Editors: | F. Kongoli, H. Inufasa, M. G. Boutelle , R. Compton, J.-M. Dubois, F. Murad |
Publisher: | Flogen Star OUTREACH |
Publication Year: | 2018 |
Pages: | 216 pages |
ISBN: | 978-1-987820-84-3 |
ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
The photoconversion of CO2 by artificial photosynthesis is an area of great interest [1]. In this context, there is a great search for new semiconductors able to generate charge carriers (e-/h+) when irradiated by sunlight. Thus, the present work investigated the surface modification of TiO2 nanotubes electrodes (NtTiO2) with copper porphyrins for the CO2 reduction by electrocatalysis, photocatalysis, and photoelectrocatalysis using UV/vis light and different potentials during 2h. For this, NtTiO2 were constructed by anodization [2] and modified with three different porphyrins: [Cu(T4H3MPP)] (NtTiO2-P1), [Cu(TDCPP)] (NtTiO2-P2) and [Cu(TDCSPP)] (NtTiO2-P3) (P1 and P2 = neutral copper(II)porphyrins and P3 = anionic Cu(II)porphyrin) using a wet chemical deposition method. These electrodes were characterized by SEM, XRD, linear and cyclic voltammetry. The CO2 reductions were performed in 0.1 mol L-1 Na2SO4 with CO2 using a photoelectrochemical reactor and Xe lamp of 300 W (Newport 67005) [3]. The NtTiO2-P1 electrode when compared with the other materials presented a more homogeneous surface with porphyrin dispersed on well organized nanotubes and bang gap of 2.9 eV. The XRD showed the characteristics peaks of anatase and copper oxide II phases in all materials. The photoactivity of the semiconductors presented the same behavior for the three materials, showing a good response under light incidence, as the cyclic voltammetry that showed a new peak in presence of CO2 around -0.8 V. All the semiconductors were applied in the CO2 reduction with the best results obtained under -0.8 V for photoelectrocatalysis. Methanol was formed under all semiconductors, with different concentrations: 0.35 mmol L-1 for (NtTiO2-P1) and 0.020 mmol L-1 for the other materials, while ethanol formation occurs just on NtTiO2-P1 semiconductor forming 0.03 mmol L-1.The electrocatalysis and photocatalysis presented a smaller methanol and ethanol formation applying NtTiO2-P1 electrode. [Cu(T4H3MPP)] porphyrin presented the best adsorption in the TiO2 nanotube surface and NtTiO2-P1 semiconductor yielded the higher concentration of products formation by the CO2 reduction.