metal nanoheterostructures, such as CdSe/CdS dot-in-rod nanorods with a Pt tip at one end (or CdSe/CdS-Pt), are promising materials for solar-to-fuel conversion because they allow rational integration of a light absorber, hole acceptor, and electron acceptor or catalyst in an all-inorganic triadic heterostructure as well as systematic control of relative energetics and spatial arrangement of the functional components. To provide design principles of such triadic nanorods, we examined the photocatalytic H2 generation quantum efficiency and the rates of elementary charge separation and recombination steps of CdSe/CdS-Pt and CdS-Pt nanorods. We showed that the steady-state H2 generation quantum efficiencies (QEs) depended sensitively on the electron donors and the nanorods. Using ultrafast transient absorption spectroscopy, we determined that the electron transfer efficiencies to the Pt tip were near unity for both CdS and CdSe/CdS nanorods. Hole transfer rates to the electron donor, measured by time-resolved fluorescence decay, were positively correlated with the steady-state H2 generation QEs. These results suggest that hole transfer is a key efficiency-limiting step. These insights provide possible ways for optimizing the hole transfer step to achieve efficient solar-to-fuel conversion in semiconductor-metal nanostructures.
半导体-金属纳米异质结构，如具有 Pt 尖端的 CdSe/CdS 点-棒纳米棒（或 CdSe/CdS-Pt），是用于太阳能到燃料转化的有前途的材料，因为它们允许在全无机三元异质结构中合理集成光吸收体、空穴受体和电子受体或催化剂，以及对功能组件的相对能级和空间排列进行系统控制。为了提供这种三元纳米棒的设计原则，我们研究了 CdSe/CdS-Pt 和 CdS-Pt 纳米棒的光催化 H2 生成量子效率和基本电荷分离和重组步骤的速率。我们表明，稳态 H2 生成量子效率（QE）对电子供体和纳米棒敏感。使用超快瞬态吸收光谱，我们确定对于 CdS 和 CdSe/CdS 纳米棒，电子转移到 Pt 尖端的效率接近 1。通过时间分辨荧光衰减测量的空穴转移到电子给体的速率与稳态 H2 生成 QE 呈正相关。这些结果表明空穴转移是一个关键的效率限制步骤。这些见解为优化空穴转移步骤以在半导体-金属纳米结构中实现高效太阳能到燃料转化提供了可能的途径。
