Electrochemically and Photochemically Induced Hydrogen Evolution Catalysis with Cobalt Tetraazamacrocycles Occurs Through Different Pathways

Grau, Sergi; Schilling, Mauro; Moonshiram, Dooshaye; Benet‐Buchholz, Jordi; Luber, Sandra; Llobet, Antoni; Gimbert‐Suriñach, Carolina

doi:10.1002/cssc.202000283

Cited by 18 publications

(49 citation statements)

References 26 publications

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“…[40g] A recent study by Luber, Llobet, Gimbert‐Suriñach, and co‐workers on the hydrogen production catalyzed by cobalt tetraazamacrocycle complexes [Co( R N 3 Py)Cl 2 ] + (R = H, CH 2 OH. N 3 Py = 2,12‐dimethyl‐3,7,11‐triaza‐1(2,6)‐pyridinacyclododecaphane‐2,11‐diene) suggests that the formation of Co III –H via the protonation of Co I species is the rate‐determining step in electrocatalytic hydrogen production …”

Section: Mechanistic Studies For Hydrogen Production By Co Complexmentioning

confidence: 99%

Structure‐Functional Analysis of Hydrogen Production Catalyzed by Molecular Cobalt Complexes with Pentadentate Ligands in Aqueous Solutions

et al. 2020

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Hydrogen production from sunlight and water represents one promising solution to resolve the environmental problems caused by the consumption of fossil fuels and to meet the increasing global energy demands. Catalysts based on transition metal complexes have been extensively studied for electro-and photocatalytic production of hydrogen. Among the reported catalysts, molecular cobalt complexes have received

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Section: Mechanistic Studies For Hydrogen Production By Co Complexmentioning

confidence: 99%

Structure‐Functional Analysis of Hydrogen Production Catalyzed by Molecular Cobalt Complexes with Pentadentate Ligands in Aqueous Solutions

et al. 2020

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“…The superior activity and stability of the latter, compared to the cobalt diimine-dioxime catalyst, was previously reported for photocatalytic proton reduction under fully aqueous conditions. [28][29][30][31][32][33][34][35] In parallel, the dye structure was modified from the previously published T1-Co 16 with a cyclopenta[1,2-b:5,4-b']dithiophene (CPDT) bridge to bathochromically shift the absorption and increase the extinction coefficient in the visible region. 36,37 The alkyl chains introduced on the linker are intended (i) to limit dyad-dyad interactions and (ii) to prevent dyad desorption by forming a hydrophobic layer at the surface of the NiO film.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic Investigations Provide a Rationale for the Hydrogen-Evolving Activity of Dye-Sensitized Photocathodes Based on a Cobalt Tetraazamacrocyclic Catalyst

et al. 2021

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Dye-sensitized photoelectrochemical cells (DSPECs) are a promising approach to produce solar fuels, e.g. by reduction of protons to molecular hydrogen. Here, we present functional NiO photocathodes sensitized with covalent organic dye-catalyst assemblies integrating a robust cobalt tetraazamacrocyclic complex. This catalyst proved to be decisive to improve the stability of these systems, hydrogen being produced with a 26-fold increase in turnover numbers compared to similar photocathodes based on a cobaloxime catalyst, all other conditions being strictly identical otherwise. Transient absorption spectroelectrochemical (TA-SEC) measurements observed the catalytically competent Co I state in a functional dye-sensitized photocathode, with a lifetime of up to > 1 ms, comparable to the timescale of catalysis. They also unveiled the lack of efficiency of the thermally activated electron transfer from the reduced dye to the catalyst, which firstly limits the photocurrent density for hydrogen production. A second consequence is the accumulation of photogenerated charges on the acceptor side of the dye, ultimately leading to its degradation, as observed in operando and post-operando characterization of the system. This study thus provides tracks to improve the performances of hydrogen-evolving dye-sensitized photocathodes toward their integration into functional DSPECs.

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“…In the present study, we investigate the ultrafast excited state dynamics of two novel dye-catalyst assemblies specifically designed for improved photoelectrocatalytic hydrogen production in dye-sensitized photocathodes [18]. They comprise a push-pull organic dye (T2R) covalently assembled with two different H2-evolving cobalt catalysts: either the cobalt diimine-dioxime complex Cat2 [19] or the cobalt tetraazamacrocyclic catalyst Cat1 [20][21][22] (Figure 1). The metal-free dye structure relies on a triphenylamine (TPA) donor group functionalized by two protected carboxylic acid groups for its future anchoring onto semiconducting oxide-based electrodes and a cyanoacrylate/cyanoacrylamide acceptor group, separated by the electron-rich cyclopenta[1,2b:5,4-b']dithiophene (CPDT) bridge.…”

Section: Introductionmentioning

confidence: 99%

Investigating Light-Induced Processes in Covalent Dye-Catalyst Assemblies for Hydrogen Production

et al. 2020

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The light-induced processes occurring in two dye-catalyst assemblies for light-driven hydrogen production were investigated by ultrafast transient absorption spectroscopy. These dyads consist of a push-pull organic dye based on a cyclopenta[1,2-b:5,4-b’]dithiophene (CPDT) bridge, covalently linked to two different H2-evolving cobalt catalysts. Whatever the nature of the latter, photoinduced intramolecular electron transfer from the excited state of the dye to the catalytic center was never observed. Instead, and in sharp contrast to the reference dye, a fast intersystem crossing (ISC) populates a long-lived triplet excited state, which in turn non-radiatively decays to the ground state. This study thus shows how the interplay of different structures in a dye-catalyst assembly can lead to unexpected excited state behavior and might open up new possibilities in the area of organic triplet sensitizers. More importantly, a reductive quenching mechanism with an external electron donor must be considered to drive hydrogen production with these dye-catalyst assemblies.

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Electrochemically and Photochemically Induced Hydrogen Evolution Catalysis with Cobalt Tetraazamacrocycles Occurs Through Different Pathways

Cited by 18 publications

References 26 publications

Structure‐Functional Analysis of Hydrogen Production Catalyzed by Molecular Cobalt Complexes with Pentadentate Ligands in Aqueous Solutions

Structure‐Functional Analysis of Hydrogen Production Catalyzed by Molecular Cobalt Complexes with Pentadentate Ligands in Aqueous Solutions

Spectroscopic Investigations Provide a Rationale for the Hydrogen-Evolving Activity of Dye-Sensitized Photocathodes Based on a Cobalt Tetraazamacrocyclic Catalyst

Investigating Light-Induced Processes in Covalent Dye-Catalyst Assemblies for Hydrogen Production

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