Search

Developing seawater‐based high‐performance oxygen reduction reaction (ORR) electrocatalysts is meaningful to renewable energy storage and conversion, and the Fe‐based derivatives encapsulated by nitrogen (N) doped carbon are the typical representative. Nevertheless, unrevealing the mechanism of N configuration to ORR activity and chlorine resistance is still a great challenge. In this work, a feasible strategy is developed to prepare controllable pyridinic/pyrrolic‐N doped carbon‐coated Fe‐based electrocatalysts (FexN‐NC). Drawing support from the H3PO4 blocking based in situ Fourier transform infrared spectroscopy (FTIR) test and density‐functional theory (DFT) calculation, the tandem effect of pyridinic‐N and pyrrolic‐N on ORR is proved. Additionally, the low hydrogen peroxide (H2O2) yield and 4e− pathway of FexN‐NC demonstrate that N doping effectively reduces the adsorption of Cl−, which is consistent with the low Cl− adsorption energy of DFT. The half‐wave potential (E1/2) of FexN‐NC for ORR reaches 0.874 V in alkaline seawater, and ZABs assembled with FexN‐NC as the air cathode deliver a remarkable power density (162 mW cm−2), along with excellent long‐term durability (>400 h). [ABSTRACT FROM AUTHOR]

The development of an electrocatalyst for oxygen reduction reaction (ORR) in a seawater electrolyte is the key to realizing the utilization of marine resources and application of Zn–air batteries (ZABs). Exploring the adsorption and desorption behavior of oxygen can guide the design of catalysts fundamentally and improve the catalytic performance. On this basis, WC and Co on nitrogen‐doped carbon (WC‐Co@NC) with an interfacial built‐in electric field (BEF) is designed as an ORR catalyst. The theoretical calculation certifies that the BEF of W─C─Co connections promote charge separation and directional migration, thus realizing the oxygen adsorption equilibrium and speeding up the process of ORR. These give WC‐Co@NC a high half‐wave potential of 0.872 V, and the alkaline seawater‐based ZAB with WC‐Co@NC as the air cathode has a peak power density of 188.8 mW cm−2 and excellent stability. This work can provide a basis for the rational design of the cathode of alkaline seawater‐based ZAB, and can also give a new direction for the utilization of seawater resources. [ABSTRACT FROM AUTHOR]

Rational design and synthesis of bifunctional oxygen electrocatalysts with high activity and stability are key challenges in the development of rechargeable Zn-air batteries (ZABs). In this paper, tungsten carbide (WC) and Co7Fe3 embedded in N,P co-doped hierarchical carbon (WC/Co7Fe3-NPHC) was prepared by using zeolite imidazolate frameworks as precursor. Density functional theory demonstrates that the mutual adjustment among the WC, Co7Fe3, and N,P co-doped carbon at the three-phase heterojunction interface makes the catalyst possess moderate adsorption strength, and greatly improves the conductivity and electron transfer rate of the catalyst. As a result, the WC/Co7Fe3-NPHC exhibits a low overall oxygen redox potential difference of 0.72 V, while the ZAB assembled by WC/Co7Fe3-NPHC as an air cathode exhibits ultra-long cycle stability of over 550 h. Futhermore, WC/Co7Fe3-NPHC can keep good charge and discharge stability at different bending angles when applied to flexible solid ZAB. [ABSTRACT FROM AUTHOR]

Developing low‐cost, efficient, and stable trifunctional electrocatalyst for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is still a significant challenge. Herein, this study reports a zeolitic imidazolate framework (ZIF) derived trifunctional electrocatalyst, composed of Co5.47N and Co7Fe3 (CoFeN) that embedded into 1D N‐doped carbon nanotubes modified 3D cruciform carbon matrix (NCNTs//CCM). Benefiting from the robust interfacial conjugation of Co5.47N/Co7Fe3 and the 1D/3D hierarchical structure with a large surface area, the as‐prepared CoFeN‐NCNTs//CCM display trifunctional electrocatalytic activity for ORR (half‐wave potential of 0.84 V), OER (320 mV at 10 mA cm–2), and HER (−151 mV at 10 mA cm–2). The assembled Zn‐air battery exhibits high power density (145 mW cm–2), enhanced charge–discharge performance (voltage gap of 0.76 V at 10 mA cm–2), and long‐term cycling stability (over 445 h). The resultant overall water‐splitting cell achieves a current density of 10 mA cm–2 at 1.63 V, which can compete with the best reported trifunctional catalysts. What is more, the self‐assembled Zn‐air batteries are utilized to power the overall water splitting successfully, verifying great potential of the CoFeN‐NCNTs//CCM as functional material for sustainable energy storage and conversion system. [ABSTRACT FROM AUTHOR]

BACKGROUND Selective absorption of oils by macroporous solid absorbents has been regarded as an easy, environment-friendly and economical way to gather oils for oil-water separation, oil contamination cleanup and easy transport/storage. Cheap absorbent material with high oil-absorption performance is a key factor to promote its large-scale application. RESULTS Highly oil-absorptive and water-repellent carbonized asphalt-melamine sponges ( AMS) have been prepared via a dip-coated sponge carbonization process, using deoiled asphalt ( DOA) as dip-coating reagent and melamine sponge ( MS) as template. By the combination of DOA-derived surface modification and mild carbonization at 600°C, the AMS products obtained such key properties as low density, highly selective absorption of oils against water, flexibility, good fire-resistance and thermal stability, and good recyclability. CONCLUSION These findings indicate that AMS can be a promising oil-absorbent material applicable to oil pollution control on a water surface. Benefiting from both cheap raw materials and facile economical manufacturing process, the approach proposed can contribute to the mass manufacturing of cheap oil-absorbent products with high oil-absorption performance. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This work discussed the preparation and characterization of graphene oxide (GO) modified polyvinyl alcohol (PVA) for bacteria immobilization to enhance the biodegrdation efficiency of saline organic wastewater. GO–PVA material has lamellar structure with higher surface area to support bacterial growth and high salinity tolerance. It significantly stimulated the bacterial population by 1.4 times from 2.07×10 3 CFU/mL to 5.04×10 3 CFU/mL, and the microbial structure was also improved for salinity tolerance. Acinetobacter , Pseudomonas and Thermophilic hydrogen bacilli were enriched inside GO–PVA materials for glucose biodegradation. Compared to the COD Cr removal efficiency with only PVA as the carrier (52.8%), GO–PVA material had better degradation performance (62.8%). It is proved as a good candidate for bioaugmentation to improve biodegradation efficiency in hypersaline organic wastewater. [ABSTRACT FROM AUTHOR]

Slow-release organic carbon-source (SOC) material, a new kind of electron donor forin situgroundwater denitrification, was prepared and evaluated in this study. With starch as a biologically utilized carbon source and polyvinyl alcohol (PVA) as a frame, this material performed controllable carbon release rates and demonstrated stable behaviour during the simulated denitrification process. Raman spectrum analysis showed that the PVA skeleton formed cross-linking network structures for hydrogen-bonded water molecules reset in low temperatures, and the starchy molecules filled in the interspace of the skeleton to form a two-phase interlocking/disperse phase structure. In a static system, carbon release processes followed the Fickian law with (1.294–6.560) × 10−3 mg g−1 s−1/2as the release coefficient. Under domestication andin situgroundwater simulation conditions, SOC material played a favourable role during denitrification, with 1.049 ± 0.165 as an average carbon–nitrogen ratio. The denitrification process followed the law of zero-order kinetics, while the dynamics parameterkNwas 0.563–8.753 gN m−3 d−1. Generally, SOC material was suggested to be a potential carbon source (electron donor) suitable forin situgroundwater denitrification. [ABSTRACT FROM PUBLISHER]

Based on the theories of organic polymer and chemical kinetics, the structure and mass transportation model of slow-release organic carbon-source (SOC) material was developed in this study to reveal and predict the carbon release mechanisms of polymer carbon source, which was feasible forin situdenitrification in nitrate-contaminated groundwater. Composed of polyvinyl alcohol (PVA) and starch, the SOC material formed the interlocking/disperse-phase structure. PVA performed as continuous phase and skeleton, whereas the starch or cellulose behaved as release component. Carbon release process was identified in two stages: solid-phase (inner) and interface (gel layer) diffusion. Solid-phase diffusion was affected by material porous medium parameters, for example, distance between the crosslinking points and starch free energy. The interface diffusion depended mostly on the groundwater dynamics and interface energy distribution. The interface diffusion was found as the limiting step of carbon release process, and the carbon release coefficient corresponded tokD,Ias static coefficient andkC,Ias dynamic coefficient. As the key indicator to evaluate carbon release capacity,kD,IandkC,Irepresented appropriate boundary conditions and interface properties. Sensitivity analysis showed that the key parameters of the carbon release model were the distance between the crosslinking points and the free energy of polymer, influenced by regulation of preparation technique, raw material composition and additive dosage. [ABSTRACT FROM PUBLISHER]

Fe–C alloy filler was prepared using iron powder and activated carbon. And it was proved to be efficient in getting rid of chloride from water, especially saline wastewater. Generally, biochemical treatment efficiency will be low if the concentration of chloride ion (Cl−) in water reaches 10,000 mg/L. Once the Cl−content exceeds 20,000 mg/L, most microbes will lose activity because of the high osmotic pressure. Besides, it will not only affect the microbes’ survival but also be toxic to the microorganisms. This paper studied chloride removal efficiency with iron-carbon alloy. Factors affecting the removal efficiency and the possible removal mechanism were also investigated. Treatment effect for actual salinity wastewater with the filler was reported. The results showed that the new filler could effectively remove chloride ions and chemical oxygen demand (COD). CODCrremoval rate of the chosen practical wastewater samples was higher than 55%, and the Cl−removal rates were 27%, 30% and 25%, respectively. The oxygen consumption curves of the wastewater that were obtained from chemical industries showed that the biodegradability of wastewater could be greatly improved due to removal of Cl−using the new filler. [ABSTRACT FROM PUBLISHER]

This study developed Fe 3 O 4 @cellulose nanocomposites by co-precipitation synthesis for bacteria capture and isolation. By surface modification with cellulose, the Fe 3 O 4 @cellulose nanocomposites have 20 nm average particle size and 3.3–24.9 emu/g saturation magnetization. Living bacteria could be captured by the Fe 3 O 4 @cellulose nanocomposites and harvested by magnetic field, with high efficiency (95.1%) and stability (>99.99%). By metabolizing cellulose and destroying the Fe 3 O 4 @cellulose@bacteria complex, cellulose-decomposing microorganisms lost the magnetism. They were therefore able to be isolated from the inert microbial community and the separation efficiency achieved over 99.2%. This research opened a door to cultivate the uncultivable cellulose-decomposing microorganisms in situ and further characterize their ecological functions in natural environment. [ABSTRACT FROM AUTHOR]