Synergistic Effect Of Nitrogen Doping Research Articles

Adsorption of CO2 by Petroleum Coke Nitrogen-Doped Porous Carbons Synthesized by Combining Ammoxidation with KOH Activation

The goal of our research is developing an efficient and cost-effective carbonaceous CO2 sorbent. Using petroleum coke as the precursor, porous nitrogen-doped carbons were prepared by combining ammoxidation with KOH activation. The as-synthesized samples possess highly developed microporosities and large nitrogen loadings. High CO2 adsorption capacities of 3.76–4.57 mmol/g at 25 °C and 5.80–6.62 mmol/g at 0 °C under atmospheric pressure were achieved. Specifically, the sample prepared under mild temperature (650 °C) and low KOH/precursor ratio (KOH/precursor = 2) shows a CO2 uptake of 4.57 mmol/g at 25 °C, among the highest achieved for nitrogen-doped porous carbons. This high CO2 capture capacity can be attributed to the synergistic effect of nitrogen doping and high narrow microporosity of the sorbent. However, experimental evidence suggests that nitrogen doping contributes less than narrow microporosity. Additionally, the CO2/N2 selectivity and CO2 heats of adsorption of the sorbent are as high as 22 an...

Synthesis of Ag/N-TiO2/SBA-15 Photocatalysts and Photocatalytic Reduction of CO2under Visible Light Irradiation

Silver-loaded together with nitrogen-doped highly dispersed TiO2/SBA-15 mesoporous catalysts were success- fully synthesized through solvothermal treatment and calcination method by using titanium n-butoxide (TB), carboxy- late-modified SBA-15 (COOH/SBA-15), urea and silver nitrate as raw materials. The detailed preparation procedure was as follows: 1.0 g COOH/SBA-15 powder was dispersed in solution containing 0.82 mL titanium n-butoxide (TB) and 20.0 mL acetic ether. The mixture was stirred for 30 min at room temperature, then 0.031 g AgNO3 was added into the solution by further stirring for 30 min and a certain amount of urea was added. After being stirred continuously for 3 h, the resultant solu- tion was transferred into a teflon-lined stainless autoclave and solvothermally treated at 220 ℃ for 12 h. After naturally cooling to room temperature, the resultant product was washed three times with absolute ethanol and then dried under vac- uum at 80 ℃ for 12 h. Finally the solids were calcined in air at 550 ℃ for 4 h at a heating rate of 1.5 ℃/min. The prepared samples were characterized by X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectrum (XPS), transmission electron microscopy (TEM), UV-Visible diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence spectra (PL), inductively coupled plasma atomic emission spectrum (ICP) and elemental analysis (EA). It was revealed that the highly dispersed samples consist of anatase crystalline phase were mesoporous structure. The anatase phase was retained without phase change after silver loading and nitrogen doping. Silver was deposited on the surface of catalysts in the form of metallic silver and served as an effective electron trapper which could prevent the fast recombination of the photo-generated electrons and holes, at the same time, visible light absorption of samples were enhanced by silver nanoparticle based on its surface plasmon resonance effect. Nitrogen was doped into TiO2 matrix in the form of both interstitial nitrogen and substitu- tional nitrogen, nitrogen dopants might be presented in the chemical environment of Ti-O-N and O-Ti-N. On one hand, nitro- gen doping could extend the adsorption of catalysts to the visible light region (λ>400 nm); on the other hand, appropriate amount of nitrogen doping could inhibit the recombination of the photo-generated charge carriers and increase the efficiency of the photocurrent carriers. The high photocatalytic performance could be attributed to the synergistic effect of nitrogen doping and the loaded silver nanoparticles over TiO2. The nitrogen doping concentration had an optimal value. When the loading amount of Ag was 2 wt% and the theoretical mole ratio of nitrogen to Ti was 3, the photocatalyst had the highest photocatalytic activity. The methanol yield was 45.7 μmolg -1 •h -1 .

One-pot synthesis of nitrogen-doped TiO2 nanorods with anatase/brookite structures and enhanced photocatalytic activity

Nitrogen doping in combination with a heterostructure can not only modify the band structure of TiO2 to make it more responsive to visible light, but also suppress charge recombination and lead TiO2 to have enhanced photocatalytic activity as compared to P25. Also, one-dimensional TiO2 nanostructures can serve as electron highways for efficient charge separation and, hence, increase the lifetime of charge carriers and enhance the efficiency of interfacial charge transfer to the adsorbed substrate. In this paper, a simple one-pot synthetic strategy has been designed for preparing TiO2 nanorods with good crystallinity, nitrogen doping and anatase/brookite binary structure characters, using N2H4·H2O as an in situ nitrogen doping source. The physicochemical properties of the catalysts can be tuned by simply changing the concentration ratios of N2H4·H2O to TiO2 colloids. The synergistic effect of nitrogen doping in association with a one-dimensional and anatase/brookite binary structure is suggested to account for the higher catalytic activity of the TiO2 nanorods for decomposing methyl orange and 4-chlorophenol compared to the nanoparticle counterparts under UV and/or visible light illumination.