Abstract
Most chemical reactions promoted by light and using a photosensitizer (a dye) are subject to the phenomenon of luminescence. Redistribution of light in all directions (isotropic luminescence emission) and in a new spectral range (luminescence emission spectrum) makes experimental and theoretical studies much more complex compared to a situation with a purely absorbing reaction volume. This has a significant impact on the engineering of photoreactors for industrial applications. Future developments associated with photoreactive system optimization are therefore extremely challenging, and require an in-depth description and quantitative analysis of luminescence. In this study, a radiative model describing the effect of luminescence radiation on the calculation of absorptance is presented and analyzed with the multiple inelastic-scattering approach, using Monte Carlo simulations. The formalism of successive orders of scattering expansion is used as a sophisticated analysis tool which provides, when combined with relevant physical approximations, convenient analytical approximate solutions. Its application to four photosensitizers that are representative of renewable hydrogen production via artificial photosynthesis indicates that luminescence has a significant impact on absorptance and on overall quantum yield estimation, with the contribution of multiple scattering and important spectral effects due to inelastic scattering. We show that luminescence cannot be totally neglected in that case, since photon absorption lies at the root of the chemical reaction. We propose two coupled simple and appropriate analytical approximations enabling the estimation of absorptance with a relative error below 6% in every tested situation: the zero-order scattering approximation and the gray single-scattering approximation. Finally, this theoretical approach is used to determine and discuss the overall quantum yield of a bio-inspired photoreactive system with Eosin Y as a photosensitizer, implemented in an experimental setup comprising a photoreactor dedicated to hydrogen production.
Highlights
Molecular homogeneous photoreactive systems have many applications and significant industrial interest
For TATA+, Δ ≲ 5 since at least 95% of absorption is due to ballistic radiation that is not affected by inelastic scattering
This means that a plot of the hydrogen production rate hrH2 i versus Mean Volumetric Rate of Photons Absorbed hAi (MVRPA) hAið Þ is a straight line, the slope of which being the overall quantum yield φ(): φð Þ
Summary
Molecular homogeneous photoreactive systems (i.e. chemical molecules or clusters of molecules which can interact with light and react) have many applications and significant industrial interest. New solar applications for green photochemistry [2, 3], the production of renewable hydrogen from water [4,5,6] or carbon dioxyde photoreduction [7,8,9] involving artificial photosynthesis (solar fuels) are becoming increasingly important. In the quest for cheap catalyst development, molecular catalysts synthesized from relatively abundant elements on Earth (in contrast with particle catalysts based on doped-semiconductors, which are still more effective today [6, 10,11,12] but out of the scope of this article), are an attractive prospect for the future [13,14,15] They must always be associated with one or more photosensitizers, which will initiate the reaction by elementary photon absorption leading to an excited state as a singlet or triplet. The use of these photosensitizers goes far beyond the framework of the production of solar energy vectors, since they are at the root of all the applications mentioned above
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
