From Seconds to Femtoseconds: Solar Hydrogen Production and Transient Absorption of Chalcogenorhodamine Dyes

Abstract

A series of chalcogenorhodamine dyes with oxygen, sulfur, and selenium atoms in the xanthylium core was synthesized and used as chromophores for solar hydrogen production with a platinized TiO2 catalyst. Solutions containing the selenorhodamine dye generate more hydrogen [181 turnover numbers (TONs) with respect to chromophore] than its sulfur (30 TONs) and oxygen (20 TONs) counterparts. This differs from previous work incorporating these dyes into dye-sensitized solar cells (DSSCs), where the oxygen- and selenium-containing species perform similarly. Ultrafast transient absorption spectroscopy revealed an ultrafast electron transfer under conditions for dye-sensitized solar cells and a slower electron transfer under conditions for hydrogen production, making the chromophore's triplet yield an important parameter. The selenium-containing species is the only dye for which triplet state population is significant, which explains its superior activity in hydrogen evolution. The discrepancy in rates of electron transfer appears to be caused by the presence or absence of aggregation in the system, altering the coupling between the dye and TiO2. This finding demonstrates the importance of understanding the differences between, as well as the effects of the conditions for DSSCs and solar hydrogen production.

Solar H2 evolution in water with modified diketopyrrolopyrrole dyes immobilised on molecular Co and Ni catalyst–TiO2 hybrids

“…the reversible H 2 cycling catalysts hydrogenase (H 2 ase) 55,56 and Pt. 22,32 Using hydrogenase allows establishing the biocompatibility of DPP dyes and Pt as a catalyst eliminates or at least substantially reduces kinetic limitations from catalyst turnover and allows for evaluation of the true potential of the organic dyes.…”

Light-driven generation of hydrogen: New chromophore dyads for increased activity based on Bodipy dye and Pt(diimine)(dithiolate) complexes

“…In another study using TEOA as SD, several iodinated boron-dipyrromethene (Bodipy) dyes were shown to generate H 2 , with one derivative promoting formation of 70 TONs of H 2 in 2 h (λ > 420 nm) (69) and another yielding ∼100 TONs in 25 h (λ > 420 nm) (70). Illumination of a selenorhodamine dye with whitelight light-emitting diodes (LEDs) using ascorbic acid as SD resulted in ∼300 TONs of H 2 in 67 h (65). Two other systems were reported to have much higher activity in H 2 production.…”

Dye-sensitised semiconductors modified with molecular catalysts for light-driven H2 production

“…However, they are usually more prone to surface aggregation under DSP conditions, affecting their electron transfer properties. 19 In addition, metal complexes are generally more photostable, due to the redox flexibility of their metal centre. 20 The structure of the dye can play a critical role in the efficiency of electron transfer in dye-sensitised systems.…”