ABSTRACT
The CO2 fixation mechanism by Alcaligenes faecalis ZS-1 in a biocathode microbial fuel cell (MFC) was investigated. The closed-circuit MFC (CM) exhibited a significantly higher CO2 fixation rate (10.7%) compared to the open-circuit MFC (OC) (2.0%), indicating that bioelectricity enhances CO2 capture efficiency. During the inward extracellular electron transfer (EET) process, riboflavin concentration increased in the supernatant while cytochrome levels decreased. Genome sequencing revealed diverse metabolic pathways for CO2 fixation in strain ZS-1, with potential dominance of rTCA and C4 pathways under electrotrophic conditions as evidenced by significant upregulation of the ppc gene. Differential metabolite analysis using LC-MS demonstrated that CM promoted upregulation of various lipid metabolites. These findings collectively highlight that ZS-1 simultaneously generated electricity and fixed CO2 and that the ppc associated with bioelectricity played a critical role in CO2 capture. In conclusion, bioelectricity resulted in a significant enhancement in the efficiency of CO2 fixation and lipid production.
Subject(s)
Alcaligenes faecalis , Bioelectric Energy Sources , Carbon Dioxide , Alcaligenes faecalis/genetics , Electrodes , Electricity , LipidsABSTRACT
Spatially confined photocatalysis has emerged as a viable strategy for the intensification of various redox reactions, but the influence of confined structure on reaction behavior is always overlooked in gas-solid reactions. Herein, we report a nanomembrane with confining Cs3 Bi2 Br9 nanocrystals inside vertical channels of porous insulated silica thin sheets (CBB@SBA(â¥)) for photocatalytic nitric oxide (NO) abatement. The ordered one-dimensional (1D) pore channels with mere 70â nm channel length provide a highly accessible confined space for catalytic reactions. A record-breaking NO conversion efficiency of 98.2 % under a weight hourly space velocity (WHSV) of 3.0×106 â mL g-1 h-1 , as well as exceptionally high stability over 14â h and durability over a wide humidity range (RH=15-90 %) was realized over SBA(â¥) confined Cs3 Bi2 Br9 , well beyond its nonconfined analogue and the Cs3 Bi2 Br9 confine in Santa Barbara Amorphous (SBA-15). Mechanism studies suggested that the insulated pore channels of SBA(â¥) in CBB@SBA(â¥) endow concentrated electron field and enhanced mass transfer that render high exposure of reactive species and lower reaction barrier needs for â O2 - formation and NO oxidation, as well as prevents structural degradation of Cs3 Bi2 Br9 . This work expands an innovative strategy for designing efficient photocatalysts for air pollution remediation.
ABSTRACT
Recently, zeolitic imidazolate frameworks (ZIFs) composites have emerged as promising precursors for synthesizing hollow-structured N-doped carbon-based noble-metal materials with diverse structures and compositions. Here, a strong/weak competitive coordination strategy is presented for synthesizing high-performance electrocatalysts with hollow features. During the competitive coordination process, the cubic zeolitic-imidazole framework-8 (Cube-8)@ZIF-67 with core-shell structures are transformed into Cube-8@ZIF-67@PF/POM with yolk-shell nanostructures employing phosphomolybdic acid (POM) and potassium ferricyanide (PF) as the strong chelator and the weak chelator, respectively. After calcination, the hollow Mo/Fe/Co@NC catalyst exhibits superior performance in both oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). Interestingly, the Mo/Fe/Co@NC catalyst exhibits efficient electrocatalytic performance for Zn-air batteries (ZABs), with a high power density (≈150 mW cm-2) and superior cycling life (≈500 h) compared to commercial platinum/carbon (Pt/C) and ruthenium dioxide (RuO2) mixture benchmarks catalysts. In addition, the density functional theory further proves that after the introduction of Mo and Fe atoms, the adsorption energy with the adsorption intermediates is weakened by adjusting the d-band center, thus weakening the reaction barrier and promoting the reaction kinetics of OER. Undoubtedly, this study presents novel insights into the fabrication of ZIFs-derived hollow structure bifunctional oxygen electrocatalysts for clean-energy diverse applications.
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In this study, we investigated the doping of Fe-N-C with ZnO (Fe-N-C@ZnO) to enhance its performance in the reduction of biological toxicity and degradation of enrofloxacin (ENR) in seawater. The steady-state/transient fluorescence analysis and free radical quenching test indicated an extremely low electron-hole recombination rate and the generation of reactive oxygen species in Fe-N-C@ZnO, leading to an improvement in the energy efficiency. We compared the ENR degradation efficiencies of Fe-N-C@ZnO and ZnO using both freshwater and seawater. In freshwater, Fe-N-C@ZnO exhibited a slightly higher degradation efficiency (95.00%) than ZnO (90.30%). However, the performance of Fe-N-C@ZnO was significantly improved in seawater compared to that of ZnO. The ENR degradation efficiency of Fe-N-C@ZnO (58.87%) in seawater was 68.39% higher than that of ZnO (34.96%). Furthermore, the reaction rate constant for ENR degradation by Fe-N-C@ZnO in seawater (7.31 × 10-3 min-1) was more than twice that of ZnO (3.58 × 10-3 min-1). Response surface analysis showed that the optimal reaction conditions were a pH of 7.42, a photocatalyst amount of 1.26 g L-1, and an initial ENR concentration of 6.56 mg L-1. Fe-N-C@ZnO prepared at a hydrothermal temperature of 128 °C and heating temperature of 300 °C exhibited the optimal performance for the photocatalytic degradation of ENR. Based on liquid chromatography-mass spectrometry analysis, the degradation processes of ENR were proposed as three pathways: two piperazine routes and one quinolone route.
ABSTRACT
Fabrication of S-scheme heterojunctions with enhanced redox capability offers an effective approach to address environmental remediation. In this study, high-performance Bi2Sn2O7/ß-Bi2O3 S-scheme heterojunction photocatalysts were fabricated via the in situ growth of Bi2Sn2O7 on ß-Bi2O3 microspheres. The optimized Bi2Sn2O7/ß-Bi2O3 (BSO/BO-0.4) degradation efficiency for tetracycline hydrochloride was 95.5%, which was 2.68-fold higher than that of ß-Bi2O3. This improvement originated from higher photoelectron-hole pair separation efficiency, more exposed active sites, excellent redox capacity, and efficient generation of ·O2 - and ·OH. Additionally, Bi2Sn2O7/ß-Bi2O3 exhibited good stability against photocatalytic degradation, and the degradation efficiency remained >89.7% after five cycles. The photocatalytic mechanism of Bi2Sn2O7/ß-Bi2O3 S-scheme heterojunctions was elucidated. In this study, we design and fabricate high-performance heterojunction photocatalysts for environmental remediation using S-scheme photocatalysts.
ABSTRACT
The electrochemical CO2 reduction (ECR) of high-value multicarbon products is an urgent challenge for catalysis and energy resources. Herein, we reported a simple polymer thermal treatment strategy for preparing honeycomb-like CuO@C catalysts for ECR with remarkable C2H4 activity and selectivity. The honeycomb-like structure favored the enrichment of more CO2 molecules to improve the CO2-to-C2H4 conversion. Further experimental results indicate that the CuO loaded on amorphous carbon with a calcination temperature of 600 °C (CuO@C-600) has a Faradaic efficiency (FE) as high as 60.2% towards C2H4 formation, significantly outperforming pure CuO-600 (18.3%), CuO@C-500 (45.1%) and CuO@C-700 (41.4%), respectively. The interaction between the CuO nanoparticles and amorphous carbon improves the electron transfer and accelerates the ECR process. Furthermore, in situ Raman spectra demonstrated that CuO@C-600 can adsorb more adsorbed *CO intermediates, which enriches the CC coupling kinetics and promotes C2H4 production. This finding may offer a paradigm to design high-efficiency electrocatalysts, which can be beneficial to achieve the "double carbon goal."
ABSTRACT
To improve the efficiency of photocatalytic oxidative degradation of antibiotic pollutants, it is essential to develop an efficient and stable photocatalyst. In this study, a polymer-assisted facile synthesis strategy is proposed for the polymorph-controlled α-Bi2O3/Bi2O2CO3 heterojunction retained at elevated calcination temperatures. The p-n heterojunction can effectively separate and migrate electron-hole pairs, which improves visible-light-driven photocatalytic degradation from tetracycline (TC). The BO-400@PAN-140 photocatalyst achieves the highest pollutant removal efficiency of 98.21% for photocatalytic tetracycline degradation in 1 h (λ > 420 nm), and the degradation efficiency was maintained above 95% after 5 cycles. The morphology, crystal structure, and chemical state of the composites were analysed by scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Ultraviolet-visible diffuse reflection, transient photocurrent response, and electrochemical impedance spectroscopy were adopted to identify the charge transfer and separation efficiency of photogenerated electron-hole pairs. The EPR results verified h+ and ËOH radicals as the primary active species in the photocatalytic oxidation reactions. This observation was also consistent with the results of radical trapping experiments. In addition, the key intermediate products of the photocatalytic degradation of TC over BO-400@PAN-140 were identified via high-performance liquid chromatography-mass spectrometry, which is compatible with two possible photocatalytic reaction pathways. This work provides instructive guidelines for designing heterojunction photocatalysts via a polymer-assisted semiconductor crystallographic transition pathway for TC degradation into cleaner production.
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To rapidly design nitrogen reduction reaction (NRR) electrocatalysts with superior activity and selectivity is a great challenge. Herein, we propose a simple mixture strategy including three screening steps and a descriptor to predict NRR electrocatalysts with outstanding activity and selectivity based on density functional theory (DFT). Twenty-eight candidate transition-metal dimers anchored on nitrogen-doped graphene were systematically investigated through our mixture strategy. The results show that VRu-NC exhibits a high NRR activity and suppression of the competitive hydrogen evolution reaction (HER) following the mixed mechanism with a favorable limiting potential (UL) of -0.21 V. Finally, the mechanism of the catalytic reaction pathway was investigated according to the profile of atomic orbitals and electronic properties. This work proposes a feasible strategy for rapid screening of the high-performance of double atomic electrocatalysts with excellent activity and selectivity for the NRR.
ABSTRACT
The existing polycyclic aromatic hydrocarbons (PAHs) in marine sediment has become a critical threat to biological security. Terminal electron acceptor (TEA) amendment has been applied as a potential strategy to accelerate bioremediation in sediment. HCO3-, NO3-, and SO42- were separately added to anaerobic sediment system containing five kinds of PAH, namely, phenanthrene, anthracene, fluoranthene, pyrene and benzo(a)pyrene. PAH concentration, PAH metabolites, TEA concentration, and electron transport system (ETS) activity were investigated. The HCO3- amendment group achieved the max PAH degradation efficiency of 84.98 %. SO42- group led to the highest benzo(a)pyrene removal rate of 69.26 %. NO3- had the lowest PAH degradation rate of 76.16 %. ETS activity test showed that NO3- significantly inhibited electron transport activity in the sediment. The identified PAH metabolites were the same in each group, including 4,5-dimethylphenanthrene, 3-acetylphenanthrene, 9,10-anthracenedione, pyrene-7-hydroxy-8-carboxylic acid, anthrone, and dibenzothiophene. After 126 d's anaerobic degradation at 25 °C, the utilization of HCO3- and SO42- as selected TEAs promoted the PAH biodegradation performance better than the utilization of NO3-.
Subject(s)
Polycyclic Aromatic Hydrocarbons , Anaerobiosis , Benzo(a)pyrene , Biodegradation, Environmental , Electrons , Geologic Sediments , Polycyclic Aromatic Hydrocarbons/analysisABSTRACT
Copper-deficient Cu2-xS nanoparticles (NPs) are extensively exploited as a superior cation exchange (CE) template to yield sophisticated nanostructures. Recently, it has been discovered that their CE reactions can be facilely manipulated by copper vacancy density, morphology, and NP size. However, the structural similarity of usually utilized Cu2-xS somewhat limits the manipulation of the CE reactions through the factor of crystal structure because it can strongly influence the process of the reaction. Herein, we report a methodology of crystal structure transformation to manipulate the CE reactions. Particularly, roxbyite Cu1.8S nanodisks (NDs) were converted into solid wurtzite CdS NDs and Janus-type Cu1.94S/CdS NDs by a "full"/partial CE reaction with Cd2+. Afterward, the roxbyite Cu1.8S were pseudomorphically transformed into covellite CuS NDs. Unlike Cu1.8S, the CuS was scarcely exchanged because of the unique disulfide (S-S) bonds and converted into hollow wurtzite CdS under a more reactive condition. The S-S bonds were gradually split and CuS@CdS core@shell-type NDs were generated. Therefore, our findings in the present study provide not only a versatile technique to manipulate CE reactions in Cu2-xS NPs but also a better comprehension of their reaction dynamics and pathways.
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Biofortification could improve the bioremediation efficiency of microbes in the reparation of marine environmental damage caused by oil spills. In this paper, Chlorella vulgaris LH-1 was used as a fortifier to enhance the degradation of a marine oil spill by endogenous microorganisms. The addition of C. vulgaris LH-1 increased the degradation efficiency of crude oil by 11.09-42.41% and considerably accelerated oil degradation efficiency. Adding C. vulgaris LH-1 to a crude oil environment can improve the activity of endogenous seawater microorganisms. The results of high-throughput sequencing showed that the main bacterial genera were Oceanicola, Roseibacillus, and Rhodovulum when exotrophic C. vulgaris LH-1 and seawater endogenous microorganisms degraded low-concentration crude oil together. However, the addition of high-concentration nutrient salts changed the main bacterial genera in seawater to unclassified Microbacterium, Erythrobacter, and Phaeodactylibacter. The addition of C. vulgaris LH-1 increased the abundance of marine bacteria, Rhodococcus, and Methylophaga and decreased the abundance of Pseudomonas, Cladosporium, and Aspergillus. The functional prediction results of phylogenetic investigation of communities by reconstruction of unobserved states indicated that C. vulgaris LH-1 could improve the metabolic ability of seawater endogenous microorganisms to degrade endogenous bacteria and fungi in crude oil.
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Electrochemical CO2 reduction has been acknowledged as a hopeful tactic to alleviate environmental and global energy crises. Herein, we designed an Fe@C/g-C3N4 heterogeneous nanocomposite material by a simple one-pot method, which we applied to the electrocatalytic CO2 reduction reaction (ECR). Our optimized 20 mg-Fe@C/g-C3N4-1100 catalyst displays excellent performance for the ECR and a maximum Faradaic efficiency (FE) of 88% with a low overpotential of -0.38 V vs. RHE. The Tafel slope reveals that the first electron transfer, which involves a surface-adsorbed *COOH intermediate, is the rate-determining step for 20 mg-Fe@C/C3N4-1100 during the ECR. More precisely, the coordinating capability of the g-C3N4 framework and Fe@C species as a highly active site promote the intermediate product transmission. These results indicate that the combination of temperature adjustment and precursor optimization is key to facilitating the ECR of an iron-based catalyst.
ABSTRACT
Because of high mobility of Cu+ in crystal lattice, Cu2-xS nanoparticles (NPs) utilized as cation exchange (CE) templates to produce complicated nanomaterials has been extensively investigated. Nevertheless, the structural similarity of commonly used Cu2-xS somewhat limits the exploration of crystal structure dependent CE reactions, since it may dramatically affect the reaction dynamics and pathways. Herein, we select djurleite Cu1.94S and covellite CuS nanodisks (NDs) as starting templates and show that the crystal structure has a strong effect on their CE reactions. In the case of djurleite Cu1.94S NDs, the Cu+ was immediately substituted by Cd2+ and solid wurtzite CdS NDs were produced. At a lower reaction temperature, these NDs were partially substituted, giving rise to the formation of Janus-type Cu1.94S/CdS NDs, and this process is kinetically and thermodynamically favorable. For covellite CuS NDs, they were transformed into hollow CdS NDs under a more aggressive reaction condition due to the unique disulfide covalent bonds. These disulfide bonds distributed along [0 0 1] direction were gradually ruptured/reduced and CuS@CdS core-shell NDs could be obtained. Our findings suggest that not only the CE reaction kinetics and thermodynamics, but also the intermediates and final products are intimately correlated to the crystal structure of the host material.
ABSTRACT
Photocatalytic degradation of organic pollution is a vital path to deal with environmental problems. Here, a direct Z-scheme 2D/2D heterojunction of a Fe3O4/Bi2WO6 photocatalyst is fabricated for the degradation of ciprofloxacin by a self-assembly strategy. Furthermore, to characterize the morphology of the obtained composite photocatalysts, various kinds of characterization methods were employed like XRD, XPS, SEM, and TEM. It is indicated that the flower-like photocatalyst is composed of nanosheets. Comparable photocatalysts were prepared by controlling the hydrothermal temperature and the iron content. In the photocatalytic degradation of ciprofloxacin (CIP) in water, under visible light irradiation, FB-180 (synthesized at 180 °C with 4% iron content) presents approximately 99.7% degradation efficiency in only 15 min. Meanwhile, during photocatalytic degradation reactions, the Fe3O4/Bi2WO6 heterojunction also displayed excellent stability, which still kept above 90% degradation efficiency after five consecutive cycles. UV-Vis DRS and M-S analyses showed that the Fe3O4/Bi2WO6 catalyst has a strong visible light absorption capacity and the transfer pathway of photo-induced charge carriers. PL, EIS, and TPR showed that Fe3O4/Bi2WO6 has an efficient separation and transfer rate of the photo-generated carriers. ESR analysis proved that the superoxide radical (â¢O2 -) and hydroxyl radical (â¢OH) play a major role in the Fe3O4/Bi2WO6 photocatalytic system. This special 2D/2D heterojunction we proposed may have huge potential for marine pollution treatment by photocatalysis degradation with dramatically boosted activities.
ABSTRACT
With the assistance of surfactant, Fe nanoparticles are supported on g-C3N4 nanosheets by a simple one-step calcination strategy. Meanwhile, a layer of amorphous carbon is coated on the surface of Fe nanoparticles during calcination. Transmission electron microscopy (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP) were used to characterize the morphology, structure, and composition of the catalysts. By electrochemical evaluate methods, such as linear sweep voltammetry (LSV) and cyclic voltammetry (CV), it can be found that Fe25-N-C-800 (calcinated in 800 °C, Fe loading content is 5.35 wt.%) exhibits excellent oxygen reduction reaction (ORR) activity and selectivity. In 0.1 M KOH (potassium hydroxide solution), compared with the 20 wt.% Pt/C, Fe25-N-C-800 performs larger onset potential (0.925 V versus the reversible hydrogen electrode (RHE)) and half-wave potential (0.864 V vs. RHE) and limits current density (2.90 mA cm-2, at 400 rpm). In 0.1 M HClO4, it also exhibits comparable activity. Furthermore, the Fe25-N-C-800 displays more excellent stability and methanol tolerance than Pt/C. Therefore, due to convenience synthesis strategy and excellent catalytic activity, the Fe25-N-C-800 will adapt to a suitable candidate for non-noble metal ORR catalyst in fuel cells.
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Since the first intercalation of layered silicates by using supercritical CO2 as a processing medium, considerable efforts have been dedicated to intercalating and exfoliating layered two-dimensional (2D) materials in various supercritical fluids (SCFs) to yield single- and few-layer nanosheets. Here, recent work in this area is highlighted. Motivating factors for enhancing exfoliation efficiency and product quality in SCFs, mechanisms for exfoliation and dispersion in SCFs, as well as general metrics applied to assess quality and processability of exfoliated 2D materials are critically discussed. Further, advances in formation and application of 2D material-based composites with assistance from SCFs are presented. These discussions address chemical transformations accompanying SCF processing such as doping, covalent surface modification, and heterostructure formation. Promising features, challenges, and routes to expanding SCF processing techniques are described.
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The complete mitochondrial genome of Ostorhinchus fleurieu was first determined, which was 16,521 bp in length, containing 13 protein-coding genes, two rRNA genes, 22 tRNA genes, a putative control region and one origin of replication on the light-strand. The overall base composition included C(29.2%), A(26.7%), T(26.7%) and G(17.4%). Moreover, the 13 PCGs encoded 3800 amino acids in total, twelve of which used the initiation codon ATG except for COI started with GTG. Most of them ended with complete stop codon, whereas three protein-coding genes (COII, ND4 and Cytb) used incomplete stop codon and represented as T. The phylogenetic tree based on the Neighbour Joining method was constructed to provide relationship within Apogoninae, which could be a useful basis for management of this species.
ABSTRACT
Discovering highly efficient, environmentally friendly, and low-cost exfoliating media that can both disperse and protect black phosphorus (BP) remains a challenge. Herein, we demonstrate such a new molecule, N,N'-dimethylpropyleneurea (DMPU), for effective exfoliation and dispersion of two-dimensional BP nanosheets. A very high exfoliation efficiency of up to 16% was achieved in DMPU, significantly surpassing other good solvents. Exfoliated flakes are free from structural disorder or oxidation. Nanosheets retain high stability in DMPU even after addition of 25 vol% of common solvents. The solvation shell appears to protect the nanosheets from reacting with water and air, more remarkably than the best solvent N-cyclohexyl-2-pyrrolidone reported so far. Molecular dynamics simulations of the exfoliation process show that DMPU is among the effective solvents, although energetically it does not appear as favorable as some other amides. We also demonstrate that our exfoliated BP nanosheets exhibit excellent antimicrobial activities against both Escherichia coli and Staphylococcus aureus, outperforming other common two-dimensional materials of graphene and MoS2, suggesting promise in biomedical applications.
Subject(s)
Anti-Bacterial Agents/pharmacology , Nanostructures/chemistry , Phosphorus/pharmacology , Urea/analogs & derivatives , Escherichia coli/drug effects , Graphite , Molecular Dynamics Simulation , Solvents , Staphylococcus aureus/drug effects , Urea/chemistry , WaterABSTRACT
Designing highly selective and energy-efficient electrocatalysts to minimize the competitive hydrogen evolution reaction in the electrochemical reduction of aqueous CO2 remains a challenge. In this study, we report that doping Pd with a small amount of Te could selectively convert CO2 to CO with a low overpotential. The PdTe/few-layer graphene (FLG) catalyst with a Pd/Te molar ratio of 1 : 0.05 displayed a maximum CO faradaic efficiency of about 90% at -0.8 V (vs. a reversible hydrogen electrode, RHE), CO partial current density of 4.4 mA cm-2, and CO formation turnover frequency of 0.14 s-1 at -1.0 V (vs. a RHE), which were 3.7-, 4.3-, and 10-fold higher than those of a Pd/FLG catalyst, respectively. Density functional calculations showed that Te adatoms preferentially bind at the terrace sites of Pd, thereby suppressing undesired hydrogen evolution, whereas CO2 adsorption and activation occurred on the high index sites of Pd to produce CO.
ABSTRACT
The development of highly selective, low cost, and energy-efficient electrocatalysts is crucial for CO2 electrocatalysis to mitigate energy shortages and to lower the global carbon footprint. Herein, we first report that carbon-coated Ni nanoparticles supported on N-doped carbon enable efficient electroreduction of CO2 to CO. In contrast to most previously reported Ni metal catalysts that resulted in severe hydrogen evolution during CO2 conversion, the Ni particle catalyst here presents an unprecedented CO faradaic efficiency of approximately 94% at an overpotential of 0.59 V, even comparable to that of the best single Ni sites. The catalyst also affords a high CO partial current density and a large CO turnover frequency, reaching 22.7 mA cm-2 and 697 h-1 at -1.1 V (versus the reversible hydrogen electrode), respectively. Experiments combined with density functional theory calculations showed that the carbon layer coated on Ni and N-dopants in carbon material both play important roles in improving catalytic activity for electrochemical CO2 reduction to CO by stabilizing *COOH without affecting the easy *CO desorption ability of the catalyst.