In Situ Preparation of Mo₂C Nanoparticles Embedded in Ketjenblack Carbon as Highly Efficient Electrocatalysts for Hydrogen Evolution

Recently, to enhance the catalytic activity of molybdenum carbide (Mo₂C) electrocatalysts for the hydrogen evolution reaction (HER), the conductive carbon-based materials with different structures have been used to support Mo₂C particles for providing sufficient catalytic hydrogen production sites. Nevertheless, it is always hard to use a simple method to ensure both uniform distribution of Mo₂C particles and good charge transfer between Mo₂C and carbon matrix. Herein, we used a low-cost carbonaceous material as ingredient via a facile method of in situ carbonization to design the structure of Mo₂C nanoparticles embedded in chainlike Ketjenblack carbon (KB) with strong chemical link, to achieve the Mo₂C/KB hybrid catalyst with uniform distribution of active Mo₂C nanocrystals on KB for high density of catalytic sites and excellent charge-transfer ability. Moreover, the effects of carbonization temperature and carbon content on the HER activity were investigated to optimize the Mo₂C/KB catalyst. The optimized Mo₂C/KB catalyst exhibits outstanding HER activity in both acidic and alkaline media with small Tafel slopes of 49 and 48 mV dec^–1, low overpotentials, and remarkable stability. The enhanced HER activity of Mo₂C/KB catalyst could be ascribed to its unique chainlike structure with a large specific surface area of 580.3 m² g^–1, the high electronic conductivity, and active Mo₂C nanocrystals protected by robust carbon matrix

Swollen Ammoniated MoS₂ with 1T/2H Hybrid Phases for High-Rate Electrochemical Energy Storage

Because of its lamellar structure similar to that of graphite, molybdenum disulfide has been widely explored as a lithium-ion battery and supercapacitor electrode material, but its energy storage ability is strongly hindered by the poor electrical/ionic conductivity and transfer among the intrinsic lamellar structures. Herein we propose a novel swollen ammoniated MoS₂ with 1T/2H hybrid phases (MoS₂-A), which possesses a high concentration of 1T phase and unique expanded lamellar structures, as a supercapacitor electrode material. The obtained MoS₂-A reveals superior charge-storage performance with distinct pseudocapacitive behavior, including surface redox reaction and diffusive intercalation, and even when the scan speed is increased 100-fold from 1 to 100 mV s^–1, the retention ratio of the specific capacitance can still reach 58.5%, demonstrating a superhigh rate capability. Moreover, this supercapacitor electrode also exhibits good cycling stability with a retention ratio of 95.4% after 2000 cycles. The outstanding electrochemical performance of MoS₂-A should be ascribed to the existence of the metallic 1T phase, which favors high electrical conductivity, and the swollen lamellar structures possessing an enlarged interlayer space of 0.99 nm created by in situ intercalated species, facilitating the fast and reversible diffusive intercalation of electrolyte ions

Sulfur-Decorated Molybdenum Carbide Catalysts for Enhanced Hydrogen Evolution

A highly active and stable electrocatalyst (MoS_<i>x</i>@Mo₂C) for hydrogen evolution is developed via the sulfur decoration of molybdenum carbide for the first time. Although the decoration of sulfur reduced the electrochemically active surface area and slightly enlarged the impedance resistance of Mo₂C substrates, the turnover frequency was remarkably enhanced, resulting in a great improvement in the final hydrogen evolution reaction activity. More importantly, there is a synergistic effect between MoS_<i>x</i> and Mo₂C, making the MoS_<i>x</i>@Mo₂C catalyst exhibit an excellent activity with a small Tafel slope of 44 mV dec^–1, which is among the best records for Mo₂C-based catalysts

Deactivation Mechanism of Potassium on the V₂O₅/CeO₂ Catalysts for SCR Reaction: Acidity, Reducibility and Adsorbed-NO_<i>x</i>

A series of V₂O₅/CeO₂ catalysts with different potassium loadings were prepared to investigate alkali deactivations for selective catalytic reduction of NO_<i>x</i> with NH₃. An alkali poisoning mechanism could be attributed to surface acidity, reducibility, and NO_<i>x</i> adsorption/desorption behaviors. The detailed factors are as follows: (1) decrease of surface acidity suppresses NH₃ adsorption by strong bonding of alkali to vanadia (major factor); (2) low reducibility prohibits NH₃ activation and NO oxidation by formation bonding of alkali to vanadia and ceria (important factor); (3) active NO_<i>x</i>^– species at low temperature diminish because of coverage of alkali on the surfaces (minor factor); and (4) stable, inactive nitrate species at high temperature increase by generating new basic sites (important factor)

Reduced bone length, growth plate thickness, bone content, and IGF-I as a model for poor growth in the CFTR-deficient rat

<div><p>Background</p><p>Reduced growth and osteopenia are common in individuals with cystic fibrosis (CF). Additionally, improved weight and height are associated with better lung function and overall health in the disease. Mechanisms for this reduction in growth are not understood. We utilized a new CFTR knockout rat to evaluate growth in young CF animals, via femur length, microarchitecture of bone and growth plate, as well as serum IGF-I concentrations.</p><p>Methods</p><p>Femur length was measured in wild-type (WT) and SD-<i>CFTR</i>^{<i>tm1sage</i>} (<i>Cftr-/-</i>) rats, as a surrogate marker for growth. Quantitative bone parameters in <i>Cftr-/-</i> and WT rats were measured by micro computed tomography (micro-CT). Bone histomorphometry and cartilaginous growth plates were analyzed. Serum IGF-I concentrations were also compared.</p><p>Results</p><p>Femur length was reduced in both <i>Cftr-/-</i> male and female rats compared to WT. Multiple parameters of bone microarchitecture (of both trabecular and cortical bone) were adversely affected in <i>Cftr-/-</i> rats. There was a reduction in overall growth plate thichkness in both male and female <i>Cftr-/-</i> rats, as well as hypertrophic zone thickness and mean hypertrophic cell volume in male rats, indicating abnormal growth characteristics at the plate. Serum IGF-I concentrations were severely reduced in <i>Cftr-/-</i> rats compared to WT littermates.</p><p>Conclusions</p><p>Despite absence of overt lung or pancreatic disease, reduced growth and bone content were readily detected in young <i>Cftr-/-</i> rats. Reduced size of the growth plate and decreased IGF-I concentrations suggest the mechanistic basis for this phenotype. These findings appear to be intrinsic to the CFTR deficient state and independent of significant clinical confounders, providing substantive evidence for the importance of CFTR on maintinaing normal bone growth.</p></div

Micro CT of femurs.

<p>Micro CT of femurs.</p

<i>Cftr</i>-/- rats have reduced size and femur length.

<p><b>(</b>A) <i>Cftr-/-</i> rats are notably smaller in size compared to their wild type (WT) littermates. Animal total body weights are demonstrated versus age of the animals in <i>Cftr-/-</i> rats (•) compared to WT rats (▯). These findings are consistent with previously published data by Tuggle et al [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188497#pone.0188497.ref013" target="_blank">13</a>]. (B) Excised femurs obtained at sacrifice were measured by digital calipers. Femur length is reduced in <i>Cftr-/-</i> rats (•) compared to WT rats (▯) regardless of age or gender (p<0.0001).</p

Micro CT imaging demonstrates reduced bone content.

<p>Representative 3D micro CT images of cortical and trabecular bone structures from young <i>Cftr-/-</i> and WT rats. MicroCT images demonstrate reduced bone content in <i>Cftr-/-</i> rats (more predominantly in females and detailed in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188497#pone.0188497.t001" target="_blank">Table 1</a>). MicroCT images obtained from 38 day old WT and 42 day old <i>Cftr-/-</i> male rats. Female rat microCT images are from 42 day old <i>Cftr-/-</i> and WT rats. MicroCT images are from the male and female rat femurs pictured in histology images (Figs <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188497#pone.0188497.g003" target="_blank">3</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188497#pone.0188497.g004" target="_blank">4</a>).</p

Femur histomorphometry.

<p>Femur histomorphometry.</p

Cartilaginous growth plate analysis.

<p>Cartilaginous growth plates were evaluated based on overall growth plate thickness, average proliferating zone thickness, average number of proliferating cells/column, average hypertropic zone thickness, mean volume of hypertrophic cells, and mean hypertrophic cell volume standard deviation. Pictured growth plates are from the rats included in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188497#pone.0188497.g003" target="_blank">Fig 3</a> (as well as microCT images in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0188497#pone.0188497.g002" target="_blank">Fig 2</a>). They include 38 day old WT (A) and 42 day old <i>Cftr-/-</i> (C) male rats. Female bone images are from 42 day old <i>Cftr-/-</i> (B) and WT (D) rats. Each larger image is at 2X, with inserts demonstrating areas of measurement at 20X. Green outlined cells represent the proliferative zone and blue outlined cells are the hypertrophic zone. Both male and female <i>Cftr-/-</i> rats demonstrated a reduction in overall growth plate thickness (43% reduction in males and 35% in females). However, in males there was also a reduction in the hypertrophic zone thickness, mean volume of hypertrophic cells and hypertrophic cell volume standard deviation in the <i>Cftr-/-</i> rats, but not in the proliferative zone thickness or average number of proliferating cells/column. These findings are suggestive of a difference in the maturation from the proliferative zone into the hypertrophic zone, or differences in cellular activity of the hypertrophic zone, between the <i>Cftr-/-</i> and the WT rats.</p