Hydrogen adsorption/desorption behavior plays a key role in hydrogen evolution reaction (HER) catalysis. The HER reaction rate is a trade-off between hydrogen adsorption and desorption on the ...catalyst surface. Herein, we report the rational balancing of hydrogen adsorption/desorption by orbital modulation using introduced environmental electronegative carbon/nitrogen (C/N) atoms. Theoretical calculations reveal that the empty d orbitals of iridium (Ir) sites can be reduced by interactions between the environmental electronegative C/N and Ir atoms. This balances the hydrogen adsorption/desorption around the Ir sites, accelerating the related HER process. Remarkably, by anchoring a small amount of Ir nanoparticles (7.16 wt%) in nitrogenated carbon matrixes, the resulting catalyst exhibits significantly enhanced HER performance. This includs the smallest reported overpotential at 10 mA cm
(4.5 mV), the highest mass activity at 10 mV (1.12 A mg
) and turnover frequency at 25 mV (4.21 H
s
) by far, outperforming Ir nanoparticles and commercial Pt/C.
Catalysts are at the heart of the hydrogen evolution reaction (HER) for the production of pure and clean hydrogen. For practical applications, the scalable synthesis of efficient HER catalysts, which ...work in both acidic and alkaline media, is highly desired. In this work, the mechanochemically assisted synthesis of a Ru catalyst with HER performance surpassing Pt in both acidic and alkaline media is reported. Mass production of this Ru catalyst can be achieved via a two‐step procedure: the mechanochemical reaction between graphite and dry ice produces edge‐carboxylic‐acid‐functionalized graphene nanoplatelets (CGnP); mixing a Ru precursor and the CGnP in an aqueous medium introduces Ru ions, which coordinate on the CGnP. Subsequent annealing results in uniform Ru nanoparticles (≈2 nm) anchored on the GnP matrix (Ru@GnP). The efficient Ru@GnP catalyst can be easily powered by a single silicon solar cell using a wireless integration device. The self‐powered device exhibits robust hydrogen evolution under the irradiation of standard AM 1.5 solar light. This work provides a new opportunity for the low‐cost mass production of efficient and stable catalysts for practical applications.
The mechanochemically assisted synthesis of a ruthenium (Ru) on graphene nanoplatelet (GnP) catalyst is explored to demonstrate efficient and stable hydrogen evolution performance surpassing Pt in both acidic and alkaline media. The synthesis procedures start from uniform anchoring Ru ions on mechanochemically driven edge‐carboxylic‐acid‐functionalized graphene nanoplatelets (CGnP) to produce Ru@CGnP, which becomes Ru@GnP after reduction and annealing.
In this work, a four-dimensional lattice spring model is developed for studying the mechanical responses of solids. Our results indicate that the Poisson’s ratio limitation of the classical lattice ...spring model defined in three-dimensional space can be released by introducing an extra fourth-dimensional interaction. The fourth-dimensional lattice spring model adopts central interactions only, and it can naturally represent the nonlinear dynamic responses of solids without special treatment of rigid body rotation or incremental integration of non-central/non-local interaction as used in the traditional methods. Applicability of the model is illustrated from a few numerical examples.
•The Poisson’s ratio limitation of classical LSM is released by introducing an extra fourth-dimensional interaction.•The method of constructing 4D lattice spring model is presented.•The method of parameters selection is provided.•The underlying principle is investigated using hyperelasticity analysis.
The electrochemical reduction of nitrogen into ammonia under ambient conditions is a potential strategy for sustainable ammonia production. At present, one of the main research directions in the ...field of electrochemical nitrogen fixation is to improve the current efficiency and ammonia yield by developing efficient nitrogen reduction catalysts. To optimise the selectivity and catalytic activity of nitrogen reduction catalysts more efficiently, herein, we systematically summarise the progress of research on nitrogen reduction catalysts in recent years and present some general catalyst design strategies. Considering that it is difficult for metal‐based catalysts to balance the competitive reactions of nitrogen activation and hydrogen evolution, we discuss in detail the advantages and application prospects of non‐metallic catalysts in electrochemical nitrogen fixation. Moreover, both the design strategy of surface or interface defects, and how this atomic‐level control of functionalisation helps to promote selectivity and catalytic activity are also discussed by theoretical and experimental electrochemistry. On this basis, we also discussed the future development direction, opportunities and challenges of nitrogen reduction electrocatalysts.
Herding cats: This review provides a comprehensive and critical summary of the progress of research on nitrogen reduction catalysts and some general catalyst design strategies. Considering that it is difficult for metal‐based catalysts to balance the competitive reactions of nitrogen activation and hydrogen evolution, the advantages and application prospects of non‐metallic catalysts in electrochemical nitrogen fixation are summarized and discussed.
Ammonia, one of the most important synthetic feedstocks, is mainly produced by the Haber-Bosch process at 400-500 °C and above 100 bar. The process cannot be performed under ambient conditions for ...kinetic reasons. Here, we demonstrate that ammonia can be synthesized at 45 °C and 1 bar via a mechanochemical method using an iron-based catalyst. With this process the ammonia final concentration reached 82.5 vol%, which is higher than state-of-the-art ammonia synthesis under high temperature and pressure (25 vol%, 450 °C, 200 bar). The mechanochemically induced high defect density and violent impact on the iron catalyst were responsible for the mild synthesis conditions.
WRKY transcription factors play a key role in the tolerance of biotic and abiotic stresses across various crop species, but the function of some WRKY genes, particularly in tomato, remains ...unexplored. Here, we characterize the roles of a previously unstudied WRKY gene, SlWRKY8, in the resistance to pathogen infection and the tolerance to drought and salt stresses. Expression of SlWRKY8 was up‐regulated upon Pseudomonas syringae pv. tomato DC3000 (Pst. DC3000), abiotic stresses such as drought, salt and cold, as well as ABA and SA treatments. The SlWRKY8 protein was localized to the nucleus with no transcription activation in yeast, but it could activate W‐box‐dependent transcription in plants. The overexpression of SlWRKY8 in tomato conferred a greater resistance to the pathogen Pst. DC3000 and resulted in the increased transcription levels of two pathogen‐related genes SlPR1a1 and SlPR7. Moreover, transgenic plants displayed the alleviated wilting or chlorosis phenotype under drought and salt stresses, with higher levels of stress‐induced osmotic substances like proline and higher transcript levels of the stress‐responsive genes SlAREB, SlDREB2A and SlRD29. Stomatal aperature was smaller under drought stress in transgenic plants, maintaining higher water content in leaves compared with wild‐type plants. The oxidative pressure, indicated by the concentration of hydrogen peroxide (H2O2) and malondialdehyde (MDA), was also reduced in transgenic plants, where we also observed higher levels of antioxidant enzyme activities under stress. Overall, our results suggest that SlWRKY8 functions as a positive regulator in plant immunity against pathogen infection as well as in plant responses to drought and salt stresses.
During recent years, China has become a hotspot for the domestication of mandarin fish, and this is of great commercial value. Although the food preference of domesticated mandarin fish has been ...studied, little is known about genes regulating their growth. We raised hybrid mandarin fish on artificial feed for 3 months, the results showed that the survival rate of hybrid mandarin fish was 60.00%. Their total length and body weight were 18.34 ±0.43 cm and 100.44 ±4.87 g. The absolute length and weight gain rates were 0.14 cm/d and 1.08 g/d, respectively. Finally, RNA sequencing (RNA-Seq) was performed to identify potential genes and pathways activated in response to growth performance. The transcriptome analysis generated 68, 197 transcripts and 45,871 unigenes. Among them, 1025 genes were up-regulated and 593 genes were down-regulated between the fast- and slow-growth fish. Finally, we obtained 32 differentially expressed genes, which were mainly related to fatty acid biosynthesis (e.g. FASN and ACACB), collecting duct acid secretion (e.g. ATP6E and KCC4), cell cycle (e.g. CDC20 and CCNB), and the insulin-like growth factor (IGF) system (IGFBP1). These pathways might be related to the growth of hybrid mandarin fish. In addition, more potential single nucleotide polymorphisms (SNPs) were detected in the fast-growth fish than in the slow-growth fish. The results suggest that the interaction of metabolism and abundant alleles might determine the growth of hybrid mandarin fish after food conversion.
The 16-day revisit cycle of Landsat has long limited its use for studying global biophysical processes, which evolve rapidly during the growing season. In cloudy areas of the Earth, the problem is ...compounded, and researchers are fortunate to get two to three clear images per year. At the same time, the coarse resolution of sensors such as the Advanced Very High Resolution Radiometer and Moderate Resolution Imaging Spectroradiometer (MODIS) limits the sensors' ability to quantify biophysical processes in heterogeneous landscapes. In this paper, the authors present a new spatial and temporal adaptive reflectance fusion model (STARFM) algorithm to blend Landsat and MODIS surface reflectance. Using this approach, high-frequency temporal information from MODIS and high-resolution spatial information from Landsat can be blended for applications that require high resolution in both time and space. The MODIS daily 500-m surface reflectance and the 16-day repeat cycle Landsat Enhanced Thematic Mapper Plus (ETM+) 30-m surface reflectance are used to produce a synthetic "daily" surface reflectance product at ETM+ spatial resolution. The authors present results both with simulated (model) data and actual Landsat/MODIS acquisitions. In general, the STARFM accurately predicts surface reflectance at an effective resolution close to that of the ETM+. However, the performance depends on the characteristic patch size of the landscape and degrades somewhat when used on extremely heterogeneous fine-grained landscapes
In this technical note, the problem of adaptive tracking control is investigated for a class of stochastic uncertain nonlinear systems in the presence of input saturation. To analyze the effect of ...input saturation, an auxiliary system is employed. With the help of backstepping technique, an adaptive stochastic tracking control approach is developed. Under the proposed adaptive tracking controller, the boundedness of all the signals in the closed-loop system is achieved almost surely. Moreover, distinct from most of the existing results, the ultimate tracking error can be bounded by an explicit function of design parameters and input saturation error (the error between the control input and saturated input) in the mean quartic sense. Finally, an example is given to show the effectiveness of the proposed scheme.
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