Department of Chemistry, University of Missouri-Columbia, Missouri

Transcription

1 Synthesis of an Improved TiO 2 Co-catalyst for the Breakdown of Organic Materials Taylor D. Bell, Shane E. Moore Department of Chemistry, University of Missouri-Columbia, Missouri tdbth5@mail.missouri.edu; MooreSE@health.missouri.edu 1

2 Introduction Materials and Methods Preparation of Catalyst. Materials were all made using the micro emulsion technique. CeO 2 -TiO 2 was first made using a previously obtained TiO 2 sample. A CeO 2 aqueous solution was used for the micro emulsion. After 30 minutes of agitation a stoichiometric quantity of tetramethylammonium hydroxide was introduced by a similar micro emulsion technique. Titanium tetraisopropoxide was then introduced to the previous micro emulsion drop by drop. The resulting mixture was then stirred for 24 hours, centrifuged, rinsed with methanol, and dried for 12 hours. After drying heat ramping was used (2 C min -1 ) to 500 C. For g-c 3 N 4 modified with Mn production, g-c 3 N 4 was first made by calcination techniques of melamine at 580 C. An aqueous solution of this mixed with and aqueous solution of dissolved manganese (II) chloride tetrahydrate was stirred for 1 hour at room temperature. Then it was centrifuged, washed, and dried at 60 C. The two made materials were then combined using an impregnation method by suspending the appropriate amounts of g-c 3 N 4 or g-c 3 N 4 -MnO x OH y in methanol and sonicating for 1 hour. The sample was then dried at 110 C for 24 hours to get the finished products of the g-c 3 N 4 /TiO 2, g-c 3 N 4 /CeO 2 -TiO 2, g-c 3 N 4 -MnO x OH y /TiO 2, and g-c 3 N 4 -MnO x OH y /TiO 2 -CeO 2 composite sites 2

3 Photocatalytic Experimental Details. A continuous flow annular photo reactor was used in the gas-phase photo oxidation of toluene. Activity and selectivity for the gas-phase photo-oxidation were tested with 40 mg of the photocatalytic material as a thin layer coating on a Pyrex tube. The corresponding amount of catalyst was then mixed with 1 ml ethanol and painted on the tube before allowing to dry. Gas-phase toluene was then pumped through the tube at ppmv, first for 6 hours in the dark and then for and then for 24 hours under irradiation by four UV lamps symmetrically positioned around the photo reactor. Concentrations of reactants and products were analyzed during the process using online gas chromatography equipped with HP-PLOT-Q/HP-Innowax columns (and TCD (for CO 2 measurements) / FID (organic measurement) detectors. This allowed the calculations of not only the concentrations but also the rates. Table 1. Reaction Rate of Toluene Photo-oxidation of Various Photocatalysts 1, 2 Catalyst BET Surface Area (m 2 g -1 ) Irradiation Concentration of Toluene in (M m -3 ) Concentration of Toluene out (M m -3 ) Rate g-mn/ceti % 6.69x x x10-10 mol s -1 m -2 TiO mol m -3 min -1 g/ceti ppm x10-10 mol s -1 m -2 g-mn/ceti: Graphitic carbon nitride on TiO 2 with manganese and ceria co-catalyst; g/ceti: graphitic carbon nitride on TiO 2 with ceria co-catalyst; ---: data unavailable. 3

4 Results and Discussions Conclusion Supplemental Material Available: The appendix contains a more detailed description of the preparation of our photocatalyst as well as more information of the process used to test our photo catalyst. Spectra data is also shown in and information about characterization of the product is provided as well. References (1) Kim, Sang Bum; Hong, Sung Chang. Kinetic Study for Photocatalytic Degradation of Volatile Organic Compounds in Air Using Thin Film TiO 2 Photocatalyst. App. Catal. B. 2002, 35, 4, (2) Munoz-Batista, Mario J.; Fernandez-Garcia, Marcos; Kubacka, Anna. Promotion of CeO2-TiO2 Photoactivity by g-c3n4: Ultraviolet and visible light elimination of toluene. App. Catal. B. 2015, 164,

5 Appendix Supporting Information Synthesis of an Improved TiO 2 Co-catalyst for the Breakdown of Organic Materials Taylor D. Bell, Shane E. Moore Department of Chemistry, University of Missouri-Columbia, Missouri tdbth5@mail.missouri.edu; MooreSE@health.missouri.edu S1

6 Table of Contents Preparation of Co-catalyst..3 Photocatalytic Experimental Details.4 XRD Spectroscopy of Co-catalyst.5 XPS Spectroscopy of Co-catalyst...6 Bibliography... 8 S2

7 Preparation of Catalyst. Original materials were prepared using the micro emulsion technique with n- Heptane as an organic media, Triton X-100 as a surfactant, and hexanol as a cosurfactant. A TiO 2 sample was first obtained as a first step using titanium tetraisoperoxide as a precursor. To create CeO 2 -TiO 2, cerium nitrate was introduced in the aqueous phase of micro emulsion. After 30 minutes of agitation, a stoichiometric quantity of tetramethylammonium hydroxide (TMAH) to obtain 2.5% of Ce (III) hydroxide was introduced from the aqueous phase of a similar micro emulsion. After 5 minutes, titanium tetraisopropoxide was introduced into the mixture with isopropanol (2:3). Water/(Ti+Ce) and water/ surfactant molar ratios were 110 and 18 for all samples, respectively. The resulting mixture was then stirred for 24 hours, centrifuged, separated, and rinsed with methanol and dried at 110 C for 12 hours. After drying, the materials were subject to a heating ramp (2 C min -1 ) to 500 C, maintain this temperature for 2 hours. Graphite carbon nitride (g-c 3 N 4 ) modified with Mn was synthesized by dissolving manganese (II) chloride tetrahydrate salt in deionized water to produce a 10mM solution. Then the salt solution was added to 200mL of a 0.5mg ml -1 uniformly dispersed g-c 3 N 4 aqueous solution that was obtained by previous calcination melamine at 580 C for 4 hours. The mixture was then stirred for 1 hour at room temperature, centrifuged, and washed with deionized water before being dried at 60 C. S3

8 The incipient wetness impregnation method was used to obtain the g-c 3 N 4 /TiO 2, g-c 3 N 4 /CeO 2 -TiO 2, g-c 3 N 4 -MnO x OH y /TiO 2, and g-c 3 N 4 -MnO x OH y /TiO 2 -CeO 2 composite sites. For this the appropriate amount of g-c 3 N 4 or g-c 3 N 4 -MnO x OH y was suspended in methanol and sonicated for 1 hour, deposited on the corresponding composite sample and dried at 110 C for 24 hours. Photocatalytic Experimental Details A continuous flow annular photo reactor (Panreac) was used in the gas-phase photo oxidation of toluene. Activity and selectivity for the gas-phase photo oxidation were tested with 40 mg of the photocatalytic material as a thin layer coating on a Pyrex tube. The corresponding amount of catalyst was then mixed with 1ml ethanol and painted on the tube before allowing to dry. Gas-phase toluene was then pumped through the tube at ppmv, first for 6 hours in the dark and then for and then for 24 hours under irradiation by four UV lamps symmetrically positioned around the photo reactor. Concentrations of reactants and products were analyzed during the process using online gas chromatography (Agilent GC 6890) equipped with HP-PLOT-Q/HP-Innowax columns (0.5/0.32 mm i.d. X 30 m) and TCD (for CO 2 measurements) / FID (organic measurement) detectors. S4

9 XRD Spectroscopy for Co-catalyst The X-ray diffraction pattern is used to show the phase of the TiO 2 by comparison to know patterns. Figure 1 shows that all made samples are found to be in the anatase phase only. Figure S1. XRD patterns of the made photocatalyst. S5

10 XPS Data for Co-Catalyst XPS data was used to show the relative concentrations of added ceria and g-mn clusters. The results in Figure 2 show that there is a low chemical influence of the carbon nitride in the oxide components especially with interaction of CeTi. We also observe the bonding stated of Ce-Ti to be Ce(III) and Ce(IV) oxidation states. Figure 3 Shows that CN species only start to have an effect when the presence of Mn is added. Figure S2. XPS Data for Co-catalyst. Mn 2p (A), C 1s (B), and N 1s (C), XPS data and fitting for g-mn sample; fitting results for C 1s (D) and N 1s (E) XPS peaks of the g- Mn/CeTi sample. S6

11 Figure S3. C 1s (A) and N 1s (B) XPS spectra for the g, g-mn, g/ti, g-mn/ti, g/ceti, and g-mn/ceti samples. S7

12 Bibliography Dai, Hongzhe; Gao, Xuchun; Liu, Enzhou; Yang, YuHao; Hou, WenQian; Kang, LiMin; Fan, Jun; Hu, Xiaoyun. Synthesis and Characterization of Graphitic Carbon Nitride Submicrospheres Using Microwaves Method Under Mild Condition. Diamond and Related Materials 2013, 38, Munoz-Batista, Mario J.; Fernandez-Garcia, Marcos; Kubacka, Anna. Promotion of CeO 2 -TiO 2 Photoactivity by g-c 3 N 4 : Ultraviolet and visible light elimination of toluene. App. Catal. B 2015, 164, Munoz-Batista, Mario J.; Kubacka, Anna; Fernandez-Garcia, Marcos. Effective Enhancement of TiO 2 Photocatalysis by Synergistic Interaction of Surface Species: From Promoters to Co-Catalysts. ACS Catal. 2014, 4, S8