Recent research in CO2 photoconversion has been focused on catalyst development, including significant efforts to extend photon absorption to the visible range of the solar spectrum. However, there remains a knowledge gap in understanding the dynamics of photocarriers (generation, trapping, diffusion, recombination) and how they relate to adsorption and the dynamics of adsorbed gases and intermediates on the surface of nanostructured catalysts. We have developed new techniques to elucidate these processes using continuous and pulsed laser excitation coupled with in situ electron paramagnetic resonance and diffuse reflectance IR and UV-Vis spectroscopy with product detection by mass spectroscopy. These techniques are coupled with molecular beam scattering, temperature programmed desorption, and transient absorption spectroscopy to gain insight into how charge carriers interact with adsorbed gases on the surface of semiconductor oxide catalysts. Knowledge obtained from these studies will be used to rationally design the next generation of photocatalysts for solar CO2 conversion.