Molecules and heterostructures at TiO2 surface: the cases of H2O, CO2, and organic and inorganic sensitizers

TiO2-based (nano)materials are widely exploited in systems and devices of actual technological interest, because of their outstanding physical and chemical properties, including chemical stability, long durability, non-toxicity abundance and low cost. For this they are considered ideal for many practical applications including energy-related devices, photocatalysis, but are known to have some limitations. To improve their performance and then to find more efficient materials in the energy and environmental remediation fields, at first the investigation of the surface/interface properties at the molecular scale is required. In this contribution, a critical review of advances in the field of the TiO2 surface chemistry, highlighting the role of interactions at the molecular level, grafting and assembling/fabrication of suitable heterostructures, is reported. A few case studies, from the H2O, CO2 and acetylene interactions until to the grafting of organic/inorganic systems (graphene, MoS2) at the TiO2 surface, are highlighted. The discussed case studies are argued from their principles to the technological relevance.