Owing to its excellent photoactivity, good stability and low cost, TiO2 is one of the most studied semiconductor materials to convert CO2 into useful chemicals, contributing to mitigate global warming. In this review, starting from the basic kinetic and thermodynamic principles of CO2 photoreduction, the focus is on the surface processes involved in its capture and subsequent reactivity on TiO2. In particular, the role of different TiO2 morphologies, facets and surface heterostructures is discussed. The effect of relevant co-adsorbed molecules (e.g., H2O) on the CO2 reaction pathways is also considered. Moreover, the coupling of TiO2 with graphene and metal nanoparticles to enhance the reaction rates is presented. A deeper understanding at the atomic level of these surface mechanisms could help the design of TiO2-based photocatalysts with improved efficiency and selectivity.