The TMC-1 Molecular Cloud in Taurus has been used as astrochemical laboratory to test new approaches in computational chemistry to predict molecular abundances in interstellar space. TMC-1 has been observed to contain a large variety of complex molecules such as acids, alcohols and hydrocarbons. In the laboratory, the synthesis of such prebiotic molecules has been confirmed to occur when simple ices are exposed to ionising radiation such as UV, X-rays, electron or ion bombardment. In theoretical astrochemistry, it is understood that complex molecules preferentially form on dust grain surfaces, and for this work, we use the physico-chemical ProDiMo code with latest improvements in surface chemistry (see Thi, W.-F. et al. 2017, submitted) to study the formation of complex molecules in TMC-1. The model includes a sophisticated treatment H$_2$ and HD formation on cold and warm grain surfaces, as well as on hydrogenated PAHs. We discuss the influence of surface chemistry and H$_2$-formation on the resulting molecular concentrations as function of time and compare our results to other models available in the literature.