The electronic structure, be it at the interface of molecules with surface, or at 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 revolution in the area of semiconductor processing for electrochemical, photocatalytic, solar cell and spintronic 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 a relation between binding energy and chemisorption is redefined. To enhance the charge carrier separation, a low strain TiO2/graphene heterostructure is envisaged and detailed electronic structure analysis is carried out to establish the band gap and charge related phenomena across the interfacial region. In the last part of this work, functionalization of mono/mulilayered graphene pairs is carried out to establish a long range magnetic ordering by intercalating fluorine molecules through pseduoatomization, which holds promise for futuristic applications in the area of spintronics and magnetic memory devices.