Construction of SrTiO3-BiOCl composite catalyst via facial microwave hydrothermal for highly efficient photocatalytic activity towards organic compounds degradation

This work mainly focuses on the preparation and performance study of SrTiO₃-BiOCl composite photocatalysis. The SrTiO₃-BiOCl photocatalysts are prepared via the facial microwave hydrothermal method. XRD, UV-vis DRS, SEM, TEM, XPS, N₂ adsorption and desorption isothermal experiment, FT-IR, and PL are applied to characterize the prepared samples. The spherical particles of SrTiO₃ grow on the flaky BiOCl, and the crystal size is uniform and evenly disperses on the BiOCl. The catalytic performance of the samples was evaluated over the degradation rates of methylene blue(MB). Typically, the clearance rates of MB reached to 99.65% over SrTiO₃-BiOCl-50% under visible light, which was much higher than that of SrTiO₃ and BiOCl (55.86%, 79.79%, respectively). The active species capturing experiments and ESR showed that the holes (h⁺) and ·OH are playing the main roles in the degradation process.

Peculiar Properties of the La0.25Ba0.25Sr0.5Co0.8Fe0.2O3-δ Perovskite as Oxygen Reduction Electrocatalyst

The electrochemical reduction of molecular oxygen is a fundamental process in Solid Oxide Fuel Cells and requires high efficiency cathode materials. Two La0.25Ba0.25Sr0.5Co0.8Fe0.2O3-δ-based perovskite compounds were prepared by solution combustion synthesis, and characterized for their structural, microstructural, surface, redox and electrochemical properties as potential cathodes in comparison with Ba0.5Sr0.5Co0.8Fe0.2O3-δ and La0.5Sr0.5Co0.8Fe0.2O3-δ perovskites. Results highlighted that calcination at 900 °C led to a "bi-perovskite heterostructure", where two different perovskite structures coexist, whereas at higher calcination temperatures a single-phase perovskite was formed. The results showed the effectiveness of the preparation procedures in co-doping the A-site of perovskites with barium and lanthanum as a strategy to optimize the cathode's properties. The formation of nanometric heterostructure co-doped in the A-site evidenced an improvement in oxygen vacancies' availability and in the redox properties, which promoted both processes: oxygen adsorption and oxygen ions drift, through the cathode material, to the electrolyte. A reduction in the total resistance was observed in the case of heterostructured material.

Efficient Visible-Light-Driven Tetracycline Degradation and Cr(VI) Reduction over a LaNi1-xFexO3 (0 ≤ x ≤ 1)/g-C3N4 Type-II Heterojunction Photocatalyst

The development of efficient, stable, and visible-light-responsive photocatalysts is crucial to address the pollution of water bodies by toxic heavy metal ions and organic antibiotics. Herein, a series of LaNi_1-xFe_xO₃/g-C₃N₄ heterojunction photocatalysts are prepared by a simple wet chemical method. Moreover, LaNi_0.8Fe_0.2O₃/g-C₃N₄ composites are characterized by various methods, including structure, morphology, optical, and electrochemical methods and tetracycline degradation and photocatalytic reduction of Cr(VI) under visible light irradiation. Then, the photocatalytic performance of as-prepared LaNi_0.8Fe_0.2O₃/g-C₃N₄ composites is evaluated. Compared with pure LaNi_0.8Fe_0.2O₃ and g-C₃N₄, the LaNi_0.8Fe_0.2O₃/g-C₃N₄ composite photocatalysts exhibit excellent photocatalytic performance due to synergy of doping and constructing heterojunctions. The results show that the doping of Fe ions can increase the concentration of oxygen vacancies, which is ultimately beneficial to the formation of electron traps. Moreover, the type-II heterojunction formed between LaNi_0.8Fe_0.2O₃ and g-C₃N₄ effectively strengthens the separation and transfer of photoinduced carriers, thereby promoting photocatalytic activity. Furthermore, the photocatalytic activity of the LaNi_0.8Fe_0.2O₃/g-C₃N₄ photocatalyst remains almost unchanged after three cycles, indicating long-term stability. Ultimately, the photocatalytic mechanism of the LaNi_0.8Fe_0.2O₃/g-C₃N₄ composites is proposed.

Extensive solar light utilizing by ternary C-dots/Cu2O/SrTiO3: Highly enhanced photocatalytic degradation of antibiotics and inactivation of E. coli

Fabrication of a visible-light driven photocatalyst is of great vital for the elimination of antibiotics and microorganism in the wastewater and the construction of sustainable green energy systems. In this work, carbon quantum dots (C-dots) were integrated with Cu₂O/SrTiO₃ p-n heterojunction to optimize the photocatalytic activity. The excellent photocatalytic degradation efficiency of chlortetracycline hydrochloride (CTC·HCl) (92.6% within 90 min) and E. coli inactivation efficiency were observed over C-dots/Cu₂O/SrTiO₃ under visible light irradiation. It is the synergistic effect of p-n heterojunction and modification of C-dots that facilitates the separation and transfer of electron-holes. Meanwhile, the modification of C-dots improves the harvesting of long wavelength solar light of photocatalysts due to its unique up-conversion photoluminescence (UCPL) characteristics. Eventually, the possible photocatalytic degradation path of the catalyst was inferred by LC-MS spectra, and the degradation mechanism was analyzed. This study sheds light on new possibilities for the application of photocatalysts in various light sources and has broad application prospects in water treatment.

Clarifying the Role of the Reducers-to-Oxidizers Ratio in the Solution Combustion Synthesis of Ba0.5Sr0.5Co0.8Fe0.2O3-δ Oxygen Electrocatalysts

Ba0.5Sr0.5Co0.8Fe0.2O3-δ perovskite-type compounds are well-known mixed ionic-electronic conductors for oxygen electrocatalytic applications, although their performance is strictly dependent on the selected preparation methodology and processing parameters. The reducers-to-oxidizers ratio (Φ) is a very important parameter in the solution combustion synthesis of mixed ionic-electronic conductors. Selection of Φ is not trivial and it strongly depends on the type of fuel used, the chemical composition and the specific application of the material. This work clarifies the role of Φ in the solution combustion synthesis of Ba0.5Sr0.5Co0.8Fe0.2O3-δ for application as oxygen electrocatalysts. Ba0.5Sr0.5Co0.8Fe0.2O3-δ powders were synthesized by solution combustion synthesis using sucrose-polyethylene glycol fuel mixtures with reducers-to-oxidizers ratio values between 1 (stoichiometric) and 3 (over-stoichiometric). Chemical-physical properties were studied by X-ray diffraction, scanning electron microscopy, N2 adsorption at −196 °C, H2-temperature programmed reduction and thermogravimetric analysis. The results evidenced the direct role of Φ on the intensity and redox environment of the combustion process, and its indirect influence on the Ba0.5Sr0.5Co0.8Fe0.2O3-δ electrode materials properties. Taking into account the general picture, the highly over-stoichiometric Φ was selected as the optimal one and the electrochemical activity of the corresponding powder was tested by electrochemical impedance spectroscopy on electrolyte-supported half-cells employing a Ce0.8Sm0.2O2-x electrolyte.

Influence of Lanthanum Doping on Structural and Electrical/Electrochemical Properties of Double Perovskite Sr2CoMoO6 as Anode Materials for Intermediate-Temperature Solid Oxide Fuel Cells

Lanthanum (La³⁺)-doped double perovskites Sr₂CoMoO₆ (Sr_2-xLa_xCoMoO₆, 0.00 ≤ x ≤ 0.03) were synthesized via the citrate-nitrate autocombustion route. The Reitveld refinement analysis of X-ray diffraction reveals the tetragonal symmetry as the main phase with space group I4/m and also confirms the presence of some peaks corresponding to extra phase SrMoO₄. The SEM micrograph images reflect that grains are in irregular shape and sizes for all samples. Average grain size gradually decreases with the increase of the SrMoO₄ phase. The X-ray photoelectron spectroscopy (XPS) analysis confirms the presence of mixed valence states of Mo⁵⁺/Mo⁶⁺, Co²⁺/Co³⁺, and O-lattice/O-chemisorbed/O-physisorbed species. Coefficient of thermal expansion (CTE) analysis shows that the particular composition Sr_1.97La_0.03CoMoO₆ has the lowest CTE value among the compositions studied. The electrical conductivity of Sr₂CoMoO₆ is enhanced effectively by doping La at Sr sites. The measured area-specific resistance (ASR) for the composition Sr_1.97La_0.03CoMoO₆ (SLCM03) is found to be appreciably low, ∼0.053 Ohm cm^-2 at 800 °C. The obtained highest electrical conductivity with the lowest activation energy and low ASR value for the composition Sr_1.97La_0.03CoMoO₆ encompasses it as a promising candidate for anode material in the intermediate-temperature solid oxide fuel cell (IT-SOFC) application.

Thermochemical conversion of CO2 into CH4 using oxygen deficient NiFe2O4−δ with unique selectivity

NiFe₂O₄ nanoparticles with a high concentration of oxygen vacancies were synthesized via a solvothermal route.