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Hydrogen (H2) is deemed one of the prominent energy solutions of the 21st century due to the significant scientific and technological efforts devoted to the realization of a renewable carbon-free H2-based economy. The generation of highly efficient clean H2 fuel from the electrocatalysis of earth-abundant water is one of the key aspects of sustainable clean energy technologies. Traditionally, Pt-based catalysts have demonstrated an efficient hydrogen evolution reaction (HER), but their scarcity and high cost hinder their commercial applications. Herein, we demonstrate a facile synthesis of the MnCo2S4 nanosheet catalyst that was successfully transformed from MnCo2O4 through an anion-exchange reaction. The electrochemical performance of MnCo2S4 is considerably superior compared to that of MnCo2O4, demonstrating low overpotentials of −111 and −233 mV (1 M KOH) and −124 and −323 mV (0.5 M H2SO4) at current densities of 10 and 500 mA cm−2, respectively, with a moderate Tafel slope of 63 mV dec−1. The optimized catalyst showed excellent sustainability for an ultralong H2 evolution up to 50 h at 10 and 100 mA cm−2 in both media and an admirable endurance in a voltage-step response at various current rates (10 to 100 mA cm−2). The post-stability XPS reveals the partial alteration of cobalt into a metallic state on the catalyst surface without a significant change in the surface topography. The outstanding HER performance is credited to the increased number of electrochemically active sites and enhanced electronic conductivity resulting from the conversion of the oxide phase into a sulfide phase through anion exchange. [ABSTRACT FROM AUTHOR]

Water electrolysis is a highly efficient route to produce ideally clean H2 fuel with excellent energy conversion efficiency and high gravimetric energy density, without producing carbon traces, unlike steam methane reforming, and it resolves the issues of environmental contamination via replacing the conventional fossil fuel. Particular importance lies in the advancement of highly effective non-precious catalysts for the oxygen evolution reaction (OER). The electrocatalytic activity of an active catalyst mainly depends on the material conductivity, accessible catalytically active sites, and intrinsic OER reaction kinetics, which can be tuned via introducing N heteroatoms in the catalyst structure. Herein, the efficacious nitrogenation of CuS was accomplished, synthesized using a hydrothermal procedure, and characterized for its electrocatalytic activity towards OER. The nitrogen-doped CuO@CuS (N,CuO@CuS) electrocatalyst exhibited superior OER activity compared to pristine CuS (268 and 602 mV), achieving a low overpotential of 240 and 392 mV at a current density of 10 and 100 mA/cm2, respectively, ascribed to the favorable electronic structural modification triggered by nitrogen incorporation. The N,CuO@CuS also exhibits excellent endurance under varied current rates and a static potential response over 25 h with stability measured at 10 and 100 mA/cm2. [ABSTRACT FROM AUTHOR]

The applications of organic fertilizers releasing nutrients slowly not only have a direct impact on the growing crop, but also, residual effects on the subsequent crops in the conventional crop cultivation systems. Studies on the residual effects of organic fertilizer in soilless crop cultivation are quite rare. The present study, which is a pot experiment conducted in a greenhouse, describes the dynamics of yield and chlorophyll content of kangkong as direct and residual effects of vermicompost for four consecutive plantings in soilless crop cultivation, further, compared with inorganic fertilizer treatment. The experimental design used was a randomized complete block design with different levels of vermicompost rates and a control treatment using inorganic fertilizer. The vermicompost was applied only in the first crop, while, inorganic fertilizer was supplemented in each crop. Fresh weight per plant per pot increases ~35 - 54% at the second planting compared with the first planting, thereafter, gradually decreases in subsequent planting. The content of chlorophyll A was found to be relatively constant, while the chlorophyll B content was highest in the first planting and, thereafter, subsequently decreased in further planting. The higher yields were found at 400 - 500 g pot-1 vermicompost fertilizer dose, insignificantly different from the inorganic fertilizers treatment. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) is a significant greenhouse gas (GHG) accounting for 60% of the total greenhouse effect. Soil respiration is a measure of the CO2 released from soil. Rice was the largest contributing plant commodity of total emission by 12%. In the event of growing threats of global warming due to GHG emissions, reducing CO2 emission by sequestering C in the soil is of supreme concernment. Improved management practices can rebuild C stocks in agricultural soils and help mitigate CO2 emissions. A field study to assess how organic soil amendments influence soil respiration, C-organic content, and soil properties was conducted in upland paddy field. Treatments were: chemical fertilizer (F1), combination of chemical fertilizer and cow dung manure (F2), chemical fertilizer and vermicompost (F3), chemical fertilizer and liquid vermicompost powder (F4), cow dung manure+biochar (F5), vermicompost+biochar (F6) and liquid vermicompost powder+biochar (F7). All treatments tested almost had the same pattern of respiration rates starting before the application of the organic soil amendment until three months after planting. The highest respiration rate was found at 1 month after planting. Soil amendment (F4 and F7) had the lowest soil respiration rates in some measurements. The highest organic C content at three months after planting was found in the F6 and F3 treatments. The most influential factor on the respiration rate are soil moisture content and soil temperature. The results demonstrate the viability of vermicompost either in combination with chemical fertilizers or alone for soil amendment to maintain organic soil carbon for short period of time (～ 3 months). [ABSTRACT FROM AUTHOR]

Summary: Replacing oxygen in an oxide‐based material with sulfur can produce improved flexibility and more efficient electron transport in its structure leading to enhanced electrical performance. Herein, facile template‐free growth of free‐standing cobalt (II, III) oxide (Co3O4) on Ni foam via a mild hydrothermal technique followed by its transformation to cobalt (II, III) sulfide (Co3S4) via an ion‐exchange is reported. The microstructural morphology, phase, and porosity of the prepared Co3O4 and Co3S4 are characterized by FESEM, XRD, Raman, XPS, TEM, and BET analyses. The electrochemical performance of the Co3S4 film with a microporous morphology is considerably superior to that of Co3O4, exhibiting a high specific capacitance of 1604 F g−1 (905 F g−1 for Co3O4), the excellent restorative ability of ~99% at 1 A g−1 (~96% for Co3O4), and good retention of 98% at 10 A g−1 (~70% for Co3O4). The Co3S4 electrode shows excellent capacitance endurance even after 10 000 charge/discharge cycles and a high energy density of 128.32 Wh kg−1 at 0.72 kW kg−1. A fabricated symmetric Co3S4 supercapacitor device also reveals superior charge/discharge, restorative, and retention performances compared to a Co3O4 one. The excellent supercapacitive performance of phase‐transformed Co3S4 electrode is due its large electrochemically active surface area along with synergetic effect of small charge transfer resistance and high relative diffusion coefficient. [ABSTRACT FROM AUTHOR]

Due to their atomic thicknesses and semiconducting properties, two-dimensional transition metal dichalcogenides (TMDCs) are gaining increasing research interest. Among them, Hf- and Zr-based TMDCs demonstrate the unique advantage that their oxides (HfO 2 and ZrO 2 ) are excellent dielectric materials. One possible method to precisely tune the material properties of two-dimensional atomically thin nanomaterials is to adsorb molecules on their surfaces as non-bonded dopants. In the present work, the molecular adsorption of NO 2 and NH 3 on the two-dimensional trigonal prismatic (1H) and octahedral (1T) phases of Hf and Zr dichalcogenides (S, Se, Te) is studied using dispersion-corrected periodic density functional theory (DFT) calculations. The adsorption configuration, energy, and charge-transfer properties during molecular adsorption are investigated. In addition, the effects of the molecular dopants (NH 3 and NO 2 ) on the electronic structure of the materials are studied. It was observed that the adsorbed NH 3 donates electrons to the conduction band of the Hf (Zr) dichalcogenides, while NO 2 receives electrons from the valance band. Furthermore, the NO 2 dopant affects than NH 3 significantly. The resulting band structure of the molecularly doped Zr and Hf dichalcogenides are modulated by the molecular adsorbates. This study explores, not only the properties of the two-dimensional 1H and 1T phases of Hf and Zr dichalcogenides (S, Se, Te), but also tunes their electronic properties by adsorbing non-bonded dopants.