TiO2-MWCNT and TiO2-GNP nanocomposites as well as titanate (Na2Ti3O7) nanosheets synthesized via deposition-hydrothermal (5 M NaOH, 150 °C for 10 h) technique were thoroughly characterized using XRD, TEM-SAED-EDX, UV–vis diffuse reflectance spectroscopy, PL, Raman and N2 sorptiometry. The Performances of as-synthesized photocatalysts toward methanol oxidation were evaluated by cyclic voltammetry (CV), electrochemical impedance (EIS) and Tafel plots under the influence of UV light irradiation (λ = 296–390 nm, 8 and 64 W). Amongst the photocatalysts, TiO2-MWCNT showed the highest photooxidation current density (4.5 mA cm−2) surpassing that of Na2Ti3O7 by 2.6 times. This enhancement was not only originated from the strong binding between MWCNTs and TiO2 but also due to the oxygen vacancies created on TiO2. TiO2-MWCNT also offered the highest incident photon to current efficiency (14.5%) and maximum surface area (32.0 m2 g−1). Although TiO2-GNP presented a lower band gap (1.2 eV) and higher optical absorptivity than TiO2-MWCNT, it offered lower current density (1.0 mA cm−2) due to hampering the charges separation. The EIS of TiO2-MWCNT indicated inferior charge transfer resistance comprised of 3.5 times than Na2Ti3O7 and TiO2-GNP. This was consistent with the Tafel charge transfer coefficient data. Investigating the reactive species created during methanol photooxidation suggested that O2− was the reaction intermediate. |
