Latest ArticlesDeveloping the high activity, low cost and robust large-current-density-based electrocatalysts is of great significance for the industrial electrolytic water splitting. However, the current range of most reported materials is small, which makes it difficult for them to play their roles in practical applications. Here, a self-supported amorphous FexNi1-xMoO4/IF treated with ammonium fluoride (AF0.1-FNMO/IF) is synthesized by one-step hydrothermal method. With the help of NH4F, AF0.1-FNMO/IF exhibits a vertically cross-linked nanosheet with spherical structure. Electrochemical measurement shows that AF0.1-FNMO/IF affords a large current density ordeal and only need low overpotentials of 289 and 345 mV to reach a current response of 500 mA/cm2 for oxygen evolution reaction and hydrogen evolution reaction, respectively, together with long-time stability (both at 500, 1000 and 2000 mA/cm2) in 1.0 mol/L KOH solution. Using it as bifunctional catalyst for overall water splitting, the current densities of 100, 500, 1000 and 1500 mA/cm2 are achieved at a cell voltage of 1.71, 1.88, 1.94 and 1.97 V with excellent durability, which is much better than that of most published electrodes. The work provides valuable insight for designing higher activity nickel iron-based molybdate catalysts with large current density.
Metal oxides derived from metal-organic framework (MOF) have attracted considerable attention due to its excellent performance and unique structure. Doping is considered as an effective method to improve gas-sensing performance. However, nonmetal doped metal oxides derived from MOF as gas-sensing materials have not been reported. Within this work, N atoms were successfully doped into the lattice of ZnO nanoparticles using ZIF-8 as a self-sacrificial template through a thermal treatment process with the assistant of urea. The obtained N-ZnO exhibited competitive ethanol-sensing performance, in which the response value of N-ZnO-5 to 100 ppm ethanol reached 115 at 190 ℃ with a satisfactory selectivity. It was found that the N-doping in ZnO facilitated the formation of oxygen vacancy that promoted the generation of adsorbed oxygen species to achieve the enhanced gas-sensing performance. Besides, the larger specific surface area resulting from the size reduction during the urea-assisted pyrolysis process can also be responsible for the improving of the ethanol-sensing performance.
The removal of eight typical pharmaceuticals (PhACs) (i.e., ibuprofen (IBU), ketoprofen (KET), diclofenac (DIC), sulfadiazine (SD), sulfamethoxazole (SMX), trimethoprim (TMP), ciprofloxacin (CIP) and enoxacin (ENO)) in sulfur-driven autotrophic denitrification (SdAD) process were firstly investigated via long-term operation of bioreactor coupled with batch tests. The results indicated that IBU and KET can be effectively removed (removal efficiency > 50%) compared to other six PhACs in SdAD bioreactor. Biodegradation was the primary removal route for IBU and KET with the specific biodegradation rates of 5.3±0.7~18.1±1.8 µg g−1-VSS d−1 at initial concentrations of 25-200 µg/L. The biotransformation intermediates of IBU and KET were examined, and the results indicated that IBU was biotransformed to three intermediates via hydroxylation and carboxylation. KET biotransformation could be initiated from the reduction of the keto group following with a series of oxidation/reduction reactions, and five intermediates of KET were observed in this study. The microbial community composition in the system was markedly shifted when long-term exposure to PhACs. However, the functional microbes (e.g., genus Thiobacillus) showed high tolerance to PhACs, resulting in the high efficiency for PhACs, N and S removal during long-term SdAD reactor operation. The findings provide better insight into PhACs removal in SdAD process, especially IBU and KET, and open up an innovative opportunity for the treatment of PhACs-laden wastewater using sulfur-mediated biological process.
A series of monolithic MnO2/iron mesh (IM) catalysts for oxidation of toluene were successfully prepared by using in situ hydrothermal growth. MnO2 can grow firmly on the IM substrates surface with a shedding rate of only 0.14%. Due to the highest Oads and high-valent Mn4+ and Fe3+ elements, the temperature at 50% and 90% toluene conversion (T50% and T90%) was 252 and 265 ℃, respectively for the best performance catalyst (hydrothermal temperature of 80 ℃, hydrothermal time of 12 h, and precursor manganese ion concentration of 0.03 mol/L). The catalysts also presented good water resistance and cycle performance. In-situ DRIFTS results suggesting that toluene was first rapid transformed into the reaction intermediate species (benzoate species) and then converted to CO2 and H2O. Therefore, this work provides a new direction for the research and application of IM-based monolithic catalysts.
The horizontal flow anaerobic digester indicated that high ammonia (2923 mg/L) and SO42- (3653 mg/L) would influence the performance of methane production with food waste as substrates. Therefore, bottle anaerobic digestion reactors were carried out to investigate the effect of ammonia/sulfate concentrations on the methane production. Experimental results manifested that the anaerobic digesters with an ammonia concentration of 3500 mg/L or sulfate of 1600 mg/L showed the best performance of methane production, with an average methane yield of 0.32 and 0.33 L (g VS)-1 d-1, respectively. Specifically, a higher ammonia (6500 mg/L) or sulfate (1600-3500 mg/L) level hindered the bioconversion of C from liquid to gas phase (2.68% or 1.73% CH4-Gas, respectively), while insignificantly for the hydrolyzation of C and N from solid to liquid phase. Similar to sulfate, high ammonia nitrogen seriously inhibited the methanation process, leading to a significant carbon accumulation in the anaerobic reactor, especially for propionic acid. The predominant archaea Methanosarcina at genus level indicated that aceticlastic methanogenesis was the major methanogenic pathway. Meanwhile, high ammonia level suppressed the activity of Methanosarcina, while modest sulfate improved H2-consuming methanogens activity. A large fraction of unclassified bacteria within the Firmicutes (43.78%-63.17%) and Bacteroidetes (24.20%-33.30%) phylum played an important role in substrates hydrolysis.
Due to the high decay rate of the non-radiative transition of long wavelengths, the molecular design of efficient and stable near-infrared (NIR) electroluminescent materials remains a big challenge. Herein, a new tetradentate cyclometalated platinum(Ⅱ) complex with an N∧C∧C∧N coordinated framework has been developed and used as a dopant for NIR organic light-emitting diodes (OLEDs). The complex exhibited a short-lived (0.5–1.5 μs) metal-to-ligand charge transfer (MLCT) excited state in doped and neat films. The resulting NIR OLEDs (λEL = 730 nm) achieved maximum external quantum efficiency (EQEmax) of 5.2% and radiance of 74626 mW sr-1 m–2. Of note, the device exhibited excellent stability with operational lifetime of 119 h for LT90. This work demonstrated the great potential of tetradentate platinum(Ⅱ) complexes in the field of NIR OLEDs.
Spiropyrans (SPs) are a well-known class of photochromic compounds and have found widespread application due to their unique properties. However, for many conventional SPs, high energy ultraviolet (UV) light is commonly essential to drive photoisomerization, leading to poor fatigue resistance. Moreover, the practical application of spiropyrans is hindered by their fast fading speed due to the instability of closed forms (SP) or open forms (MC). Herein, we disclose a novel strategy to address these challenges through introducing both electron-donating substituents to stabilize the SP and dynamic coordination bonds to stabilize the MC. The resulting new spiropyrans complexes exhibit negative photochromic properties, with fast visible light response, good stability of both SP and MC, and significantly improved fatigue resistance.
The development of carbon materials with high electrochemical performance for next-generation energy device is emerging, especially N, S co-doped carbon materials have sparked intensive attention. However, the exploration of N, S co-doped carbon with well-defined active sites and hierarchical porous structures are still limited. In this study, we prepared a series of edge-enriched N, S co-doped carbon materials through pyrolysis of thiourea (TU) encapsulated in zeolitic imidazolate frameworks (TU@ZIF) composites, which delivered very good oxygen reduction reaction (ORR) performance in alkaline medium with onset potential of 0.94 V vs. reversible hydrogen electrode (RHE), good stability and methanol tolerance. Density functional theory (DFT) calculations suggested that carbon atoms adjacent to N and S are probable active sites for ORR intermediates in edge-enriched N, S co-doped carbon materials because higher electron density can enhance O2 adsorption, lower formation barriers of intermediates, improving the ORR performance comparing to intact N, S co-doped carbon materials. This study might provide a new pathway for improving ORR activity by the integration engineering of edge sites, and electronic structure of heteroatom doped carbon electrocatalysts.
Realizing efficient charge separation and directional transfer is a challenge for single-component semiconductors. The spatial electric field generated by dipole moment could promote charge separation. Here, three-dimensional hierarchical CuCo2S4 microspheres with lattice distortion were prepared, and lattice distortion was modulated by changing feed Co/Cu molar ratios in synthesis. CuCo2S4 showed asymmetric crystal structure, leading to generation of dipole moment. The charge separation efficiency of CuCo2S4 was related to lattice distortion, and lattice expansion was in favor for charge separation. The CuCo2S4 with feed Cu/Co molar ratio of 1:4 (CCS-4) showed the maximum lattice expansion and exhibited the highest photocatalytic activity, which was attributable to the highest charge separation efficiency and the largest specific surface area. CCS-4 can remove 95.4% of tetracycline hydrochloride within 40 min photocatalysis, and effectively improve the biodegradability of pharmaceutical wastewater. Importantly, this study provides a new vision for constructing single-component photocatalysts with high photocatalytic performance.
The unique structure of fluorescent proteins in which the fluorophore is encapsulated by the protein shell to restrict rotation and emit light inspired the screening of chromophores that selectively bind to biomolecules to generate fluorescence. In this paper, we report a curcuminoid-BF2-like fluorescent dye N-BF2 containing 4-dimethylaniline as an electron-donating group. When this dye is combined with HSA or BSA, the fluorescence is enhanced 90/112-fold, and the fluorescence quantum yield increases from < 0.001 to 0.16/0.19. Such a large change in fluorescence enhancement is due to the encapsulation of N-BF2 in the protein cavity by HSA/BSA, which inhibits the intramolecular rotation of the aniline moiety caused by charge transfer after the fluorophore is excited by light. N-BF2 has fast and strong binding to HSA or BSA and was found to be reversible in solution and intracellularly. Since N-BF2 also has the ability to target lipid droplets, the complex of N-BF2/HSA realizes the regulation of reversible lipid droplet staining in cells.
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