Results and Discussion

4-1. Thermal analysis

To understand the thermal properties of synthesized samples, the weight loss and heat flows of samples were examined in terms of the thermogravimetric analysis (TGA) curves and differential scanning calorimetry (DSC) measurements. Figure 4-1 shows the DSC and TA/DTG profile of the as-prepared TiO2 sample under air flow. Below 200 °C, 10 wt % mass loss is due to removal of volatile species such as water, ethanol or hydrochloric acid.

Two exothermic stages at 200-300 °C and 300-425 °C, which causes remarkable 40 and 10 wt % mass losses, respectively, indicate the partial decomposition and severe oxidation of P123. The surfactant was completely burned out to result in mesoporous TiO2 powders above 425 °C.

0 100 200 300 400 500 600 700 800 900 20

40 60 80 100

-3 -2 -1 0 1 2

Exo

Temperature (

^o

C)

-0.5 0.0 0.5 1.0 1.5

He at f low ( m W )

2.0 o

De ri v . W ei g ht ( % / C)

We ig h t ( % )

Figure 4-1 The DSC and TG/DTG curves of the as-prepared TiO2 sample heated in air.

4-2. Chemical composition

The chemical compositions and chemical states at the surface sites and in the bulk lattice of catalysts were characterized using XPS and ICP-MS. Figure 4-2 shows the wide range scanned XPS spectra and high resolution scanned spectra of the mesoporous TiO2, ZrxTiO2

and Au-TiO2 samples. In addition to Ti (2p) and O (1s) photoelectron lines, Zr(3d) and Au (4f) peaks were found the wide range scanned spectra, indicating the presence the incorporated elements on the TiO2 surface (See Appendix B). The Ti⁴⁺ ions, Zr⁴⁺ ions, and Au elements were indentified from the doublet peaks of Ti (2p3/2), Ti (2p1/2), Zr (3d5/2), Zr (3d3/2), Au (4f7/2) and Au (4f5/2) centered at 458.2, 464.0, 181.8, 184.5, 83.8, and 87.4 eV, respectively^[88]. The surface Zr/Ti ratios were calculated from their integrated peak areas normalized with corresponding sensitive factors. Table 4-1 lists the surface and total Zr/Ti atomic ratios. It is noted that the surface Zr/Ti ratios were slightly larger than the bulk values when the total Zr/Ti ratio was lower than 0.08, indicating that most Zr⁴⁺ ions were doped at the TiO2 surface lattice instead of homogeneously dispersed in the bulk. The inhomogeneous distribution of Zr⁴⁺ ions was more significant at its low concentrations.

Such phenomenon is attributed to the faster gelation of TiO2 than that of ZrO2 in the presence acetyl acetone which effectively chelates to Ti⁴⁺ and Zr⁴⁺ ions to slow the hydrolysis down.

Compared to 6-coordinated Ti⁴⁺ ions, Zr⁴⁺ ions, which contain 7 or 8 coordinations, are more strongly bonded with acetyl acetone to have relatively slower hydrolysis and gelation rates.

Thus, TiO2 colloids are formed followed by co-precipitation of Zr-doped TiO2 at the surface.

Similar result was found in the non-hydrolytic sol-gel-derived Zr-doped TiO2 samples when tri-octylphosphine oxide was used as the chelating agent^[116]. The inhomogeneous distribution was inhibited when the concentration of the precursor of ZrO2 increased in the sol solution because of its increased formation rate. The surface-to-bulk Zr/Ti ratio of the doped TiO2 was only 1.0 when the total Zr/Ti ratio was 0.1. Table 4-2 lists the added and

total Au/Ti atomic ratios for the Au-load materials. The total Au/Ti ratios ranged between 0.001 and 0.008 which were similar to the added ratios at low concentrations (ranged between 0.1% and 1.0%). However, the total Au/Ti ratios ranging 2.0% to 8.0% were smaller than the added ratios by 2-5 times. These results indicate that almost Au nanoparticles were successfully loaded on TiO2 in the DP process at low concentrations.

Over amounts of Au ions led to significant loss from deposition because of limited loading capacity of the TiO2 samples.

Figure 4-3 displays the high resolution scanned O (1s) XP spectra of the TiO2 and ZrxTiO2 samples. The O (1s) spectra can be deconvoluted into M-O and M-OH species (M

= Ti or Zr) with the binding energies centered at 530.1 and 531.7 eV, respectively. Table 4-1 lists the M-OH/M-O ratios of pure TiO2 and ZrxTiO2 samples. The pure TiO2 contained at the surface M-OH/M-O ratio of 0.22. The M-OH/M-O ratio increased from 0.28 to 0.69 when the surface Zr/Ti ratios increased from 0.02 to 0.14. This result reveals that incorporation of Zr⁴⁺ ions enhances surface hydrophicility of TiO2 because of their higher coordination numbers than those of Ti⁴⁺ ions. Similar results were observed in the mesoporous TiO2-ZrO2 composites which exhibited superior hydrophilicity^[66].

1000 800 600 400 200 0

Au (4f) Zr (3d) C (1s) Ti (2p)

O (1s)

Zr_0.03TiO₂

TiO₂ 1.0% Au-TiO₂

Count s

Binding Energy (eV)

188 186 184 182 180 178

Binding Energy (eV)

Zr (3d)

Figure 4-2 (a) The wide-ranged XP spectra and high resolution of (b) Ti (2p), (c) Zr (3d) and Au (4f) XP spectra of TiO2, ZrxTiO2 and Au-TiO2 samples.

92 90 88 86 84 82 80 Au (4f)

468 466 464 462 460 458 456

In ten sity (A .U .)

Ti (2p)

(b) (c) (d)

(a)

Table 4-1 The surface chemical compositions of TiO2 and ZrxTiO2 samples.

Sample Surface Zr/Ti

Bulk Zr/Ti

Surface ratio/bulk

ratio (A/B) Ti-OH/Ti-O

TiO2 - - - 0.21

Zr0.01TiO2 0.02 0.01 2.00 0.28

Zr0.02TiO2 0.07 0.04 1.75 0.30

Zr0.03TiO2 0.08 0.06 1.33 0.33

Zr0.04TiO2 0.11 0.08 1.37 0.37

Zr0.05TiO2 0.11 0.11 1.00 0.58

Zr0.1TiO2 0.14 0.14 1.00 0.69

- represents not available.

Table 4-2 The chemical compositions of Au-TiO2 samples Sample Add Au/Ti Total Au/Ti

0.1% Au-TiO2 0.001 0.001

0.5% Au-TiO2 0.005 0.005

1.0% Au-TiO2 0.01 0.008

2.0% Au-TiO2 0.02 0.010

4.0% Au-TiO2 0.04 0.014

8.0% Au-TiO2 0.08 0.016

536 534 532 530 528 526

TiO2

Ti-O

Zr0.01TiO

2

Zr0.02TiO

2

Ti-OH

Zr0.03TiO

2

Zr0.04TiO

2

Zr0.05TiO

2

In ten si ty

Zr0.1TiO

2

Binding energy (eV)

Figure 4-3 The O (1s) XP spectra of TiO2 and ZrxTiO2 samples.

4-3. Pore Structure

Figure 4-4 shows the N2 adsorption and desorption isotherm and pore size distribution of P25 and mesoporous TiO2. The Degussa P25 exhibited type II adsorption an hysteresis loop of H3 type in the higher P/P0 range, indicating the inter-particle porous features^[117]. The TiO2, prepared in this study, exhibited typical type IV adsorption isotherm with sharp capillary condensation steps between the relative pressures (P/P0) of 0.4-0.8, implying the mesoporous structure with a narrow pore size distribution. Its hysteresis loop was close to the H2 type, revealing the presence of ink-bottle shaped or cage-type pores in the given material^[118].

Figure 4-5 displays the N2 adsorption and desorption isotherm and pore size distribution of Zr-doped TiO2 samples. Incorporation of Zr⁴⁺ ions into the TiO2 lattice changed the hysteresis loop from type H2 to H1 when the Zr/Ti ratio was ranged between 0.02 and 0.04, revealing uniform cylindrical geometry of mesoporous structure In addition, the major pore size of the mesoporous TiO2 samples shifted from 3.6 nm to 4.9 nm. The presence of impurities at low concentrations assists the stability of the porous structure against thermal induced shrinkage and distortion.) However, high concentrations of Zr⁴⁺ ions resulted in bi-modal mesoporous structures. Two size distributions centered at 3.4 and 4.6 nm were obtained. Zhou et al.^[66] found the similar structure in their ZrO2-TiO2 mesoporous samples prepared using the P123 as the template through sol-gel process. The bi-modal structure in this study is presumably due to reconstructive reaction field during the EISA process. High concentrations of Zr⁴⁺ ions overall reduced the gelation rate. The slow gelation enabled P123 self-assembling into small micelles to result in small pore size. This effect is dominant because the pore size centered at 3.4 nm contained large portion. When most solvent was evaporated from the system at the end of self-assembly, the concentrated sol

solution rapidly increased the gelation rate, thus leading to the large pore size of 4.6 nm. On the other hand, deposition of Au nanoparticles did not alter the porous structure of the TiO2

samples. All Au-TiO2 samples exhibited H2 type hysteresis loop, indicating that the Au nanoparticles were primarily deposit outside the pore channels (Figure 4-6).

Table 4-2 summarizes the BET specific surface areas, pore volumes and pore sizes of the catalysts. P25 contained a specific surface area of 48.3 m² g^-1 and an aaverage inter-particle pore size of 30.0 nm. The presence of amphiphilic triblock copolymer in the EISA process led to the mesoporous structure of TiO2 samples and contributed to the high surface area of 108 m²/g. The Au-TiO2 samples had surface areas of 102-110 m² g^-1 and mean pore sizes of 8.2-11.4 nm, which are similar to those of pure TiO2 sample. These results suggest that the Au nanoparticles obtained through deposition-precipitation method are well dispersed on the TiO2 samples and do not block the pore channels. The Zr-doped TiO2 samples possessed higher surface areas and larger pore volumes than the pure TiO2

sample, except for the Zr0.01TiO2 sample which had similar texture (surface area: 121 m²/g) as the pure TiO2. The surface areas and pore volumes of the ZrxTiO2 catalysts with the x=

0.02-0.04 were 121-151 m² g^-1 and 0.31-0.36 cm³/g, respectively. The doped Zr⁴⁺ ions suppressed pore shrinkage during the thermal treatment to effectively preserve the high surface areas and large pore volumes. High Zr⁴⁺ ion loading (Zr/Ti= 0.05-1.00) dramatically increased the surface area of the mesoporous TiO2 sample to 200-217 m² g^-1. Although the Zr0.05TiO2 and Zr0.1TiO2 samples exhibited reduced pore sizes (Dmean: 5.7-5.8 nm), they contained high pore volumes of 0.29-0.31 cm³g^-1. This finding supports the reaction-filed determined textures.

TEM images in Figure 4-7 show that composites with Zr/Ti ratios from 0.01 to 0.1 and TiO2 have typical 3-D wormhole-like mesostructure (See Appendix C). The replicated

mesoporous metal oxide exhibits a regular spherical morphology with a diameter ranging from about 7.5 to 1.5 nm. The particles are randomly oriented and the size of ZrxTiO2

samples was decreased with the Zr/Ti ratios increasing. The HRTEM micrograph indicates the presence of lattice fringes which demonstrates that the pore walls of the mesopores are composed of anatase nanocrystals (Figure 4.7 b and d). The pure mesoporous TiO2 had well anatase crystalline with a d-spacing of (1 0 1) crystallographic plan of 0.83 nm. However, the Zr0.03TiO2 samples had a relativity smaller d-spacing of 0.42 nm consistent with the XRD results discussed later. The TEM and HRTEM images obtained for the Au-loaded TiO2 are presented in Figure 4.7 e and f, respectively. The majority of mean diameter integrated upon crystallized TiO2 were estimated between 10 and 20 nm and no significant change occurs of mesoporous structure during reaction.

0.0 0.2 0.4 0.6 0.8 1.0

Relative prssure (P/P

₀)

Degussa P25

Relative prssure (P/P

₀)

TiO₂

Figure 4-4 N2 adsorption and desorption isotherm and BJH pore size distribution of pure TiO2.

2 4 6 8 10 12 14 16 18 20

0.0 0.2 0.4 0.6 0.8 1.0 Zr_0.1TiO₂

Zr_0.05TiO₂

Zr_0.04TiO₂

Zr_0.03TiO₂

Zr_0.02TiO₂

(a)

Zr_0.01TiO₂

TiO₂

V olum e adsorbed (cm

3

/g)

Relative prssure (P/P

₀

)

0 2 4 6 8 10 12 14 0.000

0.004 0.008 0.012 0.016 0.020 (b)

dV/ dD ( cm

3

/g n m )

Pore diameter (nm)

TiO2

Zr0.01TiO₂ Zr0.02TiO₂ Zr_0.03TiO₂ Zr_0.04TiO₂ Zr_0.05TiO₂ Zr_0.1TiO₂

Figure 4-5 (a) N2 adsorption and desorption isotherm and (b) pore size distribution of ZrxTiO2.

0.0 0.2 0.4 0.6 0.8 1.0 8.0% Au-TiO₂

4.0% Au-TiO₂

2.0% Au-TiO₂

1.0% Au-TiO₂

0.5% Au-TiO₂

(a)

0.1% Au-TiO₂

TiO₂

V o lum e adsorbed (cm

3

/g )

Relative prssure (P/P

₀

)

0 2 4 6 8 10 12 14 0.000

0.002 0.004 0.006 0.008 0.010

dV/ dD ( cm

3

/g n m )

(b)

Pore diameter (nm)

TiO₂

0.1% Au-TiO 0.5% Au-TiO2

1.0% Au-TiO2

2.0% Au-TiO2₂

4.0% Au-TiO₂ 8.0% Au-TiO₂

Figure 4-6 (a) N2 adsorption and desorption isotherm and (b) pore size distribution of Au-TiO2.

Table 4-3 Hysteresis loop types, Specific surface area (SBET), pore volume (Vpore), mean pore size (Dmean) and major pore size (Dmajor) of catalysts.

Sample Hysteresis loop SBET (m² g^-1) Vpore (cm³ g^-1) Dmean (nm) Dmajor (nm)

P25 H3 type 48 0.36 30.0 -

TiO2 H2 type 108 0.26 9.7 3.55

Zr0.01TiO2 H2 type 121 0.24 9.9 3.6

Zr0.02TiO2 H1 type 126 0.31 14.6 4.9

Zr0.03TiO2 H1 type 150 0.32 8.4 4.9

Zr0.04TiO2 H1 type 151 0.36 9.6 5.0

Zr0.05TiO2 bimodal 200 0.29 5.8 3.4

Zr0.1TiO2 bimodal 217 0.31 5.7 3.4

0.1% Au-TiO2 H2 type 108 0.26 10.9 3.6

0.5% Au-TiO2 H2 type 110 0.29 10.8 3.6

1.0% Au-TiO2 H2 type 108 0.24 9.1 3.6

2.0% Au-TiO2 H2 type 108 0.22 8.2 4.0

4.0% Au-TiO2 H2 type 104 0.29 11.4 4.8

8.0% Au-TiO2 H2 type 102 0.24 9.5 4.8

Figure 4-7 TEM images of (a) mesoporous TiO2, (b) Zr0.03TiO2 and (c) 1.0% Au-TiO2, and HRTEM images of (d) mesoporous TiO2, (e) Zr0.03TiO2 and (f) 1.0% Au-TiO2.

(a) (b)

(c) d

(e) (f)

Anatase (1 0 1) 0.83 nm

Anatase (1 0 1) 0.42 nm

(d)

4-4. Crystalline structure

X-ray diffraction (XRD) patterns of the TiO2, ZrxTiO2 and Au-TiO2 samples are shown in Figure 4-8. The anatase TiO2 was the only crystalline phase observed in the XRD patterns and no diffraction peaks of ZrO2, ZrTiO4 or gold were found. The anatase (101) diffraction peak of the pure TiO2 sample centered at 25.3° 2θ position. Loading Au nanoparticles and incorporation of few amounts of Zr⁴⁺ ions (total Zr/Ti=0.01) have little influence on the position of the diffraction peak. However, the Zr0.02TiO2 and Zr0.03TiO2

samples up-shifted the peak to 25.5-25.7° 2θ position, indicating the reduced d-spacing.

This phenomenon was different from the literature results[62, 64, 116] which the partial substitution of Ti⁴⁺ ions species by Zr⁴⁺ ions expanded the cell volume owning to the larger ionic radius of Zr⁴⁺ ion (0.72 Å) than that of Ti⁴⁺ ion (0.65 Å). The compression of anatase (1 0 1) profile in this study reveals that the Zr⁴⁺ ions are introduced between crystal domains not substituted for the Ti⁴⁺ ions in the TiO2 lattice. In addition, the thermal induced shrinkage of the amorphous Zr-doped TiO2 moiety in the grain boundaries might compress the TiO2 anatase crystals. The anatase (1 0 1) diffraction peak returned to 25.3° when the concentration of the Zr⁴⁺ ions increased to 4 %. It is presumably due to that excess Zr⁴⁺ ions are segregated from the amorphous doped TiO2 moiety to reduce it volume and release the stress of anatase crystals during thermal treatment. However, the ZrO2 crystals are too tiny to be detected. Poor crystallinity of Zr0.05TiO2 and Zr0.1TiO2 samples were observed. The heavy doping of Zr⁴⁺ ions retards the crystallization of TiO2.

The average crystallite sizes of the TiO2 ,ZrxTiO2 and Au-TiO2 samples are calculated according to the Scherrer formula from the broadening of diffraction peaks of the anatase (1 0 1) of TiO2 and the results are listed in Table 4-3. The TiO2 and Au-TiO2 samples have similar crystallite sizes of 9.5-9.6 nm. The Zr⁴⁺ ions at the Zr/Ti ratio of 0.01 slightly

decreased the crystallite size to 8.7 nm because of defect induced lattice strain.) When the Zr/Ti ratios increased to 0.02-0.04, reduced gelation rate increased the crystallite size to 10.3-11.6 nm. High loading of Zr⁴⁺ ions suppressed the TiO2 crystallization and resulted in small crystallite sizes of 4.5 nm.

20 30 40 50 60

8.0% Au-TiO

2

Zr_0.1TiO₂ Zr_0.05TiO₂ Zr0.04TiO

2

Zr_0.03TiO₂ Zr_0.02TiO₂ Zr0.01TiO

2

Intensi ty

2  (degree)

TiO2

Figure 4-8 XRD patterns of mesoporous TiO2 and ZrxTiO2 samples.

Table 4-4 Crystallite sizes of mesoporous TiO2 and ZrxTiO2 samples.

Sample Crystalline size (nm)

TiO2 9.6

8.0% Au-TiO2 9.5

Zr0.01TiO2 8.7

Zr0.02TiO2 10.5

Zr0.03TiO2 10.3

Zr0.04TiO2 11.6

Zr0.05TiO2 6.8

Zr0.1TiO2 4.5

4-5. Local geometric structure

The X-ray absorption spectroscopy (XAS) using synchrotron radiation is a powerful technique to investigate the local structural details and electronic properties of the X-ray absorbing atoms and about its local environment. In this research, the XANES technique offers a detailed and quantitative picture of the local structure around Ti atoms. Figure 4-9 (a) shows the XANES of Ti K-edge X-ray absorption spectra of TiO2, ZrxTiO2 samples and the reference compound: anatase TiO2. Anatase structure of the mesoporous sample was confirmed from their similar absorption features to those of the reference sample. As shown in Figure 4-9 b, the pre-edge structure at the Ti K-edge for anatase TiO2 features four peaks labeled as A1, A2, A3, and B, corresponding to transitions of the inner electron to Ti 3d, 4p, and 4s hybridized states. The origin of A1 peak was assigned to an exciton band or a transition from 1s → 1t1g, while the origins of A2 and A3 are designated to 1s → 2t2g and 1s

→ 3eg transitions in an octahedral field, respectively. The feature B is attributed to a Ti 4p character hybridized with the Ti 4s and O 2p orbitals. Luca et al.^[119] reported that the A2 feature is associated with poorly crystalline surface region and lattice distortion, respectively.

In addition, the relative intensity of A2 and A3 absorptions increase with decreasing crystallite sizes of anatase crystals. In this study, we found that the A2 intensity increased with the Zr⁴⁺ ion-loading. We attribute this phenomenon to the increased surface areas. The post-edge beyond the D transitions become poorly resolved as the Zr⁴⁺-content increased because of reduced crystallite sizes.

The EXAFS spectra of anatase crystalline, TiO2 and ZrxTiO2 samples are shown in Figure 4-10 a. Large surface portion of the doped TiO2 at high Zr-ion loading reduced the oscillation amplitude. In addition, the presence of impurities which resulted in high degree of structural disorder could diminish the fine features. The magnitude Fourier transforms

(FT) EXAFS of selected samples is shown in Figure 4-10 b. These FT-EXAFS spectra show the existence of two shells of backscattering atoms around the central Ti element. The first and second shells in these Fourier transforms are from single scattering paths, Ti-O and Ti-Ti bonds, respectively. The bond distance of Ti to the first-shell O atom and second shell Ti atom was similar. But the reduction in amplitude of the FT peaks with increasing Zr/Ti ratios, indicating the nearest Ti-O bonds and nearest neighbor Ti-Ti bonds experience an increase in mean square relative displacement (MSRD) with decreasing crystallinity. For Zr0.1TiO2 sample, the absence of Ti-Ti bonds also represents the poor crystallization of TiO2, which is in agreement with its XRD result.

Structure parameters are obtained from the fitting of the FT-EXAFS spectra. The peaks of FT-EXAFS contain many contributions from both single and multiple scattering paths and they were fitted with a single set of distances (R) and Debye-Waller factors (σ²) and then float the energy zero (e0) to calculate the coordination numbers (N). Figure 4-11 (a) shows the Ti K-edge FT-EXAFS of the pure metal oxides. The best fit parameters of coordination numbers and interatomic distances of the first and second shells around the Ti element in the mesoporous TiO2 sample are listed in Table 4-4. The Ti element had Ti-O and Ti-Ti coordinations with coordination number of 2.0 and 1.2 and bond length of 1.94 and 3.03 Å, respectively. These coordination numbers are far less than the theoretical values (6 for Ti-O and 8 for Ti-Ti coordination) because of large portion of surface TiO2 species. The Zr K-edge XAS spectra of mesoporous ZrO2 and ZrxTiO2 samples were also acquired (See Appendix D). Figure 4-11 (b) shows the Zr K-edge FT-EXAFS of the mesoporous ZrO2

and ZrxTiO2 samples. The mesoporos ZrO2 sample exhibits a tetragonal phase. Table 4-5 lists the fitting parameters for the Zr elements. The coordination number of Zr-O and Zr-Zr bond for the mesoporous ZrO2 were 2.7 and 4.4, and the corresponding bond length was 2.04 and 3.41 Å, respectively. Similar to the mesoporous TiO2 sample, the low coordination

number of the Zr element in the mesoporous ZrO2 sample is resulted from it high surface area.

It is noted that the Zr-O coordination in the Zr0.01TiO2 sample was 6.8. In addition, Zr-Ti coordinations were obtained. These features reveal the incorporation of Zr⁴⁺ ions within the TiO2 framework. The Zr-Zr coordination was additionally found when the Zr/Ti ratio was larger than 0.03. The low Zr-O coordination number (2.0) in the Zr0.03TiO2 indicates that the Zr ions were mainly doped within the TiO2 surface lattice. The result supports the microstructure of the sample deduced from its XRD pattern. When the Zr/Ti ratio increased from 0.03 to 0.05, the Zr-Ti and Zr-Zr coordination number increased from 1.0 to 2.3 and decreased from 2.2 to 1.2, respectively, indicating the high concentration of Zr⁴⁺ ions drives some of them being doped into the inside TiO2 lattice. Incorporation of the Zr⁴⁺ ions inside the TiO2 framework becomes more significant as its loading further increases. In the Zr0.1TiO2 sample, Zr-O coordination increased to 3.4. In addition, the absence the Zr-Ti coordination and the increased Zr-Zr coordination number (6) also reveal the formation of ZrO2 tiny clusters from their segregation. Such segregation allows TiO2 anatase crystals turning from the compression state back to their normal structures.

4960 4980 5000 5020 5040

4960 4964 4968 4972 4976 4980 4984

N o rm a liz ed a b so pr ito n ( a .u.)

Figure 4-9 (a) Complete Ti K-edge XANES spectra (b) and pre-edge region of crystalline anatase TiO2, mesoporous TiO2 and ZrxTiO2 samples.

(b)

(a)

2 4 6 8 10 12

k

2 

(k )

k (Å

^-1

)

Zr_0.03TiO₂ Zr_0.1TiO₂

Zr_0.05TiO₂

Zr_0.01TiO₂

TiO₂ Anatase

0 1 2 3 4

Ti-O-Ti Ti-O

M a gn itude o f F T (a .u.)

R (Å)

Zr_0.1TiO₂

Zr_0.05TiO₂

Zr_0.03TiO₂

Zr_0.01TiO₂

TiO₂

Anatase

Figure 4-10 (a) Ti K-edge EXAFS spectra and corresponding (b) FT-EXAFS spectra of anatase TiO2, mesoporous TiO2 and ZrxTiO2 samples.

(a)

(b)

0 1 2 3 4 5 6

Figure 4-11 Fitted FT-EXAFS spectra of (a) mesoporous TiO2, and (b) mesoporous ZrO2 and ZrxTiO2 samples. Solid and symbolic lines represent the experimental and fitting curves, respectively.

(a)

(b)

Table 4-5 EXAFS fitting results at Ti K-edge of mesoporous TiO2 samples.

Sample Shell N R (Å) σ² (Ų) R factor

Anatase (ref) Ti-O 4 1.93 -^(a)

- Ti-O 2 1.98 - Ti-Ti 4 3.04 - Ti-Ti 4 3.78 -

TiO2 Ti-O 2.0 1.94 0.0010

0.0035

Ti-Ti 1.2 3.03 0.0020

(a) References data.

Table 4-6 EXAFS fitting results at Zr K-edge of mesoporous ZrO2 and ZrxTiO2 samples.

Sample Shell N R (Å) σ² (Ų) R factor

Tetragonal (ref) Zr-O 4 2.10 -^(a)

Zr-O 4 2.32 - -

Zr-Zr 12 3.62 -

M-ZrO2 Zr-O 2.7 2.04 0.0050

0.0003 Zr-Zr 4.4 3.41 0.0070

Zr0.01TiO2 Zr-O 6.8 2.09 0.0065

0.0015 Zr-Ti 1.0 2.34 0.0066 Zr-Ti 3.7 3.12 0.0070

Zr0.03TiO2 Zr-O 2.0 2.06 0.0010

Zr0.03TiO2 Zr-O 2.0 2.06 0.0010

在文檔中 鋯離子摻雜與金沉積對中孔洞二氧化鈦微結構與光催化還原二氧化碳研究 (頁 60-112)