Back Electron Transfer at TiO2 Nanotube Photoanodes in the Presence of a H2O2 Hole Scavenger

2017 ◽  
Vol 9 (39) ◽  
pp. 33887-33895 ◽  
Author(s):  
Heng Zhu ◽  
Shicheng Yan ◽  
Zhaosheng Li ◽  
Zhigang Zou
Keyword(s):  
Electron Transfer ◽  
Tio2 Nanotube ◽  
Back Electron Transfer ◽  
Hole Scavenger

Electron transfer sensitized photolysis of 'onium salts

1988 ◽  
Vol 66 (2) ◽  
pp. 319-324 ◽  
Author(s):  
R. J. DeVoe ◽  
M. R. V. Sahyun ◽  
Einhard Schmidt ◽  
N. Serpone ◽  
D. K. Sharma
Keyword(s):  
Electron Transfer ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Laser Flash ◽  
Quantitative Model ◽  
Intersystem Crossing ◽  
Single Electron Transfer ◽  
Onium Salts ◽  
Encounter Complex ◽  
Back Electron Transfer

We have studied the anthracene-sensitized photolyses of both diphenyliodonium and triphenylsulphonium salts in solution using both steady-state and laser flash photolysis techniques. Photoproducts, namely, phenylated anthracenes along with iodobenzene or diphenylsulphide, respectively, are obtained from both salts with quantum efficiencies of ca. 0.1 at 375 nm. We infer the intermediacy of diphenyliodo and triphenylsulphur radicals formed by single electron transfer from the singlet-excited anthracene. We have developed a quantitative model of this chemistry, and identify the principal sources of inefficiency as back electron transfer, which occurs at nearly the theoretically limiting rate, intersystem crossing from the initially formed sensitizer–'onium salt encounter complex, and in-cage radical recombination.

Thionine–graphene oxide covalent hybrid and its interaction with light

2017 ◽  
Vol 19 (22) ◽  
pp. 14412-14423 ◽  
Author(s):  
Ewelina Krzyszkowska ◽  
Justyna Walkowiak-Kulikowska ◽  
Sven Stienen ◽  
Aleksandra Wojcik
Keyword(s):  
Electron Transfer ◽  
Graphene Oxide ◽  
Excited State ◽  
Transfer Process ◽  
Singlet Excited State ◽  
Functionalized Graphene ◽  
Electron Transfer Process ◽  
Functionalized Graphene Oxide ◽  
Back Electron Transfer

Quenching of the thionine singlet excited state in covalently functionalized graphene oxide with an efficient back electron transfer process.

A polymer and graphene layer to increase dye regeneration and suppress back electron transfer in dye sensitized solar cells

2017 ◽  
Vol 53 (49) ◽  
pp. 6629-6632 ◽  
Author(s):  
Vediappan Sudhakar ◽  
Arulraj Arulkashmir ◽  
Kothandam Krishnamoorthy
Keyword(s):  
Electron Transfer ◽  
Solar Cells ◽  
Graphene Layer ◽  
Dye Sensitized Solar Cells ◽  
Blocking Layer ◽  
Dye Sensitized ◽  
Back Electron Transfer ◽  
Dye Regeneration ◽  
Sensitized Solar Cells

A polymer–graphene blocking layer decreases back electron transfer and increases dye regeneration that improved the DSSC efficiency to 10.4%.

scholarly journals Interrogation of O-ATRP Activation Conducted by Singlet and Triplet Excited States of Phenoxazine Photocatalysts

2021 ◽  
Author(s):  
Yisrael M. Lattke ◽  
Daniel Corbin ◽  
Steven M. Sartor ◽  
Blaine G. McCarthy ◽  
Garret Miyake ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Driving Force ◽  
Catalyst Design ◽  
Rate Coefficients ◽  
Quantum Yields ◽  
Collisional Quenching ◽  
Initiator Concentration ◽  
Data Set ◽  
Back Electron Transfer ◽  
Electron Transfer Theory

Organocatalyzed ATRP (O-ATRP) is a growing field exploiting organic chromophores as photoredox catalysts (PCs) that engage in dissociative electron transfer (DET) activation of alkyl halide initiators following absorption of light. Characterizing DET rate coefficients (<i>k<sub>act</sub></i>) and photochemical yields across various reaction conditions and PC photophysical properties will inform catalyst design and efficient use during polymerization. The studies described herein consider a class of phenoxazine PCs where synthetic handles of core-substitution and <i>N</i>-aryl substitution enable tunability of the electronic and spin character of the catalyst excited state as well as DET reaction driving force ( ). Using Stern-Volmer quenching experiments through variation of diethyl 2-bromo-2-methylmalonate (DBMM) initiator concentration, collisional quenching is observed. Eight independent measurements of <i>k<sub>act </sub></i>are reported as a function of for four PCs: four triplet reactants and four singlets with <i>k<sub>act</sub></i> values ranging from 1.1´10<sup>8</sup> M<sup>-1</sup>s<sup>-1</sup> where DET itself controls the rate to 4.8´10<sup>9</sup> M<sup>-1</sup>s<sup>-1</sup> where diffusion is rate limiting. This overall data set, as well as a second one inclusive of five literature values from related systems, is readily modeled with only a single parameter of reorganization energy under the frameworks of adiabatic Marcus electron transfer theory and Marcus-Savéant theory of DET. The results provide a predictive map where <i>k<sub>act</sub></i> can be estimated if is known and highlight that DET in these systems appears insensitive to PC reactant electronic and spin properties outside of their impact on driving force. Next, on the basis of measured <i>k<sub>act</sub></i> values in selected PC systems and knowledge of their photophysics, we also consider activation yields specific to the reactant spin states as the DBMM initiator concentration is varied. In <i>N</i>-naphthyl-containing PCs characterized by near-unity intersystem crossing, the T<sub>1</sub> is certainly an important driver for efficient DET. However, at DBMM concentrations common to polymer synthesis, the S<sub>1</sub> is also active and drives 33% of DET reaction events. Even in systems with low yields of ISC, such as in <i>N</i>-phenyl-containing PCs, reaction yields can be driven to useful values by exploiting the S<sub>1</sub> under high DBMM concentration conditions. Finally, we have quantified photochemical reaction quantum yields, which take into account potential product loss processes after electron-transfer quenching events. Both S<sub>1</sub> and T<sub>1</sub> reactant states produce the PC<sup>·+</sup> radical cation with a common yield of 71%, thus offering no evidence for spin selectivity in deleterious back electron transfer. The sub-unity PC<sup>·+</sup> yields suggest that some combination of solvent (DMAc) oxidation and energy-wasting back electron transfer is likely at play and these pathways should be factored in subsequent mechanistic considerations.

PbTe quantum dots as electron transfer intermediates for the enhanced hydrogen evolution reaction of amorphous MoSx/TiO2 nanotube arrays

Nanoscale ◽  
2018 ◽  
Vol 10 (21) ◽  
pp. 10288-10295 ◽  
Author(s):  
Shiyuan Gao ◽  
Bin Wang ◽  
Xinyu Liu ◽  
Zhanhu Guo ◽  
Zhongqing Liu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Electron Transfer ◽  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Tio2 Nanotube Arrays ◽  
Tio2 Nanotube ◽  
Nanotube Arrays

PbTe quantum dots (QDs) function as electron transfer intermediates for higher electrocatalytic performances from MoSx/PbTe QDs/TNAs.

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