Photo-Induced Radicals in Carbon Nitride and their Magnetic Signature

As a metal-free semiconductor, carbon nitride is a promising material for sustainable photocatalysis. From the large number of studies, it seems apparent that the photocatalytic activity is related to the number and type of defects present in the structure. Many defects are paramagnetic and photoresponsive and, for these reasons, Electron Paramagnetic Resonance (EPR) spectroscopy is a powerful method to derive fundamental information on the structure - local, extended and electronic - of such defects which in turn impact the optical, magnetic and chemical properties of a material. This review aims at critically discussing the interpretation of EPR data of native and photoinduced radical defects in carbon nitride research highlighting strengths and limitations of this spectroscopic technique. The employment of carbon nitride as a photocatalyst is conditional to understanding its response to light and the nature of all the photogenerated species. Amongst the characterisation techniques, EPR spectroscopy occupies a central role since it permits to detect paramagnetic states and follow their fate. Here we aim to provide guidelines to employ EPR spectroscopy in the research on carbon nitride. image