The electronic structure, be it at the interface of molecules with the surface, or at the interfacial region of two materials, gives rise to unusual physical and chemical properties that are different from the bulk counterpart. As a result, the domain of surface and interface modelling has seen a revolution in the area of semiconductor processing for electrochemical, photovoltaics, and catalytic applications. In the present thesis, we have examined the adsorption mechanism of various adsorbates likes CO2 and NO2 on the TiO2 surface followed by their coadsorption with H2O and subsequent conversion process. A three-state quantum mechanical model is proposed to explain the charge transfer mechanism. A step selective reactivity order among different facets of anatase TiO2 is established and the relation between binding energy and chemisorption is redefined. Towards efficient photovoltaic applications, a low strain TiO2/graphene heterostructure is envisaged and detailed electronic structure analysis is carried out to establish the bandgap and charge related phenomena across the interfacial region. In the last part of this work, the functionalization of mono/multilayered graphene pairs is carried out to establish a long-range magnetic ordering by intercalation of fluorine molecules through pseduoatomization, which holds promise for futuristic applications in the area of spintronics and magnetic memory devices.