Xiaoshu Lv

Identification of Active Hydrogen Species on Palladium Nanoparticles for an Enhanced Electrocatalytic Hydrodechlorination of 2,4-Dichlorophenol in Water

Clarifying hydrogen evolution and identifying the active hydrogen species are crucial to the understanding of the electrocatalytic hydrodechlorination (EHDC) mechanism. Here, monodisperse palladium nanoparticles (Pd NPs) are used as a model catalyst to demonstrate the potential-dependent evolutions of three hydrogen species, including adsorbed atomic hydrogen (H*ads), absorbed atomic hydrogen (H*abs), and molecular hydrogen (H2) on Pd NPs, and then their effect on EHDC of 2,4-dichlorophenol (2,4-DCP). Our results show that H*ads, H*abs, and H2 all emerge at -0.65 V (vs Ag/AgCl) and have increased amounts at more negative potentials, except for H*ads that exhibits a reversed trend with the potential varying from -0.85 to -0.95 V. Overall, the concentrations of these three species evolve in an order of H*abs < H*ads < H2 in the potential range of -0.65 to -0.85 V, H*ads < H*abs < H2 in -0.85 to -1.00 V, and H*ads < H2 < H*abs in -1.00 to -1.10 V. By correlating the evolution of each hydrogen species with 2,4-DCP EHDC kinetics and efficiency, we find that H*ads is the active species, H*abs is inert, while H2 bubbles are detrimental to the EHDC reaction. Accordingly, for an efficient EHDC reaction, a moderate potential is desired to yield sufficient H*ads and limit H2 negative effect. Our work presents a systematic investigation on the reaction mechanism of EHDC on Pd catalysts, which should advance the application of EHDC technology in practical environmental remediation.

Noble metal-free Bi nanoparticles supported on TiO2 with plasmon-enhanced visible light photocatalytic air purification

Semimetal bismuth (Bi) is an emerging non-noble metal-based plasmonic metal, which has demonstrated exceptional behavior as a unique plasmonic photocatalyst/cocatalyst. In the present work, Bi nanoparticles were uniformly deposited on the well-known TiO2 particles (Degussa, P25) with mixed phases of anatase and rutile by a facile eco-friendly synthesis at room temperature. The Bi-deposited TiO2 nanocomposites demonstrated highly enhanced photocatalytic performance for removal of ppb-level NO in air under visible-light irradiation (λ > 420 nm). The improved photocatalytic capability was found to be crucially dependent on the catalyst architecture: Bi nanoparticles with a diameter (dBi) of 5–8 nm deposited on the surface of TiO2 particles acted as active sites for visible-light-driven electron and hole separation. The enhanced charge separation was well supported by photoluminescence, photocurrent generation and Bode-phase spectra. Significantly, the exceptionally high visible-light photocatalytic capability of the optimized Bi–Ti-50 sample (the mass ratio of Bi to TiO2 is 50%) was also superior to that of universally known non-metal-doped TiO2. The photocatalysis was enhanced through SPR-mediated activation of the Bi particles by visible light followed by consecutive electron transfer in Bi/rutile/anatase interfaces, as supported by the action spectra. The electrons produced from the plasmonic activation of Bi particles could transfer to the conduction band of rutile and then to adjacent anatase TiO2 because of the high potential difference between Bi and rutile TiO2. Also, the free electrons could transfer from Bi to the conduction band of anatase and then to rutile TiO2 owing to the high mass ratio of anatase phase in P25 resulting in the direct contact of the Bi nanoparticles and anatase TiO2. A new photocatalysis mechanism of Bi-deposited TiO2 nanocomposites was proposed on the basis of active species trapping. The catalyst architecture elucidated here for promoted plasmonic photocatalysis would be beneficial for the design and development of more effective visible-light-driven photocatalysts for environmental remediation and could open a new avenue for utilization of low-cost Bi nanoparticles as a substitute for noble metals to promote the utilization efficiency of solar energy.

Zero-valent iron nanoparticles embedded into reduced graphene oxide-alginate beads for efficient chromium (VI) removal

Zero-valent iron nanoparticles (Fe0 NPs) technologies are often challenged by poor dispersibility, chemical instability to oxidation, and mobility during processing, storage and use. This work reports a facile approach to synthesize Fe0 NPs embedded reduced graphene oxide-alginate beads (Fe@GA beads) via the immobilization of pre-synthesized Fe0 NPs into graphene oxide modified alginate gel followed by a modelling and in-situ reduction process. The structure/composition characterization of the beads finds that the graphene sheets and the Fe0 NPs (a shape of ellipsoid and a size of <100nm) are uniformly dispersed within the alginate beads. We demonstrate that these Fe@GA beads show a robust performance in aqueous Cr(VI) removal. With a optimized Fe and alginate content, Fe@GA bead can achieve a high Cr(VI) removal efficiency and an excellent mechanical strength. The initial Cr(VI) concentration, ionic strength, temperature and especially solution pH are all critical factors to control the Fe@GA beads performance in Cr(VI) removal. Fitness of the pseudo second-order adsorption model with data suggests adsorption is the rate-controlling step, and both Langmuir and Freundlich adsorption isotherm are suitable to describe the removal behavior. The possible Cr(VI) removal path by Fe@GA beads is put forward, and the synergistic effect in this ternary system implies the potentials of Fe@GA beads in pollutant removal from water body.

Calcium Sulfate Hemihydrate Nanowires: One Robust Material in Separation of Water from Water-in-Oil Emulsion

Here we report a facile and cost-effective wet-chemical approach to the synthesis of calcium sulfate hemihydrate nanowires (HH NWs, CaSO4·0.5H2O), and their robust performance in immobilizing water molecules to the crystal lattice of CaSO4 and then separating them from a surfactant-stabilized water-in-oil emulsion (mean droplet size of around 1.2 μm). Every gram of HH NWs are capable of treating 20 mL emulsion (water content: 10.00 mg mL-1) with a separation efficiency of 99.23% at room temperature, and this efficiency can be further improved by tuning the surface charge density of HH. Along with the water immobilization, HH NWs are converted to large cubic-like calcium sulfate dihydrate microparticles (DH, CaSO4·2H2O, mean size: 50 μm), and the accompanied size increment enables efficient collection of the solid phase from oil. DH microparticles can be regenerated into HH NWs, which retain the high performance of the original NWs. Such a unique renewable feature improves the economics of our method and simultaneously prevents the secondary pollution. Further economic evaluation finds that purification of every cubic meters of emulsion (water content: 10.00 mg mL-1) will cost about

Template-Free Hydrothermal Synthesis of Nanorod (RuTi)O2 Composite Cathode for Hydrogen Evolution in Alkali Solution

34.18 for HH NWs, much lower than the

Monodisperse bismuth nanoparticles decorated graphitic carbon nitride: Enhanced visible-light-response photocatalytic NO removal and reaction pathway

490.78 for the previously reported HH NPs, and

Electrocatalytic hydrodechlorination of 2,4-dichlorophenol over palladium nanoparticles and its pH-mediated tug-of-war with hydrogen evolution

11 052.05-

Immobilizing Water into Crystal Lattice of Calcium Sulfate for its Separation from Water-in-Oil Emulsion.

23 420.32 Fe3O4 NP-based adsorbents, respectively. With the high efficiency, easy collection, low cost, and renewable feature, HH NWs show highly promising applications in the field of oil purification and recycle.

Core/shell FePd/Pd catalyst with a superior activity to Pt in oxygen reduction reaction

A novel nanorod (RuTi)O2 composite cathode has been prepared via a facile and controllable approach. X-ray diffraction (XRD), scanning electron microscopy (SEM), and linear scanning voltammetry (LSV) were used to scrutinize the electrodes and the electrochemical performance. The results reveal that the designed nanorod (RuTi)O2 composite cathode displays high electrocatalytic performance for the hydrogen evolution evolution (HER) in alkali solution with a low onset overpotential. For driving a cathodic current density of 100 mA cm, it only needs overpotential of 220 mV. Such excellent performance of the NR-(RuTi)O2/Ti could be ascribed to the unique surface structure with more active sites to be utilized during the HER.