Revealing the enhanced photoelectrochemical water oxidation activity of Fe-based metal-organic polymer-modified BiVO4 photoanode.

Metal-organic polymers (MOPs) can enhance the photoelectrochemical (PEC) water oxidation performance of BiVO4 photoanodes, but their PEC mechanisms have yet to be comprehended. In this work, we constructed an active and stable composite photoelectrode by overlaying a uniform MOP on the BiVO4 surface using Fe2+ as the metal ions and 2,5-dihydroxyterephthalic acid (DHTA) as ligand. Such modification on the BiVO4 surface yielded a core-shell structure that could effectively enhance the PEC water oxidation activity of the BiVO4 photoanode. Our intensity-modulated photocurrent spectroscopy analysis revealed that the MOP overlayer could concurrently reduce the surface charge recombination rate constant (ksr) and enhance the charge transfer rate constant (ktr), thus accelerating water oxidation activity. These phenomena can be ascribed to the passivation of the surface that inhibits the recombination of the charge carrier and the MOP catalytic layer that improves the hole transfer. Our rate law analysis also demonstrated that the MOP coverage shifted the reaction order of the BiVO4 photoanode from the third-order to the first-order, resulting in a more favorable rate-determining step where only one hole accumulation is required to overcome water oxidation. This work provides new insights into the reaction mechanism of MOP-modified semiconductor photoanodes.

Construction of Cu7 S4 @CuCo2 O4 Yolk-Shell Microspheres Composite and Elucidation of Its Enhanced Photocatalytic Activity, Mechanism, and Pathway for Carbamazepine Degradation.

Water pollution caused by the massive use of medicines has caused significant environmental problems. This work first reports the synthesis and characterization of the Cu7 S4 /CuCo2 O4 (CS/CCO) yolk-shell microspheres via hydrothermal and annealing methods, and then investigates their photocatalytic performance in removing organic water pollutants. The 10-CS/CCO composite with yolk-shell microspheres exhibits the highest photodegradation rate of carbamazepine (CBZ), reaching 96.3% within 2 h. The 10-CS/CCO also demonstrates more than two times higher photodegradation rates than the pure (Cu7 S4 ) CS and (CuCo2 O4 ) CCO. This outstanding photocatalytic performance can be attributed to the unique yolk-shell structure and the Z-scheme charge transfer pathway, reducing multiple reflections of the acting light. These factors enhance the light absorption efficiency and efficiently transfer photoexcited charge carriers. In-depth, photocatalytic degradation pathways of CBZ are systematically evaluated via the identification of degradation intermediates with Fukui index calculation. The insights gained from this work can serve as a guideline for developing low-cost and efficient Z-scheme photocatalyst composites with the yolk-shell structure.

Experimental data of CaTiO3 photocatalyst for degradation of organic pollutants (Brilliant green dye) - Green synthesis, characterization and kinetic study.

The data presented here focuses on the physicochemical characterization of perovskite CaTiO3 nanoparticles (orthorhombic) as photocatalyts and the kinetic study of their photodegradation performance toward organic pollutant, i.e. brilliant green (BG) which is azo derivatives dye. The CaTiO3 nanoparticles was synthesized using chicken eggshell-derived CaCO3 and anatase TiO2 with molar ratio of (1:1), (1:3), (2:5), and (2:7). The physical and microstructural properties of CaTiO3 were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), Fourier Transform Infrared (FTIR) and UV/vis spectrometer. The effect of initial dye concentration, catalyst composition, and catalyst dosage on the adsorption mechanism of dye on CaTiO3 was investigated in jacketed photoreactor under UV irradiation. The analysis reveals that BG molecules are efficiently chemisorbed, as indicated by pseudo first order kinetic, and degraded within 120 min. Considering the low-cost preparation process and high photocatalytic performance, the resultant CaTiO3 can further be used as an efficient photocatalyst for organic pollutant removal from aqueous and industrial wastewater.

Tunable Synthesis of Mesoporous Silica Particles with Unique Radially Oriented Pore Structures from Tetramethyl Orthosilicate via Oil-Water Emulsion Process.

Numerous studies of the synthesis of mesoporous silica (MPS) particles with tailored properties have been published. Among those studies, tetraethyl orthosilicate (TEOS) is commonly used as a silica source, but tetramethyl orthosilicate (TMOS) is rarely used because its reaction is fast and difficult to control. In this study, MPS particles were synthesized via one-step controlled polymerization of styrene and hydrolysis of TMOS, followed by the addition of hexadecyltrimethylammonium bromide (CTAB) and n-octane. The MPS particles obtained from TMOS generally have small inner pores, but the MPS particles obtained in this study had a unique radially oriented structure, a high surface area up to 800 m2 g-1, and large pores, of size 20 nm. The content of styrene in the emulsion system played a key role in increasing pore sizes of the MPS particles. A plausible mechanism for particle formation based on the phase behavior and type of the emulsion system is proposed. For further research, this material is expected to be useful for various applications, such as in drug delivery, filtration, and catalyst supports.

Hollow Silica as an Optically Transparent and Thermally Insulating Polymer Additive.

We present an improved synthesis route to hollow silica particles starting from tetramethyl orthosilicate (TMOS) instead of the traditionally used ethyl ester. The silica was first deposited onto polystyrene (PS) particles that were later removed. The here introduced, apparently minor modification in synthesis, however, allowed for a very high purity material. The improved, low density hollow silica particles were successfully implemented into polymer films and permitted maintaining optical transparency while significantly improving the heat barrier properties of the composite. Mechanistic investigations revealed the dominant role of here used methanol as a cosolvent and its role in controlling the hydrolysis rate of the silicic ester, and subsequent formation of hollow silica particles. Systematic experiments using various reaction parameters revealed a transition between regions of inhomogeneous material production at fast hydrolysis rate and reliable silica deposition on the surface of PS as a core-shell structured particle. The shell-thickness was controlled from 6.2 to 17.4 nm by increasing TMOS concentration and the diameter from 95 to 430 nm through use of the different sizes of PS particles. Hollow silica particle with the shell-thickness about 6.2 nm displayed a high light transmittance intensity up to 95% at 680 nm (length of light path ∼ 1 cm). Polyethersulfone (PES)/hollow silica composite films (35 ± 5 µm thick) exhibited a much lower thermal conductivity (0.03 ± 0.005 W m·K(-1)) than pure polymer films. This indicates that the prepared hollow silica is able to be used for cost and energy effective optical devices requiring thermal insulation.