High efficiency conversion of CO2 to methanol using photoelectrocatalyst

PowerPoint Presentation High efficiency conversion of CO2 to methanol using photoelectrocatalyst Reporter Tran Thanh Phuc Class CHHO7B Lecturer Luu Cam Loc Report date March 23, 2019 Outline Introduction Methanol yield Conclusion 2 Nội dung báo cáo gồm 4 phần Giới thiệu Vật liệu và phương pháp Kết quả và thảo luận Kết luận 2 High temperature and high pressure 300°C and 500 bar Using catalyst Introduction Carbon dioxide (CO2) được giải phóng bằng cách đốt các nhiên liệu hóa thạch là nguyên nhân c.

High-efficiency conversion of

photoelectrocatalyst• Reporter : Tran Thanh Phuc

• Class : CHHO7B

• Lecturer : Luu Cam Loc

• Report date : March 23, 2019

• Introduction

• Methanol yield

• Conclusion

2

High temperature and high pressure

300°C and 500 bar

Using catalyst

Introduction

PC

The presence of light

Semiconductor materials,

which can form electrons and

holes when exposed to light

The reactions are normally either oxidation

or reduction

Activating a catalyst

by ultraviolet (UV) or

visible light

Introduction

PC

An ideal photocatalyst should have the following

properties

Introduction

PC

Under ambient temperature and pressure driven by solar energy

The PC conversion efficiency of CO2 to methanol (CH3OH) is generally low

Electrocatalytic

EC

Under ambient temperature and pressure

Low energetic efficiency, and poor selectivity

Introduction

Photo-electrocatalytic

(PEC)

Matches the energy

band for PC

reduction

Matches the small overpotential for EC

reduction

Cu2O/Fe2O3 NTs

Introduction

Fe2O3 (iron oxide)

Structure and

properties

magnetite (Fe3O4)

Transition metal oxide

wüstite (FeO)

hematite

(-Fe2O3)

maghemite (-Fe2O3)

n-type semiconductor

The cheapest semiconductor

Narrow band gap (2.0–2.2 eV) Absorbs light up to 600 nm The stability in most aqueous solutions (pH > 3)

Introduction

Fe2O3 (iron oxide)

-Fe2O3 nanotubes (NTs)

nanotubes have higher PC activity

large surface

areas

could reduce the electron–hole pairs recombination

Valence band: 2.48 eV

Conduction band: 0.28 eV

The reduction of Fe2O3 is very weak for the positive conduction band Cuprous oxide (Cu2O) was selected to couple with Fe2O3 NTs

Introduction

The CB of Cu2O is more negative than the CO2 reduction potential

and the band gap is relatively narrow (1.9–2.2 eV).

Serious photocorrosion of Cu2O in aqueous solution.

Cuprous oxide (Cu2O)

Photocorrosion of the photocathode will greatly decline

the overall reduction efficiency since most photogenerated holes are consumed by Cu2O itself.

Photocorrosion of the photocathode will greatly decline

the overall reduction efficiency since most photogenerated holes are consumed by Cu2O itself.

The p-type semiconductors

Low toxicity, low cost, earth abundant properties

Conduction band: -1.3 eV

Introduction

Cu2O/Fe2O3 NTs

The material with double-layer Cu2O spheres (Cu2O/Fe2O3 NTs-30) showed excellent PEC properties with a suitable energy band gap

(1.96 eV) and the smallest over-potential (180 mV)

Valence band: 1.09 eV Conduction band: -0.87 eV

Introduction

Cu2O/Fe2O3 NTs

V

A

CO2 in

Light

(Xenon lamp)

Cu2O/Fe2O3 NTs-30

ref

Counter electrode

Gas out

to GC

Methanol yield of the PEC,PC, and EC reduction of CO2 on Cu2O/Fe2O3 NTs-30

4.94

1.39

0.90

2.29

Methanol yield

Compared to EC or PC, the Cu2O/Fe2O3 NTs showed superior PEC reduction performance for the efficient conversion of CO2 to CH3OH

Cu2O/Fe2O3 NTs + h  Cu2O/Fe2O3 NTs (h+ + e-)

H2O +2h+  0.5O2 +2H+ +2e

-CO2 + 6H+ +6e-  CH3OH + H2O

VB CB

Comparison

The material with double-layer Cu2O spheres (Cu2O/Fe2O3 NTs-30) showed excellent PEC properties with a suitable energy band gap (1.96 eV) and

the smallest overpotential (180 mV)

Cu2O/Fe2O3 NTs-30 showed two types of synergism in the PEC reduction

of CO2: (i) between electrocatalysis and photocatalysis and (ii) between

Cu2O and Fe2O3-NTs

The faradaic efficiency and methanol yield reached 93% and 4.94 mmol L-1

cm-2 after 6 h, respectively

The excellent performance of Cu2O/Fe2O3 NTs-30 for the PEC reduction of

CO2 was well confirmed

Still used external voltage