Search

Photocatalytic CO 2 reduction in the liquid phase at neutral pH conditions has been studied employing high surface area Mn-modified cubic CeO 2 and amorphous ZrO 2 catalysts. Results of the photocatalytic reduction of CO 2 to methane are promising on Mn-modified ZrO 2 and comparable with the noble metal-based photocatalysts. The surface area of both supports CeO 2 and ZrO 2 increased with Mn addition. Two broad diffraction peaks in X-ray diffractograms indicate that the ZrO 2 support is in the amorphous phase and Mn addition showed no considerable change. High intense diffraction peaks for CeO 2 support illustrated the cubic fluorite phase and Mn addition to CeO 2 support decreased the crystallite size due to the incorporation of Mn ions into the CeO 2 lattice. XPS study revealed the stabilization of Mn in a lower oxidation state i.e., Mn2+ and Mn3+, with ZrO 2 support than with CeO 2 support. The superior specific capacitance of the Mn-modified ZrO 2 catalyst indicates the enhanced synergy of active Mn species and support. Among the studied catalysts, Mn-modified ZrO 2 photocatalyst exhibited the highest activity and selectivity for photoreduction of CO 2 to methane and CO. [Display omitted] • Mn-modified CeO 2 and ZrO 2 support for photoreduction of CO 2. • Mn-ZO 2 catalyst showed high specific surface area among the studied catalysts. • Mn stabilized in a lower oxidation state enhances the catalytic activity. • Mn-modified ZrO 2 showed superior-specific capacitance due to improved synergy. • Photoreduction of CO 2 to CH 4 and CO are significantly enhanced on Mn-ZrO 2 catalyst. [ABSTRACT FROM AUTHOR]

In this study, we explored the photocatalytic efficacy of Ti3+-doped TiO 2 -based photocatalysts for CO 2 reduction. The Ti3+ self-doped photocatalysts were synthesized using a straightforward chemical reduction with sodium borohydride (NaBH 4). Our investigation aimed to elucidate the intricate interplay between the synthesis process and the quantity of NaBH 4 reductant on the physical-chemical and photocatalytic attributes of the defective TiO 2 -based photocatalysts. We explored three different commercially available TiO 2 materials labeled P25, (S)TiO 2 , and KRONOClean7050, which were reduced (2 g of TiO 2) with 0.75 and 1.5 g of NaBH 4. The reduction with 0.75 g of NaBH 4 led to a significant decrease of photocatalytic activity in all three cases. It was caused by clogging of the photocatalysts surface by sodium ions which resulted in the surface recombination of charge carriers. Oppositely, the reduction with 1.5 g of NaBH 4 , led to an increase of the photocatalytic activity with superior performance of KRONOClean7050. The comprehensive characterization of all the samples explained this superior performance of KC7050_RED_1.5 sample. Importantly, it did not contain any amorphous phase and the crystal size was two times higher compared to other 2 samples reduced by 1.5 g of NaBH 4. In the addition to higher crystallinity, the formation of a disordered TiO 2−x layer, enriched with Ti3+ defects and oxygen vacancies, was confirmed. These structural features enhance the light absorption and mitigate undesired recombination of photogenerated charge carriers. These results would trigger farther investigation of defect engineering towards enhancement of the efficiency of metal oxide photocatalysts. • Ti3+ self-doped TiO 2 for CO 2 reduction, via NaBH 4 synthesis method. • Impact of NaBH 4 quantity on physical-chemical properties of TiO 2. • Detailed characterization of prepared defective photocatalysts. • Superior photoactivity of KRONOClean 7050 sample treated with 1.5 g of NaBH 4. • Enhanced performance attributed to preserved crystallinity and TiO 2−x layer. [ABSTRACT FROM AUTHOR]

Herein, the synthesis, characterization, and reduction properties of 2D TiO 2 aerogel powder decorated with BiVO 4 (TiO 2 /BiVO 4) were investigated for versatile applications. First, 2D TiO 2 was prepared via lyophilization and subsequently modified with BiVO 4 using a wet impregnation method. The morphology, structure, composition, and optical properties were evaluated using transmission electron microscopy (TEM), X-ray diffractometry (XRD), laser-induced breakdown spectroscopy (LIBS), and diffuse reflectance spectroscopy (DRS), respectively. Significantly enhanced photocurrent densities (by 3–15 times) were obtained for TiO 2 /BiVO 4 compared to those of pure TiO 2 and BiVO 4. The reduction of toxic Cr(VI) to Cr(III) was assessed, including the effect of pH on overall photocatalytic efficiency. Under acidic conditions (pH ∼ 2), Cr(VI) reduction efficiency reached 100% within 2 h. For photocatalytic CO 2 reduction, the highest yields of CH 4 and CO were obtained using TiO 2 /BiVO 4. A higher efficiency for both applications was achieved because of the better separation of the electron-hole pairs in TiO 2 /BiVO 4. The excellent stability of TiO 2 /BiVO 4 over repeated runs highlights its potential for use in versatile environmental applications. The efficiency of TiO 2 /BiVO 4 is due to the interplay of the structure, morphology, composition, and photoelectrochemical properties that favour the material for the presented herein photocatalytic applications. [Display omitted] • TiO2/BiVO4 nanocomposite was synthesized and optimized for photocatalysis. • TiO2/BiVO4 showed excellent photocatalytic activity for Cr(VI) and CO2 reduction. • BiVO4 decorated 2D TiO2 significantly enhanced photocatalysis. • TiO2/BiVO4 exhibited good recyclability and stability. [ABSTRACT FROM AUTHOR]