Photovoltaic and spectroscopic characteristics of perovskite/TiO2 heterostructure photoanodes for improving the efficiency of dye sensitized solar cells

Rational modification of TiO2 photoelectrodes with spinel ZnFe2O4 and Ag-doped ZnFe2O4 nanostructures highly enhanced the efficiencies of dye sensitized solar cells

To develop effective photoelectrode nanomaterials for dye-sensitized solar cells (DSSCs), spinel ZnFe₂O₄ (2.5, 5, 7.5, 10 wt%) and Ag-doped ZnFe₂O₄ (Ag_xZn_1-x/2Fe₂O₄, x = 0.1, 0.2, 0.3, 0.4 mmol) nanomaterials were added into the TiO₂ photoanodes. It was found that the DSSC fabricated with TiO₂ + 5 wt% ZnFe₂O₄ exhibited the most improved efficiency of 3.89 % among the ZnFe₂O₄ containing devices. Furthermore, the power conversion efficiency (PCE) values were boosted when the Ag⁺ cations were doped into the ZnFe₂O₄ crystalline lattice. The greatest PCE = 5.75 % was achieved for the solar cell assembled using TiO₂ + 5 wt% Ag_0.2Zn_0.90Fe₂O₄ photoanode indicating 47.81 % improved performance relative to that of the reference DSSC containing TiO₂ + 5 wt% ZnFe₂O₄ photoelectrode. The electrochemical impedance spectra (EIS) approved that the DSSC with the TiO₂ + 5 wt% Ag_0.2Zn_0.90Fe₂O₄ photoelectrode nanomaterial had the lowest charge transfer resistance but the greatest e-h recombination resistance at the interfaces of photoanode/dye/electrolyte. Hence, it had the quickest electron transport rate, and the greatest electron collecting efficiency in addition to the highest dye loading capacity and least photoluminescence (PL) intensity (charge recombination) which were all prominently beneficial for improvement of the DSSC performance.

Influence of Eu valence on the optical activity of BaTiO3 decorated with CaF2 synthesized by microwave-assisted hydrothermal method

Inorganic hybrid materials have promising applications in absorbers and for the photon harvesting of solar irradiation, such as in DSSC photoanodes. Moreover, investigation of the interactions between the photoanode constituent materials is extremely important, since it is known that the properties of the materials are strongly dependent on the nucleation and growth process. Therefore, the purpose of this work was to synthesize a system consisting of a synergic combination of two inorganic hosts, BaTiO₃ and CaF₂, synthesized together through a microwave-assisted hydrothermal method, which allows single-phase materials to be obtained after short synthesis times and at low temperatures. The increase in optical activity was investigated after the insertion of Eu ions. From the structural results, it was possible to observe that the method used to obtain the system was efficient, even using temperatures as low as 140 °C and a reaction time of one minute. The optical properties (emission and excitation) were evaluated in the visible and VUV region from 2.5 to 10.5 eV. The XANES Eu L_iii edge differences associated with the XEOL results indicate that the synthesis method incorporated Eu³⁺ in the hosts and the surface of the two compounds, BaTiO₃ and CaF₂. Therefore, the combination between the Eu³⁺ activators and the F centers of the host increased the range for photon harvesting, making these systems a promising material for future applications in photoanodes for DSSCs.

Synthesis of a heterojunction CoTiO3/Co3O4 nano-composite thin film with superior photocatalytic activity and reusability: Effect of calcination temperature on phase transformation and effect of oxidants on enhanced degradation of Indo Light Blue dye

CoTiO₃/Co₃O₄ heterojunction nano-composite was grown by a coprecipitation method at low temperature. The effects of calcination temperature on the phase composition, crystallization and morphology of the cobalt titanates were also examined. Notably, the novel nano-crystalline cobalt titanate with a narrow band gap to coulpe with cobalt oxide (Co₃O₄) by a direct coprecipitation method (CoTiO₃/Co₃O₄) was attained. The Nano-crystalline samples were systematically characterized by TG/DTG, XRD, DRS, FESEM, FT-IR, EDX and XPS techniques. The results showed that CoTiO₃/Co₃O₄ nano-composite hetero-junction was formed at 650 °C, while at 750 °C a single phase CoTiO₃ nano-crystal was prepared. Photocatalytic activities indicated the heterostructured CoTiO3/Co₃O₄ nano-composite exhibited much higher photocatalytic activity for degradation of Indo Light blue under visible light irradiation with added oxidants (K₂S₂O₈, KBrO₃, and H₂O₂). The charge separation of CoTiO3 and Co₃O₄ would result the enhanced visible-light harvesting ability and longer lifetime of photogenerated charge carriers. The stability and reusability of catalysts during four successive cycles were resulted. Finally, a possible mechanism responsible for the charge separation and improved photocatalytic activity was proposed.

Enhanced sensing of hazardous 4-nitrophenol by a graphene oxide–TiO2 composite: environmental pollutant monitoring applications

The accurate detection of hazardous 4-nitrophenol (4-NP) is deemed essential for the environment and human health.