Photocatalytic reduction of CO₂ using molybdenum-doped titanate nanotubes in a MEA solution

Abstract

In this study, the photocatalytic reduction of CO2 in monoethanolamine solution to form valuable energy sources was investigated using Mo-doped TNTs photocatalysts for the first time. The results revealed that the structure of Mo-doped TNTs was changed with the increase of calcination temperature. For Mo-doped TNTs calcined at 500 °C, the partial corruption of titanate nanotubes into anatase particles caused the reduction of Mo species from Mo 6+ to Mo 5+ and produced oxygen vacancies, which resulted in the highest CO2 reduction ability. The yield rates of CH4, CO and total combustible organic compounds were 0.52, 10.41 and 13.53 μmol/g-cat., respectively, under UVA (8W, 63μW/cm 2 ) irradiation. The photoreduction quantum efficiencies of CH4 and CO were achieved at 0.036% and 0.180%, respectively. It was found that the molybdenum structure and oxygen vacancies could be the key factors controlling the photocatalytic reduction efficiency of CO2. Possible structure transformation of Mo-doped TNTs at different calcination temperatures was inferred. And reaction mechanism for photocatalytic CO2 reduction with oxygen vacancy sites of Mo-doped TNTs was proposed.

Recent Advances in Heterogeneous Photocatalytic CO2 Conversion to Solar Fuels

“…Introduction of some metal cations (such as Cu, − Co, , Ni, Ce, , Mo, In, Ti, V, and Cr) into the host framework not only modifies the crystallinity of TiO 2 but also influences its light absorption properties. Also, the enhanced red-shifting from the UV region to longer wavelengths in the visible region can be observed with enhancing cation-doping levels. − For example, Cu-doped TiO 2 shows a slightly but steadily decreased bandgap upon enhancing Cu­(II) concentration from 0 to 3 mol % and has the potential to enhance the formation of HCOOH and CO in the presence of sulfide as an electron donor . Ola and Maroto-Valer have reported that the absorption spectra of Cu-based TiO 2 showed an increased shift in the visible light with enhancing Cu loading concentration in comparison with pure TiO 2 .…”

“…In the last 3 years, low-dimensional nanostructured TiO 2 were extensively applied in the photocatalytic CO 2 conversion. Among which, TiO 2 nanoparticles are still the most popular photocatalysts, ,,− ,− ,− ,,− ,,− , while 1D − ,,,,,, and 2D ,, nanomaterials are generally more attractive than their bulk and nanoparticle counterparts because they facilitate more efficient electron transport and exhibit higher surface-area-to-bulk-volume ratios. For instance, brookite TiO 2 nanorods with controllable aspect ratio were synthesized by using titanium ethoxide as Ti source .…”

“…38,50,59 For example, STM studies confirmed that CO 2 preferentially adsorbs on V O sites of TiO 2 , and the energy barriers for CO 2 hopping into and out of a V O were determined to be 0.09 and 0.16 eV, respectively. 59 The electron-induced dissociation of CO 2 adsorbed at the V O defect on the TiO 2 (110) surface was investigated at the single-molecule level using STM in an attempt to mimic the initial step of CO 2 activation on a photocatalyst surface, and the detected transient negative ion (CO 2…”

“…) due to the injected electron was considered to be the key process in CO 2 dissociation on TiO 2 (110) surface. 38 2.3.…”

N-doped reduced graphene oxide promoted nano TiO2 as a bifunctional adsorbent/photocatalyst for CO2 photoreduction: Effect of N species

“…The conversion of CO 2 could provide another alternative to the storage of CO 2 underground or in the deep ocean by producing value added chemicals while simultaneously addressing the energy shortage and global warming [2]. Among several existing technologies for CO 2 conversion to renewable fuels, photocatalytic reduction of CO 2 is a promising option that directly utilizes inexpensive and abundant solar energy [3][4][5]. Thus far, TiO 2 is commonly investigated for CO 2 photoreduction, however, its insufficient catalytic conversion efficiency still remains as the main bottleneck.…”