ABSTRACT
The confirmation and regulation of active sites are particularly critical for the design of methanol oxidation reaction (MOR) catalysts. Here, an acid etching method for facet control combined with defect construction was utilized to synthesize Co3O4 nanoparticles on nickel foam for preferentially exposing the (311) facet with enriched oxygen vacancies (VO). The acid-leached oxides exhibited superior MOR activity with a mass activity of 710.94 mA mg-1 and an area-specific activity of 3.390 mA cm-2 as a result of (i) abundant active sites for MOR promoted by VO along with the highly active (311) facet being exposed and (ii) phase purification-reduced adsorption energy (Eads) of methanol molecules. Ex situ X-ray photoelectron spectroscopy proved that highly active CoOOH obtained via the activation of plentiful Co2+ effectively improved the MOR. Density functional theory calculations confirmed that the selective exposed (311) facet has the lowest Eads for CH3OH molecules. This work puts forward acid etching as the facet modification and defect engineer for nanostructured non-noble catalysts, which is expected to result in superior electrochemical performance required for advanced alkaline direct methanol fuel cells.
ABSTRACT
OBJECTIVE: Astaxanthin is a natural super antioxidant. The present study was carried out to investigate the effect of astaxanthin rich Phaffia rhodozyma (PR) supplementation in diets on laying production performance, egg quality, antioxidant defenses and immune defenses in laying hens. METHODS: A total of five hundred and twelve 60-week-old Lohmann Brown laying hens (2,243±12 g) were randomly assigned to four groups, each including 4 replicates with 32 birds per replicate. Astaxanthin rich PR was added to corn-soybean meal diets to produce experimental diets containing 0 (Control), 800 mg/kg, 1,200 mg/kg, and 1,600 mg/kg PR, respectively. The astaxanthin content in the diet was 0.96 mg/kg, 1.44 mg/kg and 1.92 mg/kg respectively. RESULTS: Results showed that dietary PR supplementation tended to increase daily feed intake (p = 0.0512). There was no effect of astaxanthin rich PR on Haugh units, albumen height, egg shape index, eggshell strength, and eggshell thickness at weeks 6 (p>0.05). However, egg yolk color was significantly improved (p<0.05). In addition, astaxanthin rich PR supplementation significantly increased serum glutathione peroxidase and superoxide dismutase activity (p<0.05), increased serum immunoglobulin G content (p<0.05), and reduced malondialdehyde content (p<0.05) in laying hens. CONCLUSION: In conclusion, astaxanthin rich PR can improve the color of egg yolk, enhance the antioxidant defenses, and regulate the immune function.
ABSTRACT
Developing highly effective and inexpensive electrocatalysts for hydrogen evolution reaction (HER), particularly in a water-alkaline electrolyzer, are crucial to large-scale industrialization. The earth-abundant molybdenum disulfide (MoS2) is an ideal electrocatalyst in acidic media but suffers from a high overpotential in alkaline solution. Herein, nanospherical heterostructure Ni3S4-MoS2 was obtained via a one-pot synthesis method, in which Ni3S4 was uniformly integrated with MoS2 ultrathin nanosheets. There were abundant heterojunctions in the as-synthesized catalyst, which were verified by X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The structure features with interfacial electron redistribution was proved by XPS and density functional theory (DFT) calculations, which offered several advantages to promote the HER activity of MoS2, including increased specific surface area, exposed abundant active edge sites and improved electron transfer. Ni3S4-MoS2 exhibited a low overpotential of 116 mV at 10 mA cm-2 in an alkaline solution with a corresponding Tafel slope of 81 mV dec-1 and long-term stability of over 20 h. DFT simulations indicated that the synergistic effects in the system with the chemisorption of H on the (002) plane of MoS2 and OH on the (311) plane of Ni3S4 accelerated the rate-determining water dissociation steps of HER. This study provides a valuable route for the design and synthesis of inexpensive and efficient HER electrocatalyst, heterostructure Ni3S4-MoS2.
ABSTRACT
The performances of pseudocapacitors usually depend heavily on their hierarchical architectures and composition. Herein, we report a three-dimensional hierarchical NiAl layered double hydroxide/multiwalled carbon nanotube/nickel foam (NiAl-LDH/MWCNT/NF) electrode prepared by a facile three-step fabrication method: in situ hydrothermal growth of NiAl-LDH film on a Ni foam, followed by direct chemical vapor deposition growth of dense MWCNTs onto the NiAl-LDH film, and finally the growth of NiAl-LDH onto the surface of the MWCNTs via an in situ hydrothermal process in the presence of surfactant sodium dodecyl sulfate. The MWCNT surface was fully covered by NiAl-LDH hexagonal platelets, and this hierarchical architecture led to a much enhanced capacitance. The NiAl-LDH/MWCNT/NF electrode has an areal loading mass of 5.8 mg of LDH per cm(2) of MWCNT/NF surface. It also possesses exceptional areal capacitance (7.5 F cm(-2)), specific capacitance (1293 F g(-1)), and cycling stability (83% of its initial value was preserved after 1000 charge-discharge cycles). The NiAl-LDH/MWCNT/NF material is thus a highly promising electrode with potential applications in electrochemical energy storage.
