Isotope Effects in Photocatalysis: An Underexplored Issue

Abstract

In order to improve the performance of well-established photocatalysts and to develop new potential photocatalyst materials, an understanding of the underlying mechanisms of photocatalytic reactions is of the utmost importance. An often neglected method for studying the mechanism is the investigation of isotope effects. Although just a few studies related to isotope effects exist, it has been shown to be a powerful tool for exploring mechanisms of photocatalytic processes. Most of the reports are focused on TiO 2 , which is the most studied photocatalyst, while there is a lack of data for other photocatalyst materials. This mini-review represents an overview of research utilizing isotope effects in the area of photocatalysis. The benefits and the importance of these studies will be highlighted, and the potential for these processes to be applied for the study of further photocatalytic reactions and different photocatalyst materials will be shown.

Electrochemical and Photoelectrochemical Water Splitting: Operando Raman and Fourier Transform Infrared Spectroscopy as Useful Probing Techniques

“…[36] In situ ATR-FTIR is widely used to study isotopic labeling in photocatalytic systems, where spectra acquisition allows the study of the integration of specific atoms from molecules in the liquid phase into the surface of the photocatalyst during a photocatalytic reaction and vice versa. [149,150] This could be very useful for understanding the reaction mechanisms and revealing the rate-limiting steps.…”

The role of crystal facets and disorder on photo-electrosynthesis

“…75,76 Similar observations have been made for TiO 2 both for the OER and the oxidation of organic compounds such as benzene. [77][78][79] In contrast, NiFeO x H y surfaces have been shown not to lose lattice oxygen during the OER but Fe is incorporated from the electrolyte. [80][81][82] The reactivity and the tendency to undergo reconstructions will depend on the crystal facet and the specific terminations, for example, hydroxylated disordered structures are known to work better than the organised rutile terminations.…”

Elucidating protonation pathways in CO2 photoreduction using the kinetic isotope effect

“…The kinetic isotope effect (KIE) is a crucial and sensitive tool for investigating reaction mechanisms by tracking the transition state of the rate-determining step using isotopically-labeled reagents 23 , 24 . In this study, we employed isotopically labeled H 2 O/D 2 O to determine an inverse kinetic solvent isotope effect (KSIE) of 0.2~0.9 on the photoreduction of CO 2 to CO on TiO 2 nanoparticles.…”