Supplementary Information

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1 Supplementary Information to Mechanistic Details for Cobalt Catalyzed Photochemical Hydrogen Production in Aqueous Solution: Efficiencies of the Non-Photochemical Steps Bing Shan, Teera Baine, Xuan Anh N. Ma, Xuan Zhao and Russell H. Schmehl Department of Chemistry Tulane University New Orleans, LA Department of Chemistry University of Memphis Memphis, TN Contact

2 Actinometry for Quantum Yields In principle, any photoactive compound whose quantum yield is known could be used as an actinometer. For a good actinometer, this quantum yield should be, as much as possible, independent of excitation wavelength, temperature, concentration, trace impurities, and oxygen; moreover, the number of reacted molecules should be determined with a convenient and quick analytical method, but none of the numerous actinometers proposed in literature meets all the given criteria. 1 A general report on chemical actinometry was prepared by the Iupac Commission on Photochemistry. 2 Surveys on the most commonly used actinometers can be found in references. 3-6 Ferrioxalate actinometer is the most reliable and practical actinometer for UV and visible light up to 500 nm, proposed first by Hatchard and Parker in Under light excitation the potassium ferrioxalate decomposes according to the following equations: We used ferrioxalate actinometer for the PTI Felix 32 TM MD-5020 spectrofluorimeter whose incident light can be adjusted to exactly 458nm. But for the 150 W Xe arc lamp fitted with optical filters, the output is a bandpass between 420 nm and 520 nm. Instead of ferrioxalate actinometer, its photon flux was measured using the photooxidation of [Ru(bpy) 3 ] 2+ by S 2 O The reactions can be summarized as follows: To evaluate the efficiency of this actinometer, we firstly conducted ferrioxalate actinometry for the spectrofluorometer. After measuring the photon flux of it, the photooxadation of [Ru(bpy) 3 ] by S 2 O 8 was applied using the same conditions as the ferrioxalate actinometry (the same slit width, etc.). The quantum yield of [Ru(bpy) 3 ] 2+ photo-oxidation actinometry was calculated, which can then be applied to the actinometry for our 150 W Xe arc lamp. Experimental Section Preparation of solutions: 1, The ferrioxalate actinometer solution was prepared as follows. In a volumetric flask of 100ml, 5ml of an aqueous solution of 0.2M Fe 2 (SO 4 ) 3 and 5ml of an aqueous solution of 1.2M K 2 C 2 O 4 were added and then diluted to 100ml with distilled water. 1

3 Buffered phenanthroline 0.1%: 225g CH3COONa 3H2O, 1g of phenanthroline in 1 liter of H2SO4 0.5M. 2, [Ru(bpy) 3 ]Cl 2 was prepared by a published procedure 12. 3ml 8 (24ml) [Ru(bpy) 3 ]Cl 2 aqueous solutions which has a UV-Vis absorption at 450nm to be 3.7 was made. Instrumentation: 1, The output of the PTI Felix 32 TM MD-5020 spectrofluorimeter was focused into a 1cm 2 spectrophotometric cell. The slit width for the incident light was adjusted to 4mm.The irradiation spot size at the cell surface was 1cm in diameter. Cooling water was applied at the bottom of the cell. The ferrioxalate actinometry was carried out for the photon flux measurement. 2,The output of a 150 W Xe arc lamp, fitted with optical filters to provide a band-pass between 420 nm and 520 nm (Schott GG420 and UG1) was passed through a 5 cm path of water and focused into a 1cm 2 spectrophotometric cell. The irradiation spot size at the cell surface was approximately 1 cm in diameter. Its actinometry was carried out using the photooxidation of [Ru(bpy) 3 ] 2+ by S 2 O 2-8. Procedures: 1, 3 ml of a 0.01M solution of ferrioxalate in a spectrophotometric cell was irradiated at 458 nm, while an identical sample was maintained in the dark. At the end of the irradiation, 0.5 ml of buffered phenanthroline solution was added in the cells and the absorbance at 510 nm was measured immediately. Waiting for an hour between irradiation and addition of phenanthroline, or after the addition, does not make any difference. Oxygen does not have to be excluded, because the quantum yield of the ferrioxalate actinometer is independent of the presence of oxygen 3, 7. The irradiation time must be short enough in order to avoid more than 10% ferrioxalate decomposition. After irradiation for variable periods of time, the ferrous ion concentration is subsequently determined via a UV-Vis spectrophotometric determination of its phenanthroline complex at 510 nm. The blank value was determined with the same procedure but without irradiating the actinometer solution and was subtracted from the values obtained by irradiating. And the ferrous ion concentration was also measured by UV-Vis spectrophotometric at 510 nm. 2, Quenching study of [Ru(bpy) 3 ] and S 2 O 8 was conducted using different concentration of potassium persulfate and [Ru(bpy) 3 ] 2+ aqueous solution (A 450nm = 0.5). Stern-Volmer luminescence quenching measurements were carried out in aerated solutions using a PTI Felix 32TM MD-5020 spectrofluorimeter. By monitoring the luminescent decay of Ru* at 610nm, we can get the quenching ratio for different concentrations of the quencher. 3, Actinometry for both of the spectrofluorometer and the arc lamp was carried out using aqueous solutions of [Ru(bpy) 3 ] 2+ containing potassium persulfate that irreversibly oxidizes the Ru(II) upon photolysis. 10 The irradiation time must be short enough in order to avoid the change of the fraction of light that absorbed by

4 [Ru(bpy) 3 ] 2+. After irradiate for a short time (table below), UV-Vis spectra were taken to get the absorbance for Ru(Ⅲ) at 670nm. The blank value was determined with the same procedure but without irradiating the actinometer solution and was subtracted from the values obtained by irradiating. Results 1, Ferrioxalate actinometry for the spectrofluorometer at 458nm: The moles of ferrous ions formed in the irradiated volume are given by moles where V 1 is the irradiated volume, V 2 is the aliquot of the irradiated solution taken for the determination of the ferrous ions, V 3 is the final volume after complexation with phenanthroline (all in ml), l is the optical path-length of the irradiation cell, ΔA(510 nm) the optical difference in absorbance between the irradiated solution and that taken in the dark, ε(510 nm) is that of the complex Fe(phen) Thus, the moles of photons absorbed by the irradiated solution per time unit (N p ν / t) are: 1 cm optical pathlength (l), ε 510nm = L mol -1 cm -1. V1 actinometer irradiated(ml) V2 withdrawn solution for UV-Vis measurement(1ml) V3 volumetric flask used for dilution of irradiated aliquot (10mL) A 510nm = 0.05 Φ 458nm = 1.12 Table1, Ferrioxalate Actinometry Data: Phton Flux Average for spectrofluorometer at 458nm: quanta/s = quanta/min.

5 2, Quenching study of [Ru(bpy) 3 ] 2+ and S 2 O 8 2- : Figure 1, Fluorescent quenching spectra for Ru* by S 2 O Intensity [K 2 S 2 O 8 ]/M Intensity [K 2 S 2 O 8 ]/M wavelength/nm wavelength/nm Figure 2, Stern-Volmer relationship plot: I o /I a = [K 2 S 2 O 8 ] + 1 k q = M -1 s -1 3, Actinometry from Ru(bpy) S 2 O 8 2- for Spectrofluorometer at 458nm: Figure 3, UV-Vis spectra after irradiation from the fluorometer:

6 Absorbance non-irradiated 16s Irradiated 30s Irradiated 45s Irradiated Absorbance non-irradiated 16s Irradiated 30s Irradiated 45s Irradiated 60s Irradiated Wavelength/nm W avelength/nm Table 2, Actinometry Data for the fluorometer: Quenching Yield: φ q = 1- I a /I o = 97% Phton Flux Average for spectrofluorometer at 458nm: quanta/s = quanta/min Compared with Ferrioxalate Actinometry, the quantum yield of 94.17% of the persulfate actinometry should be considered. 4, Actinometry from Ru(bpy) S 2 O 8 2- for the 150 W Xe arc lamp: Figure 3, UV-Vis spectra after irradiation from the arc lamp:

7 Absorbance Non-Irradiated 3s Irradiated 6s Irradiated 7.5s Irradiated 9s Irradiated Absorbance Non-Irradiated 3s Irradiated 6s Irradiated 7.5s Irradiated 9s Irradiated Wavelength/nm Wavelength/nm Table 3, Actinometry Data for the arc lamp: ε 670nm = ε 670Ru(Ⅲ) ε 670Ru(Ⅲ) = 420M -1 cm -1 5M -1 cm -1 = 415M -1 cm -1 Photon Flux Average for the arc lamp: F = quanta/s = quanta/min

8 References (1) Montalti, M.; Credi, A.; Prodi, L.; Gandolfi, M. T. In Handbook of Photochemistry, Third Ed. Taylor and Francis: Boca Raton, 2006;, pp 635. (2) Kuhn, H. J.; Braslavsky, S. E.; Schmidt, R. Pure Appl. Chem. 2004, 76, (3) Bunce, N. J. In Handbook of Organic Photochemistry; Scaiano, J. C., Ed.; Boca Raton: Florida(USA), 1989; Vol. 1, pp 451. (4) Braun, A. M.; Maurette, M. -.; Oliveros, E. In Photochemical Technology; Wiley: Chichester (U. K.), 1991;, pp 559. (5) Murov, S. L.; Carmichael, I.; Hug, G. L. In Handbook of Photochemistry; Dekker, M., Ed.; New York (NY), 1993;, pp 420. (6) Favaro, G.; Albini, A.; Fasani, E. Spec. Publ. - R. Soc. Chem. 1998, 225, (7) Hatchard, C. G.; Parker, C. A. Proc. Roy. Soc. (London) 1956, A235, (8) Bolletta, F.; Juris, A.; Maestri, M.; Sandrini, D. Inorg. Chim. Acta 1980, 44, L175-L176. (9) Huang, Z.; Luo, Z.; Geletii, Y. V.; Vickers, J. W.; Yin, Q.; Wu, D.; Hou, Y.; Ding, Y.; Song, J.; Musaev, D. G.; Hill, C. L.; Lian, T. J. Am. Chem. Soc. 2011, 133, (10) Njapba, N. J.; Waltz, W. L. African Journal of Science and Technology 2001, 2, (11) Kaledin, A. L.; Huang, Z.; Geletii, Y. V.; Lian, T.; Hill, C. L.; Musaev, D. G. J Phys Chem A 2010, 114, (12) Broomhead, J. A.; Young, C. G.; Hood, P. Inorganic Synthesis 2007,