Spectroscopic investigation of charge carrier dynamics in carbon nitride photocatalysts In this thesis we focus is on the investigation of charge carrier dynamics in carbon nitride materials (PCNs) on time scales ranging from femtoseconds to microseconds by transient absorption and time resolved emission spectroscopy. This work aims to tackle the major problems that limit the photocatalytic performance of bare PCNs i.e. insufficient visible light absorption rapid charge carrier recombination low specific surface area and poor dispersion in solvents. Therefore three carbon nitride examples (R CNx {Mo3} CNx and K Na PHI) are introduced to extend our understanding in four directions:1) the impact of azo moieties formed after high temperature heat treatment on charge carrier dynamics; 2) charge carrier dynamics upon the incorporation of cocatalyst; 3) the interplay between surface functional groups and charge carrier dynamics; 4) the variation of charge carrier dynamics in the presence of chemical quenchers.