No abstract

MnO 2 with different crystallographic forms (R, γ) and morphologies (needles, rods, and spindles) was fabricated via a facile quick-precipitation procedure at a low temperature (about 83 °C) without using any templates or surfactants. The proposed mechanism is focused on the different reaction parameters that affect the behaviors of MnO 6 octahedron units (basic structural framework of MnO 2 ), which then exert an influence on the formation and stack of nuclei in the crystal growth process. Specific capacitances (C s ) calculated according to the area of the cyclic voltammograms (CV) curves were 233.5, 83.1 F 3 g -1 for the needle-and 95.5, 29.3 F 3 g -1 for the spindle-like products at the scan rate of 5, 100 mV 3 s -1 , respectively. The C s of needle-like samples calculated by discharge curves at the current density of 2 mA 3 cm 2 is 209.8 F 3 g -1 , close to the value calculated by CV curves at the scan rate of 5 mV 3 s -1 . This methodology facilitates us to synthesize MnO 2 with discrepant one-dimensional (1D) nanostructures via a quick, simple, and mild route and may be readily extended to the preparation of many other oxide nanoparticles.

No abstract

No abstract

A series of bamboo-like CN(x)() nanotubes have been synthesized from pyridine precursor by chemical vapor deposition with bimetallic Fe-Co/gamma-Al(2)O(3) catalyst in the range of 550 approximately 950 degrees C. An unusual predomination of pyridinic nitrogen over graphitic nitrogen has been observed for the CN(x)() nanotubes with reaction temperature below 750 degrees C. The pyridinic nitrogen decreases and the graphitic nitrogen increases with rising reaction temperature. A synergism mechanism of C(5)N-six-membered-ring-based growth through surface diffusion and vapor-liquid-solid growth through bulk diffusion was accordingly deduced and schematically presented. This mechanism could not only explain our own experimental results, but also understand the CN(x)()-nanotube-related experimental phenomena in the literature, as well as be in accordance with the basic principle of diffusion kinetics. A promising route to the challenging topic for synthesizing regularly arranged C(5)N or high-N-content CN(x)() nanotubes has also been suggested.

No abstract

Artificial photosynthesis, light-driving CO2 conversion into hydrocarbon fuels, is a promising strategy to synchronously overcome global warming and energy-supply issues. The quaternary AgInP2S6 atomic layer with the thickness of ~ 0.70 nm were successfully synthesized through facile ultrasonic exfoliation of the corresponding bulk crystal. The sulfur defect engineering on this atomic layer through a H2O2 etching treatment can excitingly change the CO2 photoreduction reaction pathway to steer dominant generation of ethene with the yield-based selectivity reaching ~73% and the electron-based selectivity as high as ~89%. Both DFT calculation and in-situ FTIR spectra demonstrate that as the introduction of S vacancies in AgInP2S6 causes the charge accumulation on the Ag atoms near the S vacancies, the exposed Ag sites can thus effectively capture the forming *CO molecules. It makes the catalyst surface enrich with key reaction intermediates to lower the C-C binding coupling barrier, which facilitates the production of ethene.

Photochemical conversion of CO2 into high-value C2+ products is difficult to achieve due to the energetic and mechanistic challenges in forming multiple C-C bonds. Herein, an efficient photocatalyst for the conversion of CO2 into C3H8 is prepared by implanting Cu single atoms on Ti0.91O2 atomically-thin single layers. Cu single atoms promote the formation of neighbouring oxygen vacancies (VOs) in Ti0.91O2 matrix. These oxygen vacancies modulate the electronic coupling interaction between Cu atoms and adjacent Ti atoms to form a unique Cu-Ti-VO unit in Ti0.91O2 matrix. A high electron-based selectivity of 64.8% for C3H8 (product-based selectivity of 32.4%), and 86.2% for total C2+ hydrocarbons (product-based selectivity of 50.2%) are achieved. Theoretical calculations suggest that Cu-Ti-VO unit may stabilize the key *CHOCO and *CH2OCOCO intermediates and reduce their energy levels, tuning both C1-C1 and C1-C2 couplings into thermodynamically-favourable exothermal processes. Tandem catalysis mechanism and potential reaction pathway are tentatively proposed for C3H8 formation, involving an overall (20e− – 20H+) reduction and coupling of three CO2 molecules at room temperature.