The project focuses on the direct photoelectrochemical (PEC) conversion of carbon dioxide to useful products. We vigorously study the effect of size, morphology, and surface functional groups of the photoelectrodes at the nanoscale. As a first step, we designed model systems to deconvolute the effect of the three main processes (light absorption, charge carrier transport and charge transfer), which dictate the solar-to-fuel conversion efficiency in a PEC cell. We studied bimetallic oxides, metal halide, lead halide perovskites in this vein. As the next step, we assembled hybrid photoelectrodes, where different components are responsible for the different processes. For example, nanocarbon-containing photoelectrodes outperformed their bare SC counterpart, due to enhanced charge carrier transport. We have developed and adapted different in situ electrochemical methods, to better understand the light-induced processes both inside the SC photoelectrodes, as well as at the SC/electrolyte interface. Finally, we designed, prepared and studied PEC flow cells to achieve unprecedentedly high CO2 conversion efficiencies. We have published over 18 high impact papers so far, in internationally leading journals.