Yuanhui Zuo

Facile One-Step Synthesis of Hybrid Graphitic Carbon Nitride and Carbon Composites as High-Performance Catalysts for CO2 Photocatalytic Conversion

Utilizing and reducing carbon dioxide is a key target in the fight against global warming. The photocatalytic performance of bulk graphitic carbon nitride (g-C3N4) is usually limited by its low surface area and rapid charge carrier recombination. To develop g-C3N4 more suitable for photocatalysis, researchers have to enlarge its surface area and accelerate the charge carrier separation. In this work, novel hybrid graphitic carbon nitride and carbon (H-g-C3N4/C) composites with various carbon contents have been developed for the first time by a facile one-step pyrolysis method using melamine and natural soybean oil as precursors. The effect of carbon content on the structure of H-g-C3N4/C composites and the catalytic activity for the photoreduction of CO2 with H2O were investigated. The results indicated that the introduction of carbon component can effectively improve the textural properties and electronic conductivity of the composites, which exhibited imporved photocatalytic activity for the reduction of CO2 with H2O in comparison with bulk g-C3N4. The highest CO and CH4 yield of 22.60 μmol/g-cat. and 12.5 μmol/g-cat., respectively, were acquired on the H-g-C3N4/C-6 catalyst with the carbon content of 3.77 wt % under 9 h simulated solar irradiation, which were more than twice as high as that of bulk g-C3N4. The remarkably increased photocatalytic performance arises from the synergistic effect of hybrid carbon and g-C3N4.

Hierarchically mesostructured TiO2/graphitic carbon composite as a new efficient photocatalyst for the reduction of CO2 under simulated solar irradiation

A hierarchically mesostructured TiO2/graphitic carbon composite photocatalyst with a high content of nanocrystalline TiO2 was prepared using a simple one-step nanocasting route. X-ray diffraction, thermogravimetric analysis, nitrogen adsorption–desorption, transmission electron microscopy and X-ray photoelectron spectroscopy were used to characterize this photocatalyst. It was observed that the coexistence of silica and graphitic carbon during the high temperature treatment stabilized the crystalline phase and the size of the anatase TiO2 nanocrystals (5–7 nm in diameter), which were uniformly dispersed in the graphitic carbon matrix after silica removal. The obtained hierarchically mesostructured TiO2/graphitic carbon composite photocatalyst with a high specific surface area and a high surface concentration of hydroxyl groups exhibited considerably higher activity in the photocatalytic reduction of CO2 with H2O under simulated solar irradiation compared to mesostructured anatase TiO2 prepared using a sol–gel method.

Surfactant-assisted Nanocasting Route for Synthesis of Highly Ordered Mesoporous Graphitic Carbon and Its Application in CO2 Adsorption

Highly ordered mesoporous graphitic carbon was synthesized from a simple surfactant-assisted nanocasting route, in which ordered mesoporous silica SBA-15 maintaining its triblock copolymer surfactant was used as a hard template and natural soybean oil (SBO) as a carbon precursor. The hydrophobic domain of the surfactant assisted SBO in infiltration into the template’s mesoporous channels. After the silica template was carbonized and removed, a higher yield of highly-ordered graphitic mesoporous carbon with rod-like morphology was obtained. Because of the improved structural ordering, the mesoporous carbon after amine modification could adsorb more CO2 compared with the amine-functionalized carbon prepared without the assistance of surfactant.

Heterogeneous catalysis of CO 2 -diethanolamine absorption with MgCO 3 and CaCO 3 and comparing to non-catalytic CO 2 -monoethanolamine interactions

The solid catalysts, CaCO3 and MgCO3, were adopted to accelerate CO2 absorption with diethanolamine (DEA) solvent. It turned out that these solid alkaline earth metal carbonates can accelerate CO2 absorption, with overall time reduction up to 14–28% for CaCO3, and 11–28% for MgCO3. After comparing CO2 loadings and time resolved amine concentrations, the solid chemicals can enhance the CO2 absorption of DEA and became compatible with the monoethanolamine (MEA) solution at the same CO2 loading without catalysts. The Lewis base can serve as heterogeneous catalysts for the amine scrubbing process and then facilitate CO2 absorption. These results indicated the heterogeneous catalysts can partly cover the shortage of DEA with CO2 absorption, and facilitate the amine scrubbing process with shorter column with ease.