To overcome some of the current challenges in the energy transition, heterogeneous (photo)catalysis is a key technology. However, for many relevant processes, we are still lacking the optimal catalyst materials, that are cheap and available, long-term stable and nontoxic, but remain reactive and ideally selective. To replace critical raw materials such as (noble) metal nanoparticles in such catalysts, we combine low-dimensional (semi-)metallic structures such as defects or 2D materials with (semiconducting) oxides to fabricate hybrid materials. One target is to develop these materials based on the surface-science approach: To overcome experimental limitations under technical conditions, we investigate well-defined model systems under ultra-high vacuum or so-called operando conditions (≈ few mbars). Combining insights from spectroscopy, microscopy and reactivity studies can then gain a comprehensive picture down to the atomic level.In this lecture, I will present examples for such Ti-based materials for (photo-) catalytic reactions relevant for the current energy challenges. Therein, the activation of greenhouse gas molecules (esp. N2O and CO2) on Ti3+ and Ti2+ defects will be illuminated. While such gases interact only weakly with defective rutile TiO2 under UHV conditions, higher pressures of CO2 (few mbars) combined with the presence of water as an effective H donor were found to enable a rich reduction chemistry along multiple parallel pathways in operando-XPS.In addition to oxides, nanostructured 2D titanium disulphide (TiS2) on metal and oxide surfaces will be introduced as a potential candidate for photocatalytic applications. Compared to Au (111), the TiS2 particles appear to interact more strongly with oxide substrates, here rutile TiO2 (110), leading to more elongated shapes and a limited thermal stability. NEXAFS allows a chemically sensitive identification of structural features across both substrates. Finally, these hybrid nanomaterials were studied in reductive (molecular H2) and oxidative (H2O) atmospheres, indicating relevant stability of the TiS2 basal planes.