Zhong-Jun Li

Indirect Z-Scheme BiOI/g-C3N4 Photocatalysts with Enhanced Photoreduction CO2 Activity under Visible Light Irradiation

Rational design and construction of Z-scheme photocatalysts has received much attention in the field of CO2 reduction because of its great potential to solve the current energy and environmental crises. In this study, a series of Z-scheme BiOI/g-C3N4 photocatalysts are synthesized and their photocatalytic performance for CO2 reduction to produce CO, H2 and/or CH4 is evaluated under visible light irradiation (λ > 400 nm). The results show that the as-synthesized composites exhibit more highly efficient photocatalytic activity than pure g-C3N4 and BiOI and that the product yields change remarkably depending on the reaction conditions such as irradiation light wavelength. Emphasis is placed on identifying how the charge transfers across the heterojunctions and an indirect Z-scheme charge transfer mechanism is verified by detecting the intermediate I3(-) ions. The reaction mechanism is further proposed based on the detection of the intermediate (•)OH and H2O2. This work may be useful for rationally designing of new types of Z-scheme photocatalyst and provide some illuminating insights into the Z-scheme transfer mechanism.

Enhanced Photoreduction CO2 Activity over Direct Z-Scheme α-Fe2O3/Cu2O Heterostructures under Visible Light Irradiation

Hematite-cuprous oxide (α-Fe2O3/Cu2O) nanocomposites are synthesized based on the design of Z-scheme photocatalyst for CO2 reduction. The band structure for the typical Fe2O3/Cu2O (with 1:1 mole ratio) is characterized by UV-vis reflectance spectroscopy and X-ray/ultraviolet photoelectron spectroscopy, and its heterojunction is determined to be Type II band alignment. The photoreduction CO2 activities of the heterostructures are investigated in the presence of water vapor. The CO yields are changed with Fe/Cu mole ratio, and the maximal CO yield attains 5.0 μmol·g cat(-1) after 3 h of visible-light irradiation. Besides the effect of light wavelength, H2O/CO2 molar ratio and temperature on the products is studied. The selectivity of the prepared catalysts is tunable by modulating the light wavelength. The reaction mechanism is proposed and further confirmed experimentally. The results gained herein may provide some insights into the design of Z-scheme photocatalysts for CO2 reduction.

Synergistic photocatalysis of Cr(VI) reduction and 4-Chlorophenol degradation over hydroxylated α-Fe2O3 under visible light irradiation.

A series of Fe2O3 materials with hydroxyl are synthesized in different monohydric alcohol (C2-C5) solvents by solvothermal method and characterized by XRD, BET, XPS, TG and EA. The amount of hydroxyl is demonstrated to be emerged on the surface of the as-synthesized Fe2O3 particles and their contents are determined to be from 7.99 to 3.74 wt%. The Cr(VI) reduction experiments show that the hydroxyl content of Fe2O3 samples exacts great influence on the photocatalytic activity under visible light irradiation (λ>400 nm) and that the Fe2O3 sample synthesized in n-butyl alcohol exhibits the optimal photocatalytic activity. The synergistic photocatalysis for 4-Chlorophenol (4-CP) degradation and Cr(VI) reduction over above Fe2O3 sample is further investigated. The photocatalytic ratio of Cr(VI) reduction are enhanced from 24.8% to 70.2% while that of 4-CP oxidation are increased from 13.5% to 47.8% after 1 h visible light irradiation. The Fe2O3 sample keeps good degradation rates of mixed pollutants after 9 runs. The active oxygen intermediates O2(-)˙, ˙OH and H2O2 formed in the photoreaction process are discovered by ESR measurement and UV-vis test. The photocatalytic degradation mechanism is proposed accordingly.

Facile Synthesis of 1,6-Bis(2-furyl)-2,5-bis(2-hydroxy-3-formyl-5- methylbenzyl)-2,5-diazahexane: a New Dinucleating Ligand

A convenient three-step preparation of the dinucleating ligand, 1,6-bis(2-furyl)-2,5-bis(2-hydroxy-3-formyl-5-methylbenzyl)-2,5-diazahexane (3) starting from 2,6-bis(hydroxymethyl)-4-methylphenol (4) is reported. Compound 4 was partially oxidized with preactivated manganese dioxide to form compound 5, which was converted to 2-hydroxy-3-chloromethyl-5-ethylbenzaldehyde (6) with conc.HCl/EtOH. Compound 6 in turn reacted with N,N’-bis (2-furyl)-1,2-diaminoethane (7) in the presence of K2CO3 in ethanol to give the title compound 3. No protecting groups were required in the whole process and the conditions were mild.

Hexa-μ2-benzoato-bis­(2,2′-bipyrid­yl)trimanganese(II) monohydrate

The complex molecule of the title compound, [Mn3(C7H5O2)6(C10H8N2)2]·H2O, contains a linear array of divalent manganese ions. The central MnII atom, which is located on a crystallographic inversion center, is coordinated octahedrally by six benzoate O atoms. The two terminal MnII ions are six-coordinated by four benzoate O atoms and two N atoms of 2,2′-bipyridyl. The central MnII atom and the terminal MnII ions are bridged by four benzoate ligands in a bidentate fashion, whereas the other two carboxylate ligands form bridges through one O atom only and chelate the terminal MnII atom. The molecules pack together via van der Waals attractions and C—H⋯O hydrogen bonds.

Natural sunlight driven highly efficient photocatalysis for simultaneous degradation of rhodamine B and methyl orange using I/C codoped TiO2 photocatalyst

Increasing the efficiency of dye degradation is a critical issue for the application for photocatalysis. It is one of the greatest challenges to enhance the utilization of photo generated carriers in semiconductor, especially for sunlight irradiation. In this study, I/C-codoped TiO2 was synthesized by a simple solvothermal-calcination method. The codoping interstitial carbon and substitutional iodine not only widened the light absorption range of the TiO2 photocatalysts, but also enhanced the separation of photo-induced carriers. The photocatalytic activities of RhB and MO degradation over the 4-I/C-TiO2 photocatalyst could reach 98.2% and 94.2% after 25 min visible light irradiation (λ ≥ 400 nm), respectively. Notably, 4-I/C-TiO2 showed good activity for MO and RhB mixed degradation and could also accomplish the photocatalytic degradation in the above mixed system under natural sunlight irradiation. According to the dark catalytic experiment, I/C-codoping could effectively accelerate the formation of hydroxyl radicals from the generated H2O2, which was formed for the enhanced photocatalytic activity of dye degradation. The gained knowledge may provide some insights into the photocatalytic degradation over the codoped TiO2 catalyst.

Magnetic properties of a linear trinuclear manganese compound [Mn3(PhCO2)6(Bipy)2] · H2O

The reaction of the trinuclear oxo-centered mixed-valence complex [Mn3O(O2CPh)6(Py)2(H2O)] with 2,2′-bipyridyl (Bipy) and another potential tripodal ligand affords the title compound [Mn3(PhCO2)6(Bipy)2] · H2O in good yield. The X-ray crystallographic diffraction study reveals that three mangenese ions are arranged in a linear mode with Mncenter-Mnterminal and Mnterminal-Mnterminal diatances of 3.588 and 7.176 Å, respectively. Molar magnetic susceptibility of the compound gradually decreases from 12.23 (300 K) to 4.45 cm3 K mol−1 (2 K). Taking into account the structure of this compound, the data in the 2.0–300 K range were fit to the appropriate theoretical expression to give J = −2.73 cm−1, ρ = 2.07%, Na = −0.0004 cm3 mol−1, g = 1.992, and R2 = 0.99996. The magnetization versus external magnetic field measurements at 2 K shows that the ground state is ST = 5/2.

Synthesis of fluorescent polymeric carbon nitride quantum dots in molten salts for security inks

Polymeric carbon nitride quantum dots (CNQDs) with an average size of approximately 2.5 nm were prepared directly from melamine via a one-step molten salt method. The formation mechanism and photoluminescence (PL) properties of the resulting CNQDs were investigated by means of TEM, XRD and PL spectroscopy. The CNQDs can be dispersed in water to form a transparent colloidal solution and emit blue PL with excellent photostability. Interestingly, upon addition of CuCl2 and NaHCO3 in turn, the PL of CNQDs can be turned off and on accordingly. Taking advantage of the on–off–on PL response, the CNQDs can be used as a fluorescent security ink for information coding, encryption and decryption, indicating their promising application in data security and high-level anti-counterfeiting fields.

Synthesis and characterization of Gd{sup 3+} and Nd{sup 3+} co-doped ceria by using citric acid-nitrate combustion method

A series of Ce{sub 0.8}Gd{sub 0.2-x}Nd{sub x}O{sub 2-{delta}} (x = 0-0.20) compositions have been synthesized by citric acid-nitrate combustion method. XRD measurements indicate that all the obtained materials crystallized in cubic fluorite-type structure. Lattice parameters were calculated by Rietveld method and the parameter a values in Ce{sub 0.8}Gd{sub 0.2-x}Nd{sub x}O{sub 2-{delta}} system obey Vegards law, a (A) = 5.4224 + 0.1208x. The obtained powders have good sinterability and the relative density could reach above 95% after being sintered at 1400 {sup o}C. Impedance spectroscopy measurements indicated that the conductivity of Ce{sub 0.8}Gd{sub 0.2-x}Nd{sub x}O{sub 2-{delta}} first increased and then decreased with Nd dopant content x. The maximum conductivity, {sigma}{sub 700{sup o}C} = 6.26 x 10{sup -2} S/cm, was found in Ce{sub 0.8}Gd{sub 0.12}Nd{sub 0.08}O{sub 1.9} when sintered at 1300 {sup o}C. The corresponding activation energies of conduction had a minimum value E{sub a} = 0.676 eV. The results tested experimentally the validity of the effective atomic number concept of recent density functional theory, which had suggested that co-dopant with effective atomic number between 61 (Pm) and 62 (Sm) was the ideal dopant exhibiting high ionic conductivity and low activation energy.