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
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Slide1
Slide2Introduction
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
Slide3Introduction
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
Slide4Results
Slide5Results
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
Slide6Results
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
Slide7Results
W or Mo doping into the V sites of the monoclinic BiVO4 lattice increased the PEC activity by five to six times
Slide8Results
The IPCE values of W or Mo-doped BiVO4
photoanodes
are higher than that of bare BiVO4
Slide9Results
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
Slide10Results
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
Slide11Results
The results of
capacitance
measurements
Slide12Results
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
Slide13Results
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
Slide14Results
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
Slide15Conclusions
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