Abstract
High photon conversion efficiencies and low-cost materials are crucial for implementing photocatalytic solutions in large scale applications. To improve the conversion efficiencies, knowledge on the lifetime and dynamics of photogenerated charge carriers is fundamental, for which transient absorption spectroscopy has provided important insights. Regarding the cost of the materials, one approach to decrease it is mixing the photocatalyst with cheaper additives while avoiding a significant loss in its activity. In this short review we summarize the findings of our group dealing with both aspects. A new model to fit transient absorption decays, based on fractal kinetics, is discussed. The model has been applied to the transient decays of TiO2 mixtures with binary particle size distributions and of TiO2 mixtures with a priori inert additives. In both cases, the insights obtained from the model were crucial to explain the photocatalytic activities of the mixtures.
Highlights
Despite extensive research efforts, heterogeneous photocatalysis has yet to achieve a significant deployment in technological applications [1, 2]
In this short review we summarize recent results from our research group dealing with commercial TiO2 photocatalysts and their analysis with transient absorption spectroscopy
This technique gives valuable information on the primary processes occurring after excitation of the photocatalysts, the main one being charge carrier recombination
Summary
Heterogeneous photocatalysis has yet to achieve a significant deployment in technological applications [1, 2]. Perhaps the most salient feature of this technique is the fact that photocatalyst powders or films can be readily analyzed under realistic conditions, be it in suspension, stand-alone, or under controlled atmospheres This means that, unlike other analyses that require vacuum or other specific conditions, the conclusions drawn from TAS can be directly transferred to actual photocatalytic reactions. Regarding the second optimization avenue, i.e. decrease the cost of preparing and implementing photocatalysts, our group has focused on how different additives affect the activity of commercial photocatalyst powders based on anatase TiO2. We observed a strong effect of the nature of the cation, highlighting possible challenges in the implementation of the photocatalysts This short review summarizes our findings on these topics, contextualizing them with a short description of primary processes in photocatalysis and a brief note on the analysis of TAS data. We show our work on binary mixtures based on TiO2, both for photocatalyst-pigment and photocatalystadditive compositions, employing once more TAS as a key technique to explain the differing behaviors
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