Effect of multi-interface electron transfer on water splitting and an innovative electrolytic cell for synergistic hydrogen production and degradation.

The cleaning and utilization of industry wastewater are still a big challenge. In this work, we mainly investigate the effect of electron transfer among multi-interfaces on water electrolysis reaction. Typically, the CoS2, Co3S4/CoS2 (designated as CS4-2) and Co3S4/Co9S8/CoS2 (designated as CS4-8-2) samples are prepared on a large scale by one-step molten salt method. It is found that because of the different work functions (designated as WF; WF(Co3S4) = 4.48eV, WF(CoS2) = 4.41eV, WF(Co9S8) = 4.18 eV), the effective heterojunctions at the multi-interfaces of CS4-8-2 sample, which obviously improve interface charge transfer. Thus, the CS4-8-2 sample shows an excellent oxygen evolution reaction (OER) activity (134 mV/10 mA cm-2, 40 mV dec-1). The larger double-layer capacitance (Cdl = 17.1 mF cm-2) of the CS4-8-2 sample indicates more electrochemical active sites, compared to the CoS2 and CS4-2 samples. Density functional theory (DFT) calculation proves that due to interface polarization under electric field, the multi-interfaces effectively promote electron transfer and regulate electron structure, thus promoting the adsorption of OH- and dissociation of H2O. Moreover, an innovative norfloxacin (NFX) electrolytic cell (EC) is developed through introducing NFX into the electrolyte, in which efficient NFX degradation and hydrogen production are synergistically achieved. To reach 50 mA cm-2, the required cell voltage of NFX-EC has decreased by 35.2%, compared to conventional KOH-EC. After 2h running at 1 V, 25.5% NFX was degraded in the NFX EC. This innovative NFX-EC is highly energy-efficient, which is promising for the synergistic cleaning and utilization of industry wastewater.

Boosting photocatalytic nitrogen reduction reaction by Jahn-Teller effect.

Compared with traditional the Haber-Bosch process, photocatalytic ammonia production has attracted a considerable attention due to its advantages of low energy consumption and sustainability. In this work, we mainly study the photocatalytic nitrogen reduction reaction (NRR) on MoO3·0.55H2O and α-MoO3. Structure analysis shows that compared to α-MoO6, the [MoO6] octahedrons in MoO3·0.55H2O obviously distort (Jahn-Teller distortion), leading to the formation of Lewis acid active sites that favors the adsorption and activation of N2. X-ray photoelectron spectroscopy (XPS) further confirms the formation of more Mo5+ as Lewis acid active sites in MoO3·0.55H2O. Transient photocurrent, photoluminescence and electrochemical impedance spectra (EIS) confirmed that MoO3·0.55H2O has a higher charge separation and transfer efficiency than α-MoO3. Density functional theory (DFT) calculation further confirmed that the N2 adsorption on MoO3·0.55H2O is more favorable thermodynamically than that on α-MoO3. As a result, under visible light irradiation (λ ≥ 400 nm) for 60 min, an ammonia production rate of 88.6 µmol·gcat-1 was achieved on MoO3·0.55H2O, which is about 4.6 times higher than that on α-MoO3. In comparison to other photocatalysts, MoO3·0.55H2O exhibits an excellent photocatalytic NRR activity under visible light irradiation without using sacrificial agent. This work offers a new fundamental understanding to photocatalytic NRR from the viewpoint of crystal fine structure, which benefits designing efficient photocatalysts.

Bi2WO6/C-Dots/TiO2: A Novel Z-Scheme Photocatalyst for the Degradation of Fluoroquinolone Levofloxacin from Aqueous Medium.

Photocatalytic materials and semiconductors of appropriate structural and morphological architectures as well as energy band gaps are materials needed for mitigating current environmental problems, as these materials have the ability to exploit the full spectrum of solar light in several applications. Thus, constructing a Z-scheme heterojunction is an ideal approach to overcoming the limitations of a single component or traditional heterogeneous catalysts for the competent removal of organic chemicals present in wastewater, to mention just one of the areas of application. A Z-scheme catalyst possesses many attributes, including enhanced light-harvesting capacity, strong redox ability and different oxidation and reduction positions. In the present work, a novel ternary Z-scheme photocatalyst, i.e., Bi2WO6/C-dots/TiO2, has been prepared by a facile chemical wet technique. The prepared solar light-driven Z-scheme composite was characterized by many analytical and spectroscopic practices, including powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), N2 adsorption-desorption isotherm, Fourier-transform infrared spectroscopy (FT-IR), photoluminescence (PL) and UV-vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the Bi2WO6/C-dots/TiO2 composite was evaluated by studying the degradation of fluoroquinolone drug, levofloxacin under solar light irradiation. Almost complete (99%) decomposition of the levofloxacin drug was observed in 90 min of sunlight irradiation. The effect of catalyst loading, initial substrate concentration and pH of the reaction was also optimized. The photocatalytic activity of the prepared catalyst was also compared with that of bare Bi2WO6, TiO2 and TiO2/C-dots under optimized conditions. Scavenger radical trap studies and terephthalic acid (TPA) fluorescence technique were done to understand the role of the photo-induced active radical ions that witnessed the decomposition of levofloxacin. Based on these studies, the plausible degradation trail of levofloxacin was proposed and was further supported by LC-MS analysis.

Novel synthesis of thick wall coatings of titania supported Bi poisoned Pd catalysts and application in selective hydrogenation of acetylene alcohols in capillary microreactors.

Catalysis in microreactors allows reactions to be performed in a very small volume, reducing the environmental problems and greatly intensifying the processes through easy pressure control and the elimination of heat- and mass-transfer limitations. In this study, we report a novel method for the controlled synthesis of micrometre-thick mesoporous TiO2 catalytic coatings on the walls of long channels (>1 m) of capillary microreactors in a single deposition step. The method uses elevated temperature and introduces a convenient control parameter of the deposition rate (displacement speed controlled by a stepper motor), which allows deposition from concentrated and viscous sols without channel clogging. A capillary microreactor wall-coated with titania supported Bi-poisoned Pd catalyst was obtained using the method and used for the semihydrogenation of 2-methyl-3-butyn-2-ol providing 93 ± 1.5% alkene yield for 100 h without deactivation. Although the coating method was applied only for TiO2 deposition, it is nonetheless suitable for the deposition of volatile sols.