Aryane A. Marciniak1*; Evelyn C.S.Santos2; Odivaldo C. Alves3; Flávio Garcia2; Claudio J. A. Mota1.

1Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brasil; 2Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro, Brasil;3Universidade Federal Fluminense, Niterói, Brasil. *ary.marciniak@gmail.com

Methodologies

ConclusionAcknowledgements

Introduction

• α-Fe2O3 nanorings were prepared using a microwave-driven method, which is

more sustainable than the conventional method, reducing time and energy;

• The CeFe-11 catalyst presented the best performance (7.2 mmolDMC/gcat) in

converting CO2 to organic carbonate (DMC). This result may be associated with

its high surface area (95 m2/g) and the presence of oxygen vacancies.

✓ Hematite (α-Fe2O3) is abundant in nature and can present several

morphologies, depending on the preparation method;

✓ The conventional hydrothermal procedure is the most used to prepared

nanoring-shaped hematite. However, with prolonged reaction time (48 h);

✓ Microwave-driven (MW) methods have been used to reduce time and

energy in different processes;

✓ α-Fe2O3 presents interesting properties for catalysis applications and can

be doped or impregnated with CeO2;

✓ The conversion of CO2, a greenhouse gas, to valuable products is an

important and sustainable process;

✓ In this work, we show the potential synergistic effect between CeO2 and

α-Fe2O3 nanorings (NR) as a green and sustainable catalysts in the CO2

conversion into DMC.

Microwave-driven hydrothermal synthesis of α-Fe2O3

nanorings as CeO2 catalyst support for CO2 conversion

20 30 40 50 60 70 80 90

−Fe2O

3

CeFe-21

CeFe-15

CeFe-12

* * ******

−Fe2O

3

CeFe-11

CeO2

Inte

nsi

ty (

a.u

.)

2 (degree)

*

* CeO2

Results and discussion

Powder XRD patterns: two crystalline phases,

hematite (PDF 33-0664) and CeO2 (JCPDS 34-

0394).

SEM: α-Fe2O3 presented

highly ordered nanorings,

mostly with edge lengths

between 100 and 110 nm.

TEM image of CeFe-11 shows the

presence of α-Fe2O3 nanorings well

decorated with CeO2 nanoparticles.

CeO2

+ CeO2

1:0 1:0.5 1:1 1:2 1:5 0:11

2

3

4

5

6

7

8

DM

C (

mm

ol/g

cat)

Ce:Fe Molar ratio

20

30

40

50

60

70

80

90

100

Su

rface a

rea (

m2/g

)

Catalytic performance

MeOH

15 mL

140°C/3 h

The product was

analyzed by GC-

MS

+

100 mg

Cat.

Catalyst was

separated by

centrifugation

50 bar

CO2

0 2000 4000 6000

CeFe-21

CeFe-15

CeFe-12

CeFe-11

Inte

ns

ity

(a

.u.)

Magnetic field (G)

−Fe2O

3

Ce3+(g= 1.96)

EPR was used to evaluate the presence of

oxygen vacancies (Ov) in the lattice; the α-Fe2O3

did not present Ov signals; the Ov signal

decreases according to the Ce:Fe molar ratio.

Ov (g= 2.02)

➢ All α-Fe2O3 nanoring catalysts impregnated with CeO2 showed higher DMC yield

compared to pure CeO2 (1.5 mmolDMC/gcat) and α-Fe2O3 (1.6 mmolDMC/gcat);

➢ The results may be associated with the higher surface area, which seems to be

essential in the synthesis of DMC;

➢ The CeFe-11 presented the best catalytic activity for CO2 conversion to DMC.