Surface modification of layered perovskite Sr2TiO4 for improved CO2 photoreduction with H2O to CH4

Abstract

Layered perovskite Sr2TiO4 photocatalyst was synthesized by using sol-gel method with citric acid. In order to increase the surface area of layered perovskite Sr2TiO4, and thus to improve its photocatalytic activity for CO2 reduction, its surface was modified via hydrogen treatment or exfoliation. The physical and chemical properties of the prepared catalysts were characterized by X-ray diffraction, high-resolution transmission electron microscopy, elemental mapping analysis, energy-dispersive X-ray spectroscopy, N2 adsorption-desorption, UV-Vis spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, and electrophoretic light scattering. CO2 photoreduction was performed in a closed reactor under 6 W/cm2 UV irradiation. The gaseous products were analyzed using a gas chromatograph equipped with flame ionization and thermal conductivity detectors. The exfoliated Sr2TiO4 catalyst (E-Sr2TiO4) exhibited a narrow band gap, a large surface area, and high dispersion. Owing to these advantageous properties, E-Sr2TiO4 photocatalyst showed an excellent catalytic performance for CO2 photoreduction reaction. The rate of CH4 production from the photoreduction of CO2 with H2O using E-Sr2TiO4 was about 3431.77 μmol/gcat after 8 h.

Ruddlesden–Popper Oxide (La0.6Sr0.4)2(Co,Fe)O4 with Exsolved CoFe Nanoparticles for a Solid Oxide Fuel Cell Anode Catalyst

“…Considering the peaks appeared at 31.3 , 32.6 , 42.52 , 43.48 , 46.74 , 55.38 , 57.24 , and 65.08 , the Ruddlesden-Popper structure was successfully generated as a result of the reduction process with an indication of n ¼ 1 with a tetragonal structure. [32] Furthermore, any impurity phases such as La 2 O 3 and SrO, which could be formed undesirably during the exsolution process, were not observed. After its exposure to an oxidizing atmosphere, it can be observed that the CoFe-R.P.LSCF could be returned to the original LSCF without any formation of impurity phases; this result suggests that the LSCF has fairly good reversibility between two structures and reveals the possibility that LSCF can be used as a symmetric SOFC.…”

Improving the Photocatalytic activity for Hydrogen Evolution of LaBaInO4 via Topochemical Fluorination to LaBaInO3F2

“…Instead a pattern which is indicative for fluorinated RP-type phases with significant shifts of reflections to higher angles as well as splitting of some of the reflections (see Figure 2) is observed. This pattern could be indexed in the monoclinic crystal system with lattice parameters of a = 13.6284(3) Å, b = 5.99217(10) Å, c = 5.92016(11) Å, and β = 90.886(2)° with additional indication for a C-centered cell, which is in contrast to the tetragonal symmetry found for the starting material (a = 4.17797(5) Å, and c = 12.97255 (19) Å; please note that also lower symmetries have been reported for LaBaInO4 with a small orthorhombic distortion and space group Pbca, a = 12.933(3) Å, b = 5.911(1) Å, c = 5.905(1) Å 23,36 ). In addition to this phase, another phase with a broader reflection was observed at ~ 28° 2θ, which is, according to our experience, indicative for higher fluorine content RP-type phases with a larger c lattice parameter (c = 16.502(12) Å).…”

“…Such substitutive topochemical fluorination reactions, can be performed with fluoride-containing polymers such as polyvinylidene difluoride (PVDF, (CH2CF2)n) 17,18 . A few RP-type materials such as strontium titanate (Sr2TiO4), lithium calcium-tantalates (Li2CaTa2O7, A(Ca/Sr/Ba)La4Ti4O15), and strontium tin oxides (Sr2SnO4) have been reported to be efficient hydrogen evolution catalysts with bandgap values of 3.52 eV, 4.36 eV, 4.6 eV, respectively 4,8,10,19 . Limitations are imposed by the wide bandgap, making them only active in UV light which is not sustainable to harvest solar energy.…”

Inside‐and‐Out Semiconductor Engineering for CO2 Photoreduction: From Recent Advances to New Trends

“…Acidic sites on the surface of photocatalysts are beneficial for CO 2 reduction as well as for specific molecular bonding, which depends on their adequate separation of photogenerated charge carriers. [ 326 ] Proper surface acid sites grown on the Nb 2 O 5 photocatalyst can control the activity and selectivity of CO 2 conversion. [ 327 ] It was proved that CO and HCOOH were produced under high surface acidity, while low surface acidity tended to generate CH 4 .…”