Iron oxide nanoparticles supported on diamond

nanoparticles as efficient and stable catalyst for the visible

light assisted Fenton reaction

Juan C. Espinosa, Cristina Catalá, Sergio Navalón,1,* Belén Ferrer, Mercedes Álvaro,1

Hermenegildo García1,2,*

1 Departamento de Química and Instituto Universitario de Tecnología Química CSIC-UPV,

Universitat Politècnica de València, Consejo Superior de Investigaciones Científicas, Av. de

los Naranjos s/n, 46022 Valencia, Spain

2 Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah,

Saudi Arabia

Supporting information

0-1 1-2 2-3 3-4 4-5 5-60

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Fe particle size (nm)

d)

20 nm 20 nm

0-1 1-2 2-3 3-4 4-5 5-60

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Fe particle size (nm)

c)

20 nm 20 nm

0-1 1-2 2-3 3-5 5-6 6-7 7-9 9-110

10

20

30

40

50Fe

dis

trib

utio

n (%

)

Fe particle size (nm)

b)

10 nm100 nm

0-1 1-2 2-3 3-5 5-6 6-7 7-9 9-110

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Fe particle size (nm)

a)

20 nm100 nm

Figure S1. Representative DF-TEM images and particle size distribution of supported Feox

NPs (0.2 wt%) on D1 (a), D2 (b) and D3 (c) as well as iron NPs (1.0 wt %) supported on D3

(d).

0-2 0-2 2-4 4-6 6-8 8-10 10-1212-160

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Fe particle size (nm)

c)

200 nm 100 nm

0-2 0-2 2-4 4-6 6-8 8-10 10-1212-160

10

20

30

40

50Fe

dis

trib

utio

n (%

)

Fe particle size (nm)

b)

200 nm 50 nm

a)

0-2 2-4 4-6 6-8 8-12 12-1616-2020-220

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Fe particle size (nm)

200 nm 100 nm

Figure S2. Representative DF-TEM images and particle size distribution of supported Feox

NPs (0.2 wt%) on AC1 (a), AC2 (b) and AC3 (c).

0-2 2-6 6-8 8-9 9-10 10-11 11-120

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Fe particle size (nm)

c)

50 nm 20 nm

0-2 2-6 6-8 8-10 10-11 11-12 12-160

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Fe particle size (nm)

100 nm 100 nm

a)

0-2 2-6 6-8 8-9 9-10 10-11 11-120

10

20

30

40

50Fe

dis

trib

utio

n (%

)

Fe particle size (nm)

100 nm 20 nm

b)

Figure S3. Representative DF-TEM images and particle size distribution of supported Feox

NPs (0.2 wt%) on G1 (a), G2 (b) and G3 (c).

0-2 2-3 3-4 4-5 5-6 6-7 7-80

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Fe particle size (nm)

a)

b)

50 nm50 nm

Figure S4. Representative DF-TEM images and particle size distribution of supported Feox

NPs (0.2 wt%) on TiO2 (a) and representative EDX analysis (b). The Ni detected in EDX

analysis is due to the composition of the TEM grid used as sample holder.

a) b)

Spectrum 12c)

d)

Figure S5. DF-STEM images (a, b), EDX analysis (c) and EDX mapping spectra (d) of

Feox(0.2 wt%)/D3 sample. Ni appearing in panels c and d is due to the composition of the

TEM grid used as sample holder.

CarbonCopper

Oxygen Iron

STEM-DF image

a)

b)

Figure S6. Representative STEM-DF image and EDX mapping spectra (a), and

representative EDX analysis (b) taken for Feox(0.2 wt%)/D3 sample using a Cu grid as sample

holder, showing in this case the absence of Ni (present in Figures S4 and S5) and the

presence of Cu due to the composition of the holder.

a)

b)

Figure S7. Representative DF-TEM image (a) and EDX analysis (b) of Feox(0.2 wt%)/D3

sample. Note that, in contrast to Figures S4 and S5, no Ni is present in the EDX analysis and

the presence of Cu is due to the composition of the grid used as sample holder.

10 20 30 40 50 60 70 80 90

e)

d)

c)

b)

a)

2 (º)

(111)* (220)

*

Figure S8. PXRD of Feox NPs supported on D3 at 0.2 wt % (a), compared to theoretical

diffractions peaks of Fe (b), Fe2O3 (c), Fe3O4 (d) and FeO (e). Characteristic reported

diamond diffraction patterns are indicated (*). The broadness of the diffraction peaks is a

reflection of their small particle size.

200 300 400 500 600 700 800

Abs

orba

nce

(a.u

.)

Wavelength (nm)

a)

b)c)

d)

e)

Figure S9. Diffuse reflectance spectra of D3 (a), Feox(0.2 wt%)/D3 (b), Feox(1.0wt%)D3 (c),

Fe2O3 standard (d) and Fe3O4 standard (e).

200 300 400 500 600 700 800

Abs

orba

nce

(a.u

.)

Wavelength (nm)

a)

b

c)

d)

a)

b)

c, d)

Figure S10. Photographs and UV-Vis spectra of an Fe (III) solution before (a) and after

addition of NaBH4 recorded at 1 (b), 5 (c) and 24 h (d).

650 600 550 500 450 400

e)

d)

Tr

ansm

ittan

ce (%

)

Wavenumber (cm-1)

c)

4000 3500 3000 2500 2000 1500 1000 500

Tran

smitt

ance

(%)

Wavenumber (cm-1)

a)

b)

c)d)e)

Zoom in

Figure S11. FT-IR spectra of commercial Fe3O4 (a), Fe2O3 (b), D3 (c), Feox(0.2 wt%)/D3 (d)

and Feox(1.0 wt%)/D3 (e). A zoom of the selected area for D3 (c), Feox/D3 (d) and Feox(1.0 wt

%)/D3 is presented, and arrows indicate vibration bands of Fe-O.

3000 3200 3400 3600 3800

Inte

nsity

(a.u

.)

Magnetic field (G)

a)b)

Figure S12. EPR spectra of fresh Feox(0.2 wt%)/D3 (a) and four times used Feox(0.2 wt%)/D3

(b).

700 705 710 715 720

Fe(III) satellite

CPS

Binding energy (eV)

Fe(III)

700 705 710 715 720

CPS

Binding energy (eV)

a) b)

1)

2)

Figure S13. XPS spectra of the Fe 2p peak for the Feox(0.2wt%)/D3 (a1) and Feox(1.0

wt%)/D3 (a2). Deconvolution of Fe 2p spectrum for the Feox(1.0wt%)/D3 (b).

0 2 4 60

20

40

60

80

100

Phen

ol (m

g L-1

)

Time (h)0 2 4 6

0

40

80

120

160

200

H2O

2 (m

g L-1

)

Time (h)

a) b)

Figure S14. Blank control experiments for phenol disappearance (a) and H2O2 decomposition

(b) at pH 4. Legend: Using Feox/D3 as catalyst (100 mg L-1) under dark conditions (∆); under

artificial solar light irradiation but in the absence of catalyst (); under artificial solar light

irradiation but in the absence of H2O2 (■).

0 1 2 3 40

20

40

60

80

100Ph

enol

(mg

L-1)

Time (h)0 1 2 3 4

0

40

80

120

160

200

H2O

2 (m

g L-1

)

Time (h)

0 1 2 3 40

20

40

60

80

100

Phen

ol (m

g L-1

)

Time (h)0 1 2 3 4

0

40

80

120

160

200

H2O

2 (m

g L-1

)

Time (h)

0 1 2 3 40

20

40

60

80

100

Phen

ol (m

g L-1

)

Time (h)0 1 2 3 4

0

40

80

120

160

200

H2O

2 (m

g L-1

)

Time (h)

a) b)

c) d)

e) f)

Figure S15. Phenol disappearance (a, c, e) and H2O2 decomposition (b, d, f) using active

carbon (a, b), diamond nanoparticles (c, d) and graphite (e, f) as catalyst. Legend: a, b) AC1

(■), AC2 (○), AC3 (▲); c, d) D1 (■), D2 (○), D3 (▲); e, f) G1 (■), G2 (○), G3 (▲).

Reaction conditions: catalyst (100 mg L-1), phenol (100 mg L-1), H2O2 (200 mg L-1), pH 4,

artificial solar light irradiation.

0 1 2 3 4 5 60

20

40

60

80

100

Phen

ol (m

g L-1

)

t (h)0 1 2 3 4 5 6

0

40

80

120

160

200

H2O

2 (m

g L-1

)

t (h)

0 1 2 3 4 5 60

20

40

60

80

100

Phen

ol (m

g L-1

)

t (h)0 1 2 3 4 5 6

0

40

80

120

160

200

H2O

2 (m

g L-1

)

t (h)

0 1 2 3 4 5 60

20

40

60

80

100

Phen

ol (m

g L-1

)

t (h)0 1 2 3 4 5 6

0

40

80

120

160

200

H2O

2 (m

g L-1

)

t (h)

a) b)

c) d)

d) e)

Figure S16. Temporal profiles for phenol degradation (a, c, d) and H2O2 decomposition (c, d,

e) using Feox(0.2wt%)/D (a, b), G (c, d) or AC (d, e) based materials under simulated sunlight

irradiation. Commercial carbonaceous support (■), Fenton-treated carbons (○), Fenton-

treated followed by H2 annealing (●). Reaction conditions: catalyst (0.0071 mM supported

iron on D3), phenol (100 mg L-1; 1.06 mM), H2O2 (200 mg L-1; 5.88 mM), initial pH 4, 20 ºC.

0 1 2 3 4 5 60

20

40

60

80

100Ph

enol

(mg

L-1)

t (h)0 1 2 3 4 5

0

50

100

150

200

H2O

2 (m

g L-1

)

t (h)

a) b)

Figure S17. Phenol degradation (a) and H2O2 decomposition (b) using Feox(0.2 wt%)/D3 (●),

Feox(1 wt%)/D3 (■) or unsupported Feox NPs (○) under simulated sunlight irradiation.

Reaction conditions: Catalyst (0.0071 mM of supported or unsupported iron), phenol (100 mg

L-1; 1.06 mM), H2O2 (200 mg L-1; 5.88 mM), initial pH 4, 20 ºC.

0 1 2 3 4 5 6 7 80

20

40

60

80

100[P

heno

l and

reac

tion

inte

rmed

iate

s] (m

g L-1

)

t (h)0 1 2 3 4 5 6

0

50

100

150

200

H2O

2 (m

g L-1

)

t (h)

a) b)

c) d)

0 1 2 3 4 5 60

20

40

60

80

100

[Phe

nol a

nd re

actio

nin

term

edia

tes]

(mg

L-1)

t (h)

0 1 2 3 4 5 60

40

80

120

160

200

H2O

2 (m

g L-1

)

t (h)

Figure S18. Concentration of phenol and reaction intermediates formed in the degradation

(a,c) and H2O2 decomposition (b,d) using Feox/TiO2 (a,b) and TiO2 (c,d) under visible light

irradiation. Legend: Phenol (■), catechol (∆), hydroquinone (○) and p-benzoquinone (□).

Reaction conditions: catalyst (0.0071 mM supported iron NPs on TiO2, or 5 mg of TiO2),

phenol (100 mg L-1; 1.06 mM), H2O2 (200 mg L-1; 5.88 mM), initial pH 4, 20 ºC.

0 1 2 3 40

20

40

60

80

100

Phen

ol (m

g L-1

)

t (h)0 1 2 3 4

0

40

80

120

160

200

H2O

2 (m

g L-1

)t (h)

a) b)

Figure S19. Phenol degradation (a) and H2O2 decomposition (b) using Ag (○), Cu (□) or Feox

(●) NPs supported on D3 under simulated sunlight irradiation. Reaction conditions: catalyst

(0.0071 mM supported metal NPs on D3), phenol (100 mg L-1; 1.06 mM), H2O2 (200 mg L-1;

5.88 mM), initial pH 4, 20 ºC.

0 1 2 3 4 5 60

20

40

60

80

100

Phen

ol (m

g L-1

)

t (h)0 1 2 3 4 5 6

0

40

80

120

160

200

H2O

2 (m

g L-1

)

t (h)

a) b)

Figure S20. Phenol degradation (a) and H2O2 decomposition (b) using the heterogeneous

Feox(0.2 wt%)/D3 catalyst (■), Fe(II) (○) or Fe(III) (●) salts as homogeneous catalysts.

Reaction conditions: Catalyst: Feox(0.2 wt%)/D3 (200 mg L-1, 0.4 mg L-1 as Fe) or Fe salts

(0.0078 mg L-1) corresponding to the leached amount found at the end of the reaction using

the heterogeneous Feox(0.2 wt%)/D3 catalyst), phenol (100 mg L-1; 1.06 mM), H2O2 (200 mg

L-1; 5.88 mM), initial pH 4, 20 ºC.

0 1 2 3 4 5 6 7 85

10

15

20

25

Phen

ol (g

L-1)

t(h)0 1 2 3 4 5 6 7 8

10

20

30

40

50

H2O

2 (g

L-1)

t (h)

a) b)

Figure S21. Productivity test for phenol degradation (a) and H2O2 decomposition (b) using

Feox(0.2 wt%)/D3 as photocatalyst under visible light irradiation. Reaction conditions:

catalyst (0.0071 mM supported iron NPs on D3), phenol (25 g L -1; 265 mM), H2O2 (50 g L-1;

1.47 M), initial pH 4, 20 ºC, sunlight intensity (100 mW cm-2).

0-1 1-2 2-3 3-4 4-5 5-60

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Feox particle size (nm)

0-1 1-2 2-3 3-4 4-5 5-6 6-70

10

20

30

40

50

Fe d

istr

ibut

ion

(%)

Feox particle size (nm)

a)

b)

Figure S22. DF-STEM images and histograms of particle size distribution of four times (a)

and eight times (b) Feox(0.2 wt%)/D3 catalyst used at pH 6.

4000 3000 2000 1000

5003)

2)

Tran

smita

nce

(%)

Wavenumber (cm-1)

1)

622

200 300 400 500 600 700 800

3)2)

F(R

) (a.

u.)

Wavelength (nm)

1)

a) b)

Figure S23. FT-IR (a) and diffuse reflectance (b) spectra of fresh Feox/D3 catalyst (1) and

used Feox/D3 catalyst at pH 4 (2) and pH 6 (3).

705 710 715 720 725 730 735 740

Fe 2p1/2

CPS

Binding energy (eV)

3)

2)

1)

Fe 2p3/2

Satellite

200 300 400 500 600 700 800

3)

2)

F(R

) (a.

u.)

Wavelength (nm)

1)

4000 3000 2000 1000

3)2)

3137

Inte

nsity

(a.u

.)

Wavenumber (cm-1)

748

1)

500 1000 1500 2000

3)

2)

Inte

nsity

(a.u

.)

Raman shift (cm-1)

1)

a) b)

c) d)

Figure S24. FT-IR (a), Raman (b), diffuse reflectance (c) and XPS (d) spectra of fresh

unsupported Feox NPs (1) and used Feox NPs at pH 4 (2) and 6 (3).