Latest ArticlesIn order to realize the sulfur and water resistance and facilitate the CO oxidation reactions, the effects of strain on the adsorption of CO, O2, SO2 and H2O molecules on Ni single-atom-catalyst supported by single-carbon-vacancy graphene (Ni-SG) have been studied based on first principles calculations. It shows that the compressive strain increases the adsorption energies of all above mentioned molecules on Ni-SG, where SO2 is adsorbed more strongly on Ni-SG than CO. However, in the presence of tensile strain, the adsorption energies decreases significantly when the molecules (O2 and SO2) obtain electrons from Ni-SG, while the adsorption energies just slightly decrease when the molecules (CO and H2O) lose electrons to Ni-SG, which finally achieves the preferential adsorption of CO and O2 molecules on Ni-SG by tensile strain. In addition, with tensile strain increasing to 10%, the rate-limited energy barrier along Eley-Rideal (ER) path monotonically increases from 0.77 eV to 0.98 eV, while the rate-limited energy barrier along Langmuir-Hinshelwood (LH) path monotonically decreases from 0.54 eV to 0.44 eV, indicating that the tensile strain can facilitate the LH mechanism while imped the ER mechanism on Ni-SG. The Hirshfeld charge and orbital levels of O2 and CO molecules are modulated by the tensile strain, which plays an important role for the decreasing of energy barriers for CO oxidation. Overall, the tensile strain can enhance the sulfur and water resistance of Ni-SG, as well as boost the CO oxidation reactions.
It is essential to develop efficient electrocatalysts to generate hydrogen from water electrolysis for hydrogen economy. In this work, platinum (Pt) and nickel (Ni) co-doped porous carbon nanofibers (Pt/Ni-PCNFs) with low Pt content were prepared via an electrospinning, carbonization and galvanic replacement reaction. Because of the high electrical conductivity, abundant electrochemical active sites and synergistic effect between Pt and Ni nanoparticles, the optimized Pt/Ni-PCNFs catalyst shows an excellent HER activity with overpotentials of 20 mV in 0.5 mol/L H2SO4 and 46 mV in 1 mol/L KOH at a current density of 10 mA/cm2. Furthermore, over 35-h long-term stability has been achieved without significant attenuation. This work provides a simple route to prepare highly efficient electrocatalysts for water splitting and has great prospects in the field of renewable energy.
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.
The morphology and heterojunction engineering are effective ways to boost the performance of Cu-based catalysts. Herein, we have reported the designed synthesis of two-dimensional Cu-CuO heterojunction nanosheets (2D Cu-CuO NS) based on 3-aminopropyl-triethoxysilane (APTES, KH550) aided synthetic strategy. The APTES can act as both the ligand and alkali (-OH) source to guide the large-scale synthesis of 2D Cu-based precursor, which can transform into 2D Cu-CuO NS by the controllable post-treatment. The Si species from APTES can protect the particles from the severe aggregation and growth, guaranteeing the formation of 2D sheets composed of small-sized Cu-CuO heterojunction (about 20 nm). The heterojunction interfaces can provide plentiful active sites to boost the catalytic ability. The 2D sheets can provide large accessible surface, being conducive to the contact of the catalyst and reactants. Benefiting from above virtues, the 2D Cu-CuO NS showed the superior catalytic performance for the reduction of a series of nitro compounds, being superior to most reported non-noble metal-based catalysts. Notably, it exhibited good re-cycled performance with no obvious performance degradation after 10 consecutive catalysis. The present study will be promising to promote the application of the Cu-based catalysts, due to its ability to control the morphology and potential for the large-scale synthesis.
Pyrogenic carbonaceous matter (PCM) catalyzes azo dye decolorization by sulfide, but the nitrogen doping catalytic mechanisms are poorly understood. In this study, we found that stagnate time of azo dye methyl orange (MO) decolorization was reduced to 0.54-18.28 min in the presence of various nitrogen-doped graphenes (NGs), remarkably lower compared to graphene itself. Particularly, graphitic nitrogen played a critical role in NGs-catalyzed MO decolorization by sulfide. Gas chromatography-mass spectrometry and in-situ surface Raman analysis demonstrated that doping nitrogen, especially graphite one facilitated reactive intermediate polysulfides formation. This is attributed to the improved electron conductivity through graphitic nitrogen doping, and the enhanced interactions between sulfide and carbon atoms bonded to graphitic nitrogen. This study not only provides a better understanding of PCM impact on transformations and fates of organic pollutants in natural environments, but also offer a new regulation strategy for more efficient wastewater treatment processes in PCM-catalyzed engineering systems.
Screening of foodborne pathogens is important to prevent contaminated foods from their supply chains. In this study, a portable detection device was developed for rapid, sensitive and simple detection of viable Salmonella using a finger-actuated microfluidic chip and an improved recombinase aided amplification (RAA) assay. Improved propidium monoazide (PMAxx) was combined with RAA to enable this device to distinguish viable bacteria from dead ones. The modification of PMAxx into dead bacteria, the magnetic extraction of nucleic acids from viable bacteria and the RAA detection of extracted nucleic acids were performed using the microfluidic chip on its supporting device by finger press-release operations. The fluorescent signal resulting from RAA amplification of the nucleic acids was collected using a USB camera and analyzed using a self-developed smartphone App to quantitatively determine the bacterial concentration. This device could detect Salmonella typhimurium in spiked chicken meats from 1.3 × 102 CFU/mL to 1.3 × 107 CFU/mL in 2 h with a lower detection limit of 130 CFU/mL, and has shown its potential for on-site detection of foodborne pathogens.
With the help of the redox mediator, decoupled water-splitting allows O2 and H2 to be produced at different times, at different rates, and even in different cells, which promotes both the operation safety and the utilization of renewable power sources. However, the current densities and stabilities of these redox mediators are commonly low, which require further improvements for practical applications. Here, we propose to use supercapacitors as solid state redox mediators for decoupled water splitting. For demonstration, Na0.5MnO2 (pseudocapacitor) and active carbon (double layer capacitor), are both used as the redox mediator. These supercapacitors show superior current density (1 A/cm2) and ultralong cycle-life (8000 cycles) compared with commonly investigated battery-based mediators (NiOOH/Ni(OH)2). Our research proves supercapacitors can be used as redox relay with high current density and stability, which may bring new insights in the design of decoupled water splitting systems.
Thermally regenerative batteries (TRBs) are promising for harvesting low-grade waste heat into electrical power. However, the ammonia crossover from anode to cathode causes self-discharge and then leads to the decay of capacity. To alleviate the ammonia crossover and improve electricity generation, a stable graphene oxide (GO) modified anion exchange membrane (AEM) was proposed. Compared with the original AEM, the GO modified AEM with a 39.5% lower ammonia permeability induces a 24.3% higher maximal power output and 20.2% higher energy density in TRBs. Together with the visualization result, it was demonstrated the ammonia crossover was effectively alleviated by GO modifying the AEM not at a cost of the reduced battery performance, indicating the promising application in future TRBs.
A practical synthetic method for 4-thiocyanato-1H-pyrazoles through the electrochemical cascade reaction of hydrazines, 1, 3-diones and NH4SCN under metal-, chemical oxidant- and external electrolyte-free conditions was established. Importantly, both a gram-scale synthesis of 4-thiocyanato-1H-pyrazoles and five one-pot sequential transformations starting from hydrazine were successfully accomplished.
Bimetallic catalysts usually exhibit better performance than monometallic catalysts due to synergistic effect. However, there is a lack of exploring the synergistic effect on catalytic performance caused by the introduction of inactive metal ion. In this work, we design a molecular model system that can precisely regulate the metal site number and catalytic property. When these molecular metal compounds are used as homogeneous catalysts for photocatalytic CO2 reduction, the dinuclear heterometallic CuNi-L2 shows the highest CO2-to-CO conversion, which is 2.1 and 3.0 times higher than that of dinuclear homometallic Ni2-L2 and mononuclear Ni-L1. Density functional theory calculations demonstrate that, in CuNi-L2, the introduction of inactive CuII is easier to promote the photo-generated electrons transferring to the coupled active NiII site to achieve the highest activity. In addition, this work also provides insights to design and construct more efficient bimetallic catalysts in future.
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