scholarly journals Interplay between charge accumulation and oxygen reduction catalysis in nanostructured TiO2 electrodes functionalized with a molecular catalyst

2021 ◽  
Author(s):  
Yee-Seul Kim ◽  
Sébastien Kriegel ◽  
Alla Bessmertnykh-Lemeune ◽  
Kenneth Harris ◽  
Benoît Limoges ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Charge Accumulation ◽  
Nanostructured Tio2 ◽  
Molecular Catalyst

scholarly journals Interplay Between Charge Accumulation and Oxygen Reduction Catalysis in Nanostructured TiO 2 Electrodes Functionalized with a Molecular Catalyst

2021 ◽  
Author(s):  
Yee‐Seul Kim ◽  
Sébastien Kriegel ◽  
Alla Bessmertnykh‐Lemeune ◽  
Kenneth D. Harris ◽  
Benoît Limoges ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Charge Accumulation ◽  
Molecular Catalyst

Synergistic Dual‐Atom Molecular Catalyst Derived from Low‐Temperature Pyrolyzed Heterobimetallic Macrocycle‐N4 Corrole Complex for Oxygen Reduction

Small ◽  
2021 ◽  
pp. 2103823
Author(s):  
Satyanarayana Samireddi ◽  
V. Aishwarya ◽  
Indrajit Shown ◽  
Saravanakumar Muthusamy ◽  
Sreekuttan M. Unni ◽  
...  
Keyword(s):  
Low Temperature ◽  
Oxygen Reduction ◽  
Molecular Catalyst ◽  
Dual Atom

scholarly journals Charge Accumulation Kinetics in Multi-redox Molecular Catalysts Immobilised on TiO2

2020 ◽  
Author(s):  
Carlota Bozal-Ginesta ◽  
Camilo A. Mesa ◽  
Annika Eisenschmidt ◽  
Ravi Shankar ◽  
Laia Francàs ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Redox Potentials ◽  
Charge Accumulation ◽  
Excitation Light ◽  
Molecular Catalyst ◽  
Hole Scavenger ◽  
Accumulation Kinetics ◽  
Molecular Catalysts

Multi-redox catalysis requires the transfer of more than one charge carrier and is crucial for solar energy conversion into fuels and valuable chemicals. In photo(electro)chemical systems, however, the necessary accumulation of multiple, long-lived charges is challenged by recombination with their counterparts. Herein, we investigate charge accumulation in two model multi-redox molecular catalysts for proton and CO<sub>2</sub> reduction attached onto mesoporous TiO<sub>2</sub> electrodes. Transient absorption spectroscopy and spectroelectrochemical techniques have been employed to study the kinetics of photoinduced electron transfer from the TiO<sub>2</sub> to the molecular catalysts in acetonitrile, with triethanolamine as the hole scavenger. At high light intensities, we detect charge accumulation in the millisecond timescale in the form of multi-reduced species. The redox potentials of the catalysts and the capacity of TiO<sub>2</sub> to accumulate electrons play an essential role in the charge accumulation process at the molecular catalyst. Recombination of reduced species with valence band holes in TiO<sub>2</sub> is observed to be faster than microseconds, while electron transfer from multi-reduced species to the conduction band or the electrolyte occurs in the millisecond timescale. Finally, under light irradiation, we show how charge accumulation on the catalyst is regulated as a function of the applied bias and the excitation light intensity.

scholarly journals Charge Accumulation Kinetics in Multi-redox Molecular Catalysts Immobilised on TiO2

2020 ◽  
Author(s):  
Carlota Bozal-Ginesta ◽  
Camilo A. Mesa ◽  
Annika Eisenschmidt ◽  
Ravi Shankar ◽  
Laia Francàs ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Transient Absorption ◽  
Transient Absorption Spectroscopy ◽  
Redox Potentials ◽  
Charge Accumulation ◽  
Excitation Light ◽  
Molecular Catalyst ◽  
Hole Scavenger ◽  
Accumulation Kinetics ◽  
Molecular Catalysts

Multi-redox catalysis requires the transfer of more than one charge carrier and is crucial for solar energy conversion into fuels and valuable chemicals. In photo(electro)chemical systems, however, the necessary accumulation of multiple, long-lived charges is challenged by recombination with their counterparts. Herein, we investigate charge accumulation in two model multi-redox molecular catalysts for proton and CO<sub>2</sub> reduction attached onto mesoporous TiO<sub>2</sub> electrodes. Transient absorption spectroscopy and spectroelectrochemical techniques have been employed to study the kinetics of photoinduced electron transfer from the TiO<sub>2</sub> to the molecular catalysts in acetonitrile, with triethanolamine as the hole scavenger. At high light intensities, we detect charge accumulation in the millisecond timescale in the form of multi-reduced species. The redox potentials of the catalysts and the capacity of TiO<sub>2</sub> to accumulate electrons play an essential role in the charge accumulation process at the molecular catalyst. Recombination of reduced species with valence band holes in TiO<sub>2</sub> is observed to be faster than microseconds, while electron transfer from multi-reduced species to the conduction band or the electrolyte occurs in the millisecond timescale. Finally, under light irradiation, we show how charge accumulation on the catalyst is regulated as a function of the applied bias and the excitation light intensity.

Synergistic Dual‐Atom Molecular Catalyst Derived from Low‐Temperature Pyrolyzed Heterobimetallic Macrocycle‐N4 Corrole Complex for Oxygen Reduction (Small 46/2021)

Small ◽  
2021 ◽  
Vol 17 (46) ◽  
pp. 2170243
Author(s):  
Satyanarayana Samireddi ◽  
V. Aishwarya ◽  
Indrajit Shown ◽  
Saravanakumar Muthusamy ◽  
Sreekuttan M. Unni ◽  
...  
Keyword(s):  
Low Temperature ◽  
Oxygen Reduction ◽  
Molecular Catalyst ◽  
Dual Atom

Rational prediction of multifunctional bilayer single atom catalysts for the hydrogen evolution, oxygen evolution and oxygen reduction reactions

Nanoscale ◽  
2020 ◽  
Vol 12 (39) ◽  
pp. 20413-20424
Author(s):  
Riming Hu ◽  
Yongcheng Li ◽  
Fuhe Wang ◽  
Jiaxiang Shang
Keyword(s):  
Oxygen Reduction ◽  
Hydrogen Evolution ◽  
Oxygen Evolution ◽  
Single Atom ◽  
Reduction Reactions ◽  
Oxygen Reduction Reactions

Bilayer single atom catalysts can serve as promising multifunctional electrocatalysts for the HER, ORR, and OER.

Influence of Space Charge Accumulation by Pre-stress on Partial Discharge Inception Voltage

2020 ◽  
Vol 140 (5) ◽  
pp. 276-284
Author(s):  
Maimi Mima ◽  
Tokihiro Narita ◽  
Hiroaki Miyake ◽  
Yasuhiro Tanaka ◽  
Masahiro Kozako ◽  
...  
Keyword(s):  
Space Charge ◽  
Partial Discharge ◽  
Charge Accumulation ◽  
Inception Voltage

A Pyridinic Fe-N4 Macrocycle Effectively Models the Active Sites in Fe/N-Doped Carbon Electrocatalysts

2020 ◽  
Author(s):  
Travis Marshall-Roth ◽  
Nicole J. Libretto ◽  
Alexandra T. Wrobel ◽  
Kevin Anderton ◽  
Nathan D. Ricke ◽  
...  
Keyword(s):  
Oxygen Reduction ◽  
Active Sites ◽  
Catalytic Properties ◽  
Reduction Reaction ◽  
Iron Phthalocyanine ◽  
Electrochemical Studies ◽  
Onset Potential ◽  
Nitrogen Doped Carbon ◽  
Iron Active Sites

Iron- and nitrogen-doped carbon (Fe-N-C) materials are leading candidates to replace platinum in fuel cells, but their active site structures are poorly understood. A leading postulate is that iron active sites in this class of materials exist in an Fe-N<sub>4</sub> pyridinic ligation environment. Yet, molecular Fe-based catalysts for the oxygen reduction reaction (ORR) generally feature pyrrolic coordination and pyridinic Fe-N<sub>4</sub> catalysts are, to the best of our knowledge, non-existent. We report the synthesis and characterization of a molecular pyridinic hexaazacyclophane macrocycle, (phen<sub>2</sub>N<sub>2</sub>)Fe, and compare its spectroscopic, electrochemical, and catalytic properties for oxygen reduction to a prototypical Fe-N-C material, as well as iron phthalocyanine, (Pc)Fe, and iron octaethylporphyrin, (OEP)Fe, prototypical pyrrolic iron macrocycles. N 1s XPS signatures for coordinated N atoms in (phen<sub>2</sub>N<sub>2</sub>)Fe are positively shifted relative to (Pc)Fe and (OEP)Fe, and overlay with those of Fe-N-C. Likewise, spectroscopic XAS signatures of (phen<sub>2</sub>N<sub>2</sub>)Fe are distinct from those of both (Pc)Fe and (OEP)Fe, and are remarkably similar to those of Fe-N-C with compressed Fe–N bond lengths of 1.97 Å in (phen<sub>2</sub>N<sub>2</sub>)Fe that are close to the average 1.94 Å length in Fe-N-C. Electrochemical studies establish that both (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe have relatively high Fe(III/II) potentials at ~0.6 V, ~300 mV positive of (OEP)Fe. The ORR onset potential is found to directly correlate with the Fe(III/II) potential leading to a ~300 mV positive shift in the onset of ORR for (Pc)Fe and (phen<sub>2</sub>N<sub>2</sub>)Fe relative to (OEP)Fe. Consequently, the ORR onset for (phen<sub>2</sub>N<sub>2</sub>)Fe and (Pc)Fe is within 150 mV of Fe-N-C. Unlike (OEP)Fe and (Pc)Fe, (phen<sub>2</sub>N<sub>2</sub>)Fe displays excellent selectivity for 4-electron ORR with <4% maximum H<sub>2</sub>O<sub>2</sub> production, comparable to Fe-N-C materials. The aggregate spectroscopic and electrochemical data establish (phen<sub>2</sub>N<sub>2</sub>)Fe as a pyridinic iron macrocycle that effectively models Fe-N-C active sites, thereby providing a rich molecular platform for understanding this important class of catalytic materials.<p><b></b></p>

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