• Energy Research

Nanocomposites consisting of paraffin/graphene nanoplatelets mix embedded in carbon foams via vacuum infiltration were fabricated with the aim of developing new phase change material (PCM) formulation with excellent shape stabilization, improved thermal conductivity and outstanding thermal reliability and structural stability. Physicochemical and thermal properties of the nanocomposites were evaluated using a suite of techniques such as scanning and transmission electron microscopy, X-ray diffraction, attenuated total reflection - Fourier transform infrared spectroscopy, nitrogen adsorption analyzer, differential scanning calorimetry, mechanical tester, Raman spectroscopy, thermal conductivity analyzer and thermogravimetric analyzer. The carbon foams exhibited good cyclic compressive behavior at a strain of up to 95% and kept part of their elastic properties after cyclic testing. Due to the robust mechanical integrity and layered meso-/macroporous morphology of these carbon foams, the nanocomposites are well equipped to cope with volume changes without leaking during thermal cycling. A 141% thermal conductivity enhancement observed for the carbon foam nanocomposite demonstrates the contributing role of the carbon foam in creating effective heat transfer through its conductive 3D network. The results have shown that proper chemical modification and subsequent carbonization of the low cost porous foams can lead to ultralight multifunctional materials with high mechanical and physical properties suitable for thermal energy storage applications.

Pavlova microalga was pyrolysed in presence of titania based catalysts in a fixed bed reactor at various temperatures. The effects of catalysts on Pavlova microalga pyrolysis were investigated. A large fraction of the starting energy (∼ 63–74% daf) was recovered in the bio-oils when the catalysts were used. The bio-oil yield was 20% higher in presence of Ni/TiO2 (22.55 wt%) at 500 °C. The High Heating Values of the produced bio-oils were in the range of ∼ 35–37 MJ/kg and suffered strong deoxygenation, with O content (% daf) diminished from 51 wt% to ∼ 9–12 wt%. The 1H Nuclear Magnetic Resounance and Gas Chromatography Mass Spectrometry suggested that the titania catalysts enlarged the aliphatics and aromatic compounds and decreased oxygenates in the bio-oils. Ni/TiO2 had the greatest activity in increasing aliphatic protons (60%) and decreasing coke formation. Its enhanced cracking activity was due to its higher availability on the catalyst surface, compared to Co and Ce, and to strong interaction between Ni and TiO2 support. Despite the fact that the bio-oils were partially de-nitrogenated, the N-content still represent a major limitation for their use as bio-fuels without further upgrading.

Abstract As a promising way to control greenhouse gas emission and alleviate global energy shortage, photocatalytic reduction of carbon dioxide attracts more attentions in recent years since it can produce fuels efficiently with the combination of H 2 through water splitting. In this work, a computational model which characterizes the photocatalytic reduction of carbon dioxide by CO co-feed in a novel twin reactor is developed with three subsidiaries of chemical reaction kinetics, gas–liquid mass transfer, and transient sun light intensity distribution. Thanks to previous experimental work as the reliable verification for the numerical simulation, the variations of the CH 3 OH concentration with the CO/CO 2 ratio of gas mixture, pressure and temperature are obtained and analyzed. The results show that the carbon in CO can form CH 3 OH directly, however the excessive CO will react with HCOOCH 3 to form CH 3 CHO, which results in a reduced CH 3 OH concentration. Besides, the CH 3 OH concentration subsequently increases as the temperature and pressure increase, and the CH 3 OH product and reaction rate vary widely with time due to the changing sun light intensity during the day.

Photocatalytic reduction of carbon dioxide to produce methanol is a promising approach to restrain greenhouse gases emissions and mitigate energy shortage, which attracts extensive concerns in recent years. The optical fiber monolith reactor with solid glass balls for photocatalytic carbon dioxide reduction is proposed in this work to increase the product concentration, and the glass balls are transparent and coated with photocatalysts evenly to absorb light. The photocatalytic reduction of carbon dioxide in optical fiber monolith reactor is numerically investigated, by which the effects of glass ball number, location, circle and layer on the production are analyzed. The results show that in the single-circle and single-layer model, the outlet methanol concentration increases with increasing the ball number. The closer to the fiber and reactor inlet the balls keep, the higher the methanol production is. As the circle and layer numbers increase, the methanol concentration also increases. The outlet methanol average concentration of the optical fiber monolith reactor with 3-circle and 5-layer balls gets 11.43% higher than the case without glass balls.

Abstract The production of valued added fuels and chemicals via photocatalytic carbon dioxide reduction has attracted increasing attentions in recent years. Based on the traditional twin reactor configuration, a novel bubbling twin reactor is proposed to improve the conversion of carbon dioxide to methanol in this work. The multiphysical model for the bubbling twin reactor is developed and numerically simulated. The variations of the methanol production with the gas inlet flow velocity and gas inlet number are obtained. The results show that the bubbling twin reactor has a higher carbon dioxide conversion efficiency than the traditional one. Moreover, the methanol production subsequently increases as the gas inlet velocity increases. With the constant inlet gas volumetric flow rate, the production of methanol can be improved by increasing the gas inlet number.

AbstractCO2 utilization by direct catalytic conversion of CO2 driven by solar energy is an attractive approach for producing alternative value added products suitable for end-use infrastructure. In order to fully harness the solar spectrum and increase photocatalytic activity and selectivity, Cr-TiO2 based films were deposited on ceramic honeycomb monoliths with varying concentrations synthesized by sol-gel technique and dip coating route. The improved photocatalytic activity of the Cr-TiO2 monoliths in the visible light region compared to pure TiO2 can be attributed to increased visible light absorption and accessible active metal sites arising from the appropriate metal dispersion and loading amount.

In this work, dendritic tin-based carbon nanostructures with different morphologies were synthesized by a facile two-step carbonization and chemical vapor deposition method and were then evaluated for their performance in hydrogen evolution reaction.

AbstractThe transformation of CO2 using semiconductor photocatalysts is a promising alternative for developing sustainable energy sources. Nickel (Ni) based TiO2 photocatalysts immobilized onto quartz plate was assembled in a unique reactor configuration to provide a high ratio of illuminated catalyst surface area for the reduction of CO2 to fuels under visible light. The improved conversion efficiency is ascribed to the presence of the metal, Ni, which served as electrons traps that suppressed recombination, resulting in effective charge separation and CO2 reduction. More importantly, the quantum efficiency is higher than those reported in the literature that used similar reactor configurations.