Turning Carbon Dioxide and Ethane into Ethanol by Solar-Driven Heterogeneous Photocatalysis over RuO<sub>2</sub>- and NiO-co-Doped SrTiO<sub>3</sub>

oleh: Larissa O. Paulista, Josep Albero, Ramiro J. E. Martins, Rui A. R. Boaventura, Vítor J. P. Vilar, Tânia F. C. V. Silva, Hermenegildo García

Format: Article
Diterbitkan: MDPI AG 2021-04-01

Deskripsi

The current work focused on the sunlight-driven thermo-photocatalytic reduction of carbon dioxide (CO<sub>2</sub>), the primary greenhouse gas, by ethane (C<sub>2</sub>H<sub>6</sub>), the second most abundant element in shale gas, aiming at the generation of ethanol (EtOH), a renewable fuel. To promote this process, a hybrid catalyst was prepared and properly characterized, comprising of strontium titanate (SrTiO<sub>3</sub>) co-doped with ruthenium oxide (RuO<sub>2</sub>) and nickel oxide (NiO). The photocatalytic activity towards EtOH production was assessed in batch-mode and at gas-phase, under the influence of different conditions: (i) dopant loading; (ii) temperature; (iii) optical radiation wavelength; (vi) consecutive uses; and (v) electron scavenger addition. From the results here obtained, it was found that: (i) the functionalization of the SrTiO<sub>3</sub> with RuO<sub>2</sub> and NiO allows the visible light harvest and narrows the band gap energy (ca. 14–20%); (ii) the selectivity towards EtOH depends on the presence of Ni and irradiation; (iii) the catalyst photoresponse is mainly due to the visible photons; (iv) the photocatalyst loses > 50% efficiency right after the 2nd use; (v) the reaction mechanism is based on the photogenerated electron-hole pair charge separation; and (vi) a maximum yield of 64 μmol EtOH g<sub>cat</sub><sup>−1</sup> was obtained after 45-min (85 μmol EtOH g<sub>cat</sub><sup>−1</sup> h<sup>−1</sup>) of simulated solar irradiation (1000 W m<sup>−2</sup>) at 200 °C, using 0.4 g L<sup>−1</sup> of SrTiO<sub>3</sub>:RuO<sub>2</sub>:NiO (0.8 wt.% Ru) with [CO<sub>2</sub>]:[C<sub>2</sub>H<sub>6</sub>] and [Ru]:[Ni] molar ratios of 1:3 and 1:1, respectively. Notwithstanding, despite its exploratory nature, this study offers an alternative route to solar fuels’ synthesis from the underutilized C<sub>2</sub>H<sub>6</sub> and CO<sub>2</sub>.