An MgO passivation layer and hydrotalcite derived spinel Co2AlO4 synergically promote photoelectrochemical water oxidation conducted using BiVO4-based photoanodes.

MxCo3-xO4 co-catalysed photoanodes with high potential for improvement in PEC water-oxidizing properties are reported. However, it is difficult to control the recombination of photogenerated carriers at the interface between the catalyst and cocatalyst. Here, an ultra-thin MgO passivation layer was introduced into the MxCo3-xO4/BiVO4 coupling system to construct a ternary composite photoanode Co2AlO4/MgO/BiVO4. The photocurrent density of the electrode is 3.52 mA cm-2, which is 3.2 times that of BiVO4 (at 1.23 V vs. RHE). The photocurrent is practically increased by 0.86 mA cm-2 and 1.56 mA cm-2 in comparison with that of Co2AlO4/BiVO4 and MgO/BiVO4 electrodes, respectively. Meanwhile, the Co2AlO4/MgO/BiVO4 electrode has the highest charge separation efficiency, the lowest charge transfer resistance (Rct) and best stability. The excellent PEC performance could be attributed to the inhibitive effect provided by the MgO passivation layer that efficaciously suppresses the electron-hole recombination at the interface and drives the hole transfer outward, which is induced by Co2AlO4 to capture the electrode/electrolyte interface for efficient water oxidation reaction. In order to understand the origin of this improvement, first-principles calculations with density functional theory (DFT) were performed. The theoretical investigation converges to our experimental results. This work proposes a novel idea for restraining the recombination of photogenerated carriers between interfaces and the rational design of efficient photoanodes.

Highly efficient photocatalytic hydrogen production by ZnCdS composite catalyst modified with NiCoP nanosheets prepared by LDH precursor.

The unique characteristics and diverse applications of 2D transition metal phosphides have aroused significant interest. In this paper, we successfully prepared 2D NiCoP modified ZnCdS composite. The NiCoP nanosheets were successfully obtained by phosphating layered double hydroxide (LDH) precursor. The results show that the ZnCdS-8%NiCoP has the highest photocatalytic performance among all the composite photocatalysts with the H2 evolution rate of 1370.1 µmol h-1, which is 17.9 folds higher than obtained with pure ZnCdS. Detailed analysis reveal that NiCoP nanosheets functions as an excellent electron acceptor, speeding up the directed migration of electrons. Furthermore, the rational mechanism of photocatalytic has been presented based on density function theory (DFT) calculations, which is well congruent with experimental results. Our research offers a simple, environmentally benign, and scalable technique for making highly effective photocatalysts, as well as a novel perspective on transition metal phosphides rational design.

Defect Engineering in CuSx/COF Hybridized Heterostructures: Synergistic Facilitation of the Charge Migration for an Efficacious Photocatalytic Conversion of CO2 into CO.

The photocatalytic CO2 reduction reaction (CO2RR) provides an attractive approach to tackling environmental issues. To actualize the optimal catalytic efficiency, one efficacious strategy is to rationally modulate the charge migration for the adopted heterogeneous catalysts. Herein, by virtue of a one-step hydrothermal method, Cu2S nanospheres and defect-rich Cu2S (CuSx) nanosheets are wrapped by a triazine-containing covalent framework (TP-TA COF), resulting in CuSx/TP-TA and Cu2S/TP-TA. Owing to the heterojunction construction that suppresses the carrier recombination, both hybridized structures present enhanced charge migration in comparison to that of their corresponding sulfides and COF constituents. It is worth emphasizing that CuSx/TP-TA proffers a significantly greater photocurrent than Cu2S/TP-TA. The subsequent photocatalytic reduction of CO2 also exhibits an apparently higher CO evolution rate, about 2.8 times higher than the Cu2S/TP-TA photocatalyst. The above evident improvement owes much to the heterostructure establishment between CuSx and TP-TA COF, as well as the synergistic effect provided by the defect engineering for CuSx, both of which are able to enhance the separation efficiency of photoinduced carriers. Our work sheds light on the rational construction of heterogeneous structures between organic and inorganic photocatalysts, which emphasizes the possible synergistic effect of defect centers for enhancing photocatalytic performance.

The hydrophilic treatment of a novel co-catalyst for greatly improving the solar water splitting performance over Mo-doped bismuth vanadate.

In this work, Molybdenum (Mo) doped bismuth vanadate (BiVO4) is carried out by traditional calcination method, while carbon-based cobalt (Co-Ci) is prepared by photoelectric deposition (PED) and used as co-catalyst to decorate the surface, its photocurrent density reached 3.15 mA/cm2 at 1.23 V vs RHE. More importantly, the H-Co-Ci/Mo: BiVO4 photoanode obtained by plasma etching of Co-Ci/Mo: BiVO4 has greatly improved surface hydrophilicity. The photocurrent density of H-Co-Ci/Mo: BiVO4 photoanode is 4.8 times that of BiVO4 photoanode, reaching 3.95 mA/cm2. In addition, the incident photon-current conversion efficiency (IPCE) value of the H-Co-Ci/Mo: BiVO4 photoanode is as high as 60%, and both the injection and separation efficiency have also been enhanced. The enhanced photoelectrochemical (PEC) performance is attributed to the good wettability of the material surface and improvement of water oxidation kinetics. These findings provide a mild and efficient modification method for improving BiVO4 used for water splitting, and are expected to provide new ideas for other photoanodes.

Construction of ternary CuO/CuFe2O4/g-C3N4 composite and its enhanced photocatalytic degradation of tetracycline hydrochloride with persulfate under simulated sunlight.

In this study, a graphitic carbon nitride (g-C3N4) based ternary catalyst CuO/CuFe2O4/g-C3N4 (CCCN) is successfully prepared thorough calcination method. After confirming the structure and composition of CCCN, the as-synthesized composites are utilized to activate persulfate (PS) for the degradation of organic contaminant. While using tetracycline hydrochloride (TC) as pollutant surrogate, the effects of initial pH, PS and catalyst concentration on the degradation rate are systematically studied. Under the optimized reaction condition, CCCN/PS is able to give 99% degradation extent and 74% chemical oxygen demand removal in assistance of simulated solar light, both of which are apparently greater than that of either CuO/CuFe2O4 and pristine g-C3N4. The great improvement in degradation can be assignable to the effective separation of photoinduced carriers thanks to the integration between CuO/CuFe2O4 and g-C3N4, as well as the increased reaction sites given by the g-C3N4 substrate. Moreover, the scavenging trials imply that the major oxidative matters involved in the decomposition are hydroxyl radicals (•OH), superoxide radicals (•O2-) and photo-induced holes (h+).

Facile loading of cobalt oxide on bismuth vanadate: Proved construction of p-n junction for efficient photoelectrochemical water oxidation.

Cobalt oxide is an excellent water oxidation cocatalyst used in photoelectrochemical (PEC) water splitting field. Finding a facial way to load cobalt oxide on a semiconductor anode is important to effectively realize PEC water splitting on a large scale. In this work, a simple impregnation and calcination method is developed to fabricate CoOx/BiVO4 anode. The constructed CoOx/BiVO4 anode provides a photocurrent of 3.1 mA cm-2 at 1.23 V vs. RHE, about 2.8 times that of BiVO4 anode (1.1 mA cm-2). Furthermore, both the charge separation and injection efficiency are improved by loading CoOx nanoparticles onto the BiVO4 layer. Importantly, input voltage-output current characteristic curves are used for the first time to prove the formation of p-n junction between CoOx and BiVO4, which benefits to the separation of photogenerated holes and electrons. All results indicate that the impregnation and calcination method is efficacious for facile fabrication of CoOx/BiVO4 photoanode with high performance.

Metal (Ni2+/Co2+) sulfides modified BiVO4 for effective improvement in photoelectrochemical water splitting.

The performance of BiVO4 for photoelectrocatalytic (PEC) water decomposition is commonly limited by reaction kinetics. In this work, NiS and CoS nanospheres were respectively loaded on BiVO4 thin films (NiS/BiVO4 and CoS/BiVO4 composites) to improve its reaction kinetics for PEC water decomposition. Both physical and chemical properties of these composites were characterized by XRD, SEM, TEM, PL and UV-DRS. The photoelectric properties of the samples were verified by testing LSV, i-t, EIS and IPCE. The formation of the composites can effectively prevent the recombination of carriers and consequently accelerate the separation of electrons and holes. NiS/BiVO4 and CoS/BiVO4 can reach photocurrent of 2.1 mA cm-2 and 2.7 mA cm-2 under light respectively, at 1.23 V vs. RHE, which are 1.75 times and 2.25 times that of BiVO4 (1.2 mA cm-2). The hydrogen production of the NiS/BiVO4 and CoS/BiVO4 photoanodes was 4.7 and 7.3 times higher than that of BiVO4 photoanode, respectively.

In-situ incorporation of Copper(II) porphyrin functionalized zirconium MOF and TiO2 for efficient photocatalytic CO2 reduction.

As one of the highly effective methods to prepare catalysts for photocatalytic reduction of CO2 into value-added chemicals, using metalloporphyrin as light-harvesting mixed ligand to modify metal-organic framework (MOF) is very valuable since it can greatly improve the prophyrin dispersibility and consequently inhibit its potential agglomeration. Herein, we employed a one-pot synthetic strategy to chemically immobilize Cu(II) tetra(4-carboxylphenyl)porphyrin (CuTCPP) into UiO-66 MOF structure through coordination mode. Meanwhile, in-situ growth of TiO2 nanoparticles onto the MOF is actualized with the generation of CuTCPP ⊂ UiO-66/TiO2 (CTU/TiO2) composites. Under Xe lamp irradiation (λ > 300 nm), the catalytic result presents that an optimal value of 31.32 µmol g-1 h-1 CO evolution amount, about 7 times higher than that of pure TiO2 was obtained through the photocatalysis. It is supposed owning to a consistent augment of light absorption derived from chemically implanted porphyrin derivative, which is simultaneously functioning with an efficacious separation of photo-induced carries given by the newly engendered composites between MOF and TiO2, an effective catalytic activity and approving recyclability of CTU/TiO2 can be achieved in the photocatalytic reduction of CO2 into CO.

Photocatalytic Activation of Saturated C-H Bond Over the CdS Mixed-Phase Under Visible Light Irradiation.

Selective activation of saturated C-H bond in hydrocarbons to produce high-value-added chemicals is of great significance for chemical synthesis and transformation. Herein, we present a facile procedure to achieve Ni-doped CdS nanoparticles with mixed (cubic and hexagonal) phases, as well as its application to the photocatalytic activation of saturated primary C-H bond of toluene and its derivatives. The photocatalytic oxidation rate of toluene into benzaldehyde of formation reached up to 216.7 µmolh-1g-1 under visible light irradiation. The excellent photocatalytic performance of Ni(II)-doped CdS [Ni(II)/CdS] can be attributed to its unique structural assembly with cubic and hexagonal phases and also the addition of Ni ions, together taking effect in promoting the separation of photogenerated charge carriers. The possible reaction mechanism for the photocatalytic selective oxidation is illustrated in this work. The band width of the as-prepared mixed phase CdS is reduced, which can effectively expand the response range and improve photocatalytic performance.

Superhydrophobic meshes that can repel hot water and strong corrosive liquids used for efficient gravity-driven oil/water separation.

Oil-polluted water has become a worldwide problem due to increasing industrial oily wastewater as well as frequent oil-spill pollution. Compared with underwater superoleophobic (water-removing) filtration membranes, superhydrophobic/superoleophilic (oil-removing) materials have advantages as they can be used for the filtration of heavy oil or the absorption of floating oil from water/oil mixtures. However, most of the superhydrophobic materials used for oil/water separation lose their superhydrophobicity when exposed to hot (e.g. >50 °C) water and strong corrosive liquids. Herein, we demonstrate superhydrophobic overlapped candle soot (CS) and silica coated meshes that can repel hot water (about 92 °C) and strong corrosive liquids, and were used for the gravity driven separation of oil-water mixtures in hot water and strong acidic, alkaline, and salty environments. To the best of our knowledge, we are unaware of any previously reported studies on the use of superhydrophobic materials for the separation of oil from hot water and corrosive aqueous media. In addition, the as-prepared robust superhydrophobic CS and silica coated meshes can separate a series of oils and organic solvents like kerosene, toluene, petroleum ether, heptane and chloroform from water with a separation efficiency larger than 99.0%. Moreover, the as-prepared coated mesh still maintained a separation efficiency above 98.5% and stable recyclability after 55 cycles of separation. The robust superhydrophobic meshes developed in this work can therefore be practically used as a highly efficient filtration membrane for the separation of oil from harsh water conditions, benefiting the environment and human health.

Manganese catalyzed C-H functionalization of indoles with alkynes to synthesize bis/trisubstituted indolylalkenes and carbazoles: the acid is the key to control selectivity.

The Mn-catalyzed C-H alkenylation reactions of indole with terminal- and internal-alkynes have been developed. In the presence of a catalytic amount of acid, the procedure efficiently affords bis/trisubstituted indolyl-alkenes in a highly regio- and stereo-selective manner. Without the addition of acid, the reaction undergoes a [2+2+2] cyclization process to give carbazoles with release of hydrogen gas. Notably, the directing pyrimidyl group can be readily removed. Experimental studies reveal that the reaction is initiated by a C-H activation step and the acid is the selectivity controller via a hydrogen transfer process.

N,N'-[(2E,3E)-Butane-2,3-diylidene]bis[4-fluoro-2-(1-phenyl-eth-yl)aniline].

The title mol-ecule, C32H30F2N2, a product of the condensation reaction of butane-2,3-dione and 4-fluoro-2-(1-phenyl-eth-yl)aniline, is located about an inversion centre. In the asymmetric unit, the dihedral angle between the planes of the benzene and phenyl rings is 84.27 (5)°. Neither hydrogen bonding nor aromatic stacking is observed in the crystal structure.

Preparation of anisotropic transition metal phosphide nanocrystals: the case of nickel phosphide nanoplatelets, nanorods, and nanowires.

We have synthesized anisotropic nickel phosphide nanocrystals, including triangular/hexagonal nanoplatelets, nanorods and nanowires, via a solution-phase synthetic method that uses nickel(II) acetylacetonate as a metal precursor and trioctylphosphine as a phosphorus source. Nickel phosphide nanoplatelets have been prepared from a one-pot reaction, and their dimensions in the length mostly vary from 20 to 50 nm, while their thicknesses are in a narrow range of 7-9 nm. Nickel phosphide nanorods with a width of approximately 6 nm and a typical length of 25-32 nm can be synthesized from either the one-pot reaction or the multi-injection approach, although the latter can generate nanorods with a much higher uniformity. A continuous injection approach has been used to synthesize nanowires that have a typical width of approximately 6 nm and a length ranging from tens of nanometers up to several hundred nanometers. Major factors that influence the growth of nickel phosphide nanocrystals have been investigated, and a multi-surfactant system is found to be essential for the formation of anisotropic nanostructure. Magnetic studies have revealed paramagnetic characteristics for all the synthesized samples.

A nonaqueous approach to the preparation of iron phosphide nanowires.

Previous preparation of iron phosphide nanowires usually employed toxic and unstable iron carbonyl compounds as precursor. In this study, we demonstrate that iron phosphide nanowires can be synthesized via a facile nonaqueous chemical route that utilizes a commonly available iron precursor, iron (III) acetylacetonate. In the synthesis, trioctylphosphine (TOP) and trioctylphosphine oxide (TOPO) have been used as surfactants, and oleylamine has been used as solvent. The crystalline structure and morphology of the as-synthesized products were characterized by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). The obtained iron phosphide nanowires have a typical width of ~16 nm and a length of several hundred nanometers. Structural and compositional characterization reveals a hexagonal Fe2P crystalline phase. The morphology of as-synthesized products is greatly influenced by the ratio of TOP/TOPO. The presence of TOPO has been found to be essential for the growth of high-quality iron phosphide nanowires. Magnetic measurements reveal ferromagnetic characteristics, and hysteresis behaviors below the blocking temperature have been observed.

Chemical synthesis of monodisperse Fe-Ni nanoparticles via a diffusion-based approach.

We report a chemical route for the preparation of monodisperse Fe-Ni nanoparticles with tunable compositions and sizes. Unlike commonly used synthetic approaches that involve the simultaneous reduction of metal precursors in the presence of reducing agents, the approach developed in this study utilizes pre-formed Ni nanoparticles to react with Fe(III) acetylacetonate in high boiling-point solvents, wherein newly-generated Fe atoms diffuse into Ni nanoparticles to form Fe-Ni nanoparticles. The analytic results of powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) show that the as-synthesized Fe-Ni nanoparticles possess a face-centered cubic (fcc) crystalline structure and have a spherical or near-spherical morphology. X-ray photoelectron spectroscopy (XPS) study reveals metallic characteristics for the chemical state of Fe and Ni. The particle morphology and size distribution of the as-synthesized Fe-Ni nanoparticles are regulated by the pre-formed Ni nanoparticles, while the composition can be adjusted to some extent by the ratio of Fe precursor to Ni nanoparticles. Magnetic measurements reveal a superparamagnetic characteristic above the blocking temperature for the as-synthesized Fe-Ni nanoparticles. The synthetic approach may also be applied to other bimetallic nanoparticle systems.

Size- and structure-controlled synthesis and characterization of nickel nanoparticles.

Nearly monodisperse face-centered cubic (fcc) and hexagonal close-packed (hcp) nickel nanoparticles have been prepared via the thermal decomposition of nickel organometallic precursors in a reaction mixture containing alkylamine, and characterized by powder X-ray diffraction, transmission electron microscopy and magnetic measurement. The employed alkylamine can serve as both solvent and reducing agent. The as-synthesized nickel nanoparticles are air-stable, and their sizes can be readily tuned by the variation of surfactant concentration and reaction temperature. The crystalline phase control was achieved by adjusting alkylamine concentration, heating rate and reaction temperature. Magnetic measurements showed that hcp Ni nanoparticles have quite different magnetic properties compared to fcc Ni nanoparticles.