Silver/Platinum Supported on Tio2 P25 Nanocatalysts for Non-Photocatalytic and Photocatalytic

Supplementary Information

Silver/Platinum supported on TiO2 P25 nanocatalysts for non-photocatalytic and photocatalytic denitration of water

Ana M. Antolín1,2, Sandra Contreras1*, Francesc Medina1, Didier Tichit2**

1Departament d’Enginyeria Química, Universitat Rovira i Virgili, Campus Sescelades. Avda.

Països Catalans, 26. 43007 Tarragona, Spain.

2Equipe MACS, Institut Charles Gerhardt, ENSCM. 8, rue de l’Ecole Normale. 34296,

Montpellier cedex 5, France.

Corresponding authors: [email protected]*, [email protected]**

1. X-Ray Diffraction (XRD)

Fig. 2 XRD patterns of TiO2 P25 and TiO2 P25 calcined at 400 ºC

1 2. Nitrogen physisorption (N2 Physisorption)

Fig. 3 Nitrogen adsorption-desorption isotherms of: A) TiO2 P25 and TiO2 P25 400 ºC; B)

Ag/P25 and Pt/P25(H); and C) Ag-Pt/P25(H) and Pt-Ag/P25(H)

Table 1 Specific surface area, pore volume and mean pore diameter of P25, P25 calcined at 400

ºC and selected monometallic catalysts

S V ØPore Catalyst BET Pore (m2g-1) (cm3g-1) (nm) P25 55 0.3 33 P25 400 °C 50 0.3 33 Ag/P25 45 0.5 25 Pt/P25(H) 50 0.4 26 Ag-Pt/P25(H) 44 0.4 26 Pt-Ag/P25(H) 42 0.4 26

2 3. X-ray photoelectron spectroscopy (XPS)

The Oxygen O1s and Titanium Ti2p species of the support P25 from the catalyst

Ag(2)/P25 are depicted in Fig. 7, which is representative of the typical scan obtained for each catalyst studied. The peaks are identified by a letter for recognition. The values of BE of O1s and Ti2p in the spectra of the different catalysts are very similar and reported in Table 3.

Fig. 7 O1s and Ti2p scan of Ag(2)/P25

Table 3 Binding energies of Oxygen and Titanium species obtained by XPS

BE (eV) Catalyst A B C D E 4+ 4+ O1s O1s O1s Ti 2p1/2 Ti 2p3/2 Ag/P25 529.5 531.2 533 458.3 464.2 Ag-Pt/P25(K) 529.6 531.3 533 458.4 464.2 Pt-Ag/P25(K) 529.5 531.1 532.8 458.3 464.2

4. Photocatalytic nitrite reduction

To verify the platinum addition effect, tests with Pt monometallic catalysts were performed using NaNO2 (Riser S.A.) as nitrite source, under λ = 365 nm UV-A irradiation and hydrogen flow (150 mL/min). The Pt loading was 4% wt. and precursors were varied

3 (H2PtCl6∙6H2O; K2PtCl6). Initial nitrite solution was fixed to 50 mg/L, because it was the highest nitrite concentration obtained in the overall catalytic nitrate reduction tests.

Nitrite conversions are higher when increasing the amount of Pt, and using K 2PtCl6 instead of H2PtCl6∙6H2O. Although conversions are not high enough to reach the EU Normative

- - + (50 mg/L NO3 , 0.5 mg/L NO2 , 0.3 mg/L NH4 ) [1], it could be seen a tendency toward nitrogen selectivity against intermediate and by-product compounds. Thus, Pt addition benefits the selectivity to desired N2 gas.

Table 6 Catalytic performances of Pt/P25(H) and Pt/P25(K) in the photocatalytic reduction of

- NO2 after 6 hours of reaction

Conv - Sel - Sel + Sel Catalyst NO2 NO3 NH4 N2 (%) (%) (%) (%) Pt/P25(H) 19 20 28 52 Pt/P25(K) 34 12 43 46 - Experimental conditions: 0.2g catalyst/350 mL; 50 ppm NO2 ; 120 mL/min Ar

4. References

1. S.I-No.106 (2007) European Communities Drinking Water Regulations.