One-Step Hydrothermal Synthesis of Precious Metal-Doped Titanium Dioxide–Graphene Oxide Composites for Photocatalytic Conversion of CO₂ to Ethanol

Abstract

We utilized a one-step hydrothermal process for the synthesis of precious metal-doped titanium dioxide (TiO 2 )/graphene oxide (GO) composites. The metal-doped TiO 2 /GO composites, including silver–TiO 2 /GO (Ag–TiO 2 /GO), palladium–TiO 2 /GO (Pd–TiO 2 /GO), and copper–TiO 2 /GO (Cu–TiO 2 /GO), were synthesized by mixing a metal precursor, titanium butoxide, and graphene oxide in a water–ethanol mixture in an autoclave hydrothermal reactor. The photocatalytic performance of the composites was tested in the photoreduction of carbon dioxide (CO 2 ) to ethanol. Ag–TiO 2 /GO, Pd–TiO 2 /GO, and Cu–TiO 2 /GO exhibited an ethanol production rate of 109, 125, and 233 μmol/g cat h, respectively. The outstanding performances of Cu–TiO 2 /GO can be attributed to a combined effect of key parameters, including optical band gap, crystallite size, and BET surface area.

Soft template-assisted copper-doped sodium dititanate nanosheet/graphene oxide heterostructure for photoreduction of carbon dioxide to liquid fuels

“…6(a), right), which agrees well with the reported value of 3.2 eV. 6,19 The CT (Fig. 6(b), le) shows an enhanced light absorption ability since Cu reduces the electron-hole pairing rate and provides a transition state for photoelectrons to rest on.…”

“…For CTG, the production rates of 11, 30, 125 and 45 μmol g cat −1 h −1 are determined for acetone, methanol, ethanol, and i-propanol, highlighting enhanced photocatalytic performance as a result of Cu doping. Photoactivity of the CTG was previously studied by our research group, 6 in which the CO 2 photoreduction took place in a borosilicate glass photoreactor that allowed part of the UVA and UVB but none of the UVC to penetrate. The CTG produced only ethanol (C2) at a production rate of 232 ± 98 μmol g cat −1 h −1 , or a total carbon consumption rate of 466 μmol g cat −1 h −1 .…”

“…The mechanism for the photoreduction of CO 2 was not clearly understood, as discussed in our previous work. 6 An infinite pathway for CO 2 conversion needs to be monitored in situ using high-precision spectroscopy in a controlled environment. Based on our understanding, the photo-excited photocatalyst can produce photoelectrons that couple with dissolved CO 2 .…”

“…Their photocatalyst yield CO 2 photoreduction products of formaldehyde and ethanol at a production rate of 25 and 4.6 μmol g cat −1 h −1 , respectively. N. Lertthanaphol and his team 6 (our previous work) utilized the one-step hydrothermal technique in synthesizing the Cu–TiO 2 /GO composite. The composite exhibited good photoactivity in reducing CO 2 to ethanol at a production rate of 233 μmol g cat −1 h −1 .…”

“…The approach concerns not only the removal of CO 2 but also the generation of commodities, such as methane, 1–3 carbon monoxide, 2,3 formaldehyde, 4 methanol, 4,5 and ethanol. 6,7…”