Dynamics of Electron Injection in SnO₂/TiO₂ Core/Shell Electrodes for Water-Splitting Dye-Sensitized Photoelectrochemical Cells

Abstract

Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) rely on photoinduced charge separation at a dye/semiconductor interface to supply electrons and holes for water splitting. To improve the efficiency of charge separation and reduce charge recombination in these devices, it is possible to use core/shell structures in which photoinduced electron transfer occurs stepwise through a series of progressively more positive acceptor states. Here, we use steady-state emission studies and time-resolved terahertz spectroscopy to follow the dynamics of electron injection from a photoexcited ruthenium polypyridyl dye as a function of the TiO2 shell thickness on SnO2 nanoparticles. Electron injection proceeds directly into the SnO2 core when the thickness of the TiO2 shell is less than 5 Å. For thicker shells, electrons are injected into the TiO2 shell and trapped, and are then released into the SnO2 core on a time scale of hundreds of picoseconds. As the TiO2 shell increases in thickness, the probability of electron trapping in nonmobile states within the shell increases. Conduction band electrons in the TiO2 shell and the SnO2 core can be differentiated on the basis of their mobility. These observations help explain the observation of an optimum shell thickness for core/shell water-splitting electrodes.

Inorganic Photochemistry and Solar Energy Harvesting: Current Developments and Challenges to Solar Fuel Production

“…Alibabaei et al [131] have shown that DSPECs with SnO 2 /TiO 2 core/shell-nanostructured electrodes prepared by atomic layer deposition (ALD) can reach photocurrents up to 1.97 mA cm −2 depending on the shell thickness. Later, McCool and coworkers [101] 9 International Journal of Photoenergy SnO 2 core when the TiO 2 shell has a thickness smaller than 5 Å. For thicker layers, the electron is transferred to TiO 2 and then to the SnO 2 core.…”

Comparative Study of Synthesis of CdO-ZnO Nanocomposite Thin Films by Different Methods: A Review

“…All the curves demonstrate the semiconductor type of behaviour. The resistance per unit length decreased with the increase in temperature from 150 (2) Comparative Study of Synthesis of CdO-ZnO Nanocomposite Thin Films by Different Methods: A Review K up to nearly (325 K) for all prepared films. This should help in designing a particular Cd:ZnO film for its use in solar energy storage devices.…”

“…reported structural properties of CdO-ZnO nanocompopsite thin films. The samples with higher Zn ratio alloy thin films are of hexagonal wurtzite structures and highly (2) Comparative Study of Synthesis of CdO-ZnO Nanocomposite Thin Films by Different Methods: A Review Copyright: © 2016 Rajput and Purohit c-axis oriented and slightly shifted for Cd ratio with small grain 18.3 nm to 9.7 nm. The samples with higher Cd ratio alloy films show rock salt structure with (200) orientation.…”

“…Binary nanocomposites such as CdO-ZnO, CdS-ZnS, ZnO-MgO, ZrO 2 -Y 2 O 3 , SnO 2 -TiO 2 and CdSe-CdS show very good stable transport properties and lead different electronic devices [1][2][3][4][5][6]. CdO-ZnO nanocomposites have interesting properties for different applications.…”

Sequential Chemistry Toward Core–Shell Structured Metal Sulfides as Stable and Highly Efficient Visible‐Light Photocatalysts

“…[1] More importantly,t he interactions between the core and shell components can greatly improve physical and chemical properties,p rovide active interfaces,a nd even generate new synergetic properties. [2] Fore xample,i nm etal sulfide coreshell structures,t he larger band gap shell enables the charge carrier confinement within the cores,w hich can greatly improve the photoluminescence quantum yield and stability against photo bleaching.T he staggered alignment shells can promote the spatial charge-carrier separation, leading to reduced charge recombination and thus longer radiative lifetimes. [3] To date,v arious strategies have been developed for the synthesis of metal sulfide core-shell structures including the thermal-cycling coupled single precursor, [4] hot-injection method, [5] successive ion layer adhesion and reaction, [6] and colloidal atomic layer deposition.…”