A Noble‐Metal‐Free System for Photocatalytic Hydrogen Production from Water

Abstract

A series of heteroleptic copper(I) complexes with bidentate PP and NN chelate ligands was prepared and successfully applied as photosensitizers in the light-driven production of hydrogen, by using [Fe3(CO)12] as a water-reduction catalyst (WRC). These systems efficiently reduces protons from water/THF/triethylamine mixtures, in which the amine serves as a sacrificial electron donor (SR). Turnover numbers (for H) up to 1330 were obtained with these fully noble-metal-free systems. The new complexes were electrochemically and photophysically characterized. They exhibited a correlation between the lifetimes of the MLCT excited state and their efficiency as photosensitizers in proton-reduction systems. Within these experiments, considerably long excited-state lifetimes of up to 54 μs were observed. Quenching studies with the SR, in the presence and absence of the WRC, showed that intramolecular deactivation was more efficient in the former case, thus suggesting the predominance of an oxidative quenching pathway.

Optimization of Hydrogen‐Evolving Photochemical Molecular Devices

“…[10] Furthermore also noble-metal-free systems using heteroleptic Cu I complexes as photosensitizers instead of [Ru(bpy) 3 ] 2+ in combination with [Fe 3 (CO) 12 ]asthe reducing catalyst can efficiently produce molecular hydrogen from water. [11] Besides these intermolecular approaches,i ntramolecular photocatalysts can also effectively produce hydrogen from aqueous solution under visible-light irradiation. [12,13] These so called photochemical molecular devices (PMDs) combine the photocenter,the electron relay,and the catalytic center in one single molecule and offer the potential for as pecific modification of the single modules to optimize the PMDs efficiencya nd stability during catalysis.Aparticular example of this approach, which has been investigated in great detail, [14] is shown in Figure 1.…”

Light to Hydrogen: Photocatalytic Hydrogen Generation from Water with Molecularly-Defined Iron Complexes

“…A number of molecularly-defined Cu-PS has been synthesized based on various combinations of bidentate phosphines and amines. Subsequent tests as PS in the photocatalytic proton reduction in the presence of [Fe3(CO)12] as WRC and TEA as SR (THF:TEA:H2O = 4:3:1) revealed a TON of up to 1330 for the Cu-PS (Scheme 3) [144,145]. Thus, these noble metal-free systems already achieved productivities in the same order of magnitude as those containing Ru-or Ir-PS.…”

“…This concentration is also applied in the photocatalytic experiments, but results already in some self-quenching of the PS. If it is reduced to 0.02 mM, the lifetime doubles to 6.4 µs [145]. Adding TEA (17 vol %) causes a moderate reduction of the luminescence lifetime to 1 µs, while it strongly decreases down to 50 ns if the TEA solution also contains 0.5 mM of the WRC.…”

Time-resolved X-ray absorption spectroscopy for the study of molecular systems relevant for artificial photosynthesis

“…They have strong absorption in the blue part of the visible spectrum, comparable with that of the Rubenchmarks. Due to these properties Cu-complexes are actively investigated for applications in dye sensitized solar cells (DSSC) [74] and have been applied recently in multicomponent H 2 evolving systems [75,76].…”