Ascorbate as an electron relay between an irreversible electron donor and Ru(ii) or Re(i) photosensitizers

Abstract

Ascorbate acts as a reversible electron shuttle between tris(2-carboxyethyl) phosphine (TCEP) and Re(I) or Ru(II) photosensitizers. Oxidized ascorbate is recycled up to 50 times by the TCEP → TCEP[double bond, length as m-dash]O redox process which enables 30 000 TONs per WRC in photocatalytic hydrogen production, thus exceeding the performance with pure ascorbate by far.

Photo-induced redox catalysis for proton reduction to hydrogen with homogeneous molecular systems using rhodium-based catalysts

“…Nonetheless, the A species is a good electron acceptor and is also capable to turn back to HA − by re-oxidizing the reduced PS or the reduced Cat, contributing to the deactivation of the photocatalytic process. Actually, some groups such as those of Creutz [110], Tabushi [13], and Alberto [41,52] consider that HA − is not a real sacrificial donor but a reversible electron donor.…”

“…Some of these homogeneous photocatalytic systems can operate very efficiently (in terms of number of catalytic cycles or turnover number (TON)) in organic or mixed aqueous-organic solvents. Those reaching a turnover number versus catalyst (TON Cat ) above 100 in fully aqueous solution were rare and limited to rhodium [36][37][38][39] and platinum [40] but, since two years, several examples with cobalt [41][42][43][44][45][46][47][48][49][50][51][52][53][54], iron [55][56][57][58] nickel [59] were reported. Developing H 2 -evolving photocatalytic systems functioning in pure water is essential for their coupling with water oxidation systems in photoelectrochemical water-splitting devices.…”

A computational mechanistic investigation of hydrogen production in water using the [RhIII(dmbpy)2Cl2]+/[RuII(bpy)3]2+/ascorbic acid photocatalytic system

“…1 In this context, efficient photocatalytic production of dihydrogen (H 2 ) under visible-light irradiation, which is believed to be a convenient clean energy carrier for the future, is an important goal. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] Those operating efficiently in fully aqueous solution were rare and limited to noble-metal based catalysts (rhodium and platinum) [22][23][24][25][26][27] until 2012, when several examples with cobalt, [28][29][30][31][32][33][34][35][36][37][38][39][40][41] iron [42][43][44][45] and nickel-based 46 catalysts were reported. Numerous photocatalytic systems in literature exhibit high activity in organic media or in mixtures of aqueous/organic solvents.…”

Nickel‐Containing Keggin‐Type Polyoxometalates as Hydrogen Evolution Catalysts: Photochemical Structure–Activity Relationships

“…Related effects werep reviously reported for am olecular cobalt-based WRC and preventedb yi ntroducing the additional electron donor tris(2-carboxyethyl)phosphine, which is capable of reducing the dehydroascorbate to prevent back electron transfer. [42] Herein, we did not block back electron transfer in the first place because such information may be crucial for interpreting the observed hydrogen evolution trends.A ttempts have been made to keep the assay system as straightforward as possible to avoid an overlayo fS AR and additional factors.…”