Material Katalis dan Fotokatalis (MKF)

• Material Katalis• Material Fotokatalis

SILABI MATERIAL KATALIS DAN FOTOKATALIS ( MKF )

1. Sejarah dan Perkembangan Material Katalis 2. Konsep Dasar Reaksi Katalisasi 3. Material Katalis Homogen dan Heterogen : Reaksi, Desain Sintesis,

Karakterisasi dan Uji Unjuk Kerja Katalis4. Sejarah dan Perkembangan Material Fotokatalis 5. Sintesis dan Karakterisasi Material Fotokatalis6. Aplikasi Material Fotoaktif : Fotokatalisasi oksidasi dan reduksi serta

Unjuk kerja, Fotokatalis dalam sistem Fotovoltaik dan Unjuk Kerja7. Perkembangan terkini sintesis material fotokatalis : material

responsif cahaya tampak, material core-shell, material nanostruktur (nanorod,nanotube,nanowire)

Prasyarat : KIMIA DASAR SEMESTER GENAPDosen Pengasuh : Prof Dr Wega Trisunaryati

Dr Indriana KartiniDr. Akhmad S

HETEROGENEOUS CATALYSTS

• Solid catalyst• Photocatalysis by semiconductor

materials

• A CATALYST is a substance that increases the rate at which a chemical reaction approaches equilibrium, while not being consumed in the process – kinetic aspect

• catalyst provides alternative reaction mechanism of lower activation energy

• materials used: insoluble, nonvolatile solid as catalyst

• important properties:– activity– selectivity

• advantages of using solid catalyst in a fluid-phase reaction – heterogeneous catalyst :– minimal lost of the catalyst– minimal contamination of the reaction products– stay physically in place of the reaction chambers

• Heterogeneous catalysis of a reaction between two molecules can occur only when both molecules are adsorbed on to a solid surface

Photocatalysis

Photocatalyst

Starch + O2

Organic compound

Chlorophyll

CO2

H2O

CO2 + H2O

Organic Compound

+ H2O + O2

Photocatalytic Applications

Antimicrobial Effect

Antimicrobial Effect

Self-Cleaning Effect

When water hit surfaces

Hydrophilic surface=wetting

Water spreads

Hydrophobic surface= beading

Water beads

Contact angle differences

Contact angles below 90 indicate good wetting, while contact angles above 90 indicate poor wetting (beading).

Poor wetting (beading)Contact angle > 90°

Good wetting Contact angle < 90°

THE LOTUS LEAF EFFECT

The leaves of Lotus plants have the unique ability to avoid getting dirty.They are coated with wax crystals around 1 nanometre in diameter and have a special rough surface.Droplets falling onto the leaves form beads and roll off taking dirt with them, meaning the leaves are self-cleaning.Sometimes referred to as“The Lotus Leaf effect”

SELF CLEANING GLASS

Scientists have mimicked nature at the nanoscale to create glass surfaces that are ‘self-cleaning’ like the Lotus leaf.

No more scrubbing of shower screens!

Self cleaning glass Normal glass

No more Spiderman window cleaner!

SELF CLEANING GLASS

HOW DOES IT WORK?

Glass is coated with a layer of nanocrystalline titanium dioxide (TiO2). The titanium dioxide reacts to the ultraviolet (UV) component of sunlight causing a gradual break down and loosening of dirt. This isknown as the ‘photocatalytic’ stage.

SELF CLEANING GLASS

HOW DOES IT WORK?

The reaction also causes the glass surface to become super hydrophilic. This forces water to spread across the surface like a sheet, rather than beading, thereby washing away the looseneddebris on the surface ofThe glass as it falls.This is the ‘hydrophilic’ stage.

SELF CLEANING GLASS

HOW DOES IT WORK?

• Another type of self cleaning glass uses hydrophobicity, not hydrophilicity.

• This type of glass is given a coating which makes it super hydrophobic, meaning water forms beads and runs of the glass.

• This type of glass is used indoors, such as in shower screens, where there is no sunlight enable use of the other type of glass.

Photocatalysts

Vacuum level

-3.0

-4.0

-5.0

-6.0

-7.0

-8.0

0

-4.5

TiO2

Rutile

3.0

TiO2

Anatase

3.2

SrTiO3

3.2

FeTiO3

2.7

2.8

MnTiO3

3.2

ZrO2

BaTiO3

5.0

Nb2O5

3.4

3.4

KTaO3WO3

2.8

2.2

ZnO2

3.2

Fe2O3

SnO23.

8

GaP

2.3

1.1

Si

SiC

3.0

CdSe

CdS

1.7

2.5

E vs. NHE

@ pH = 0

H+/H2

-1.0

+2.0

+1.0

+3.0

0

Band Gap Positions in Various Semiconductors

eV

O2/H+

Upper edge position of VB

Lower edge position of CB

Mechanism of photocatalysis

+

+

B

B+

-

-

A

A-

h

CB

VBh+

e-

hv

+ +Volume recombination

++

surface recombination

photogenerated hole – highly oxidizing

O2

O2-, H2O2

H2O2, OH-, R

OH● , R+

Why TiO2?

1 n-type TiO2 electrode 2 platinum black counter electrode

3 ionically conducting separator 4 gas buret

5 load resistance 6 voltmeter

Fujishima A.Honda K.,Nature， 1972， 37(1):238-

245.

• Good photoactivity (band gap=3.2ev) oxidation of most VOC & water (Strong oxidizing power)• High Photo & chemical stability, non-toxicity• Low cost, ease of availability, can be reused• Photocatalysis takes place at ambient temperature• Atmospheric oxygen is used for the reaction

Photocatalysis goes to TiO2 era

Redox potential of h+

1. The redox potential for photogenerated h+ is +2.53 V vs. the

SHE

2. After reaction with water, these h+ can produce •OH

3. Both h+ and •OH are more positive compare to ozone

Introduction: Photocatalytic Process

Photo-generation

electron/hole pairs

Formation of radicals

Radical oxidation of organic

compound.

TiO 2 hv

e- + h+

h+ + H 2O OH + H+

e- + O 2 O2-

O2- + H+ HO 2

TOC + Ox TOC(partially oxidized species) + CO2 + H 2O

Photocatalytic ReactionsTiO2 + h TiO2 (e- + h+)

h+ + H2O OH + H+

O2 + e- O2 -

O2 - + H+ HO2

HO2 + HO2 H2O2 + O2

O2 - HO2+

H2O2

O2 + HO2-

HO2- +

H2O2 + h OH2

H2O2 + O2 - HO + OH- + O2

H2O2 + e-HO + OH-

The applications of TiO2 is a function of specific physicochemical properties

like:

– High Surface area

– Small Crystalline Size

– Anatase form of TiO2

– High crystallinity

– Porous structure

– Activation light source

An appropriate synthetic procedure can provide TiO2 with promising

efficiency

Entail Physicochemical Properties of TiO2

Challenge of TiO2!!!

Because TiO2 has a high band gap (~ 3.2 eV), it is excited only by UV light (λ <388 nm) to inject electrons into the conduction band. Thus, this limits the use of sunlight (3~5%) or visible light as an irradiation source in photocatalytic reactions on TiO2 .

In addition, the high rate of electron–hole recombination on TiO2 particles results in a low efficiency of photocatalysis

next will be on:fundamental concepts for

photocatalyst material