Introduction BiVO 4 is an effective - PowerPoint Presentation

Introduction BiVO 4  is an effective
Introduction BiVO 4  is an effective

Introduction BiVO 4 is an effective - Description


photocatalytic material for solar water oxidation reaction because of nontoxicity and photochemical stability However bare BiVO 4 exhibits low water photooxidation due to an inefficient separation of ID: 808481 Download

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results bivo water doping bivo results doping water carrier oxidation bivo4 transfer doped dopants bare charge density light activity

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Slide1

Slide2

Introduction

BiVO

4

is an effective

photocatalytic

material for solar water oxidation reaction because of nontoxicity and photochemical stability

However, bare BiVO

4

exhibits low water photo-oxidation due to an inefficient separation of

photoexcited

electron-hole pairs

Through impurity doping into BiVO

4

, significant improvements in the water photo-oxidation ability of BiVO

4

structure have been reported

Slide3

Introduction

In particular, incorporation of tungsten or molybdenum into BiVO

4

was shown to significantly improve its

photoactivity

for the water oxidation reaction

However, there has been neither a systematic screening study to find other suitable dopants nor one on the relative magnitude of the effect of different dopants

Thus, in this study, 12 dopants (Mo, W, Ti, Cr, Fe, Zn,

Nb

,

Ru

,

Pt

,

Sn

,

Ce

, and Ta) are screened and

a drastic improvement in the visible-light-induced water oxidation activity of bare BiVO

4

only with W or Mo doping is observed

Slide4

Results

Slide5

Results

Relative to

undoped

BiVO

4

powder, the

photocatalytic

water oxidation activity of W

: BiVO

4

or Mo

: BiVO

4

powder is dramatically improved

Mo

doping shows a greater

photoactivity

improvement than that of W

doping

Both W and Mo impurities are efficient dopants to enhance the visible-light-induced water oxidation activity of a BiVO

4

photocatalyst

Slide6

Results

The high intensity and sharp peak patterns of all three powder samples are well matched to a monoclinic phase of BiVO

4

Both

W and Mo impurities have been effectively incorporated into the crystal lattice of BiVO4

W or Mo doping has no significant effect on the light absorption characteristics of a bare BiVO

4

structure

Slide7

Results

W or Mo doping into the V sites of the monoclinic BiVO4 lattice increased the PEC activity by five to six times

Slide8

Results

The IPCE values of W or Mo-doped BiVO4

photoanodes

are higher than that of bare BiVO4

Slide9

Results

To find any changes in the transport properties of the carrier, M-S analysis for capacitance and electrochemical impedance spectroscopy (EIS) measurements for charge-transfer resistance were carried out for the all three

photoanodes

Slide10

Results

Mo-doped BiVO4 has the best charge-transfer efficiency, as seen by the low value of R

CT

whereas the high R

CT

value of an

undoped

BiVO4

photoanode

indicates poor charge-transfer ability

The results of EIS measurements

Slide11

Results

The results of

capacitance

measurements

Slide12

Results

The carrier density can be obtained by the slope of tangent lines of the M-S plots

A smaller slope means a higher carrier concentration

Thus,

W or Mo doping increases the carrier density and reduces the electrical resistance of a monoclinic BiVO

4

system

Slide13

Results

The DOS moves to a lower energy and the Fermi level (E

F

) moves closer to the CB edge in W- or Mo-doped BiVO

4

Slide14

Results

The extra electron donated by the dopants like W or Mo will enhance carrier density when they substitute for V positions of BiVO

4

system

Such increased carrier density can accelerate charge transfer and superior

photoactivity

Slide15

Conclusions

A remarkable doping effect was confirmed in Mo- or W-doped BiVO

4

for visible-light-induced

photocatalytic

O

2

evolution from water and PEC current

generation

W- or Mo-doped BiVO

4

photoanodes

exhibited high photocurrents and incident photon-to-current conversion efficiency

Relative to bare BiVO

4

, a carrier concentration is about 1.6-2 times higher and charge-transfer resistance suppressed by 3-4 times

Mo functions as a more efficient electron donor than W

Shom More....
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