TY - JOUR
T1 - Proton-Induced Trap States, Injection and Recombination Dynamics in Water-Splitting Dye-Sensitized Photoelectrochemical Cells
AU - McCool, Nicholas S.
AU - Swierk, John R.
AU - Nemes, Coleen T.
AU - Saunders, Timothy P.
AU - Schmuttenmaer, Charles A.
AU - Mallouk, Thomas E.
N1 - Funding Information:
This work was supported by the Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, and Energy Biosciences, Department of Energy, under Contracts DE-FG02-07ER15911 and DE-FG02-07ER15909. N.S.M. thanks the National Science Foundation for support as agraduate fellow under Grant DGE1255832.
Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/7/6
Y1 - 2016/7/6
N2 - Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) utilize a sensitized metal oxide and a water oxidation catalyst in order to generate hydrogen and oxygen from water. Although the Faradaic efficiency of water splitting is close to unity, the recombination of photogenerated electrons with oxidized dye molecules causes the quantum efficiency of these devices to be low. It is therefore important to understand recombination mechanisms in order to develop strategies to minimize them. In this paper, we discuss the role of proton intercalation in the formation of recombination centers. Proton intercalation forms nonmobile surface trap states that persist on time scales that are orders of magnitude longer than the electron lifetime in TiO2. As a result of electron trapping, recombination with surface-bound oxidized dye molecules occurs. We report a method for effectively removing the surface trap states by mildly heating the electrodes under vacuum, which appears to primarily improve the injection kinetics without affecting bulk trapping dynamics, further stressing the importance of proton control in WS-DSPECs.
AB - Water-splitting dye-sensitized photoelectrochemical cells (WS-DSPECs) utilize a sensitized metal oxide and a water oxidation catalyst in order to generate hydrogen and oxygen from water. Although the Faradaic efficiency of water splitting is close to unity, the recombination of photogenerated electrons with oxidized dye molecules causes the quantum efficiency of these devices to be low. It is therefore important to understand recombination mechanisms in order to develop strategies to minimize them. In this paper, we discuss the role of proton intercalation in the formation of recombination centers. Proton intercalation forms nonmobile surface trap states that persist on time scales that are orders of magnitude longer than the electron lifetime in TiO2. As a result of electron trapping, recombination with surface-bound oxidized dye molecules occurs. We report a method for effectively removing the surface trap states by mildly heating the electrodes under vacuum, which appears to primarily improve the injection kinetics without affecting bulk trapping dynamics, further stressing the importance of proton control in WS-DSPECs.
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U2 - 10.1021/acsami.6b05362
DO - 10.1021/acsami.6b05362
M3 - Article
AN - SCOPUS:84977635915
SN - 1944-8244
VL - 8
SP - 16727
EP - 16735
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 26
ER -