RhB Adsorption Performance of Magnetic Adsorbent Fe_3O_4/RGO Composite and Its Regeneration through A Fenton-like Reaction

Adsorption is one of the most effective technologies in the treatment of colored matter containing wastewater. Graphene related composites display potential to be an effective adsorbent. However, the adsorption mechanism and their regeneration approach are still demanding more efforts. An effective magnetically separable absorbent, Fe3O4 and reduced graphene oxide(RGO) composite has been prepared by an in situ coprecipitation and reduction method. According to the characterizations of TEM, XRD, XPS, Raman spectra and BET analyses, Fe3O4 nanoparticles in sizes of 10-20 nm are well dispersed over the RGO nanosheets, resulting in a highest specific area of 296.2 m2/g. The rhodamine B adsorption mechanism on the composites was investigated by the adsorption kinetics and isotherms. The isotherms are fitting better by Langmuir model, and the adsorption kinetic rates depend much on the chemical components of RGO. Compared to active carbon, the composite shows 3.7 times higher adsorption capacity and thirty times faster adsorption rates. Furthermore,with Fe3O4 nanoparticles as the in situ catalysts, the adsorption performance of composites can be restored by carrying out a Fenton-like reaction, which could be a promising regeneration way for the adsorbents in the organic pollutant removal of wastewater.

BiVO4/TiO2(N2) Nanotubes Heterojunction Photoanode for Highly Efficient Photoelectrocatalytic Applications

We report the development of a novel visible response BiVO_4/TiO_2(N_2) nanotubes photoanode for photoelectrocatalytic applications. The nitrogen-treated TiO_2 nanotube shows a high carrier concentration rate, thus resulting in a high efficient charge transportation and low electron–hole recombination in the TiO_2–BiVO_4. Therefore, the BiVO_4/TiO_2(N_2) NTs photoanode enabled with a significantly enhanced photocurrent of 2.73 mA cm^(-2)(at 1 V vs. Ag/Ag Cl) and a degradation efficiency in the oxidation of dyes under visible light. Field emission scanning electron microscopy, X-ray diffractometry, energy-dispersive X-ray spectrometer, and UV–Vis absorption spectrum were conducted to characterize the photoanode and demonstrated the presence of both metal oxides as a junction composite.

The Inhibition Effect of Tert-Butyl Alcohol on the TiO_2 Nano Assays Photoelectrocatalytic Degradation of Different Organics and Its Mechanism

The inhibition effect of tert-butyl alcohol(TBA), identified as the·OH radical inhibitor, on the TiO_2 nano assays(TNA) photoelectrocatalytic oxidation of different organics such as glucose and phthalate was reported. The adsorption performance of these organics on the TNA photoelectrode was investigated by using the instantaneous photocurrent value, and the degradation property was examined by using the exhausted reaction. The results showed that glucose exhibited the poor adsorption and easy degradation performance, phthalate showed the strong adsorption and harddegradation, but TBA showed the weak adsorption and was the most difficult to be degraded. The degradation of both glucose and phthalate could be inhibited evidently by TBA. But the effect on glucose was more obvious. The different inhibition effects of TBA on different organics could be attributed to the differences in the adsorption and the degradation property. For instance, phthalate of the strong adsorption property could avoid from the capture of·OH radicals by TBA in TNA photoelectrocatalytic process.

Enhanced Photoelectrochemical Properties of Cu_2O-loaded Short TiO_2 Nanotube Array Electrode Prepared by Sonoelectrochemical Deposition

Copper and titanium remain relatively plentiful in earth crust.Therefore,using them in solar energy conversion technologies are of significant interest.In this work,cuprous oxide（Cu2O）-modified short TiO2 nanotube array electrode was prepared based on the following two design ideas:first,the short titania nanotubes obtained from sonoelectrochemical anodization possess excellent charge separation and transportation properties as well as desirable mechanical stability;second,the sonoelectrochemical deposition technique favours the improvement in the combination between Cu2O and TiO2 nanotubes,and favours the dispersion of Cu2O particles.UV-Vis absorption and photo-electronchemical measurements proved that the Cu2O coating extended the visible spectrum absorption and the solar spectrum-induced photocurrent response.Under AM1.5 irradiation,the photocurrent density of the composite electrode（i.e.sonoelectrochemical deposition for 5 min） was more than 4.75 times as high as the pure nanotube electrode.Comparing the photoactivity of the Cu2O/TiO2 electrode obtained using sonoelectrochemical deposition with others that synthesized using plain electrochemical deposition,the photocurrent density of the former electrode was 2.2 times higher than that of the latter when biased at 1.0 V（vs.Ag/AgCl）.The reproducible photocurrent response under intermittent illumination demonstrated the excellent stability of the composite electrode.Such kind of composite electrode material will have many potential applications in solar cell and other fields.

The Promotion Effect of Low-Molecular Hydroxyl Compounds on the Nano-Photoelectrocatalytic Degradation of Fulvic Acid and Mechanism

A significant promotion effect of low-molecular hydroxyl compounds(LMHCs) was found in the nano-photoelectrocatalytic(NPEC) degradation of fulvic acid(FA),which is a typical kind of humic acid existing widely in natural water bodies,and its influence mechanism was proposed.A TiO_2 nanotube arrays(TNAs) material is served as the photoanode.Methanol,ethanediol,and glycerol were chosen as the representative of LMHCs in this study.The adsorption performance of organics on the surface of TNAs was investigated by using the instantaneous photocurrent value.The adsorption constants of FA,methanol,ethanediol,and glycerol were 43.44,19.32,7.00,and 1.30,respectively,which indicates that FA has the strongest adsorption property.The degradation performance of these organics and their mixture were observed in a thin-layer reactor.It shows that FA could hardly achieve exhausted mineralization alone,while LMHCs could be easily oxidized completely in the same condition.The degradation degree of FA,which is added LMHCs,improves significantly and the best promotion effect is achieved by glycerol.The promotion effect of LMHCs in the degradation of FA could be contributed to the formation of a tremendous amount of hydroxyl radicals in the NPEC process.The hydroxyl radicals could facilitate the complete degradation of both FA and its intermediate products.Among the chosen LMHCs,glycerol molecule which has three hydroxyls could generate the most hydroxyl radicals and contribute the best effective promotion.This work provides a new way to promote the NPEC degradation of FA and a direction to remove humus from polluted water.

BiVO_4 Photoanode with Exposed(040) Facets for Enhanced Photoelectrochemical Performance

A BiVO_4 photoanode with exposed(040) facets was prepared to enhance its photoelectrochemical performance.The exposure of the(040) crystal planes of the BiVO_4 film was induced by adding NaCl to the precursor solution. The asprepared BiVO_4 photoanode exhibits higher solar-light absorption and charge-separation efficiency compared to those of an anode prepared without adding Na Cl. To our knowledge,the photocurrent density(1.26 m A cm^(-2) at 1.23 V vs. RHE) of as-prepared BiVO_4 photoanode is the highest according to the reports for bare BiVO_4 films under simulated AM1.5 G solar light, and the incident photon-to-current conversion efficiency is above 35% at 400 nm. The photoelectrochemical(PEC)water-splitting performance was also dramatically improvedwith a hydrogen evolution rate of 9.11 lmol cm^(-2) h^(-1), which is five times compared with the BiVO_4 photoanode prepared without NaCl(1.82 lmol cm^(-2) h^(-1)). Intensity-modulated photocurrent spectroscopy and transient photocurrent measurements show a higher charge-carrier-transfer rate for this photoanode. These results demonstrate a promising approach for the development of high-performance BiVO_4 photoanodes which can be used for efficient PEC water splitting and degradation of organic pollutants.

Efficient H_(2)O_(2)Electrosynthesis and Its Electro-Fenton Application for Refractory Organics Degradation

Hydrogen peroxide(H_(2)O_(2))in situ electrosynthesis by O_(2)reduction reaction is a promising alternative to the conventional Fenton treatment of refractory wastewater.However,O_(2)mass transfer limitation,cathodic catalyst selectivity,and electron transfer in O_(2)reduction remain major engineering obstacles.Here,we have proposed a systematic solution for efficient H_(2)O_(2)generation and its electro-Fenton(EF)application for refractory organic degradation based on the fabrication of a novel ZrO_(2)/CMK-3/PTFE cathode,in which polytetrafluoroethylene(PTFE)acted as a hydrophobic modifier to strengthen the O_(2)mass transfer,ZrO_(2)was adopted as a hydrophilic modifier to enhance the electron transfer of O_(2)reduction,and mesoporous carbon CMK-3 was utilized as a catalyst substrate to provide catalytic active sites.Moreover,feasible mass transfer of O_(2)from the hydrophobic to the hydrophilic layer was designed to increase the contact between O_(2)and the reaction interface.The H_(2)O_(2)yield of the ZrO_(2)/CMK-3/PTFE cathode was significantly improved by approximately 7.56 times compared to that of the co nventional gas diffusion cathode under the same conditions.The H_(2)O_(2)generation rate and Faraday efficiency reached125.98 mg·cm^(-2)·h^(-1)(normalized to 5674.04 mmol·g^(-1)·h^(-1)by catalyst loading)and 78.24%at-1.3 V versus standard hydrogen electrode(current density of-252 mA·cm^(-2)),respectively.The high H_(2)O_(2)yield ensured that sufficient OH was produced for excellent EF performance,resulting in a degradation efficiency of over 96%for refractory organics.This study offers a novel engineering solution for the efficient treatment of refractory wastewater using EF technology based on in situ high-yield H_(2)O_(2)electrosynthesis.

Support work-function dependent Fenton-like catalytic activity of Co single atoms for selective cobalt(IV)=O generation

In Fenton-like reactions,high-valent cobalt-oxo(Co^(IV)=O)has attracted increasing interests due to high redox potential,long lifetime,and anti-interference properties,but its generation is hindered by the electron repulsion between the electron rich oxo-and cobalt centers.Here,we demonstrate Co^(IV)=O generation from peroxymonosulfate(PMS)activation over cobalt single-atom catalysts(Co-SACs)using in-situ Co K-edge X-ray absorption spectra,and discern that Co^(IV)=O generation is dependent on the support work-function(WF)due to the strong electronic metal-support interaction(EMSI).Supports with a high WF value like anatase-TiO_(2)facilitate the binding of PMS-terminal oxo-ligand to Co sites by extracting Cod electrons,thus decreasing the generation barrier for the critical intermediate(Co-OOSO_(3)^(2-)).The Co atoms anchored on anatase-TiO_(2)(Co-TiO_(2))exhibited enhanced Co^(IV)=O generation and superior activity for sulfamethoxazole(SMX)degradation during PMS activation.The normalized steady-state concentration of Co^(IV)=O in Co-TiO_(2)/PMS system was three orders of magnitude higher than that of free radicals,and 1.3-to 11-fold higher than that generated in other Co-SACs/PMS systems.Co-TiO_(2)/PMS sustained efficient removal of SMX with minimal Co^(2+)leaching under continuous flow operation,suggesting its attractive water purification potential.Overall,these results underscore the significance of support selection for enhanced generation of high-valent metal-oxo species and efficient PMS activation in supported metal SACs.

Extraordinary ductility enhancement of Mg-Nd-Zn-Zr alloy achieved by electropulsing treatment

Mg-Nd-Zn-Zr(JDBM)alloy was studied as a candidate for biodegradable implant material because of its moderate mechanical properties,good biocompatibility,and favorable uniform degradation behavior.To verify whether JDBM alloy exhibits electroplasticity effect and then study the mechanism of electropulsing treatment on JDBM alloy,in this study,homogenized and pre-tensile deformed samples were treated by electropulsing.After the electropulsing treatment,the average grain size was refined due to recrystallization,micron-scale Mg12Nd secondary phases precipitated slightly,while the morphology of nanoscale Zr particles changed from rodlike to ellipsoidal shape.The elongation to failure(EL)increased obviously for the homogenized and pre-tensile deformed JDBM alloy samples after electropulsing treatment,accompanying with no obvious sacrifice of the yield strength(YS)for the former and an evident decrease of YS for the latter,mainly due to the reduction of the dislocation density.The YS decrement and EL increment(77.57%)for the latter are more apparent attributed to the higher density of dislocations introduced by pre-tensile deformation.Therefore,the electropulsing treatment can obviously improve the mechanical properties of JDBM alloy,especially for the plasticity.The present work opens a new window for the fabrication of JDBM alloy profiles with high mechanical properties,especially for the plasticity,such as the cold drawing wires and tubes for biomedical applications.It also could provide theoretical references for other magnesium alloy processing.

Highly-active,metal-free,carbon-based ORR cathode for efficient organics removal and electricity generation in a PFC system

A highly-active,metal-free,carbon-based oxygen reduction reaction(ORR)cathode,i.e.,graphitized Ndoped carbon felt(GNCF),was prepared,for the first time,by in-situ modifying the doping species of polyacrylonitrile(PAN)-based carbon felt(CF)via a facile annealing process in Ar atmosphere.It was applied for dramatically enhanced organics degradation and electricity generation in a photocatalytic fuel cell(PFC)system.The GNCF showed enhanced specific surface area,improved graphitization and raised ratio of graphitic N,therefore resulting in excellently improved ORR performance compared to the CF.When applying the GNCF as a cathode in a PFC system,the proposed PFC showed significant improvement in degrading various model organic contaminants and outputing electricity simultaneously when compared with the PFC with CF.For instance,the apparent rate constant and electricity output efficiency showed~10.6 times and~7.2 times,respectively,improvement when using rhodamine B as model waste.Further improved performance was also achieved by aeration of air or O^(2) due to the fu rther enhanced ORR.The proposed PFC was also efficient in a wide pH,and kept outsta nding stability in long-term utilization.

Photoelectrocatalytic generation of H_(2)and S from toxic H2S by using a novel BiOI/WO_(3)nanoflake array photoanode

In this paper,a photoelectrocatalytic(PEC)recovery of toxic H_(2)S into H_(2)and S system was proposed using a novel bismuth oxyiodide(BiOI)/tungsten trioxide(WO_(3))nano-flake arrays(NFA)photoanode.The BiOI/WO_(3)NFA with a vertically aligned nanostructure were uniformly prepared on the conductive substrate via transformation of tungstate following an impregnating hydroxylation of BiI3.Compared to pure WO_(3)NFA,the BiOI/WO_(3)NFA promotes a significant increase of photocurrent by 200%.Owing to the excellent stability and photoactivity of the BiOI/WO_(3)NFA photoanode and I-/I-3 catalytic system,the PEC system toward splitting of H_(2)S totally converted S_(2)-into S without any polysulfide(Sn-x)under solar-light irradiation.Moreover,H_(2)was simultaneously generated at a rate of about 0.867 mL/(h·cm).The proposed PEC H_(2)S splitting system provides an efficient and sustainable route to recover H_(2)and S.