2022, Boga, Bíborka, Steinfeldt, Norbert, Moustakas, Nikolaos G., Peppel, Tim, Lund, Henrik, Rabeah, Jabor, Pap, Zsolt, Cristea, Vasile-Mircea, Strunk, Jennifer

Perovskites such as SrTiO3 are interesting for photocatalytic applications due to their structure-related and electronic properties. These properties are influenced by the presence of SrCO3 which is often formed simultaneously during the hydrothermal synthesis of SrTiO3. In this study, SrTiO3-SrCO3 composites with different contents of SrCO3 (5–24 wt%) were synthesized. Their morphological, structural, and optical properties were investigated using complementary methods such as scanning electron microscopy (SEM), X-ray diffraction (XRD), nitrogen sorption, and diffuse reflectance spectroscopy (DRS). Their photocatalytic activity was assessed during the degradation of diclofenac (DCFNa) in aqueous solution and CO2 photoreduction under Xe lamp irradiation. Improved photocatalytic efficiency in DCFNa degradation was observed for all the studied composites in comparison with SrTiO3, and the highest mineralization efficiency was obtained for the sample with 21 wt% SrCO3 content. The presence of SrCO3 led to an increased concentration of active species, such as •OH radicals. Otherwise, its presence inhibits CH4 and C2H6 production during CO2 photoreduction compared with pure SrTiO3.

2019, Handoko, Chanel Tri, Moustakas, Nikolaos G., Peppel, Tim, Springer, Armin, Oropeza, Freddy E., Huda, Adri, Bustan, Muhammad Djoni, Yudono, Bambang, Gulo, Fakhili, Strunk, Jennifer

Commercial TiO 2 (anatase) was successfully modified with Ag nanoparticles at different nominal loadings (1%-4%) using a liquid impregnation method. The prepared materials retained the anatase structure and contained a mixture of Ag 0 and Ag I species. Samples exhibited extended light absorption to the visible region. The effect of Ag loading on TiO 2 is studied for the photocatalytic reduction of CO 2 to CH 4 in a gas-solid process under high-purity conditions. It is remarkable that the reference TiO 2 used in this work is entirely inactive in this reaction, but it allows for studying the effect of Ag on the photocatalytic process in more detail. Only in the case of 2% Ag/TiO 2 was the formation of CH 4 from CO 2 observed. Using different light sources, an influence of the localized surface plasmon resonance (LSPR) effect of Ag is verified. A sample in which all Ag has been reduced to the metallic state was less active than the respective sample containing both Ag 0 and Ag + , indicating that a mixed oxidation state is beneficial for photocatalytic performance. These results contribute to a better understanding of the effect of metal modification of TiO 2 in photocatalytic CO 2 reduction. © 2019 by the authors. Licensee MDPI, Basel, Switzerland.

2019, Dilla, Martin, Moustakas, Nikolaos G., Becerikli, Ahmet E., Peppel, Tim, Springer, Armin, Schlögl, Robert, Strunk, Jennifer, Ristig, Simon

In this study we assess the general applicability of the widely used P25-TiO2 in gas-phase photocatalytic CO2 reduction based on experimentally determined reactivity descriptors from classical heterogeneous catalysis (productivity) and photochemistry (apparent quantum yield/AQY). A comparison of the results with reports on the use of P25 for thermodynamically more feasible reactions and our own previous studies on P25-TiO2 as photocatalyst imply that the catalytic functionality of this material, rather than its properties as photoabsorber, limits its applicability in the heterogeneous photocatalytic CO2 reduction in the gas phase. The AQY of IrOx/TiO2 in overall water splitting in a similar high-purity gas-solid process was four times as high, but still far from commercial viability.