RESUMEN
Seeking highly efficient non-preference electrocatalytic materials that serve photoelectrochemical (PEC) water splitting in acidic systems is expectant in the context of environmentally friendly production. We designed Ni2P electrocatalysts synthesized in oil phases via the hot-bubbling method with superb stability in air and sulfuric acid solution for PEC, which were found with excellent hydrogen evolution performance. A tunable particle size and highly exposed (001) planes of Ni2P nanocrystals were achieved. The designed catalysts achieved a notable promotion in the hydrogen evolution reaction activity compared to that of Ni2P synthesized in the water phase. More specifically, the electrode prepared by self-assembled Ni2P nanoparticles was found to have decent over-potential of η10 = 164 mV in darkness and was further decreased to 129 mV with irradiation of visible light. The cyclic stability tests manifested brilliant durability in 0.5 M H2SO4. Measurement of the transient photocurrent response and PEC water splitting catalytic performance indicated that the Ni2P had high carrier concentration upon irradiation, lower carrier recombination probability, and prolonged photo-response lifetime (3.03-3.14 s).
RESUMEN
Metal organic framework, a novel class of organic inorganic hybrid functional materials, has been widely used in the fields of gas adsorption, catalysis, separation, and biological medicine due to its large specific surface area, diverse structural, and adjustable channel. In this work, a new amine-functionalized magnetic metal-organic framework material was synthesized. Nano-Fe3O4 was prepared by a solvothermal method, after which polyvinyl pyrrolidone was employed to modify Fe3O4. Finally, amino groups were introduced to prepare Fe3O4@NH2-MIL-53(Al). The crystal structure and functional groups of the material were characterized by means of X-ray diffraction (XRD) and Fourier transform infrared spectrometry (FT-IR). Combined with flame atomic absorption spectroscopy (FAAS), the adsorption of lead by the magnetic adsorbent was investigated. The magnetic adsorbent possesses high adsorption capacity because of the large specific surface area of Fe3O4@NH2-MIL-53(Al) and the coordination between amino group and lead. Experimental conditions affecting the adsorption percentage were discussed and the experimental operation parameters were optimized (pH value of 6.0 and adsorption time of 120 min). Kinetics and thermodynamics studies were conducted for the adsorption process. Langmuir/Freundlich and pseudo-first-order/pseudo-second-order models were applied to analyze the experimental data. Thermodynamic functions, i. e., changes of Gibbs energy, entropy, and enthalpy, were calculated from temperature experiments. In addition, the regeneration of the adsorbent was considered with hydrochloric acid as the desorption solution. Several adsorption and desorption experiments were carried out, illustrating that the Fe3O4@NH2-MIL-53(Al) adsorbent can be used repeatedly.
RESUMEN
A type of highly stable and recyclable clay-based composite was developed for sequestration of CO2, which was synthesized by loading melamine (MEL) onto attapulgite (ATT) via a wet impregnation method. The synthesized materials were characterized by N2 adsorption-desorption, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TG), and transmission electron microscopy (TEM). By means of thermal and acidic treatments more active sites of ATT were exposed, and large surface areas were obtained. The MEL molecules were well combined with those exposed sites, which enhanced stability and cyclability for CO2 sequestration. On the basis of CO2 adsorption-desorption measurements, the composite of ATT-MEL was found to have a higher CO2 adsorption capacity (4.91 cm3/g) which was much higher than that of CO2 absorption on bare MEL (1.30 cm3/g) at 30 °C. After ten cycles of reusing, the composite exhibited even higher capacity for CO2 adsorption by an increased percentage of 5.91% (30 °C) and 5.77% (70 °C) compared to the capacity in the first cycle. The reason lies in the strong interaction between melamine and attapulgite matrix which was further confirmed by DFT calculations. The MEL was validated to have advantages over aliphatic amines (TEPA) in modifying ATT to get high stability of CO2-adsorbents.
RESUMEN
Although the surface organic modification of smectite has been investigated widely, the swelling behavior of clays has been scarcely studied with consideration of civil engineering applications. In this work a facile strategy of liquid-immersion (dilute H2SO4 aqeuous solution) was proposed, and the 3-aminopropyltrimethoxysilane (APS) was utilized as surface modifier to suppress expansibility of black cotton soil (BCS) which is a type of highly swelling soils in tropical areas. Factors such as the incorporation dosage of APS, surface characters of soil treated by solution of H2SO4 or Na2CO3, and reaction temperatures/time were investigated to get lower swelling ratios. The treatment of BCS by H2SO4 was found more effective in immobilizing APS molecules, and hydronium ions were suppressed after the APS modification. The free swelling index (FSI) of BCS was decreased from 120% to 15% after treatment with H2SO4 and appropriate amount of APS modification. The reaction can be completed within several hours at the room temperature to ~80 °C. The soil samples were characterized by different means including the X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscope, thermogravimetric analysis and Zeta potential measurements. The APS molecules were found to react with -OH groups of the clay, and the hydrophobic groups provide surface hydrophobicity, which prevents hydration of cations within clay minerals. The APS was indicated to re-constructed lamellar structures of smectites after H2SO4 treatment, which suppressed the intra-crystalline and the subsequent osmotic swelling. This research highlights the liquid immersion and surface modification is applicable in diminishing swelling ratios of highly expansive black cotton soil.