Latest ArticlesThe electroreduction of CO2 (CO2RR) into value-added chemicals is a sustainable strategy for mitigating global warming and managing the global carbon balance. However, developing an efficient and selective catalyst is still the central challenge. Here, we developed a simple two-step pyrolysis method to confine low-valent Ni-based nanoparticles within nitrogen-doped carbon (Ni-NC). As a result, such Ni-based nanoparticles can effectively reduce CO2 to CO, with a maximum CO Faradaic efficiency (FE) of 98% at an overpotential of 0.8 V, as long as good stability. Experimental and the density functional theory (DFT) calculation results reveal that low-valent Ni plays a key role in activity and selectivity enhancement. This study presents a new understanding of Ni-based CO2RR, and provides a simple, scalable approach to the synthesis of low-valent catalysts towards efficient CO2RR.
Anaerobic digestion (AD) is a promising technology for the treatment of waste activated sludge (WAS) with energy recovery. However, the low methane yield and slow methanogenesis limit its broad application. In this study, the NiFe2O4 nanoparticles (NPs) were fabricated and applied as a conductive material to enhance the AD via promoting the direct interspecies electron transfer (DIET). The crystal structure, specific surface area, morphology and elemental composition of the as-prepared NiFe2O4 NPs were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The biochemical methane potential (BMP) test was performed (lasting for 35 days) to evaluate the energy recovery in AD with the addition of the NiFe2O4 NPs. The results illustrate that NiFe2O4 NPs could accelerate both the hydrolysis, acidogenesis and methanogenesis, i.e., the cumulative methane production and daily methane yield increased from 96.76 ± 1.70 mL/gVS and 8.24 ± 1.26 mL gVS−1 d−1 in the absence of NiFe2O4 NPs (Group A) to 123.69 ± 3.20 mL/gVS and 9.71 ± 0.77 mL gVS−1 d−1 in the presence of NiFe2O4 NPs (Group B). The model simulation results showed that both the first-order kinetic model and the modified Gompertz model can well simulate the experimental results. The hydrolysis rate constant k increased from 0.04 ± 0.01 d−1 in Group A to 0.06 ± 0.01 d−1 in Group B. And the maximum methane production potential and activity were both improved after adding NiFe2O4. The microbial community analysis revealed that the microorganisms associated with hydrolysis and acidogenesis were more abundant in the presence of NiFe2O4. And the methanogenic archaea were enriched to a larger extent, resulted in the higher methanogenesis activities via dosing NiFe2O4.
Formaldehyde is an important air pollutant and its removal is essential to protect human health and meet environmental regulations. Ag-based catalyst has a considerable potential for HCHO oxidation in low temperature range. The valence state of Ag is one of the key roles in formaldehyde catalytic oxidation. However, its effect on activity is still ambiguous. Non-thermal plasma and conventional calcination were employed to regulate Ag valence state in this study. Three Ag-Co/CeO2 catalysts with totally different distribution of Ag species were obtained. A special mixed Ag valence state, ~50% Ag+ with a few Ag0 and Ag+, was achieved by plasma activation. It had the merits of both good activity and stability. A close relationship between Ag valence state and the activity for HCHO oxidation was established. The activity of different Ag species follows the order: Ag+ + Ag0 + Ag+ > Ag+ > Ag0 > Ag+.
Carbonate radical is among the most important environmental relevant reactive species which govern the transformation and fate of pharmaceutical contaminants (PCs). However, reaction rate constants between carbonate radical and most of the PCs have not been experimentally determined, and quantitative structural-activity relationships (QSARs) have not been established for rate estimation. This study applied MaxMin data processing method and used molecular fingerprints (MF) as the input of a deep neural network (DNN) to predict the rate constants between carbonate radical and organic compounds. MF parameters and the hyper-structure of the DNN were adjusted to yield satisfactory accuracy of rate prediction. The vector length of 512 bits with radius of 1 for MF and 5 hidden layers gave the best performance. The optimized MaxMin-MF-DNN model was compared with some of the most commonly used QSARs and machine learning methods, including random data splitting, molecular descriptors, supporting vector machine, decision tree, etc. Results showed that the MF-DNN model out-performed the other methods by more than 10% increase in prediction accuracy. Applying this MF-DNN model, we estimated reaction rates between carbonate radical and pharmaceuticals used in human medicine (1576) and veterinary practice (390). Among them, 46 drugs were identified as fast-reacting compounds, suggesting the important relations of their environmental fate with carbonate radical.
This study synthesized UiO-66 (Zr) in situ on wood via a one-step solvothermal method. UiO-66/wood was successfully prepared and its catalytic performance for the ofloxacin (OFX) photodegradation under simulate sunlight was also explored. UiO-66/wood exhibited a better catalytic performance, and its degradation rate constant was about 1.2 and 1.5 times than that of UiO-66 and wood, respectively. The effects of solution initial concentration, pH of the system and dosage of the photocatalyst were explored. Additionally, the active species trapping experiments and UV–vis diffused reflectance spectra measurements were conducted to investigated the photocatalytic mechanism of the UiO-66/wood composite, superoxide radical (O2•–) and hydroxyl radical (•OH) were the main reactive species. In addition, the possible degradation pathways of OFX were analyzed by LC-MS. Meanwhile, the UiO-66/wood showed outstanding stability and reusability after 4 cycles experiments. The removal performance of UiO-66/wood towards real samples showed it has potential in actual application.
A great concern has been raised regarding the issue of fluoroquinolones (FQs) in the environment. In this work, the transformation of FQs by commonly used oxidant permanganate (Mn(Ⅶ)) in the absence and presence of humic acid (HA), ubiquitously existing in aquatic environments, was systematically investigated. Here, the catalytic role of in-situ formed MnO2 on Mn(Ⅶ) oxidation of FQs depending on solution pH and co-existing substrates was firstly reported. It was interestingly found that HA could appreciably accelerate FQs degradation by Mn(Ⅶ) at environmentally relevant pH. HA as a reductant in accelerating FQs by Mn(Ⅶ) oxidation was distinctly elucidated for the first time, where MnO2 in situ formed from the reduction of Mn(Ⅶ) by HA served as a catalyst. Similar products were observed in the presence versus absence of HA. Considering that the accelerating role of HA was related to its reducing ability, an activation method based on Mn(Ⅶ) and reductant (i.e., Fe(Ⅱ), Mn(Ⅱ) and (bi)sulfite) was proposed, which exhibited considerable potential for application in the treatment of FQs contaminated water.
Anodic oxygen evolution reaction (OER) is the key bottleneck for water electrolysis technique owing to its sluggish reaction kinetics. Interfacial engineering on the rationally designed heterostructure can regulate the electronic states efficiently for intrinsic activity improvement. Here, we report a co-phosphorization approach to construct a VPO4-Ni2P heterostructure on nickel foam with strongly chemical binding, wherein phosphate acts as electronic modifier for Ni2P electrocatalyst. Profiting from the interfacial interaction, it is uncovered that electron shifts from Ni2P to VPO4 to render valence increment in Ni species. Such an electronic manipulation rationalizes the chemical affinities of various oxygen intermediates in OER pathway, giving a substantially reduced energy barrier. As a result, the advanced VPO4-Ni2P heterostructure only requires an overpotential of 289 mV to deliver a high current density of 350 mA/cm2 for OER in alkaline electrolyte, together with a Tafel slope as low as 28 mV/dec. This work brings fresh insights into interfacial engineering for advanced electrocatalyst design.
Li‒S batteries have shown great potential as secondary energy batteries. However, the side reaction between Li anodes and polysulfides seriously limited their practical application. Herein, the artificial protective film, which is consisted of Li-Nafion and TiO2, was designed and successfully prepared to achieve a corrosion-resistant Li anode in Li-S battery. In the composite protective film, the Li-Nafion could efficiently prevent the contact between Li anodes and polysulfides, and the incorporation of TiO2 nanoparticles into the Nafion could significantly increase the ionic conductivity and mechanical strength of the protective film. Li-Li symmetric cells with an optimal artificial protective film exhibited an extended cycle-life of 750 h at a current density of 1 mA/cm2 in Li2S8 electrolyte. Moreover, the Li‒S full battery with an optimal protective Li anode exhibited higher capacity retention of 777.4 mAh/g after 100 cycles at 0.1 C as well as better rate performance than the cell with a pure Li anode. This work provides alternative insights to suppress the side reaction for Li‒S batteries with high capacity retention.
Hierarchical superstructures assembled by nanosheets can effectively prevent aggregation of nanosheets and improve performance in energy storage. Therefore, we proposed a facile hydrothermal method to obtain three-dimensional (3D) superstructure assembled by nanosheets. We found that the ratio of Co2+/HMTA affected the morphology of the samples, and the 3D hierarchical structures of are obtained while the ratio of Co2+/HMTA is 12:25. The hierarchical structures with sufficient interior space preserves the original sheet-like dimensional components and results in sufficient active sites and efficient mass diffusion. Hence, the 3D Co2V2O7·nH2O hierarchical structure exhibits good rate capability and high stability while as electrode materials. Meanwhile, when power density is 745.13 W/kg, the assembled CVO-2//AC shows an energy density of 47.7 Wh/kg. The work displays a facile method for fabrication of 3D superstructure assembled by 2D nanosheets that can be applied in energy storage.
Single-component organic solar cells (SCOSCs) with high stability and simplified fabrication process are supposed to accelerate the commercialization of organic photovoltaics. However, the types of photo-active materials and photovoltaic performance of SCOSCs are still far lagging behind the bulk-heterojunction type organic solar cells (BHJ OSCs). It is still an arduous task to introduce new photo-active materials into SCOSCs, aiming to improve the efficiencies of SCOSCs. One feasible way is to construct double-cable polymers with new structures and tune conformation, morphology and mobility for the improvement in power conversion efficiencies (PCEs). Hence, in this work, we constructed a new double-cable polymer PBTT-BPTI by introducing fused core 5,7-dibromo-2,3-bis(2-ethylhexyl)benzo[1,2-b:4,5-c']dithiophene-4,8-dione (TTDO) into the main backbone and benzo[ghi]-perylene triimide (BPTI) unit into the side chain. Both of the two units show strong electron-withdrawing property, which are expected to broaden absorption spectra and enhance intermolecular interaction. The double-cable polymer exhibited a broad absorption in the range of 300-700 nm with an optical band gap (Eg) of 1.79 eV. The PCE of PBTT-BPTI-based SCOSCs was 2.15%, which may be limited by the unconstructed efficient electron transporting channels.
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